Characterization of a monoclonal antibody specific for the Ras-related GTP-binding protein Rho A

The Rho family of small GTP-binding proteins is one of the three subgroups which, together with the Ras and Rab families, constitute the Ras-related superfamily. The Rho subgroup contains at least seven highly homologous members including 4 Rho proteins (RhoA, RhoC, RhoB, and RhoG), the Rac1 and Rac2 proteins, and CDC42Hs, which are involved in various aspects of cytoskeleton organisation and cell polarity. We have raised antibodies to individual members of the Rho family, and we report here the characterization of a monoclonal antibody (26C4) specific for RhoA. When used in western blot experiments, the 26C4 antibody recognizes the recombinant RhoA protein but not the almost identical RhoC or the RhoG, Rac and CDC42Hs proteins. Furthermore the 26C4 antibody identifies the natural RhoA protein in human lymphocyte cell extracts and was used to study the level of RhoA expression in several lymphoblastoid cell lines, and its association with the cell membrane.