Watanabe N, Madaule P, Reid T, Ishizaki T, Watanabe G, Kakizuka A, Saito Y, Nakao K, Jockusch B M, Narumiya S
Department of Pharmacology, Kyoto University Faculty of Medicine, Sakyo, Japan.
EMBO J. 1997 Jun 2;16(11):3044-56. doi: 10.1093/emboj/16.11.3044.
Rho small GTPase regulates cell morphology, adhesion and cytokinesis through the actin cytoskeleton. We have identified a protein, p140mDia, as a downstream effector of Rho. It is a mammalian homolog of Drosophila diaphanous, a protein required for cytokinesis, and belongs to a family of formin-related proteins containing repetitive polyproline stretches. p140mDia binds selectively to the GTP-bound form of Rho and also binds to profilin. p140mDia, profilin and RhoA are co-localized in the spreading lamellae of cultured fibroblasts. They are also co-localized in membrane ruffles of phorbol ester-stimulated sMDCK2 cells, which extend these structures in a Rho-dependent manner. The three proteins are recruited around phagocytic cups induced by fibronectin-coated beads. Their recruitment is not induced after Rho is inactivated by microinjection of botulinum C3 exoenzyme. Overexpression of p140mDia in COS-7 cells induced homogeneous actin filament formation. These results suggest that Rho regulates actin polymerization by targeting profilin via p140mDia beneath the specific plasma membranes.
Rho小GTP酶通过肌动蛋白细胞骨架调节细胞形态、黏附及胞质分裂。我们已鉴定出一种蛋白p140mDia，它是Rho的下游效应分子。它是果蝇透明蛋白的哺乳动物同源物，透明蛋白是胞质分裂所必需的一种蛋白，且属于含有重复多聚脯氨酸序列的formin相关蛋白家族。p140mDia选择性地结合Rho的GTP结合形式，也结合原肌球蛋白。p140mDia、原肌球蛋白和RhoA共定位于培养的成纤维细胞的伸展片层中。它们也共定位于佛波酯刺激的sMDCK2细胞的膜皱褶中，这些细胞以Rho依赖的方式延伸这些结构。这三种蛋白在纤连蛋白包被的珠子诱导的吞噬杯周围聚集。在通过显微注射肉毒杆菌C3外毒素使Rho失活后，它们的聚集不会被诱导。在COS-7细胞中过表达p140mDia会诱导均匀的肌动蛋白丝形成。这些结果表明，Rho通过在特定质膜下方经由p140mDia靶向原肌球蛋白来调节肌动蛋白聚合。
