Transforming growth factor- 1 regulates macrophage migration via RhoA

Brief treatment with transforming growth factor (TGF)– 1 stimulated the migration of macrophages, whereas long-term exposure decreased their migration. Cell migration stimulated by TGF1 was markedly inhibited by 10 g/mL Tat-C3 exoenzyme. TGF1 increased mRNA and protein levels of macrophage inflammatory protein (MIP)–1 in the initial period, and these effects also were inhibited by 10 g/mL Tat-C3 and a dominant-negative (DN)–RhoA (N19RhoA). Cycloheximide, actinomycin D, and antibodies against MIP-1 and monocyte chemoattractant protein-1 (MCP-1) abolished the stimulation of cell migration by TGF1. These findings suggest that migration of these cells is regulated directly and indirectly via the expression of chemokines such as MIP-1 and MCP-1 mediated by RhoA in response to TGF1. TGF1 activated RhoA in the initial period, and thereafter inactivated them, suggesting that the inactivation of RhoA may be the cause of the reduced cell migration in response to TGF1 at later times. We therefore attempted to elucidate the molecular mechanism of the inactivation of RhoA by TGF1. First, TGF1 phosphorylated RhoA via protein kinase A, leading to inactivation of RhoA. Second, wild-type p190 Rho GTPase activating protein (p190RhoGAP) reduced and DN-p190RhoGAP reversed the reduction of cell migration induced by TGF, suggesting that it inactivated RhoA via p190 Rho GAP. (Blood. 2006; 108:1821-1829)