Nagao M, Kaziro Y, Itoh H
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Oncogene. 1999 Aug 5;18(31):4425-34. doi: 10.1038/sj.onc.1202832.
Gt12, a member of alpha subunit of heterotrimeric G protein G12 subfamily, has been shown to stimulate c-Jun N-terminal kinase (JNK) activity through the low molecular weight GTP-binding proteins Ras, Rac, and Cdc42. In this study using the transient expression of a constitutively activated mutant of Galpha12 (Galpha12Q229L) in human embryonic kidney (HEK) 293 cells, we found that Rho and Src family kinase are also involved in the Galpha12-induced activation of JNK. The activation of JNK by Galpha12Q229L was inhibited by dominant-negative RhoA(T19N), and botulinum C3 exoenzyme which specifically inactivates Rho. In addition, the expression of activated RhoA(G14V) elevated JNK activity in HEK 293 cells. The Galpha12Q229L-stimulated activation of JNK was blocked by a specific inhibitor of protein tyrosine kinases (PP2), and C-terminal Src kinase (Csk). Moreover, we observed that Galpha12Q229L stimulated Src family kinase activity and v-Src induced JNK activation. Interestingly, the v-Src-induced activation of JNK was inhibited by dominant-negative RhoA(T19N). In contrast, Csk did not inhibit the JNK activation by activated RhoA(G14V). These results suggest that Rho and Src family kinase are required for the Galpha12-induced JNK activation, and that Src family kinase acts upstream of Rho activation in the JNK pathway.
Gt12是异三聚体G蛋白G12亚家族α亚基的成员，已被证明可通过低分子量GTP结合蛋白Ras、Rac和Cdc42刺激c-Jun氨基末端激酶（JNK）的活性。在本研究中，通过在人胚肾（HEK）293细胞中瞬时表达组成型激活的Gα12突变体（Gα12Q229L），我们发现Rho和Src家族激酶也参与了Gα12诱导的JNK激活。Gα12Q229L对JNK的激活被显性负性RhoA（T19N）和特异性使Rho失活的肉毒杆菌C3外毒素所抑制。此外，激活的RhoA（G14V）的表达提高了HEK 293细胞中JNK的活性。Gα12Q229L刺激的JNK激活被蛋白酪氨酸激酶（PP2）和C末端Src激酶（Csk）的特异性抑制剂所阻断。此外，我们观察到Gα12Q229L刺激了Src家族激酶的活性，并且v-Src诱导了JNK的激活。有趣的是，v-Src诱导的JNK激活被显性负性RhoA（T19N）所抑制。相反，Csk并不抑制激活的RhoA（G14V）对JNK的激活。这些结果表明，Rho和Src家族激酶是Gα12诱导的JNK激活所必需的，并且Src家族激酶在JNK途径中Rho激活的上游起作用。
