Role for plastin in host defense distinguishes integrin signaling from cell adhesion and spreading

Integrin ligation activates both cell adhesion and signal transduction, in part through reorganization of the actin cytoskeleton. Plastins (also known as fimbrins) are actin-crosslinking proteins of the cortical cytoskeleton present in all cells and conserved from yeast to mammals. Here we show that plastin-deficient polymorphonuclear neutrophils (PMN) are deficient in killing the bacterial pathogen Staphylococcus aureus in vivo and in vitro, despite normal phagocytosis. Like integrin β2-deficient PMN, plastin-deficient PMN cannot generate an adhesion-dependent respiratory burst, because of markedly diminished integrin-dependent syk activation. Unlike β2^-/- PMN, plastin-deficient PMN adhere and spread normally. Deficiency of plastin thus separates the classical integrin receptor functions of adhesion and spreading from intracellular signal transduction.