Role of the tyrosine kinase pyk2 in the integrin-dependent activation of human neutrophils by TNF

Secretion of inflammatory products from neutrophils can be induced by a com bination of signals from ligated integrins and receptors for soluble, physi ological agonists such as TNF. Here we identify pyk2 in primary human neutr ophils; localize it to focal adhesions and podosomes; and demonstrate its t yrosine phosphorylation, activation, and association with paxillin during s timulation of adherent cells by TNF. Tyrphostin A9 emerged as the most pote nt and selective of 51 tyrosine kinase inhibitors tested against the TNF-in duced respiratory burst. Tyrphostin A9 inhibited TNF-induced tyrosine phosp horylation of pyk2 without blocking the cells' bactericidal activity. Wortm annin, an inhibitor of phosphatidylinositol-3-kinase, potently blocked the TNF-induced respiratory burst and selectively inhibited tyrosine phosphoryl ation of pyk2. Thus, pyk2 appears to play an essential role in the ability of neutrophils to integrate signals from beta(2) integrins and TNF receptor s.