Lee Hyangkyu, Xie Laiping, Luo Yong, Lee Seung-Yub, Lawrence David S, Wang Xiao Bo, Sotgia Federica, Lisanti Michael P, Zhang Zhong-Yin
Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
Biochemistry. 2006 Jan 10;45(1):234-40. doi: 10.1021/bi051560j.
Protein tyrosine phosphatase 1B (PTP1B) is implicated in a number of signaling pathways including those mediated by insulin, epidermal growth factor (EGF), and the Src family kinases. The scaffolding protein caveolin-1 is also a participant in these pathways and is specifically phosphorylated on tyrosine 14, when these pathways are activated. Here, we provide evidence that PTP1B can efficiently catalyze the removal of the phosphoryl group from phosphocaveolin-1. Overexpression of PTP1B decreases tyrosine 14 phosphorylation in caveolin-1, while expression of the substrate-trapping mutant PTP1B/D181A causes the accumulation of phosphocaveolin-1 and prevents its dephosphorylation by endogenous PTPs. We further demonstrate that PTP1B physically associates with caveolin-1. Finally, we show that inhibition of PTP1B activity with a potent and specific small molecule PTP1B inhibitor blocks the PTP1B-catalyzed caveolin-1 dephosphorylation both in vitro and in vivo. Taken together, the results strongly suggest that caveolin-1 is a specific substrate for PTP1B. Identification of caveolin-1 as a PTP1B substrate represents an important new step in further understanding the signaling pathways regulated by PTP1B.
蛋白酪氨酸磷酸酶1B（PTP1B）涉及多种信号通路，包括由胰岛素、表皮生长因子（EGF）和Src家族激酶介导的信号通路。支架蛋白小窝蛋白-1也是这些信号通路的参与者，当这些信号通路被激活时，它在酪氨酸14位点发生特异性磷酸化。在此，我们提供证据表明，PTP1B能够有效地催化从小窝蛋白-1磷酸化形式上去除磷酸基团。PTP1B的过表达会降低小窝蛋白-1酪氨酸14位点的磷酸化水平，而底物捕获突变体PTP1B/D181A的表达会导致磷酸化小窝蛋白-1的积累，并阻止其被内源性磷酸酶去磷酸化。我们进一步证明，PTP1B与小窝蛋白-1存在物理相互作用。最后，我们表明，用一种强效且特异性的小分子PTP1B抑制剂抑制PTP1B活性，在体外和体内均能阻断PTP1B催化的小窝蛋白-1去磷酸化。综上所述，这些结果强烈表明小窝蛋白-1是PTP1B的特异性底物。将小窝蛋白-1鉴定为PTP1B底物是进一步理解由PTP1B调节的信号通路的重要新进展。
