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-homology 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 contains a regulator of G protein signaling domain that downmodulates G alpha (12) and G alpha (13). Lsc is expressed primarily in the hematopoietic system and links the activation of G alpha (12) and G alpha (13)-coupled receptors to actin polymerization in B and T cells. Lsc is essential for marginal zone B (MZB) cell homeostasis and for the generation of immune responses. Although I-sc-deficient lymphocytes show reduced basal motility, MZB cells show enhanced migration after serum activation. Thus, Lsc is a critical regulator of MZB cells and immune functions.