Dynamics of insulin signaling in 3T3-L1 adipocytes - Differential compartmentalization and trafficking of insulin receptor substrate (IRS)-1 and IRS-2
Dynamics of insulin signaling in 3T3-L1 adipocytes - Differential compartmentalization and trafficking of insulin receptor substrate (IRS)-1 and IRS-2
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DOI：
10.1074/jbc.273.19.11548
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发表时间：
1998-05-08
影响因子：
4.8
通讯作者：
Kahn, CR
中科院分区：
文献类型：
--
作者：
Inoue, G;Cheatham, B;Kahn, CR
胰岛素受体对多种底物的磷酸化能力及其在细胞内的定位是导致信号多样性的两个决定因素，我们发现胰岛素受体底物(IRS)-1在细胞内膜(IM)中的浓度是胞浆的2倍，而IRS-2在胞浆中的浓度是IM的2倍。胰岛素刺激诱导IRS-1和IRS-2的快速酪氨酸磷酸化。这主要发生在IM室，尽管IR-S主要定位于胞浆，而且胰岛素刺激后，IR-1和IR-2都从IRI转运到胞浆，t(1/2)为3.5min。使用体外重建实验，我们已经证明了IRS-1与内膜之间的联系，并证明了IRS-1与IM的解离依赖于IM的丝氨酸/苏氨酸磷酸化。相比之下，在胰岛素刺激后1min内，磷脂酰肌醇3-激酶(P85)85 kDa亚基总库的40%被从胞浆招募到IM，其中大部分可通过与IM中存在的IRS-1结合来解释。与IRS-2相关的P85结合和磷脂酰肌醇3-激酶活性在IM和胞浆中迅速下降，而与IRS-1相关的P85结合和磷脂酰肌醇3-激酶活性在IM中保持在相对较高的水平，并随着时间的推移而在胞浆中增加，尽管P85返回到胞浆中，并降低了胞浆IRS-1的酪氨酸磷酸化。这些数据表明，IRS-1和IRS-2在细胞内的分布是不同的，并且在胰岛素刺激后从IRI转移到胞浆。胰岛素刺激的IRS-1和IRS-S信号主要发生在IM中，呈现不同的动力学特征；IRS-L介导的信号更稳定，而IRS-a介导的信号更具瞬时性。这些底物利用和区隔的差异可能导致胰岛素信号网络的复杂性和多样性。
The ability of the insulin receptor to phosphorylate multiple substrates and their subcellular localization are two of the determinants that contribute to diversity of signaling, We find that insulin receptor substrate (IRS)-1 is 2-fold more concentrated in the intracellular membrane (IM) compartment than in cytosol, whereas IRS-2 is 2-fold more concentrated in cytosol than in IM. Insulin stimulation induces rapid tyrosine phosphorylation of both IRS-1 and IRS-2. This occurs mainly in the IM compartment, even though IRS-S is located predominantly in cytosol, Furthermore, after insulin stimulation, both IRS-1 and IRS-2 translocate from IRI to cytosol with a t(1/2) of 3.5 min. Using an in vitro reconstitution assay, we have demonstrated an association between IRS-1 and internal membranes and have shown that the dissociation of IRS-1 from IM is dependent on serine/ threonine phosphorylation of IM. By comparison, within 1 min after insulin stimulation, 40% of the total pool of the 85-kDa subunit of phosphatidylinositol 3-kinase (p85) is recruited from cytosol to IM, the greater part of which can be accounted for by binding to IRS-1 present in the IM. The p85 binding and phosphatidylinositol 3-kinase activity associated with IRS-2 rapidly decrease in both IM and cytosol, whereas those associated with IRS-1 stay at a relatively high level in IM and increase with time in cytosol despite a return of p85 to the cytosol and decreasing tyrosine phosphorylation of cytosolic IRS-1. These data indicate that IRS-1 and IRS-2 are differentially distributed in the cell and move from IRI to cytosol following insulin stimulation. Insulin-stimulated IRS-1 and IRS-S signaling occurs mainly in the IM and shows different kinetics; IRS-l-mediated signaling is more stable, whereas IRS-a-mediated signaling is more transient. These differences in substrate utilization and compartmentalization may contribute to the complexity and diversity of the insulin signaling network.