Activation of PI 3-kinase in 3T3-L1 adipocytes by association with insulin receptor substrate-1

Lamphere, Lou; Carpenter, Christopher L.; Sheng, Zu-Fang; Kallen, Roland G.; Lienhard, Gustav E.

doi:10.1152/ajpendo.1994.266.3.e486

Cited by 27 publications

(35 citation statements)

References 29 publications

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“…The translocated molecules and the IRS 1 already present in the cytosol co~ild participate in the activation of PtdIns 3-kinase in this fraction. Such activation of the enzyme has been reported in the cytosolic fraction of insulintreated cells [8,381, although one group disagreed with this finding [29, 301. In the plasma membranes, activation of PtdIns 3-kinase does not correlate with the relatively low level of tyrosine-phosphorylated IRS 1. This finding could suggest that PtdIns 3-kinase is activated after association with other molecules such as tyrosine-phosphorylated insulin receptor [39].…”

Section: Discussionmentioning

confidence: 89%

Different Effects of Insulin and Platelet‐Derived Growth Factor on Phosphatidylinositol 3‐Kinase at the Subcellular Level in 3T3‐L1 Adipocytes

Ricort

Tanti

Obberghen

et al. 1996

European Journal of Biochemistry

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Insulin stimulates glucose uptake by induction of the translocation of vesicles that contain the glucose transporter Glut 4 to the plasma membrane. Phosphatidylinositol 3-kinase (Ptdlns 3-kinase), which is thought to be involved in intracellular trafficking, could play a critical role in insulin-induced glucose transport. In 3T3-Ll adipocytes, insulin and platelet-derived-growth-factor (PDGF) stimulated glucose uptake by 5.8-fold and 2.4-fold, respectively, but PDGF had no significant effect on Glut 4 translocation. Nevertheless, both hormones activated PtdIns 3-kinase activity in total cell extracts. However, insulin and PDGF had different effects on the stimulation of PtdIns 3-kinase activity in several subcellular fractions, and the movements of insulin-receptor substrate (IRS) 1 and the p85 subunit of PtdIns 3-kinase between subcellular compartments. PDGF stimulated PtdIns 3-kinase activity almost exclusively in the plasma membrane, and induced translocation of the p85 subunit from the cytosol to the plasma membrane, where the PDGF receptor was phosphorylated on tyrosine residues. In contrast, insulin stimulated Ptdlns 3-kinase activity in the plasma membrane, in low-density microsomes (LDM) and in cytosol. Furthermore, insulin induced the translocation of p85 from the cytosol to LDM and the translocation of IRS 1 from LDM to the cytosol. These data indicate that insulin and PDGF have different effects on the activation of Ptdlns 3-kinase and on the movement of IRS 1 and PtdIns 3-kinase between subcellular compartments. We would like to suggest that a crucial event in the stimulation of glucose uptake by insulin could be that insulin, but not PDGF, induces activation of PtdIns 3-kinase in the cytosol and in LDM, the compartment enriched in Glut-4-containing vesicles.

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Section: Discussionmentioning

confidence: 89%

Different Effects of Insulin and Platelet‐Derived Growth Factor on Phosphatidylinositol 3‐Kinase at the Subcellular Level in 3T3‐L1 Adipocytes

Ricort

Tanti

Obberghen

et al. 1996

European Journal of Biochemistry

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“…4PS Associates with and Activates PI 3-Kinase in Insulinstimulated Mice-Previous studies in cultured cells have demonstrated that phosphorylated IRS-1 and phosphorylated 4PS can bind to and activate PI 3-kinase (5)(6)(7)(8)28), and, in the case of IRS-1, this appears to link insulin action to stimulation of glucose transport (9,10). Similarly, in control mice, the p85 subunit of PI 3-kinase associated with phosphorylated IRS-1 following insulin stimulation ( Fig.…”

Section: Ps Is Tyrosine-phosphorylated Following In Vivo Insulinmentioning

confidence: 99%

4PS/Insulin Receptor Substrate (IRS)-2 Is the Alternative Substrate of the Insulin Receptor in IRS-1-deficient Mice

Patti

Sun

Bruening

et al. 1995

Journal of Biological Chemistry

213

145

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(1995) Nature 377, 173-177) purified and cloned 4PS, the major substrate of the IL-4 receptor-associated tyrosine kinase in myeloid cells, which has significant structural similarity to IRS-1. To determine if 4PS is the alternative substrate of the insulin receptor in IRS-1-deficient mice, we performed immunoprecipitation, immunoblotting, and phosphatidylinositol (PI) 3-kinase assays using specific antibodies to 4PS. Following insulin stimulation, 4PS is rapidly phosphorylated in liver and muscle, binds to the p85 subunit of PI 3-kinase, and activates the enzyme. Insulin stimulation also results in the association of 4PS with Grb 2 in both liver and muscle. In IRS-1-deficient mice, both the phosphorylation of 4PS and associated PI 3-kinase activity are enhanced, without an increase in protein expression. Immunodepletion of 4PS from liver and muscle homogenates removes most of the phosphotyrosine-associated PI 3-kinase activity in IRS-1-deficient mice. Thus, 4PS is the primary alternative substrate, i.e. IRS-2, which plays a major role in physiologic insulin signal transduction via both PI 3-kinase activation and Grb 2/Sos association. In IRS-1-deficient mice, 4PS/IRS-2 provides signal transduction to these two major pathways of insulin signaling.Stimulation of the insulin and IGF-1 1 receptor tyrosine kinases results in rapid autophosphorylation and subsequent phosphorylation of cytoplasmic substrates. A major substrate of the insulin receptor is IRS-1, a cytoplasmic protein of 160 -185 kDa on SDS-PAGE (1-3). Following insulin/IGF-1 stimulation, IRS-1 is rapidly phosphorylated on multiple tyrosines (4). This results in docking of several SH2 domain proteins, including: the p85 subunit of PI 3-kinase (5-8), an upstream element in insulin-stimulated glucose transport and activation of p70 S6 kinase (9, 10); Grb 2, an adapter molecule linking IRS-1 to activation of Ras and mitogen-activated protein kinase (11-13); and the tyrosine phosphatase SHPTP2 (14, 15). Insulin and IGF-1 receptors can also phosphorylate other cytoplasmic proteins. These include Shc, a cytoplasmic protein which binds to Grb 2 (16), a p62 protein which associates with Ras-GAP (17), and a 55-60-kDa protein which associates with PI 3-kinase (18,19).Abundant evidence from Xenopus oocytes (20), cell culture systems (21-23), and animal models (24,25) has demonstrated the central role of IRS-1 in mediating downstream effects of insulin and IGF-1. Recently, we (26) and others (27) have shown that mice made IRS-1-deficient by targeted gene knockout exhibit hyperinsulinemia, glucose intolerance, and marked growth retardation. However, IRS-1-deficient mice continue to exhibit some insulin-stimulated glucose disposal and phosphotyrosine-associated PI 3-kinase activation, suggesting the presence of an IRS-1-independent pathway of signaling. Immunoblots from both liver and muscle tissue of IRS-1 (Ϫ/Ϫ) animals reveal a ϳ180-kDa protein (tentatively designated IRS-2) which is tyrosine-phosphorylated within 1 min of insulin stimulation and binds to PI 3-kinase...

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“…Following insulin stimulation this stoichiometry was reduced by approximately 35 % in the muscle of pregnant rats (n = 4). Previous studies [19][20][21][22][23] have suggested that there is a relatively stable, high affinity interaction between IRS-1 and the 85 kDa subunit of PI 3-kinase, such that both proteins are co-precipitated by antibodies to each protein. In samples from muscle previously immunoprecipitated with anti-IRS-1 antibody and immunoblotted with antibodies directed against the 85 kDa subunit of PI 3-kinase, there was little or no detectable PI 3-kinase immunoreactivity in the basal state in either virgin or pregnant rats (Fig.…”

Section: The Effect Of Pregnancy On Insulin Receptor and Irs-1 Phosphmentioning

confidence: 99%

“…IRS-1 is also phosphorylated in response to insulin-like growth factor-1, interleukin-4 and angiotensin II [8-11, 17, 18] and, following its phosphorylation, it can associate with proteins containing Src homology 2 (SH2) domains through specific tyrosyl phosphorylation sites [19,20]. In cells in culture and in animal tissues, phosphorylated IRS-1 associates with the lipid metabolizing enzyme phosphatidylinositol 3-kinase (PI 3-kinase) thereby activating the enzyme [21][22][23]. The insulin receptor, IRS-1 and PI-3-kinase therefore represent three of the earliest steps in insulin action, and each of these can be demonstrated and regulated in two of the main target tissues for the metabolic actions of insulin in vivo, namely liver and muscle [24][25][26].…”

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confidence: 99%

Defects in insulin signal transduction in liver and muscle of pregnant rats

et al. 1997

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Insulin resistance during pregnancy has been reported both in women and in experimental animals [1][2][3][4][5][6][7], but the mechanism of this resistance remains unclear. In vivo studies have shown that pregnant rats become progressively resistant to insulin after day 16 of gestation [5]. In these animals, the insulin resistance of skeletal muscle has been clearly demonstrated in vitro, while the insulin resistance in vivo in peripheral tissues and liver has been substantiated in studies using the euglycaemic-hyperinsulinaemic clamp technique [6,7].Insulin initiates its metabolic and growth-promoting effects by binding to the a subunit of its tetrameric receptor, thereby activating the kinase in the b subunit [8]. This interaction catalyses the intramolecular autophosphorylation of specific tyrosine residues of the b subunit which further enhances the tyrosine kinase activity of the receptor toward other protein substrates [8]. In most cells, this primary event leads to the subsequent tyrosyl phosphorylation of a cytoplasmic protein with an apparent molecular weight of 160-185 kDa, called insulin receptor substrate 1 (IRS-1) [9][10][11]. Considerable evidence indicates that insulin receptor tyrosine Diabetologia (1997) 40: 179-186 Defects in insulin signal transduction in liver and muscle of pregnant rats Summary Pregnancy is known to induce insulin resistance, but the exact molecular mechanism involved is unknown. In the present study, we have examined the levels and phosphorylation state of the insulin receptor and of insulin receptor substrate 1(IRS-1), as well as the association between IRS-1 and phosphatidylinositol 3-kinase (PI 3-kinase) in the liver and muscle of pregnant rats (day 20 of gestation) by immunoprecipitation and immunoblotting with anti-insulin receptor, anti-IRS-1, anti-PI 3-kinase and antiphosphotyrosine antibodies. There were no changes in the insulin receptor concentration in the liver and muscle of pregnant rats. However, insulin stimulation of receptor autophosphorylation, as determined by immunoblotting with antiphosphotyrosine antibody, was reduced by 30 ± 6 % (p < 0.02) in muscle and 36 ± 5 % (p < 0.01) in liver at day 20 of gestation. IRS-1 protein levels decreased by 45 ± 6 % (p < 0.002) in liver and by 56 ± 9 % (p < 0.002) in muscle of pregnant rats. In samples previously immunoprecipitated with anti-IRS-1 antibody and blotted with antiphosphotyrosine antibody, the insulin-stimulated IRS-1 phosphorylation levels in the muscle and liver of pregnant rats decreased by 70 ± 9 % (p < 0.01) and 75 ± 8 % (p < 0.01), respectively. The insulin-stimulated IRS-1 association with PI 3-kinase decreased by 81 ± 6 % in muscle (p < 0.01) and 79 ± 11 % (p < 0.01) in the liver during pregnancy. These data suggest that changes in the early steps of insulin signal transduction may have a role in the insulin resistance observed in pregnancy. [Diabetologia (1997) 40: 179-186]

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Activation of PI 3-kinase in 3T3-L1 adipocytes by association with insulin receptor substrate-1

Cited by 27 publications

References 29 publications

Different Effects of Insulin and Platelet‐Derived Growth Factor on Phosphatidylinositol 3‐Kinase at the Subcellular Level in 3T3‐L1 Adipocytes

Different Effects of Insulin and Platelet‐Derived Growth Factor on Phosphatidylinositol 3‐Kinase at the Subcellular Level in 3T3‐L1 Adipocytes

4PS/Insulin Receptor Substrate (IRS)-2 Is the Alternative Substrate of the Insulin Receptor in IRS-1-deficient Mice

Defects in insulin signal transduction in liver and muscle of pregnant rats

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