Interaction of the Grb7 adapter protein with Rnd1, a new member of the Rhofamily

Grb7 is a member of a family of molecular adapters which are able to contri bute positively but also negatively to signal transduction and whose precis e roles remain obscure. Rnd1 is a member of the Rho family, but, as opposed to usual GTPases, it is constitutively bound to GTP, We show here that Rnd 1 and Grb7 interact, in two-hybrid assays, in vitro, and in pull-down exper iments performed with SK-BR3, a breast cancer cell line that overexpresses Grb7, This interaction involves switch II loop of Rnd1, a region crucial fo r guanine nucleotide exchange in all GTPases, and a Grb7 SH2 domain, a regi on crucial for Grb7 interaction with several activated receptors, The contr ibution of the interaction between Rnd1 and Grb7 to their respective functi ons and properties is discussed. (C) 2000 Federation of European Biochemica l Societies.