PTP-PEST - A PROTEIN-TYROSINE-PHOSPHATASE REGULATED BY SERINE PHOSPHORYLATION
PTP-PEST - A PROTEIN-TYROSINE-PHOSPHATASE REGULATED BY SERINE PHOSPHORYLATION
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DOI：
10.1002/j.1460-2075.1994.tb06687.x
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发表时间：
1994-08-15
期刊：
影响因子：
11.4
通讯作者：
TONKS, NK
中科院分区：
文献类型：
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作者：
GARTON, AJ;TONKS, NK
蛋白酪氨酸磷酸酶PTP-PEST是一种88 kDa的胞浆酶，广泛存在于哺乳动物组织中。我们利用重组杆状病毒表达了PTP-PEST，并对该蛋白进行了纯化，以研究磷酸化作为该酶潜在调控机制的可能性。PTP-PEST在体外被环磷酸腺苷依赖的蛋白激酶(PKA)和蛋白激酶C(PKC)两个主要位点所磷酸化，我们已经确定这两个位点是Ser39和Ser435。在用TPA、Forsklin或异丁基甲基黄嘌呤(IBMX)处理完整的HeLa细胞后，Ser39和Ser435上的PTP-PEST也被磷酸化。Ser39的体外磷酸化通过降低其与底物的亲和力来降低PTP-PEST的活性。此外，从TPA处理的细胞中提取的PTP-PEST免疫沉淀物的PTP活性显著低于未处理的细胞。我们的结果表明，PKC和PKA都能够在体内磷酸化PTP-PEST，从而抑制体内的PTP-PEST，从而提供了一种机制，即通过PKA或PKC作用的信号转导通路可能直接影响涉及可逆酪氨酸磷酸化的细胞过程。
The protein tyrosine phosphatase PTP-PEST is an 88 kDa cytosolic enzyme which is ubiquitously expressed in mammalian tissues. We have expressed PTP-PEST using recombinant baculovirus, and purified the protein essentially to homogeneity in order to investigate phosphorylation as a potential mechanism of regulation of the enzyme. PTP-PEST is phosphorylated in vitro by both cyclic AMP-dependent protein kinase (PKA) and protein kinase C (PKC) at two major sites, which we have identified as Ser39 and Ser435. PTP-PEST is also phosphorylated on both Ser39 and Ser435 following treatment of intact HeLa cells with TPA, forskolin or isobutyl methyl xanthine (IBMX). Phosphorylation of Ser39 in vitro decreases the activity of PTP-PEST by reducing its affinity for substrate. In addition, PTP-PEST immunoprecipitated from TPA-treated cells displayed significantly lower PTP activity than enzyme obtained from untreated cells. Our results suggest that both PKC and PKA are capable of phosphorylating, and therefore inhibiting, PTP-PEST in vivo, offering a mechanism whereby signal transduction pathways acting through either PKA or PKC may directly influence cellular processes involving reversible tyrosine phosphorylation.