Li G, D'Souza-Schorey C, Barbieri M A, Cooper J A, Stahl P D
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Biol Chem. 1997 Apr 18;272(16):10337-40.
Activation of Ras stimulates cell surface membrane ruffling and pinocytosis. Although seen as coupled events, our study demonstrates that membrane ruffling and pinocytosis are regulated by distinct Ras signal transduction pathways. Ras controls membrane ruffling via the small GTPase Rac. In BHK-21 cells, expression of the constitutively active Rac1(G12V) mutant, via a Sindbis virus vector, resulted in a dramatic stimulation of membrane ruffling without affecting the uptake of horseradish peroxidase. Expression of Ha-Ras(G12V), an activated Ras mutant, stimulated both membrane ruffling and horseradish peroxidase uptake. The Ha-Ras(G12V)-stimulated pinocytosis but not membrane ruffling was abolished by either wortmannin or co-expression with a dominant negative mutant of Rab5, Rab5(S34N). Expression of the activated Rab5(Q79L) mutant mimics the stimulatory effect of Ha-Ras(G12V) on pinocytosis but not membrane ruffling. Our data indicate that Ha-Ras(G12V) separately activates Rab5-dependent pinocytosis and Rac1-dependent membrane ruffling.
Ras的激活会刺激细胞表面膜褶皱和胞饮作用。尽管这两个过程被视为相关联的事件，但我们的研究表明，膜褶皱和胞饮作用是由不同的Ras信号转导途径调控的。Ras通过小GTP酶Rac控制膜褶皱。在BHK - 21细胞中，通过辛德毕斯病毒载体表达组成型激活的Rac1(G12V)突变体，会显著刺激膜褶皱，但不影响辣根过氧化物酶的摄取。激活的Ras突变体Ha - Ras(G12V)的表达，既刺激了膜褶皱，也刺激了辣根过氧化物酶的摄取。渥曼青霉素或与Rab5的显性负性突变体Rab5(S34N)共表达可消除Ha - Ras(G12V)刺激的胞饮作用，但不影响膜褶皱。激活的Rab5(Q79L)突变体的表达模拟了Ha - Ras(G12V)对胞饮作用的刺激作用，但不影响膜褶皱。我们的数据表明，Ha - Ras(G12V)分别激活Rab5依赖的胞饮作用和Rac1依赖的膜褶皱。
