National Institutes of Health (NIH)
The concentrations of many membrane-embedded receptors are dynamically regulated as a result of ligand binding to cell surfaces. It has long been known, for example, that receptors for fMLP and other chemoattractants are down regulated during cell activation, thereby affecting the tendency for leukocytes to undergo directed locomotion. More recently, experimental evidence has been developed illustrating a link between the ability of neutrophils to migrate on endothelial-like cells and the receptor-mediated endocytosis of P-selectins from the endothelial cell surfaces. Hence, we here discuss several aspects of clathrin-coat mediation of vesicle formation from plasma membranes. Among these are: 1) an analysis of the relative rigidities of intrinsic membrane and associated clathrin coat, and the influence of these components on determining vesicle size; 2) the energetics of the triskelion rearrangements occurring during clathrin coat formation; 3) a possible role for local, membrane-bound charge in vesicle budding; and 3) ways that cargo might act as a physical factor in endocytosis.