Integrin-mediated signaling in human neutrophil functioning

Integrins are important signal transducers for virtually all neutrophil functions. Although a variety of signals ultimately result in integrin activation, the intracellular targets of integrin-initiated signals are poorly delineated to date. Polymorphonuclear (PMN) leukocyte responses to inflammation are dependent on both the stimulants and the extracellular environment encountered. Integrin ligation, by cell-cell or cell-matrix interactions, activates a variety of signaling cascades. These events dictate the nature of PMN responses to the encountered stimulus. The complex system of effector molecule recruitment and permissive signaling by integrins serves to strictly regulate PMN functions such as cell adhesion, motility, oxidant production, and protein synthesis. Moreover, there is evidence that cross-talk between integrins exists to prime integrin populations for subsequent functioning. This review summarizes the current understanding of signaling mechanisms for integrin priming and activation. In this connection, the role of specific signaling molecules in key PMN functions are examined.