Constitutive phosphorylation of a Rac GAP MgcRacGAP is implicated in v-Src-induced transformation of NIH3T3 cells
Constitutive phosphorylation of a Rac GAP MgcRacGAP is implicated in v-Src-induced transformation of NIH3T3 cells
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DOI：
10.1111/j.1349-7006.2009.01235.x
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发表时间：
2009-09-01
期刊：
影响因子：
5.7
通讯作者：
Kitamura, Toshio
中科院分区：
文献类型：
--
作者：
Doki, Noriko;Kawashima, Toshiyuki;Kitamura, Toshio
MgcRacGAP通过调节Rho家族小GTP酶在细胞分裂中起关键作用。如我们先前所报道的，在胞质分裂期间，Aurora B激酶在中间体诱导丝氨酸387（S387）上的MgcRacGAP磷酸化，这是胞质分裂的关键步骤。S387-MgcRacGAP的磷酸化将其从RacGAP转化为RhoGAP，导致胞质分裂的完成。在这里，我们表明，MgcRacGAP是显着磷酸化的S387，即使在间期的v-Src转化的NIH 3 T3细胞的细胞质中，但不是在间期的亲本NIH 3 T3或H-RasV 12转化的NIH 3 T3细胞。有趣的是，S387（pS387）上的磷酸化水平与v-Src转化的NIH 3 T3细胞的软琼脂集落形成能力相关。磷酸化模拟突变体MgcRacGAP-S387 D的表达增强了v-Src转化的NIH 3 T3细胞的集落形成。令人惊讶的是，Rac 1抑制剂而非激酶抑制剂（包括Aurora B激酶抑制剂）特异性抑制v-Src转化的NIH 3 T3细胞中S387-MgcRac GAP的磷酸化，表明v-Src诱导的病理性正反馈机制朝向使用pS387-MgcRac GAP的Rac 1活化。这些结果表明v-Src-和H-RasV 12-诱导转化的机制之间的差异，并应阐明在v-Src-诱导的细胞转化中MgcRacGAP在S387处的无序磷酸化的病理作用。（《癌症科学》2009; 100：1675-1679）。
MgcRacGAP plays critical roles in cell division through regulating Rho family small GTPases. As we previously reported, phosphorylation of MgcRacGAP on serine 387 (S387) is induced by Aurora B kinase at the midbody during cytokinesis, which is a critical step of cytokinesis. Phosphorylation of S387-MgcRacGAP converts it from RacGAP to RhoGAP, leading to completion of cytokinesis. Here we show that MgcRacGAP is prominently phosphorylated on S387 even in the interphase of v-Src-transformed NIH3T3 cells in the cytoplasm, but not in the interphase of parental NIH3T3 or H-RasV12-transformed NIH3T3 cells. Interestingly, levels of phosphorylation on S387 (pS387) correlated with soft agar colony-forming abilities of v-Src-transformed NIH3T3 cells. Expression of a phosphorylation-mimic mutant MgcRacGAP-S387D enhanced colony formation of v-Src-transformed NIH3T3 cells. Surprisingly, a Rac1 inhibitor but not kinase inhibitors including Aurora B kinase inhibitor specifically inhibited phosphorylation of S387-MgcRacGAP in v-Src-transformed NIH3T3 cells, suggesting the v-Src-induced pathological positive feedback mechanisms towards Rac1 activation using pS387-MgcRacGAP. These results indicated the difference in the mechanisms between v-Src- and H-RasV12-induced transformation, and should shed some light on pathological roles of disordered phosphorylation of MgcRacGAP at S387 in v-Src-induced cell transformation. (Cancer Sci 2009; 100: 1675-1679).