Lsc is required for marginal zone B cells, regulation of lymphocyte motility and immune responses

Lsc (the murine homolog of human p115 Rho GEF) is a member of the Dbl-homol ogy family of GTP exchange factors and is a specific activator of Rho. Lsc is activated by the G alpha (13) subunit of heterotrimeric G proteins and c ontains a regulator of G protein signaling domain that downmodulates G alph a (12) and G alpha (13). Lsc is expressed primarily in the hematopoietic sy stem and links the activation of G alpha (12) and G alpha (13)-coupled rece ptors to actin polymerization in B and T cells. Lsc is essential for margin al zone B (MZB) cell homeostasis and for the generation of immune responses . Although I-sc-deficient lymphocytes show reduced basal motility, MZB cell s show enhanced migration after serum activation. Thus, Lsc is a critical r egulator of MZB cells and immune functions.