IRS-1 mediates inhibition of Ca2+ mobilization by insulin via the inhibitory G-protein Gi
IRS-1 mediates inhibition of Ca2+ mobilization by insulin via the inhibitory G-protein Gi
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DOI：
10.1074/jbc.m305474200
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发表时间：
2004-01-30
影响因子：
4.8
通讯作者：
Akkerman, JWN
中科院分区：
文献类型：
--
作者：
Ferreira, IA;Eybrechts, KL;Akkerman, JWN
血小板激动剂通过激活与G蛋白G（q）偶联的受体，从而升高胞质Ca 2 +[Ca 2 +]（i），启动聚集和分泌。腺苷酸环化酶G（i）的抑制性G蛋白抑制cAMP形成，从而促进[Ca 2 +]（i）的升高。由于胰岛素减弱血小板活化，我们研究了胰岛素是否干扰cAMP调节。在这里，我们报告胰岛素（0.5-200 nmol/L）干扰激动剂诱导的[Ca 2 +]（i）（ADP，凝血酶），cAMP抑制（凝血酶）和聚集（ADP）的增加。胰岛素的作用如下：（i）不依赖于P2 Y（12）受体，其介导ADP诱导的cAMP降低;（ii）在G（s）介导的cAMP形成过程中未观察到;（iii）不受影响磷酸二酯酶（3-异丁基-1-甲基黄嘌呤）的治疗影响;（iv）不受干扰NO介导的cAMP降解调节（N-G-单甲基-L-精氨酸）的影响。因此，胰岛素可能会干扰G（i）。事实上，胰岛素诱导以下：（i）胰岛素受体、胰岛素受体底物-1（IRS-1）和G（i）α（2）的酪氨酸磷酸化;（ii）IRS-1与G（i）α（2）共沉淀，但不与其他G α亚基共沉淀。尽管持续的受体激活，IRS-1与G（i）α（2）的结合是短暂的，在5分钟和1 nmol/L胰岛素时是最佳的，这足以抑制ADP的Ca 2+信号传导，在10分钟和100 nmol/L胰岛素时是最佳的，这是抑制凝血酶的Ca 2+信号传导所需的。肾上腺素是一种已知的血小板增敏剂和胰岛素拮抗剂，通过干扰胰岛素受体β亚基的磷酸化，消除胰岛素对[Ca 2 +]（i）、G（i）α（2）的酪氨酸磷酸化和聚集的作用。我们的结论是，胰岛素通过IRS-1和G（i）干扰cAMP抑制而减弱血小板功能。
Platelet agonists initiate aggregation and secretion by activating receptors coupled to the G-protein G(q), thereby raising cytosolic Ca2+, [Ca2+](i). The rise in [Ca2+](i) is facilitated via inhibition of cAMP formation by the inhibitory G-protein of adenylyl cyclase, G(i). Since insulin attenuates platelet activation, we investigated whether insulin interferes with cAMP regulation. Here we report that insulin (0.5-200 nmol/liter) interferes with agonist-induced increases in [Ca2+](i) (ADP, thrombin), cAMP suppression (thrombin), and aggregation (ADP). The effects of insulin are as follows: ( i) independent of the P2Y(12) receptor, which mediates ADP-induced cAMP lowering; (ii) not observed during G(s)-mediated cAMP formation; (iii) unaffected by treatments that affect phosphodiesterases (3-isobutyl-1-methylxanthine); and (iv) not changed by interfering with NO-mediated regulation of cAMP degradation (N-G-monomethyl-L-arginine). Hence, insulin might interfere with G(i). Indeed, insulin induces the following: (i) tyrosine phosphorylation of the insulin receptor, the insulin receptor substrate-1 (IRS-1) and G(i)alpha(2); (ii) co-precipitation of IRS-1 with G(i)alpha(2) but not with other Galpha subunits. Despite persistent receptor activation, the association of IRS-1 with G(i)alpha(2) is transient, being optimal at 5 min and 1 nmol/liter insulin, which is sufficient to suppress Ca2+ signaling by ADP, and at 10 min and 100 nmol/liter insulin, which is required to suppress Ca2+ signaling by thrombin. Epinephrine, a known platelet sensitizer and antagonist of insulin, abolishes the effect of insulin on [Ca2+](i), tyrosine phosphorylation of G(i)alpha(2), and aggregation by interfering with the phosphorylation of the insulin receptor beta subunit. We conclude that insulin attenuates platelet functions by interfering with cAMP suppression through IRS-1 and G(i).