SH2-containing inositol phosphatase 2 predominantly regulates Akt2, and not Akt1, phosphorylation at the plasma membrane in response to insulin in 3T3-L1 adipocytes
SH2-containing inositol phosphatase 2 predominantly regulates Akt2, and not Akt1, phosphorylation at the plasma membrane in response to insulin in 3T3-L1 adipocytes
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DOI：
10.1074/jbc.m311534200
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发表时间：
2004-04-09
影响因子：
4.8
通讯作者：
Kobayashi, M
中科院分区：
文献类型：
--
作者：
Sasaoka, T;Wada, T;Kobayashi, M
含有 SH2 的肌醇磷酸酶 2 (SHIP2) 是生理上重要的胰岛素信号负调节剂，通过水解胰岛素靶组织中的磷脂酰肌醇 (PI) 3-激酶产物 PI 3,4,5-三磷酸。对小鼠 SHIP2 基因进行靶向破坏可提高胰岛素敏感性，且不会影响胰岛素信号传导以外的生物系统。因此，我们研究了SHIP2特异性调节3T3-L1脂肪细胞中胰岛素诱导的代谢信号传导的分子机制。胰岛素诱导的 Akt（PI3 激酶下游分子之一）的磷酸化受到野生型 SHIP2 表达的抑制，而全细胞裂解物中 5'-磷酸酶缺陷型 (DeltaIP) SHIP2 的表达则增加了 Akt 的磷酸化。 SHIP2的调节作用主要出现在质膜（PM）和低密度微粒体中，但不在细胞质中。在这方面，在胰岛素刺激后，一部分 Akt2（而非 Akt1）似乎从细胞质重新分配到 PM。因此，PM 时胰岛素诱导的 Akt2 磷酸化主要受 SHIP2 调节，而 Akt1 磷酸化仅受到最小程度的影响。有趣的是，胰岛素还引起野生型和 DeltaIP-SHIP2 从细胞质到 PM 的亚细胞重新分配。这种重新分布的程度在一定程度上受到 PI3 激酶抑制剂预处理的抑制。尽管 PI3 激酶 myr-p110 的组成型活性形式的表达也引起 SHIP2 向 PM 的亚细胞重新分配，但 SHIP2 的表达似乎影响 myr-p110 诱导的 Akt2 磷酸化，而不是易位。此外，在缺乏胰岛素受体底物 1 或胰岛素受体底物 2 的基因敲除小鼠的胚胎成纤维细胞中，胰岛素诱导的 Akt 磷酸化受到 SHIP2 的有效调节。这些结果表明，胰岛素特异性地刺激 SHIP2 从胞质溶胶到 PM 的重新分布，而与 5'-磷酸酶活性无关，从而调节胰岛素诱导的 PM 上 Akt2 的易位和磷酸化。
SH2-containing inositol phosphatase 2 (SHIP2) is a physiologically important negative regulator of insulin signaling by hydrolyzing the phosphatidylinositol (PI) 3-kinase product PI 3,4,5-trisphosphate in the target tissues of insulin. Targeted disruption of the SHIP2 gene in mice resulted in increased insulin sensitivity without affecting biological systems other than insulin signaling. Therefore, we investigated the molecular mechanisms by which SHIP2 specifically regulates insulin-induced metabolic signaling in 3T3-L1 adipocytes. Insulin-induced phosphorylation of Akt, one of the molecules downstream of PI3-kinase, was inhibited by expression of wild-type SHIP2, whereas it was increased by expression of 5'-phosphatase- defective (DeltaIP) SHIP2 in whole cell lysates. The regulatory effect of SHIP2 was mainly seen in the plasma membrane (PM) and low density microsomes but not in the cytosol. In this regard, following insulin stimulation, a proportion of Akt2, and not Akt1, appeared to redistribute from the cytosol to the PM. Thus, insulin-induced phosphorylation of Akt2 at the PM was predominantly regulated by SHIP2, whereas the phosphorylation of Akt1 was only minimally affected. Interestingly, insulin also elicited a subcellular redistribution of both wild-type and DeltaIP-SHIP2 from the cytosol to the PM. The degree of this redistribution was inhibited in part by pretreatment with PI3-kinase inhibitor. Although the expression of a constitutively active form of PI3-kinase myr-p110 also elicited a subcellular redistribution of SHIP2 to the PM, expression of SHIP2 appeared to affect the myr-p110-induced phosphorylation, and not the translocation, of Akt2. Furthermore, insulin-induced phosphorylation of Akt was effectively regulated by SHIP2 in embryonic fibroblasts derived from knockout mice lacking either insulin receptor substrate-1 or insulin receptor substrate-2. These results indicate that insulin specifically stimulates the redistribution of SHIP2 from the cytosol to the PM independent of 5'-phosphatase activity, thereby regulating the insulin-induced translocation and phosphorylation of Akt2 at the PM.