title: A novel strategy for specifically down-regulating individual Rho GTPase activity in tumor cells.
abstract: The Rho family GTPases RhoA, RhoB, and RhoC regulate the actin cytoskeleton, cell movement, and cell growth. Unlike Ras, up-regulation or overexpression of these GDP/GTP binding molecular switches, but not activating point mutations, has been associated with human cancer. Although they share over 85% sequence identity, RhoA, RhoB, and RhoC appear to play distinct roles in cell transformation and metastasis. In NIH 3T3 cells, RhoA or RhoB overexpression causes transformation whereas RhoC increases the cell migration rate. To specifically target RhoA, RhoB, or RhoC function, we have generated a set of chimeric molecules by fusing the RhoGAP domain of p190, a GTPase-activating protein that accelerates the intrinsic GTPase activity of all three Rho GTPases, with the C-terminal hypervariable sequences of RhoA, RhoB, or RhoC. The p190-Rho chimeras were active as GTPase-activating proteins toward RhoA in vitro, co-localized with the respective active Rho proteins, and specifically down-regulated Rho protein activities in cells depending on which Rho GTPase sequences were included in the chimeras. In particular, the p190-RhoA-C chimera specifically inhibited RhoA-induced transformation whereas p190-RhoC-C specifically reversed the migration phenotype induced by the active RhoC. In human mammary epithelial-RhoC breast cancer cells, p190-RhoC-C, but not p190-RhoA-C or p190-RhoB-C, reversed the anchorage-independent growth and invasion phenotypes caused by RhoC overexpression. In the highly metastatic A375-M human melanoma cells, p190-RhoC-C specifically reversed migration, and invasion phenotypes attributed to RhoC up-regulation. Thus, we have developed a novel strategy utilizing RhoGAP-Rho chimeras to specifically down-regulate individual Rho activity and demonstrate that this approach may be applied to multiple human tumor cells to reverse the growth and/or invasion phenotypes associated with disregulation of a distinct subtype of Rho GTPase.
authors.affiliation: Division of Experimental Hematology and Molecular Developmental Biology Program, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, Ohio 45229, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Linda
authors.initials: L
authors.lastname: Yang
authors.forename: Yongneng
authors.initials: Y
authors.lastname: Luo
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D005455:Fluorescent Antibody Technique; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D041681:NIH 3T3 Cells; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology; D011993:Recombinant Fusion Proteins; D014162:Transfection; D014407:Tumor Cells, Cultured; D018631:ras Proteins; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D020743:rhoB GTP-Binding Protein / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D000075024:rhoC GTP-Binding Protein
chemical_list: D020690:GTPase-Activating Proteins; D011993:Recombinant Fusion Proteins; C085379:rho GTPase-activating protein; C066690:RHOC protein, human; C512911:Rhoc protein, mouse; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein; D000075024:rhoC GTP-Binding Protein