Dynamics of protein-tyrosine phosphatases in rat adipocytes
Dynamics of protein-tyrosine phosphatases in rat adipocytes
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DOI：
10.1074/jbc.275.9.6308
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发表时间：
2000-03-03
影响因子：
4.8
通讯作者：
Pilch, PF
中科院分区：
文献类型：
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作者：
Calera, MR;Vallega, G;Pilch, PF
蛋白酪氨酸磷酸酶（Protein-tyrosine phosphatases，PTPases）在维持胰岛素受体（Insulin receptor，Ht）及其底物蛋白如胰岛素受体底物1（insulin receptor substrate 1，IRS-1）的稳态酪氨酸磷酸化中起着关键作用。在这里，我们分析了几个PTPases在大鼠脂肪细胞中的亚细胞分布，这些PTPases被认为参与了胰岛素信号的反调节。我们发现，跨膜酶，蛋白酪氨酸磷酸酶（PTP）-α和白细胞共同抗原相关（ZAR），主要在质膜中检测到，并在较低程度上在重微粒体中，分布类似于胰岛素受体，PTP-1B和IRS-1存在于轻微粒体和胞质溶胶中，而SHPTP 2/Syp只存在于胞质溶胶中。胰岛素诱导PTP-α以与受体平行的方式从质膜重新分布到重微粒体。PTP-1B在静息脂肪细胞轻微粒体中的分布与IRS-1的分布相似，这是通过蔗糖速度梯度分离确定的。对部分纯化的大鼠脂肪细胞PTP-α和LAR以及重组PTP-1B的催化活性的分析表明，所有三种PTP酶都能使IR去磷酸化。当IR/IRS-1的混合物用作底物时，PTP-1B在使IRS-1去磷酸化方面特别有效。考虑到IR和IRS-1可以在来自大鼠脂肪细胞的内膜区室中去磷酸化（Kublaoui，B.，李，J.，和Pilch，P.F.（1995）J，Biol. Chem. 270，59-65）和PTP-α。和PTP-1B是这些组分中各自的PTPases，我们得出结论，这些PTPases负责那里的胰岛素信号的反调节，而LAR和PTP-α都可能作用于细胞表面胰岛素受体。
Protein-tyrosine phosphatases (PTPases) play a key role in maintaining the steady-state tyrosine phosphorylation of the insulin receptor (Ht) and its substrate proteins such as insulin receptor substrate 1 (IRS-1), However, the PTPase(s) that inactivate IR and IRS-1 under physiological conditions remain unidentified. Here, we analyze the subcellular distribution in rat adipocytes of several PTPases thought to be involved in the counterregulation of insulin signaling. We found that the transmembrane enzymes, protein-tyrosine phosphatase (PTP)-alpha and leukocyte common antigen-related (ZAR), were detected predominantly in the plasma membrane and to a lesser extent in the heavy microsomes, a distribution similar to that of insulin receptor, PTP-1B and IRS-1 were present in light microsomes and cytosol, whereas SHPTP2/Syp was exclusively cytosolic. Insulin induced a redistribution of PTP-alpha from the plasma membrane to the heavy microsomes in a parallel fashion with the receptor. The distribution of PTP-1B in the light microsomes from resting adipocytes was similar to that of IRS-1 as determined by sucrose velocity gradient fractionation. Analysis of the catalytic activity of partially purified rat adipocyte PTP-alpha and LAR and recombinant PTP-1B showed that all three PTPases dephosphorylate IR When a mix of IR/IRS-1 was used as a substrate, PTP-1B was particularly effective in dephosphorylating IRS-1. Considering that IR and IRS-1 can be dephosphorylated in internal membrane compartments from rat adipocytes (Kublaoui, B., Lee, J., and Pilch, P.F. (1995) J, Biol. Chem. 270, 59-65) and that PTP-alpha. and PTP-1B are the respective PTPases in these fractions, we conclude that these PTPases are responsible for the counterregulation of insulin signaling there, whereas both LAR and PTP-alpha may act upon cell surface insulin receptors.