scholarly journals YMXM motifs and signaling by an insulin receptor substrate 1 molecule without tyrosine phosphorylation sites.

1996 ◽  
Vol 16 (8) ◽  
pp. 4147-4155 ◽  
Author(s):  
M G Myers ◽  
Y Zhang ◽  
G A Aldaz ◽  
T Grammer ◽  
E M Glasheen ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Binding Sites ◽  
Insulin Receptor Substrate ◽  
Phosphorylation Sites ◽  
Mitogenic Response ◽  
Insulin Receptor Substrate 1 ◽  
Mitogen Activated Protein ◽  
High Insulin ◽  
P70 S6k

Tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) by the activated receptors for insulin, IGF-1, and various cytokines creates binding sites for signaling proteins with Src homology 2 domains (SH2 proteins). Determining the role of specific SH2 proteins during insulin signaling has been difficult because IRS-1 possesses as many as 18 potential tyrosine phosphorylation sites, several of which contain redundant motifs. Using 32D cells, which contain no endogenous IRS proteins, we compared the signaling ability of an IRS-1 molecule in which 18 potential tyrosine phosphorylation sites were replaced by phenylalanine (IRS-1(F18)) with two derivative molecules which retained three YMXM motifs (IRS-1(3YMXM)) or the two COOH-terminal SHP2-Fyn binding sites (IRS-1(YCT)). During insulin stimulation, IRS-1(F18) failed to undergo tyrosine phosphorylation or mediate activation of the phosphotidylinositol (PI) 3'-kinase or p70(s6k); IRS-1(YCT) was tyrosine phosphorylated but also failed to mediate these signaling events. Neither IRS-1(3YMXM) nor IRS-1(YCT) mediated activation of mitogen-activated protein kinases. IRS-1(F18) and IRS-1(YCT) partially mediated similar levels of insulin-stimulated mitogenesis at high insulin concentrations, however, suggesting that IRS-1 contains phosphotyrosine-independent elements which effect mitogenic signals, and that the sites in IRS-l(YCT) do not augment this signal. IRS-1(3YMXM) mediated the maximal mitogenic response to insulin, although the response to insulin was more sensitive with wild-type IRS-1. By contrast, the association of IRS-1(3YMXM) with PI 3'-kinase was more sensitive to insulin than the association with IRS-1. Thus, the binding of SH2 proteins (such as PI 3'-kinase) by YMXM motifs in IRS-1 is an important element in the mitogenic response, but other elements are essential for full mitogenic sensitivity.

scholarly journals Mechanism of feedback regulation of insulin receptor substrate-1 phosphorylation in primary adipocytes

2005 ◽  
Vol 388 (2) ◽  
pp. 713-720 ◽  
Author(s):  
Ingeborg HERS ◽  
Jeremy M. TAVARÉ
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Mammalian Target Of Rapamycin ◽  
Feedback Regulation ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
P70s6 Kinase ◽  
Mitogen Activated Protein ◽  
Phosphoinositide 3 Kinase

Serine and threonine phosphorylation of IRS-1 (insulin receptor substrate-1) has been reported to decrease its ability to be tyrosine-phosphorylated by the insulin receptor. Insulin itself may negatively regulate tyrosine phosphorylation of IRS-1 through a PI3K (phosphoinositide 3-kinase)-dependent feedback pathway. In the present study, we examined the regulation and role of IRS-1 serine phosphorylation in the modulation of IRS-1 tyrosine phosphorylation in physiologically relevant cells, namely freshly isolated primary adipocytes. We show that insulin-stimulated phosphorylation of Ser312 and Ser616 in IRS-1 was relatively slow, with maximal phosphorylation achieved after 20 and 5 min respectively. The effect of insulin on phosphorylation of both these sites required the activation of PI3K and the MAPKs (mitogen-activated protein kinases) ERK1/2 (extracellular-signal-regulated kinase 1 and 2), but not the activation of mTOR (mammalian target of rapamycin)/p70S6 kinase, JNK (c-Jun N-terminal kinase) or p38MAPK. Although inhibition of PI3K and ERK1/2 both substantially decreased insulin-stimulated phosphorylation of Ser312 and Ser616, only wortmannin enhanced insulin-stimulated tyrosine phosphorylation of IRS-1. Furthermore, inhibition of mTOR/p70S6 kinase, JNK or p38MAPK had no effect on insulin-stimulated IRS-1 tyrosine phosphorylation. The differential effect of inhibition of ERK1/2 on insulin-stimulated IRS-1 phosphorylation of Ser312/Ser616 and tyrosine indicates that these events are independent of each other and that phosphorylation of Ser312/Ser616 is not responsible for the negative regulation of IRS-1 tyrosine phosphorylation mediated by PI3K in primary adipocytes.

scholarly journals The insulin receptor substrate-1-related 4PS substrate but not the interleukin-2R gamma chain is involved in interleukin-13-mediated signal transduction

Blood ◽  
1995 ◽  
Vol 86 (11) ◽  
pp. 4218-4227 ◽  
Author(s):  
LM Wang ◽  
P Michieli ◽  
WR Lie ◽  
F Liu ◽  
CC Lee ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Mitogenic Response ◽  
Gamma Chain ◽  
Insulin Receptor Substrate 1 ◽  
Gamma Subunit ◽  
Interleukin 13 ◽  
Sh2 Domains ◽  
Stimulation Of

Interleukin-13 (IL-13) induced a potent mitogenic response in IL-3- dependent TF-1 cells and DNA synthesis to a lesser extent in MO7E and FDC-P1 cells. IL-13 stimulation of these lines, like IL-4 and insulin- like growth factor-1 (IGF-1), resulted in tyrosine phosphorylation of a 170-kD substrate. The tyrosine-phosphorylated 170-kD substrate strongly associated with the 85-kD subunit of phosphoinositol-3 (PI-3) kinase and with Grb-2. Anti-4PS serum readily detected the 170-kD substrate in lysates from both TF-1 and FDC-P1 cells stimulated with IL-13 or IL-4. These data provide evidence that IL-13 induces tyrosine phosphorylation of the 4PS substrate, providing an essential interface between the IL- 13 receptor and signaling molecules containing SH2 domains. IL-13 and IL-4 stimulation of murine L cell fibroblasts, which endogenously express the IL-4 receptor (IL-4R alpha) and lack expression of the IL-2 receptor gamma subunit (IL-2R gamma), resulted in tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1)/4PS. Enhanced tyrosine phosphorylation of IRS-1/4PS was observed in response to IL-4, but not IL-13 treatment of L cells transfected with the IL-2R gamma chain. These results indicate that IL-13 does not use the IL-2R gamma subunit in its receptor complex and that expression of IL-2R gamma enhances, but is not absolutely required for mediating IL-4-induced tyrosine phosphorylation of IRS-1/4PS.

scholarly journals Insulin receptor substrate 1 rescues insulin action in CHO cells expressing mutant insulin receptors that lack a juxtamembrane NPXY motif.

1995 ◽  
Vol 15 (9) ◽  
pp. 4711-4717 ◽  
Author(s):  
D Chen ◽  
D J Van Horn ◽  
M F White ◽  
J M Backer
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Cho Cells ◽  
Glycogen Synthesis ◽  
Insulin Receptors ◽  
Insulin Receptor Substrate ◽  
Insulin Stimulation ◽  
Insulin Receptor Substrate 1 ◽  
Npxy Motif ◽  
Stimulation Of

Insulin signals are mediated through tyrosine phosphorylation of specific proteins such as insulin receptor substrate 1 (IRS-1) and Shc by the activated insulin receptor (IR). Phosphorylation of both proteins is nearly abolished by an alanine substitution at Tyr-960 (A960) in the beta-subunit of the receptor. However, overexpression of IRS-1 in CHO cells expressing the mutant receptor (A960 cells) restored sufficient tyrosine phosphorylation of IRS-1 to rescue IRS-1/Grb-2 binding and phosphatidylinositol 3' kinase activation during insulin stimulation. Shc tyrosine phosphorylation and its binding to Grb-2 were impaired in the A960 cells and were unaffected by overexpression of IRS-1. Although overexpression of IRS-1 increased IRS-1 binding to Grb-2, ERK-1/ERK-2 activation was not rescued. These data suggest that signaling molecules other than IRS-1, perhaps including Shc, are critical for insulin stimulation of p21ras. Interestingly, overexpression of IRS-1 in the A960 cells restored insulin-stimulated mitogenesis and partially restored insulin stimulation of glycogen synthesis. Thus, IRS-1 tyrosine phosphorylation is sufficient to increase the mitogenic response to insulin, whereas insulin stimulation of glycogen synthesis appears to involve other factors. Moreover, IRS-1 phosphorylation is either not sufficient or not involved in insulin stimulation of ERK.

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