Agonist-induced trafficking of the low-affinity formyl peptide receptor FPRL1

The formyl peptide-like receptor FPRL1 is a member of the chemoattractant subfamily of G protein- coupled receptors involved in regulating leukocyte migration in inflammation. To elucidate mechanisms underlying the internalization of ligand-bound FPRL1 and possible receptor recycling, we characterized the endocytic itinerary of FPRL1. We show that agonist-triggered internalization from the plasma membrane into intracellular compartments is prevented by perturbation of clathrin-mediated endocytosis, such as expression of the dominant-negative clathrin Hub mutant, siRNA-mediated depletion of cellular clathrin and expression of a dominant-negative mutant of the large GTPase dynamin. Internalized FPRL1 co-localized with endocytosed transferrin and the small GTPases Rab4 and Rab11 in vesicular structures most resembling recycling endosomes. Recycling of FPRL1 was significantly reduced by pretreatment with PI3-kinase inhibitors. Thus, ligand-bound FPRL1 undergoes primarily clathrin-mediated and dynamin-dependent endocytosis and the receptor recycles via a rapid PI3-kinase-sensitive route as well as pathways involving perinuclear recycling endosomes.Received 19 March 2004; received after revision 26 April 2004; accepted 12 May 2004     

The cellular functions of clathrin

Membranes and proteins are moved around the cell in small vesicles. A protein coat aids the budding of such vesicles from donor membranes. The major type of coat used by the cell is composed of clathrin, a three-legged protein that can form lattice-like coats on membranes destined for trafficking. In this review, I outline what we know about clathrin and discuss some recent advances in understanding the basic biology of this fascinating molecule, which include building a molecular model of a clathrin lattice and discovery of a new function for clathrin that occurs during mitosis. Received 12 December 2005; received after revision 21 March 2006; accepted 29 March 2006