Constitutive phosphorylation of a Rac GAP MgcRacGAP is implicated in v-Src-induced transformation of NIH3T3 cells.
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.
Doki
Noriko
N
Division of Cellular Therapy, The Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan.
Kawashima
Toshiyuki
T
Nomura
Yasushi
Y
Tsuchiya
Akiho
A
Oneyama
Chitose
C
Akagi
Tsuyoshi
T
Nojima
Yoshihisa
Y
Kitamura
Toshio
T
D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D064107:Aurora Kinase B; D064127:Aurora Kinases; D015153:Blotting, Western; D002471:Cell Transformation, Neoplastic; D003114:Colony-Forming Units Assay; D020690:GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D000634:Aminoquinolines; D020690:GTPase-Activating Proteins; C487513:NSC 23766; D011743:Pyrimidines; C115995:mgcRacGAP; D015688:Oncogene Protein pp60(v-src); C576924:Aurkb protein, mouse; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D020830:rac1 GTP-Binding Protein