MONOCYTE CHEMOATTRACTANT PROTEIN-1-INDUCED CCR2B RECEPTOR DESENSITIZATION MEDIATED BY THE G-PROTEIN-COUPLED RECEPTOR KINASE-2

Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokin e cytokine family, whose physiological function is mediated by binding to the CCR2 and CCR4 receptors, which are members of the G protein-co upled receptor family. MCP-1 plays a critical role in both activation and migration of leukocytes. Rapid chemokine receptor desensitization is very likely essential for accurate chemotaxis. In this report, we s how that MCP-1 binding to the CCR2 receptor in Mono Mac 1 cells promot es the rapid desensitization of MCP-1-induced calcium flux responses. This desensitization correlates with the Ser/Thr phosphorylation of th e receptor and with the transient translocation of the G protein-coupl ed receptor kinase 2 (GRK2, also called beta-adrenergic kinase 1 or be ta ARK1) to the membrane. We also demonstrate that GRK2 and the uncoup ling protein beta-arrestin associate with the receptor, forming a macr omolecular complex shortly after MCP-1 binding. Calcium flux responses to MCP-1 in HEK293 cells expressing the CCR2B receptor were also mark edly reduced upon cotransfection with GRK2 or the homologous kinase GR K3. Nevertheless, expression of the GRK2 dominant-negative mutant beta ARK-K220R did not affect the initial calcium response, but favored re ceptor response to a subsequent challenge by agonists. The modulation of the CCR2B receptor by GRK2 suggests an important role for this kina se in the regulation of monocyte and lymphocyte response to chemokines .