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Hypertension-Endocrine Branch National Heart, Lung, and Blood Institute (L.-N.C., H.C., Y.L., M.J.Q.) and Diabetes Branch National Institute of Diabetes and Digestive and Kidney Diseases (L.Z., M.A.M., S.I.T.) National Institutes of Health Bethesda, Maryland 20892
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Akt is a protooncogene encoding a serine-threonine kinase (also known as PKB or RAC-PK). Recently, Akt has been identified as a downstream target of PI3K that mediates mitogenic actions and antiapoptotic effects of growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor, insulin-like growth factor I, and insulin that are initiated by their cognate receptor tyrosine kinases (for review see Ref.10). Interestingly, overexpression of constitutively active mutants of Akt in 3T3-L1 cells results in spontaneous differentiation of these preadipose cells into an adipocyte-like phenotype and also results in increased glucose uptake and elevated levels of cell surface GLUT4 in the absence of insulin in the differentiated cells (11, 12). Furthermore, glycogen synthase kinase-3 (GSK3, an enzyme involved with the regulation of glycogen synthesis by insulin) has been identified as a physiological substrate for Akt (13). These studies suggest that Akt may participate in metabolic signaling pathways for insulin (in addition to its mitogenic functions). However, overexpression of constitutively active mutants in tissue culture cells may result in effects that do not reflect what occurs under physiological conditions. In this study, we have overexpressed wild-type, constitutively active, or dominant inhibitory forms of Akt in primary cultures of rat adipose cells. Overexpression of wild type and constitutively active Akt resulted in increased levels of cell surface GLUT4 in the absence of insulin. More importantly, overexpression of a dominant inhibitory mutant of Akt resulted in inhibition of insulin-stimulated translocation of GLUT4. The dominant inhibitory mutant of Akt that we use in this study is a kinase-deficient Akt that results from the substitution of alanine for lysine at position 179 in the canonical ATP-binding domain. This mutant is not only catalytically inactive but has been shown to inhibit the activity and actions of endogenous Akt (presumably by competing with endogenous Akt for other upstream or downstream molecules) (14, 15, 16). Our results, in a bona fide insulin target cell, suggest a physiological role for Akt in insulin-stimulated glucose transport that may also apply to other metabolic actions of insulin.
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RESULTS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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). In the lane containing cell
extracts from control cells transfected with the empty expression
vector pCIS2, there is a faint band representing endogenous rat Akt.
Lanes containing extracts from groups of cells transfected with
recombinant Akt constructs show overexpression of recombinant Akt at
levels that are much higher than the endogenous Akt levels. Since only
5% of the adipose cells that have undergone electroporation are
actually transfected (1), we estimate that there is at least 100-fold
overexpression of the recombinant Akt constructs relative to endogenous
Akt in the transfected cells. The constructs with a mutation in the
ATP-binding site (Akt-K179A and Myr-K179A) are predicted to act in a
dominant inhibitory manner that depends on the level of overexpression.
Therefore, we tested the effect of increasing the concentration of
plasmid DNA used for transfection on expression levels for these
constructs. As expected, increasing the concentration of DNA from 4
µg/cuvette to 7 µg/cuvette significantly increased the levels of
overexpression for Akt-K179A (Fig. 1, compare lanes 4 and 5).
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). Whole cell
homogenates derived from groups of transfected cells treated without or
with insulin were subjected to immunoprecipitation with an Akt
antibody, and the ability of the immunoprecipitates to stimulate
incorporation of [32P]ATP into the substrate histone 2B
was measured. In control cells transfected with the empty expression
vector pCIS2, there was a small increase in endogenous Akt activity
caused by insulin stimulation. Cells overexpressing Akt-WT showed a
marked increase in detectable Akt activity upon insulin stimulation
(compared with control cells) while cells overexpressing the
constitutively active Akt-myr had high levels of Akt activity in both
the basal and insulin-stimulated states as expected. We did not measure
Akt activity in cells transfected with the kinase-inactive mutants
because complete inhibition of Akt activity in the 5% of cells
that are transiently transfected would be difficult to detect against
the background of 95% untransfected cells.
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). Interestingly, in the absence of
insulin, overexpression of Akt-WT resulted in significant translocation
of the cotransfected GLUT4-HA to the cell surface to levels that were
approximately 80% of that seen in the control cells treated with a
maximally stimulating dose of insulin. Treatment of cells
overexpressing Akt-WT with insulin increased the amount of GLUT4-HA at
the cell surface to levels that were comparable to levels observed in
the control cells treated with 60 nM insulin. These results
demonstrate that overexpression of wild type Akt is sufficient to cause
translocation of GLUT4 in adipose cells.
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). These results are consistent with the idea that
endogenous Akt contributes significantly to insulin-stimulated glucose
transport in a bona fide insulin target tissue under
physiological conditions.
To help rule out the possibility that differences we observed in the
insulin dose-response curves for cells overexpressing the various Akt
constructs are due to effects of these constructs on expression of
GLUT4-HA, we evaluated total levels of GLUT4-HA in cells cotransfected
with GLUT4-HA and the various Akt constructs. Total membrane fractions
derived from each group of transfected cells were immunoblotted with an
anti-HA antibody (Fig. 4). The results of
this experiment demonstrate that there is no detectable effect of
overexpressing the various Akt constructs on the total level of
GLUT4-HA in transfected cells. Thus, any differences in the insulin
dose-response curves of cells overexpressing the Akt constructs are
most likely due to effects of these constructs on signal transduction
pathways related to translocation of GLUT4.
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). Interestingly, this effect was not
influenced significantly by insulin treatment. These results
demonstrate that targeting wild type Akt to the cell membrane is
sufficient to generate a signal for translocation of GLUT4 that exceeds
that produced by maximal insulin stimulation under physiological
conditions.
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). These results demonstrate that targeting of Akt to the cell
membrane is not sufficient to mediate translocation of GLUT4 in the
absence of kinase activity. Furthermore, the inhibitory effect of
overexpression of Myr-K179A is consistent with a physiological role for
endogenous Akt in insulin-stimulated translocation of GLUT4. As with
Akt-WT and Akt-K179A, the fact that overexpression of Akt-myr and
Myr-K179A did not significantly affect expression of GLUT4-HA (Fig. 4)
suggests that any differences observed in the insulin dose-response
curves for cells overexpressing Akt-myr or Myr-K179A are due to effects
of these Akt constructs on signaling pathways. |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Recently, Akt has been identified as a direct downstream target of PI3K that plays an important role in mediating the mitogenic and antiapoptotic effects of several growth factors including insulin (10, 14, 15, 16, 23, 24, 25, 26, 27). Products of PI3K such as phosphatidylinositol-3,4-diphosphate bind to the N-terminal PH domain of Akt and may serve to recruit Akt to the cell membrane and activate its serine-threonine kinase activity (28, 29). The oncogenic form of Akt (v-Akt) contains a Gag sequence that is myristoylated and results in targeting of v-Akt to the cell membrane and constitutive activation (30). Using a myristoylated form of Akt lacking the PH domain, Kohn et al. (12) recently showed that overexpression of this constitutively active mutant resulted in recruitment of GLUT4 to the cell surface in differentiated 3T3-L1 cells. Although these experiments suggest activated Akt is sufficient to recruit GLUT4, they did not determine whether Akt is a necessary factor in insulin-stimulated translocation of GLUT4.
The 3T3-L1 cell line is a tissue culture model derived from primitive mouse mesodermal cells that can differentiate into an adipocyte-like phenotype under the appropriate conditions (31). These tissue culture cells have been extremely useful for understanding the regulation and control of adipocyte differentiation (32, 33). However, these cells do not always differentiate completely or uniformly. Furthermore, they do not display the full repertoire of genes expressed in primary adipose cells. For example, ob gene mRNA levels in differentiated 3T3-L1 cells are <1% of the levels observed in freshly isolated rat adipose cells. Finally, these tissue culture cells are much less responsive than isolated rat adipose cells with respect to the effects of insulin and other hormones on glucose transport and metabolism.
To address the physiological role of Akt in insulin-stimulated glucose transport in a bona fide insulin target cell, we have overexpressed a dominant inhibitory mutant of Akt in primary cultures of rat adipose cells to determine whether endogenous Akt is necessary for insulin-stimulated translocation of GLUT4.
Overexpression of Akt Constructs in Adipose Cells
Transfection of rat adipose cells with the various Akt constructs
resulted in high levels of overexpression similar to what we previously
observed with other recombinant genes in our system (1, 3, 34, 35). In
addition, we were able to demonstrate that increasing the concentration
of DNA during transfection for the K179A construct led to a comparable
increase in the expression of these constructs. Interestingly, Akt-WT
had somewhat higher levels of expression than Akt-K179A when the
same concentrations of DNA were used for transfection. This finding is
similar to a previous report in transfected 293 cells overexpressing
wild type and kinase-dead forms of Akt (15). In the case of Akt-WT and
Akt-myr, we were also able to demonstrate that overexpression of these
recombinant proteins resulted in Akt activity that was consistent with
the level of expression and expected kinase activity. That is, the
ability of Akt-WT to phosphorylate histone 2B was increased in response
to insulin while Akt-myr showed high constitutive kinase activity.
Unfortunately, the 5% transfection efficiency of our adipose cell
transfection system (1) limits our ability to directly measure
decreases in Akt activity expected with the kinase-inactive mutants
Akt-K179A and Myr-K179A because of the background activity of 95%
of the untransfected cells.
As discussed previously (35), the use of epitope-tagged GLUT4 allows us to distinguish and study transfected cells without interference from nontransfected cells. The fact that levels of GLUT4-HA were comparable in all groups of transfected cells suggests that changes in cell surface GLUT4 caused by overexpression of the various Akt constructs are due to effects on insulin signal transduction pathways rather than effects on the total level of expression of GLUT4. Although highly unlikely, it is formally possible that effects of the Akt constructs on translocation of GLUT4 are due, in part, to effects of Akt on levels of expression of upstream signaling molecules such as the insulin receptor or IRS-1. We do not believe this is the case, however, because we have previously demonstrated that 20-fold overexpression of these upstream molecules does not have as large an effect on translocation of GLUT4 as overexpression of the constitutively active Akt (1, 2). Nevertheless, it is difficult for us to directly rule out an effect of Akt on expression level of these upstream signaling molecules because it is not possible for us to assess the amounts of endogenous insulin receptor and IRS-1 exclusively in the 5% of cells that are transfected with the Akt constructs. In our cotransfection experiments, we used at least twice as much DNA for the Akt constructs as we did for GLUT4-HA to increase the likelihood that cells transfected with GLUT4-HA were also transfected with the vector of interest. If some fraction of cells were transfected only with GLUT4-HA, our results would underestimate the differences between control and experimental groups. We estimate that at least 95% of cells expressing GLUT4-HA also express the cotransfected second plasmid under our experimental conditions (3).
Recruitment of GLUT4 by Akt-WT and Akt-myr
Overexpression of Akt-WT resulted in significant translocation of
GLUT4 to the cell surface in the absence of insulin. These results are
similar to what we previously observed with overexpression of either
wild type insulin receptors or IRS-1 in adipose cells (1, 2).
Presumably, there is a small signal present even in the absence of
insulin that can be amplified by an excess of Akt-WT. The existence of
this basal level of signaling is also supported by our recent
demonstration that overexpression of the protein tyrosine phosphatase
PTP1B in adipose cells led to a decrease in the amount of cell surface
GLUT4 present in both the absence and presence of insulin (35). As with
overexpression of the insulin receptor or IRS-1, insulin stimulation of
adipose cells overexpressing Akt-WT resulted in a further increase in
the amount of cell surface GLUT4 to a level that was comparable to that
observed in control cells treated with a maximally stimulating
concentration of insulin. Thus, although overexpression of Akt-WT was
sufficient to recruit GLUT4, this did not result in a larger effect
than insulin alone could elicit. In contrast, overexpression of the
constitutively active mutant Akt-myr resulted in dramatic translocation
of GLUT4 to the cell surface at levels that significantly exceeded
those achievable by insulin stimulation of the control cells.
Furthermore, this effect was independent of insulin. It is likely that
overexpression of Akt-myr results in a higher level of Akt activity at
the cell membrane than is achievable by insulin stimulation of
endogenous Akt in the control cells. However, this is not merely a
function of the amount of Akt present because comparable overexpression
of Akt-WT did not have as large an effect as Akt-myr (even with insulin
stimulation). It is also possible that targeting of overexpressed Akt
to the cell membrane stimulates pathways for signaling recruitment of
GLUT4 that may not be operative under physiological conditions. For
example, even though Ras probably does not contribute to
insulin-stimulated translocation of GLUT4 under physiological
conditions, we previously reported that overexpression of
constitutively active mutants of Ras results in a similarly large
effect to recruit GLUT4 in adipose cells (although in this case,
insulin treatment results in a further increase in cell surface GLUT4)
(3). Our results with Akt-myr are consistent with those of Kohn
et al. (12), who showed that overexpression of a
myristoylated mutant of Akt lacking its PH domain had similar effects
on translocation of GLUT4 in differentiated 3T3-L1 adipocytes.
Akt-K179A and Myr-K179A Inhibit Translocation of GLUT4
Because overexpression of a signaling protein can lead to events
that are not related to the physiological functions of that protein, it
is useful to assess the effects of inhibiting endogenous Akt on
insulin-stimulated translocation of GLUT4. Toward this end we used Akt
constructs that have a mutation in the ATP-binding domain rendering the
kinase catalytically inactive. Importantly, the PH domain and other
regions of the molecule are intact so that overexpressed Akt-K179A
or Myr-K179A can presumably compete with endogenous Akt for upstream or
downstream factors. Indeed, the catalytically inactive mutant Akt-K179A
has been extensively characterized (15, 25, 26, 36) and has been shown
to have dominant inhibitory effects in other contexts (23, 24, 28).
When Akt-K179A was transfected into adipose cells using the same concentration of DNA as was used for Akt-WT and Akt-Myr, the resulting insulin dose-response curve was similar to that of the control cells. This suggests that intact kinase activity is important for mediating the effect of Akt-WT on translocation of GLUT4. When higher concentrations of Akt-K179A were used, we observed inhibition of insulin-stimulated translocation of GLUT4 with significant decreases in both insulin sensitivity and responsiveness. Thus, endogenous Akt is likely to contribute importantly to the physiological regulation of GLUT4 by insulin. The significance of these results is highlighted by comparison with results from our previous study on the role of Ras in insulin-stimulated translocation of GLUT4 (3). In that study, we showed that while overexpression of constitutively active mutants of Ras leads to recruitment of GLUT4, overexpression of a dominant inhibitory mutant had no effect on insulin-stimulated translocation of GLUT4, leading us to conclude that Ras does not play a physiological role in insulin-stimulated glucose transport. Our observation of an expression level-dependent effect of Akt-K179A on inhibition of GLUT4 recruitment is consistent with the putative dominant inhibitory mechanism of Akt-K179A (i.e. competition with endogenous Akt for limiting factors). Using a dominant inhibitory mutant of PI3K, we previously demonstrated nearly complete inhibition of insulin-stimulated translocation of GLUT4 in adipose cells (3). Interestingly, even though Akt is a direct downstream target of PI3K, overexpression of Akt-K179A did not have as large an effect as the dominant inhibitory mutant of PI3K. It is possible that a further increase in the level of expression of Akt-K179A would result in further inhibition of GLUT4 recruitment. Because of limitations on the total amounts of DNA that we can use in our system (37), we were not able to test this possibility. It is also likely that there are multiple downstream effectors of PI3K or other signaling molecules that contribute to the effect of insulin on recruitment of GLUT4. For example, using a catalytically inactive mutant of Syp we recently demonstrated a small role for Syp in insulin-stimulated translocation of GLUT4 in adipose cells (35). Thus, maximal inhibition of endogenous Akt may lead to only partial inhibition of translocation of GLUT4 because there are other effectors of PI3K that contribute to this effect.
Overexpression of Myr-K179A had an inhibitory effect on recruitment of GLUT4 that was similar to that seen with Akt-K179A. This suggests that localization of Akt to the membrane is not sufficient to mediate effects on recruitment of GLUT4 in the absence of kinase activity. Furthermore, even when localized to the cell membrane, Myr-K179A is presumably able to compete with endogenous Akt for limiting factors and results in inhibition of insulin-stimulated translocation of GLUT4. In addition, the magnitude of inhibition caused by both Akt-K179A and Myr-K179A was similar and supports the idea that endogenous Akt is not the only effector of PI3K in this action of insulin. These results further support a physiological role for Akt in insulin-stimulated glucose transport.
In summary, overexpression of a constitutively active Akt has a greater effect on recruitment of GLUT4 than overexpression of wild-type Akt. More importantly, overexpression of catalytically inactive mutants of Akt in primary cultures of rat adipose cells inhibits insulin-stimulated translocation of GLUT4. Our results strongly suggest a physiological role for Akt in insulin-stimulated glucose transport in insulin target tissues.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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An expression vector that generates high expression levels in transfected rat adipose cells (37) was used as the parent vector for subsequent constructions.
GLUT4-HA
Complementary DNA coding for human GLUT4 with the influenza
hemagglutinin epitope (HA1) inserted in the first exofacial loop of
GLUT4 was subcloned into the pCIS2 vector (1).
Akt-WT
A 1.4-kb XbaI/BamHI fragment containing the cDNA
for mouse Akt-1 [the generous gift of Drs. P. N. Tsichlis and K.
Datta (27)] was blunt-ended and ligated in the sense orientation into
the HpaI site in the multiple cloning region of pCIS2.
Akt-myr
BglII/BamHI fragment containing the cDNA for
mouse Akt-1 with a myristoylation sequence from pp60 c-src
(38) fused in-frame with the N terminus of Akt (a generous gift from
Drs. P.N. Tsichlis and K. Datta) was blunt-ended and ligated in the
sense orientation into the HpaI site in the multiple cloning
region of pCIS2.
Akt-K179A
Point mutant of Akt-WT with a substitution of alanine for lysine at
position 179 was constructed using a mutagenic oligonucleotide 5'-GC
TAC TAT GCC ATG GCG ATC CTC AAG AAG G-3' and the
MORPH site-specific plasmid DNA mutagenesis kit according to the
manufacturers instructions (5 prime 3 prime, Inc., Boulder, CO). The
creation of the mutation introduced a new NcoI site. In
addition, the mutation was confirmed by direct sequencing.
Myr-K179A
Point mutant of Akt-myr with a substitution of alanine for lysine at
position 179 was constructed exactly as described above for
Akt-K179A.
Isolated Rat Adipose Cell Preparation
Isolated adipose cells were prepared from the epididymal fat
pads of male rats (170–200 g, CD strain, Charles River Breeding
Laboratories, Wilmington, MA) by collagenase digestion as described
(37, 39).
Electroporation
Isolated adipose cells were transfected by electroporation as
described (35, 37). Cells from multiple cuvettes were pooled to obtain
the necessary volume of cells for each experiment as described (see
Table 1 for number of cuvettes and amount
of DNA used).
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Immunoblotting of Akt and GLUT4-HA
Expression of recombinant Akt-WT, Akt-myr, Akt-K179A, Myr-K179A,
and GLUT4-HA was confirmed by immunoblotting extracts of cells that
were prepared at the same time and had undergone transfection in
parallel with the cells used for the translocation assay described
above. Cells from 12 cuvettes were pooled for each group. Whole cell
homogenates were prepared from cells cotransfected with GLUT4-HA
(2 µg/cuvette) and either pCIS2, Akt-WT, Akt-myr, (4
µg/cuvette) or Akt-K179A or Myr-K179A (7 µg/cuvette). To determine
relative levels of GLUT4-HA in each group of transfected cells, total
membrane fractions were prepared from the whole cell homogenate by
centrifuging 30 min at 400,000 x g at 4 C. The pellet
containing the total membrane fraction was resuspended in 300 µl TES
buffer (20 mM Tris, 1 mM EDTA, 8.73% sucrose,
10 µg/ml leupeptin, 10 µg/ml aprotinin, 10 µg/ml soybean trypsin
inhibitor, 10 µg/ml BSA, 1 mM phenylmethylsulfonyl
fluoride, pH 7.4, 4 C). The protein concentration in each sample was
measured and aliquots containing 60 µg of protein were subjected to
SDS-PAGE. The contents of the gel were transferred to nitrocellulose
and immunblotted with the monoclonal anti-HA antibody HA-11 (final
concentration, 5 µg/ml). Immunolabeled bands were visualized using an
antibody against mouse IgG in conjunction with an enhanced
chemiluminescent detection system (ECL, Amersham, Arlington Heights,
IL).
For immunodetection of Akt constructs, whole cell homogenates containing equal amounts of protein (80 µg) were solubilized in Laemmli sample buffer and subjected to SDS-PAGE. The contents of the gel were transferred to nitrocellulose, and the Akt protein was detected with a polyclonal anti-Akt antibody (Upstate Biotechnology Inc., Lake Placid, NY) at a final concentration of 1 µg/ml. Bands were visualized using an antibody against mouse IgG in conjunction with an ECL detection system (Amersham).
Akt Kinase Assay
To assess the kinase activity of the recombinant Akt-WT and
Akt-myr in transfected adipose cells, cells were transfected with
either the empty expression vector pCIS2, Akt-WT, or Akt-myr (4 µg
DNA/cuvette, 15 cuvettes per group) and treated without or with insulin
(60 nM) for 2 min, and whole cell homogenates of each group
were prepared as described above. Samples containing 200 µg protein
from each group were subjected to immunoprecipitation with an antibody
against Akt, and kinase activity in the immunoprecipitates was assessed
by incorporation of [32P]ATP into the substrate histone
2B as described (27). Samples were separated on a 12% SDS-PAGE, and
the phosphorylation of histone 2B in each sample was quantified using
PhosphorImager analysis of the gel (Molecular Dynamics, Sunnyvale,
CA).
Statistical Analysis
Insulin dose-response curves were compared using multivariate
ANOVA. Paired t tests were used to compare individual points
where appropriate. P values of less than 0.05 were
considered statistically significant. The insulin dose-response
curves were fit to the equation y = a + b [x/(x + k)] using a
Marquardt-Levenberg nonlinear least squares algorithm. When plotted on
linear-log axes, this equation gives a sigmoidal curve where the
parameters are associated with the following properties: a = basal
response; a + b = maximal response; k = half-maximal dose
(ED50); and x = concentration of insulin.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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This work was supported in part by a Research Award from the American Diabetes Association (to M.J.Q.).
Received for publication June 3, 1997. Revision received August 20, 1997. Accepted for publication September 5, 1997.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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T. Matsui, T. Nagoshi, E.-G. Hong, I. Luptak, K. Hartil, L. Li, N. Gorovits, M. J. Charron, J. K. Kim, R. Tian, et al. Effects of chronic Akt activation on glucose uptake in the heart Am J Physiol Endocrinol Metab, May 1, 2006; 290(5): E789 - E797. [Abstract] [Full Text] [PDF]
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 K. Nagira, T. Sasaoka, T. Wada, K. Fukui, M. Ikubo, S. Hori, H. Tsuneki, S. Saito, and M. Kobayashi Altered Subcellular Distribution of Estrogen Receptor {alpha} Is Implicated in Estradiol-Induced Dual Regulation of Insulin Signaling in 3T3-L1 Adipocytes Endocrinology, February 1, 2006; 147(2): 1020 - 1028. [Abstract] [Full Text] [PDF]
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G. J. O. Evans, J. W. Barclay, G. R. Prescott, S.-R. Jo, R. D. Burgoyne, M. J. Birnbaum, and A. Morgan Protein Kinase B/Akt Is a Novel Cysteine String Protein Kinase That Regulates Exocytosis Release Kinetics and Quantal Size J. Biol. Chem., January 20, 2006; 281(3): 1564 - 1572. [Abstract] [Full Text] [PDF]
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 M. F. Arteaga and C. M. Canessa Functional specificity of Sgk1 and Akt1 on ENaC activity Am J Physiol Renal Physiol, July 1, 2005; 289(1): F90 - F96. [Abstract] [Full Text] [PDF]
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J.-a Kim, D. C. Yeh, M. Ver, Y. Li, A. Carranza, T. P. Conrads, T. D. Veenstra, M. A. Harrington, and M. J. Quon Phosphorylation of Ser24 in the Pleckstrin Homology Domain of Insulin Receptor Substrate-1 by Mouse Pelle-like Kinase/Interleukin-1 Receptor-associated Kinase: CROSS-TALK BETWEEN INFLAMMATORY SIGNALING AND INSULIN SIGNALING THAT MAY CONTRIBUTE TO INSULIN RESISTANCE J. Biol. Chem., June 17, 2005; 280(24): 23173 - 23183. [Abstract] [Full Text] [PDF]
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 H. J. Herr, J. R. Bernard, D. W. Reeder, D. A. Rivas, J. J. Limon, and B. B. Yaspelkis III Insulin-stimulated plasma membrane association and activation of Akt2, aPKC {zeta} and aPKC {lambda} in high fat fed rodent skeletal muscle J. Physiol., June 1, 2005; 565(2): 627 - 636. [Abstract] [Full Text] [PDF]
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E. M. van Dam, R. Govers, and D. E. James Akt Activation Is Required at a Late Stage of Insulin-Induced GLUT4 Translocation to the Plasma Membrane Mol. Endocrinol., April 1, 2005; 19(4): 1067 - 1077. [Abstract] [Full Text] [PDF]
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 Z. Li, J. Jaboin, P. A. Dennis, and C. J. Thiele Genetic and Pharmacologic Identification of Akt as a Mediator of Brain-Derived Neurotrophic Factor/TrkB Rescue of Neuroblastoma Cells from Chemotherapy-Induced Cell Death Cancer Res., March 15, 2005; 65(6): 2070 - 2075. [Abstract] [Full Text] [PDF]
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 S. M. Brachmann, K. Ueki, J. A. Engelman, R. C. Kahn, and L. C. Cantley Phosphoinositide 3-Kinase Catalytic Subunit Deletion and Regulatory Subunit Deletion Have Opposite Effects on Insulin Sensitivity in Mice Mol. Cell. Biol., March 1, 2005; 25(5): 1596 - 1607. [Abstract] [Full Text] [PDF]
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 C. Morisco, G. Condorelli, V. Trimarco, A. Bellis, C. Marrone, G. Condorelli, J. Sadoshima, and B. Trimarco Akt Mediates the Cross-Talk Between {beta}-Adrenergic and Insulin Receptors in Neonatal Cardiomyocytes Circ. Res., February 4, 2005; 96(2): 180 - 188. [Abstract] [Full Text] [PDF]
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H. Shiue, M. W. Musch, Y. Wang, E. B. Chang, and J. R. Turner Akt2 Phosphorylates Ezrin to Trigger NHE3 Translocation and Activation J. Biol. Chem., January 14, 2005; 280(2): 1688 - 1695. [Abstract] [Full Text] [PDF]
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 D. C. Berwick, G. C. Dell, G. I. Welsh, K. J. Heesom, I. Hers, L. M. Fletcher, F. T. Cooke, and J. M. Tavare Protein kinase B phosphorylation of PIKfyve regulates the trafficking of GLUT4 vesicles J. Cell Sci., December 1, 2004; 117(25): 5985 - 5993. [Abstract] [Full Text] [PDF]
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 A. Navarrete Santos, S. Tonack, M. Kirstein, M. Pantaleon, P. Kaye, and B. Fischer Insulin acts via mitogen-activated protein kinase phosphorylation in rabbit blastocysts Reproduction, November 1, 2004; 128(5): 517 - 526. [Abstract] [Full Text] [PDF]
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G. Sweeney, R. R. Garg, R. B. Ceddia, D. Li, M. Ishiki, R. Somwar, L. J. Foster, P. O. Neilsen, G. D. Prestwich, A. Rudich, et al. Intracellular Delivery of Phosphatidylinositol (3,4,5)-Trisphosphate Causes Incorporation of Glucose Transporter 4 into the Plasma Membrane of Muscle and Fat Cells without Increasing Glucose Uptake J. Biol. Chem., July 30, 2004; 279(31): 32233 - 32242. [Abstract] [Full Text] [PDF]
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 M. Lundgren, J. Buren, T. Ruge, T. Myrnas, and J. W. Eriksson Glucocorticoids Down-Regulate Glucose Uptake Capacity and Insulin-Signaling Proteins in Omental But Not Subcutaneous Human Adipocytes J. Clin. Endocrinol. Metab., June 1, 2004; 89(6): 2989 - 2997. [Abstract] [Full Text] [PDF]
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 A. Natali, S. Baldeweg, E. Toschi, B. Capaldo, D. Barbaro, A. Gastaldelli, J. S. Yudkin, and E. Ferrannini Vascular Effects of Improving Metabolic Control With Metformin or Rosiglitazone in Type 2 Diabetes Diabetes Care, June 1, 2004; 27(6): 1349 - 1357. [Abstract] [Full Text] [PDF]
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 K. A. Frauwirth and C. B. Thompson Regulation of T Lymphocyte Metabolism J. Immunol., April 15, 2004; 172(8): 4661 - 4665. [Abstract] [Full Text] [PDF]
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T. Sasaoka, T. Wada, K. Fukui, S. Murakami, H. Ishihara, R. Suzuki, K. Tobe, T. Kadowaki, and M. Kobayashi SH2-containing Inositol Phosphatase 2 Predominantly Regulates Akt2, and Not Akt1, Phosphorylation at the Plasma Membrane in Response to Insulin in 3T3-L1 Adipocytes J. Biol. Chem., April 9, 2004; 279(15): 14835 - 14843. [Abstract] [Full Text] [PDF]
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 K. L. Hoehn, S. F. Hudachek, S. A. Summers, and G. L. Florant Seasonal, tissue-specific regulation of Akt/protein kinase B and glycogen synthase in hibernators Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2004; 286(3): R498 - R504. [Abstract] [Full Text] [PDF]
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 X.-d. Peng, P.-Z. Xu, M.-L. Chen, A. Hahn-Windgassen, J. Skeen, J. Jacobs, D. Sundararajan, W. S. Chen, S. E. Crawford, K. G. Coleman, et al. Dwarfism, impaired skin development, skeletal muscle atrophy, delayed bone development, and impeded adipogenesis in mice lacking Akt1 and Akt2 Genes & Dev., June 1, 2003; 17(11): 1352 - 1365. [Abstract] [Full Text] [PDF]
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W. Lee-Kwon, K. Kawano, J. W. Choi, J. H. Kim, and M. Donowitz Lysophosphatidic Acid Stimulates Brush Border Na+/H+ Exchanger 3 (NHE3) Activity by Increasing Its Exocytosis by an NHE3 Kinase A Regulatory Protein-dependent Mechanism J. Biol. Chem., May 2, 2003; 278(19): 16494 - 16501. [Abstract] [Full Text] [PDF]
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Y. Levy, D. Ronen, A. D. Bershadsky, and Y. Zick Sustained Induction of ERK, Protein Kinase B, and p70 S6 Kinase Regulates Cell Spreading and Formation of F-actin Microspikes Upon Ligation of Integrins by Galectin-8, a Mammalian Lectin J. Biol. Chem., April 11, 2003; 278(16): 14533 - 14542. [Abstract] [Full Text] [PDF]
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J. T. Brozinick Jr, B. R. Roberts, and G. L. Dohm Defective Signaling Through Akt-2 and -3 But Not Akt-1 in Insulin-Resistant Human Skeletal Muscle: Potential Role in Insulin Resistance Diabetes, April 1, 2003; 52(4): 935 - 941. [Abstract] [Full Text] [PDF]
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A. R. Sedaghat, A. Sherman, and M. J. Quon A mathematical model of metabolic insulin signaling pathways Am J Physiol Endocrinol Metab, November 1, 2002; 283(5): E1084 - E1101. [Abstract] [Full Text] [PDF]
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D. C. Berwick, I. Hers, K. J. Heesom, S. K. Moule, and J. M. Tavare The Identification of ATP-citrate Lyase as a Protein Kinase B (Akt) Substrate in Primary Adipocytes J. Biol. Chem., September 6, 2002; 277(37): 33895 - 33900. [Abstract] [Full Text] [PDF]
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Y.-B. Kim, G. I. Shulman, and B. B. Kahn Fatty Acid Infusion Selectively Impairs Insulin Action on Akt1 and Protein Kinase C lambda /zeta but Not on Glycogen Synthase Kinase-3 J. Biol. Chem., August 30, 2002; 277(36): 32915 - 32922. [Abstract] [Full Text] [PDF]
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M. Montagnani, L. V. Ravichandran, H. Chen, D. L. Esposito, and M. J. Quon Insulin Receptor Substrate-1 and Phosphoinositide-Dependent Kinase-1 Are Required for Insulin-Stimulated Production of Nitric Oxide in Endothelial Cells Mol. Endocrinol., August 1, 2002; 16(8): 1931 - 1942. [Abstract] [Full Text] [PDF]
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M. Tsuru, H. Katagiri, T. Asano, T. Yamada, S. Ohno, T. Ogihara, and Y. Oka Role of PKC isoforms in glucose transport in 3T3-L1 adipocytes: insignificance of atypical PKC Am J Physiol Endocrinol Metab, August 1, 2002; 283(2): E338 - E345. [Abstract] [Full Text] [PDF]
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P.-H. Ducluzeau, L. M. Fletcher, G. I. Welsh, and J. M. Tavare Functional consequence of targeting protein kinase B/Akt to GLUT4 vesicles J. Cell Sci., July 15, 2002; 115(14): 2857 - 2866. [Abstract] [Full Text] [PDF]
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M. Kanzaki and J. E. Pessin Caveolin-associated Filamentous Actin (Cav-actin) Defines a Novel F-actin Structure in Adipocytes J. Biol. Chem., July 12, 2002; 277(29): 25867 - 25869. [Abstract] [Full Text] [PDF]
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T. Matsui, L. Li, J. C. Wu, S. A. Cook, T. Nagoshi, M. H. Picard, R. Liao, and A. Rosenzweig Phenotypic Spectrum Caused by Transgenic Overexpression of Activated Akt in the Heart J. Biol. Chem., June 14, 2002; 277(25): 22896 - 22901. [Abstract] [Full Text] [PDF]
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P. M. Snyder The Epithelial Na+ Channel: Cell Surface Insertion and Retrieval in Na+ Homeostasis and Hypertension Endocr. Rev., April 1, 2002; 23(2): 258 - 275. [Abstract] [Full Text] [PDF]
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P. Vollenweider, B. Menard, and P. Nicod Insulin Resistance, Defective Insulin Receptor Substrate 2--Associated Phosphatidylinositol-3' Kinase Activation, and Impaired Atypical Protein Kinase C ({zeta}/{lambda}) Activation in Myotubes From Obese Patients With Impaired Glucose Tolerance Diabetes, April 1, 2002; 51(4): 1052 - 1059. [Abstract] [Full Text] [PDF]
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G. Bandyopadhyay, M. P. Sajan, Y. Kanoh, M. L. Standaert, M. J. Quon, R. Lea-Currie, A. Sen, and R. V. Farese PKC-{zeta} Mediates Insulin Effects on Glucose Transport in Cultured Preadipocyte-Derived Human Adipocytes J. Clin. Endocrinol. Metab., February 1, 2002; 87(2): 716 - 723. [Abstract] [Full Text] [PDF]
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J. Shao, H. Yamashita, L. Qiao, B. Draznin, and J. E. Friedman Phosphatidylinositol 3-Kinase Redistribution Is Associated With Skeletal Muscle Insulin Resistance in Gestational Diabetes Mellitus Diabetes, January 1, 2002; 51(1): 19 - 29. [Abstract] [Full Text] [PDF]
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S. T. Nadler, J. P. Stoehr, M. E. Rabaglia, K. L. Schueler, M. J. Birnbaum, and A. D. Attie Normal Akt/PKB with reduced PI3K activation in insulin-resistant mice Am J Physiol Endocrinol Metab, December 1, 2001; 281(6): E1249 - E1254. [Abstract] [Full Text] [PDF]
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R. Somwar, W. Niu, D. Y. Kim, G. Sweeney, V. K. Randhawa, C. Huang, T. Ramlal, and A. Klip Differential Effects of Phosphatidylinositol 3-Kinase Inhibition on Intracellular Signals Regulating GLUT4 Translocation and Glucose Transport J. Biol. Chem., November 30, 2001; 276(49): 46079 - 46087. [Abstract] [Full Text] [PDF]
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M. Kanzaki and J. E. Pessin Insulin-stimulated GLUT4 Translocation in Adipocytes Is Dependent upon Cortical Actin Remodeling J. Biol. Chem., November 2, 2001; 276(45): 42436 - 42444. [Abstract] [Full Text] [PDF]
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T. Teruel, R. Hernandez, and M. Lorenzo Ceramide Mediates Insulin Resistance by Tumor Necrosis Factor-{alpha} in Brown Adipocytes by Maintaining Akt in an Inactive Dephosphorylated State Diabetes, November 1, 2001; 50(11): 2563 - 2571. [Abstract] [Full Text] [PDF]
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L. V. Ravichandran, H. Chen, Y. Li, and M. J. Quon Phosphorylation of PTP1B at Ser50 by Akt Impairs Its Ability to Dephosphorylate the Insulin Receptor Mol. Endocrinol., October 1, 2001; 15(10): 1768 - 1780. [Abstract] [Full Text] [PDF]
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W. S. Chen, P.-Z. Xu, K. Gottlob, M.-L. Chen, K. Sokol, T. Shiyanova, I. Roninson, W. Weng, R. Suzuki, K. Tobe, et al. Growth retardation and increased apoptosis in mice with homozygous disruption of the akt1 gene Genes & Dev., September 1, 2001; 15(17): 2203 - 2208. [Abstract] [Full Text] [PDF]
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S. Fan, Y. X. Ma, M. Gao, R.-Q. Yuan, Q. Meng, I. D. Goldberg, and E. M. Rosen The Multisubstrate Adapter Gab1 Regulates Hepatocyte Growth Factor (Scatter Factor)-c-Met Signaling for Cell Survival and DNA Repair Mol. Cell. Biol., August 1, 2001; 21(15): 4968 - 4984. [Abstract] [Full Text] [PDF]
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H. Ono, H. Katagiri, M. Funaki, M. Anai, K. Inukai, Y. Fukushima, H. Sakoda, T. Ogihara, Y. Onishi, M. Fujishiro, et al. Regulation of Phosphoinositide Metabolism, Akt Phosphorylation, and Glucose Transport by PTEN (Phosphatase and Tensin Homolog Deleted on Chromosome 10) in 3T3-L1 Adipocytes Mol. Endocrinol., August 1, 2001; 15(8): 1411 - 1422. [Abstract] [Full Text] [PDF]
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X. Zhang, J. P. Gaspard, and D. C. Chung Regulation of Vascular Endothelial Growth Factor by the Wnt and K-ras Pathways in Colonic Neoplasia Cancer Res., August 1, 2001; 61(16): 6050 - 6054. [Abstract] [Full Text] [PDF]
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K. Gottlob, N. Majewski, S. Kennedy, E. Kandel, R. B. Robey, and N. Hay Inhibition of early apoptotic events by Akt/PKB is dependent on the first committed step of glycolysis and mitochondrial hexokinase Genes & Dev., June 1, 2001; 15(11): 1406 - 1418. [Abstract] [Full Text] [PDF]
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T. Wada, T. Sasaoka, M. Funaki, H. Hori, S. Murakami, M. Ishiki, T. Haruta, T. Asano, W. Ogawa, H. Ishihara, et al. Overexpression of SH2-Containing Inositol Phosphatase 2 Results in Negative Regulation of Insulin-Induced Metabolic Actions in 3T3-L1 Adipocytes via Its 5'-Phosphatase Catalytic Activity Mol. Cell. Biol., March 1, 2001; 21(5): 1633 - 1646. [Abstract] [Full Text]
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G. Bandyopadhyay, Y. Kanoh, M. P. Sajan, M. L. Standaert, and R. V. Farese Effects of Adenoviral Gene Transfer of Wild-Type, Constitutively Active, and Kinase-Defective Protein Kinase C-{lambda} on Insulin-Stimulated Glucose Transport in L6 Myotubes Endocrinology, November 1, 2000; 141(11): 4120 - 4127. [Abstract] [Full Text] [PDF]
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K. Shigematsu, H. Koyama, N. E. Olson, A. Cho, and M. A. Reidy Phosphatidylinositol 3-Kinase Signaling Is Important for Smooth Muscle Cell Replication After Arterial Injury Arterioscler Thromb Vasc Biol, November 1, 2000; 20(11): 2373 - 2378. [Abstract] [Full Text] [PDF]
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J. J. Wilkes and A. Bonen Reduced insulin-stimulated glucose transport in denervated muscle is associated with impaired Akt-alpha activation Am J Physiol Endocrinol Metab, October 1, 2000; 279(4): E912 - E919. [Abstract] [Full Text] [PDF]
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D. C. Bowers, S. Fan, K. A. Walter, R. Abounader, J. A. Williams, E. M. Rosen, and J. Laterra Scatter Factor/Hepatocyte Growth Factor Protects against Cytotoxic Death in Human Glioblastoma via Phosphatidylinositol 3-Kinase- and AKT-dependent Pathways Cancer Res., August 1, 2000; 60(15): 4277 - 4283. [Abstract] [Full Text]
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M. L. Hribal, M. Federici, O. Porzio, D. Lauro, P. Borboni, D. Accili, R. Lauro, and G. Sesti The Gly->Arg972 Amino Acid Polymorphism in Insulin Receptor Substrate-1 Affects Glucose Metabolism in Skeletal Muscle Cells J. Clin. Endocrinol. Metab., May 1, 2000; 85(5): 2004 - 2013. [Abstract] [Full Text]
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F. Ahmad, L.-N. Cong, L. Stenson Holst, L.-M. Wang, T. Rahn Landstrom, J. H. Pierce, M. J. Quon, E. Degerman, and V. C. Manganiello Cyclic Nucleotide Phosphodiesterase 3B Is a Downstream Target of Protein Kinase B and May Be Involved in Regulation of Effects of Protein Kinase B on Thymidine Incorporation in FDCP2 Cells J. Immunol., May 1, 2000; 164(9): 4678 - 4688. [Abstract] [Full Text] [PDF]
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N. Nakashima, P. M. Sharma, T. Imamura, R. Bookstein, and J. M. Olefsky The Tumor Suppressor PTEN Negatively Regulates Insulin Signaling in 3T3-L1 Adipocytes J. Biol. Chem., April 21, 2000; 275(17): 12889 - 12895. [Abstract] [Full Text] [PDF]
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H. Tong, W. Chen, R. E. London, E. Murphy, and C. Steenbergen Preconditioning Enhanced Glucose Uptake Is Mediated by p38 MAP Kinase Not by Phosphatidylinositol 3-Kinase J. Biol. Chem., April 14, 2000; 275(16): 11981 - 11986. [Abstract] [Full Text] [PDF]
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G. Zeng, F. H. Nystrom, L. V. Ravichandran, L.-N. Cong, M. Kirby, H. Mostowski, and M. J. Quon Roles for Insulin Receptor, PI3-Kinase, and Akt in Insulin-Signaling Pathways Related to Production of Nitric Oxide in Human Vascular Endothelial Cells Circulation, April 4, 2000; 101(13): 1539 - 1545. [Abstract] [Full Text] [PDF]
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K. D. Sims, D. J. Straff, and M. B. Robinson Platelet-derived Growth Factor Rapidly Increases Activity and Cell Surface Expression of the EAAC1 Subtype of Glutamate Transporter through Activation of Phosphatidylinositol 3-Kinase J. Biol. Chem., February 18, 2000; 275(7): 5228 - 5237. [Abstract] [Full Text] [PDF]
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A. A. Troussard, C. Tan, T. N. Yoganathan, and S. Dedhar Cell-Extracellular Matrix Interactions Stimulate the AP-1 Transcription Factor in an Integrin-Linked Kinase- and Glycogen Synthase Kinase 3-Dependent Manner Mol. Cell. Biol., November 1, 1999; 19(11): 7420 - 7427. [Abstract] [Full Text] [PDF]
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M. M. Hill, S. F. Clark, D. F. Tucker, M. J. Birnbaum, D. E. James, and S. L. Macaulay A Role for Protein Kinase Bbeta /Akt2 in Insulin-Stimulated GLUT4 Translocation in Adipocytes Mol. Cell. Biol., November 1, 1999; 19(11): 7771 - 7781. [Abstract] [Full Text] [PDF]
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G. Bandyopadhyay, M. L. Standaert, M. P. Sajan, L. M. Karnitz, L. Cong, M. J. Quon, and R. V. Farese Dependence of Insulin-Stimulated Glucose Transporter 4 Translocation on 3-Phosphoinositide-Dependent Protein Kinase-1 and Its Target Threonine-410 in the Activation Loop of Protein Kinase C-{zeta} Mol. Endocrinol., October 1, 1999; 13(10): 1766 - 1772. [Abstract] [Full Text]
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P. G. P. Foran, L. M. Fletcher, P. B. Oatey, N. Mohammed, J. O. Dolly, and J. M. Tavare Protein Kinase B Stimulates the Translocation of GLUT4 but Not GLUT1 or Transferrin Receptors in 3T3-L1 Adipocytes by a Pathway Involving SNAP-23, Synaptobrevin-2, and/or Cellubrevin J. Biol. Chem., October 1, 1999; 274(40): 28087 - 28095. [Abstract] [Full Text] [PDF]
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K. Paz, Y.-F. Liu, H. Shorer, R. Hemi, D. LeRoith, M. Quan, H. Kanety, R. Seger, and Y. Zick Phosphorylation of Insulin Receptor Substrate-1 (IRS-1) by Protein Kinase B Positively Regulates IRS-1 Function J. Biol. Chem., October 1, 1999; 274(40): 28816 - 28822. [Abstract] [Full Text] [PDF]
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A. Thorell, M. F. Hirshman, J. Nygren, L. Jorfeldt, J. F. P. Wojtaszewski, S. D. Dufresne, E. S. Horton, O. Ljungqvist, and L. J. Goodyear Exercise and insulin cause GLUT-4 translocation in human skeletal muscle Am J Physiol Endocrinol Metab, October 1, 1999; 277(4): E733 - E741. [Abstract] [Full Text] [PDF]
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M. J. Brady, P. M. Kartha, A. A. Aysola, and A. R. Saltiel The Role of Glucose Metabolites in the Activation and Translocation of Glycogen Synthase by Insulin in 3T3-L1 Adipocytes J. Biol. Chem., September 24, 1999; 274(39): 27497 - 27504. [Abstract] [Full Text] [PDF]
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S. A. Summers, E. L. Whiteman, H. Cho, L. Lipfert, and M. J. Birnbaum Differentiation-dependent Suppression of Platelet-derived Growth Factor Signaling in Cultured Adipocytes J. Biol. Chem., August 20, 1999; 274(34): 23858 - 23867. [Abstract] [Full Text] [PDF]
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J. Gu, M. Tamura, R. Pankov, E. H.J. Danen, T. Takino, K. Matsumoto, and K. M. Yamada Shc and Fak Differentially Regulate Cell Motility and Directionality Modulated by Pten J. Cell Biol., July 26, 1999; 146(2): 389 - 404. [Abstract] [Full Text] [PDF]
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D. Chen, R. V. Fucini, A. L. Olson, B. A. Hemmings, and J. E. Pessin Osmotic Shock Inhibits Insulin Signaling by Maintaining Akt/Protein Kinase B in an Inactive Dephosphorylated State Mol. Cell. Biol., July 1, 1999; 19(7): 4684 - 4694. [Abstract] [Full Text] [PDF]
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N. Filippa, C. L. Sable, C. Filloux, B. Hemmings, and E. Van Obberghen Mechanism of Protein Kinase B Activation by Cyclic AMP-Dependent Protein Kinase Mol. Cell. Biol., July 1, 1999; 19(7): 4989 - 5000. [Abstract] [Full Text] [PDF]
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Q. Wang, R. Somwar, P. J. Bilan, Z. Liu, J. Jin, J. R. Woodgett, and A. Klip Protein Kinase B/Akt Participates in GLUT4 Translocation by Insulin in L6 Myoblasts Mol. Cell. Biol., June 1, 1999; 19(6): 4008 - 4018. [Abstract] [Full Text] [PDF]
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M. L. Standaert, G. Bandyopadhyay, M. P. Sajan, L. Cong, M. J. Quon, and R. V. Farese Okadaic Acid Activates Atypical Protein Kinase C (zeta /lambda ) in Rat and 3T3/L1 Adipocytes. AN APPARENT REQUIREMENT FOR ACTIVATION OF GLUT4 TRANSLOCATION AND GLUCOSE TRANSPORT J. Biol. Chem., May 14, 1999; 274(20): 14074 - 14078. [Abstract] [Full Text] [PDF]
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A. Tirosh, R. Potashnik, N. Bashan, and A. Rudich Oxidative Stress Disrupts Insulin-induced Cellular Redistribution of Insulin Receptor Substrate-1 and Phosphatidylinositol 3-Kinase in 3T3-L1 Adipocytes. A PUTATIVE CELLULAR MECHANISM FOR IMPAIRED PROTEIN KINASE B ACTIVATION AND GLUT4 TRANSLOCATION J. Biol. Chem., April 9, 1999; 274(15): 10595 - 10602. [Abstract] [Full Text] [PDF]
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J. E. Pessin, D. C. Thurmond, J. S. Elmendorf, K. J. Coker, and S. Okada Molecular Basis of Insulin-stimulated GLUT4 Vesicle Trafficking. LOCATION! LOCATION! LOCATION! J. Biol. Chem., January 29, 1999; 274(5): 2593 - 2596. [Full Text] [PDF]
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M. P. Czech and S. Corvera Signaling Mechanisms That Regulate Glucose Transport J. Biol. Chem., January 22, 1999; 274(4): 1865 - 1868. [Full Text] [PDF]
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T. A. Kupriyanova and K. V. Kandror Akt-2 Binds to Glut4-containing Vesicles and Phosphorylates Their Component Proteins in Response to Insulin J. Biol. Chem., January 15, 1999; 274(3): 1458 - 1464. [Abstract] [Full Text] [PDF]
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J. F. Markuns, R. Napoli, M. F. Hirshman, A. M. Davalli, B. Cheatham, and L. J. Goodyear Effects of Streptozocin-Induced Diabetes and Islet Cell Transplantation on Insulin Signaling in Rat Skeletal Muscle Endocrinology, January 1, 1999; 140(1): 106 - 111. [Abstract] [Full Text]
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J. Turinsky and A. Damrau-Abney Akt kinases and 2-deoxyglucose uptake in rat skeletal muscles in vivo: study with insulin and exercise Am J Physiol Regulatory Integrative Comp Physiol, January 1, 1999; 276(1): R277 - R282. [Abstract] [Full Text] [PDF]
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K. Kotani, W. Ogawa, M. Matsumoto, T. Kitamura, H. Sakaue, Y. Hino, K. Miyake, W. Sano, K. Akimoto, S. Ohno, et al. Requirement of Atypical Protein Kinase Clambda for Insulin Stimulation of Glucose Uptake but Not for Akt Activation in 3T3-L1 Adipocytes Mol. Cell. Biol., December 1, 1998; 18(12): 6971 - 6982. [Abstract] [Full Text]
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J. Liao, A. Barthel, K. Nakatani, and R. A. Roth Activation of Protein Kinase B/Akt Is Sufficient to Repress the Glucocorticoid and cAMP Induction of Phosphoenolpyruvate Carboxykinase Gene J. Biol. Chem., October 16, 1998; 273(42): 27320 - 27324. [Abstract] [Full Text] [PDF]
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). Results are the mean ± SEM of
five independent experiments. The actual value for the specific
cell-associated radioactivity for the control group at 60
nM insulin was 1082 ± 250 cpm. The best-fit curve
generated from the mean data for the control group had an
ED50 = 0.06 nM. The level of cell surface
GLUT4-HA in the Akt-WT group in the absence of insulin was
approximately 80% of the level seen in the control group maximally
stimulated with insulin. At maximally stimulating concentrations of
insulin (60 nM), there was no significant difference in the
level of cell surface GLUT4-HA between the two groups. The two curves
are significantly different when analyzed by multivariate ANOVA (F
= 12.4, P < 0.001). B, Recruitment of
epitope-tagged GLUT4 to the cell surface of cells cotransfected with
either Akt-K179A/GLUT4-HA (
) or pCIS2/GLUT4-HA (
