Regulation of p190 Rho-GAP by v-Src is linked to cytoskeletal disruption during transformation.
The v-Src oncoprotein perturbs the dynamic regulation of the cellular cytoskeletal and adhesion network by a mechanism that is poorly understood. Here, we have examined in detail the effects of a temperature-dependent v-Src protein on the regulation of p190 RhoGAP, a GTPase activating protein (GAP) that has been implicated in disruption of the organised actin cytoskeleton, and addressed the dependence of v-Src-induced stress fibre loss on inhibition of Rho activity. We found that activation of v-Src induced association of tyrosine phosphorylated p190 with p120(RasGAP) and stimulation of p120(RasGAP)-associated RhoGAP activity, although p120(RasGAP) itself was not a target for phosphorylation by v-Src in chicken embryo cells. These events required the catalytic activity of v-Src and were linked to loss of actin stress fibres during morphological transformation and not mitogenic signalling. Furthermore, these effects were rapidly reversible since switching off v-Src led to dissociation of the p190/p120(RasGAP) complex, inactivation of p120(RasGAP)-associated RhoGAP activity and re-induction of actin stress fibres. In addition, transient transfection of Val14-RhoA, a constitutively active Rho protein that is insensitive to RhoGAPs, suppressed v-Src-induced stress fibre loss and cell transformation. Thus, we show here for the first time that an activated Src kinase requires the inactivation of Rho-mediated actin stress fibre assembly to induce its effects on actin disorganisation. Moreover, our work supports p190 as a strong candidate effector of v-Src-induced cytoskeletal disruption, most likely mediated by antagonism of the cellular function of Rho.
Fincham
V J
VJ
The Beatson Institute for Cancer Research, CRC Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
Chudleigh
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D000199:Actins / Q000502:physiology; D000818:Animals; D048429:Cell Size; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D016391:Genes, src; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D020742:rhoA GTP-Binding Protein
D000199:Actins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; D011994:Recombinant Proteins; D015688:Oncogene Protein pp60(v-src); D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein