Rho GTPases control migration and polarization of adhesion molecules and cytoskeletal ERM components in T lymphocytes

Motile lymphocytes adopt a polarized morphology with different adhesion mol ecules (ICAM, CD43 and CD44) and ERM actin-binding proteins concentrated on the uropod, a slender posterior appendage with important functions in cell -cell interactions and lymphocyte recruitment. We have studied the role of Rho family of GTPases (Rho, Rac and Cdc42) in the control of lymphocyte pol arity and migration by analyzing the effects of exogenously introduced Rho GTPase mutants. Transfection of T cell lines that constitutively display a polarized motile morphology with activated mutants of RhoA, Rad and Cdc42 i mpaired cell polarization. A guanosine nucleotide exchange factor for Rac, Tiam-1, induced the same effect as activated Rad. Conversely, dominant nega tive forms of the three GTP-binding proteins induced a polarized phenotype in constitutively round-shaped T cells with redistribution of ICAM-3 and mo esin to the uropod in an integrin-dependent manner. On the other hand, over expression of dominant negative Cdc42 and activated mutants of all three Rh o GTPases significantly inhibited SDF-1 alpha-induced T cell chemotaxis. To gether, these data demonstrate that Rho GTPases regulate lymphocyte polariz ation and chemokine-induced migration, and underscore the key role of Cdc42 in lymphocyte directional migration.