TUSC4/NPRL2, a novel PDK1-interacting protein, inhibits PDK1 tyrosine phosphorylation and its downstream signaling
TUSC4/NPRL2, a novel PDK1-interacting protein, inhibits PDK1 tyrosine phosphorylation and its downstream signaling
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DOI：
10.1111/j.1349-7006.2008.00874.x
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发表时间：
2008-09-01
期刊：
影响因子：
5.7
通讯作者：
Fujita, Naoya
中科院分区：
文献类型：
--
作者：
Kurata, Atsuo;Katayama, Ryohei;Fujita, Naoya
3-磷酸肌肽依赖蛋白激酶-1 （PDK1）是细胞增殖和生存信号转导的关键调节因子。PDK1已知具有组成活性，并可通过src介导的酪氨酸-9、-373和-376残基磷酸化进一步激活。为了鉴定PDK1的新调节因子，我们进行了基于大肠杆菌的双杂交筛选，发现肿瘤抑制候选因子4 (TUSC4)，也称为氮渗透酶调节因子样2 (NPRL2)，在体外和细胞中与PDK1形成复合物，抑制src依赖性酪氨酸磷酸化和PDK1的激活。TUSC4的NH(2)端133个氨基酸残基参与与PDK1的结合。缺失NH(2)末端结构域的TUSC4缺失突变体对PDK1酪氨酸磷酸化或激活没有抑制作用。因此，复合物的形成对于tusc4介导的PDK1失活是必不可少的。sirna介导的TUSC4下调可诱导细胞增殖，而异位TUSC4表达可使PDK1下游信号通路（包括Akt和p70核糖体蛋白S6激酶）失活，并增加癌细胞对多种抗癌药物的敏感性。我们的研究结果表明，一种新的PDK1相互作用蛋白TUSC4/NPRL2在调节Src/PDK1信号通路和细胞对多种癌症化疗药物的敏感性中发挥作用。
3-Phosphoinositide-dependent protein kinase-1 (PDK1) is a key regulator of cell proliferation and survival signal transduction. PDK1 is known to be constitutively active and is further activated by Src-mediated phosphorylation at the tyrosine-9, -373, and -376 residues. To identify novel regulators of PDK1, we performed E. coli-based two-hybrid screening and revealed that tumor suppressor candidate 4 (TUSC4), also known as nitrogen permease regulator-like 2 (NPRL2), formed a complex with PDK1 and suppressed Src-dependent tyrosine phosphorylation and activation of PDK1 in vitro and in cells. The NH(2)-terminal 133 amino acid residues of TUSC4 were involved in binding to PDK1. The deletion mutant of TUSC4 that lacked the NH(2)-terminal domain showed no inhibitory effects on PDK1 tyrosine phosphorylation or activation. Thus, complex formation is indispensable for TUSC4-mediated PDK1 inactivation. The siRNA-mediated down-regulation of TUSC4 induced cell proliferation, while ectopic TUSC4 expression inactivated the PDK1 downstream signaling pathway, including Akt and p70 ribosomal protein S6 kinase, and increased cancer cell sensitivity to several anticancer drugs. Our results suggest that TUSC4/NPRL2, a novel PDK1-interacting protein, plays a role in regulating the Src/PDK1 signaling pathway and cell sensitivity to multiple cancer chemotherapeutic drugs.