Insulin-stimulated oocyte maturation requires insulin receptor substrate 1 and interaction with the SH2 domains of phosphatidylinositol 3-kinase.
Xenopus oocytes from unprimed frogs possess insulin-like growth factor I (IGF-I) receptors but lack insulin and IGF-I receptor substrate 1 (IRS-1), the endogenous substrate of this kinase, and fail to show downstream responses to hormonal stimulation. Microinjection of recombinant IRS-1 protein enhances insulin-stimulated phosphatidylinositol (PtdIns) 3-kinase activity and restores the germinal vesicle breakdown response. Activation of PtdIns 3-kinase results from formation of a complex between phosphorylated IRS-1 and the p85 subunit of PtdIns 3-kinase. Microinjection of a phosphonopeptide containing a pYMXM motif with high affinity for the src homology 2 (SH2) domain of PtdIns 3-kinase p85 inhibits IRS-1 association with and activation of the PtdIns 3-kinase. Formation of the IRS-1-PtdIns 3-kinase complex and insulin-stimulated PtdIns 3-kinase activation are also inhibited by microinjection of a glutathione S-transferase fusion protein containing the SH2 domain of p85. This effect occurs in a concentration-dependent fashion and results in a parallel loss of hormone-stimulated oocyte maturation. These inhibitory effects are specific and are not mimicked by glutathione S-transferase fusion proteins expressing the SH2 domains of ras-GAP or phospholipase C gamma. Moreover, injection of the SH2 domains of p85, ras-GAP, and phospholipase C gamma do not interfere with progesterone-induced oocyte maturation. These data demonstrate that phosphorylation of IRS-1 plays an essential role in IGF-I and insulin signaling in oocyte maturation and that this effect occurs through interactions of the phosphorylated YMXM/YXXM motifs of IRS-1 with SH2 domains of PtdIns 3-kinase or some related molecules.
Chuang
L M
LM
Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
Myers
M G
MG
Backer
J M
JM
Shoelson
S E
SE
White
M F
MF
Birnbaum
M J
MJ
Kahn
C R
CR
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D005982:Glutathione Transferase / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007700:Kinetics; D008845:Microinjections; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases; D010748:Phosphopeptides / Q000008:administration & dosage / Q000494:pharmacology; D010750:Phosphoproteins / Q000008:administration & dosage / Q000494:pharmacology*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D014981:Xenopus; D029867:Xenopus Proteins
D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010748:Phosphopeptides; D010750:Phosphoproteins; D011994:Recombinant Proteins; D029867:Xenopus Proteins; C526294:irs1 protein, Xenopus; D007334:Insulin-Like Growth Factor I; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017871:Calcium-Calmodulin-Dependent Protein Kinases