24] Chemoattractant-induced membrane phenomena of phagocytes

Abstract

This chapter discusses the several chemoattractant-induced membrane phenomena of phagocytes. Exposure of phagocytes to chemoattractants initiates a number of biological responses, including directed migration, secretion of hydrolytic enzymes, and production of cytotoxic oxygen species. These processes are activated by second messengers that are produced upon the interaction of chemoattractants with their receptors. The chapter also presents methods for studying chemoattractant-induced changes in phospholipid metabolism. Modification of the phospholipid composition of plasma membranes is a rapid response to many hormonal stimuli, including chemoattractants. Alterations of phospholipid metabolism can have pronounced effects on the activities of membrane-associated enzymes or produce second messengers act to regulate cell responses. The role of a guanine nucleotide regulatory (N) protein in phagocyte activation by chemoattractants is described. N proteins play pivotal roles in regulating the activity of adenylate cyclase and hence cyclic adenosine monophosphate (cAMP) levels in cells. Accumulating evidence suggests that N proteins may play similar roles in coupling phospholipase C activation to receptors that stimulate polyphosphoinositide breakdown. Methods described have been used predominantly for studying the responses of human polymorphonuclear leukocytes (PMNs) to the oligopeptide chemoattractant fMet-Leu-Phe but are also applicable to other chemoattractants.