Differential regulation of CXCR2 trafficking by Rab GTPases

Abstract

Intracellular trafficking of chemokine receptors plays an important role in fine-tuning the functional responses of neutrophils and lymphocytes in the inflammatory process and HIV infection. Although many chemokine receptors internalize through clathrin-coated pits, regulation of the receptor trafficking is not fully understood. The present study demonstrated that CXCR2 was colocalized with transferrin and low-density lipoprotein (LDL) after agonist treatment for different periods of time, suggesting 2 intracellular trafficking pathways for this receptor. CXCR2 was colocalized with Rab5 and Rab11a, which are localized in early and recycling endosomes, respectively, in response to agonist stimulation for a short period of time, suggesting a recycling pathway for the receptor trafficking. However, overexpression of a dominant-negative Rab5-S34N mutant significantly attenuated CXCR2 sequestration. The internalized CXCR2 was recycled back to the cell surface after removal of the agonist and recovery of the cells, but receptor recycling was: prohibited by overexpression of a dominant-negative Rab11a-S25N mutant. After prolonged (4-hour) agonist treatment, CXCR2 exhibited significantly increased colocalization with Rab7, which is localized in late endosomes. The colocalization of CXCR2 with LDL and LAMP-1 suggests that CXCR2 is targeted to lysosomes for degradation after prolonged ligand treatment. However, the colocalization of CXCR2 with Lampl was blocked by the overexpression of a dominant-negative Rab7-T22N mutant. In cells overexpressing Rab7-T22N, CXCR2 was retained in the Rab5- and Rab11a-positive endosomes after prolonged (4-hour) agonist treatment. Our data suggest that the intracellular trafficking of CXCR2 is differentially regulated by Rab proteins. © 2003 by The American Society of Hematology.