Dissociation of Chemotaxis from Agonist-induced Receptor Internalization in a Lymphocyte Cell Line Transfected with CCR2B
EVIDENCE THAT DIRECTED MIGRATION DOES NOT REQUIRE RAPID MODULATION OF SIGNALING AT THE RECEPTOR LEVEL*
- From the Gladstone Institute of Cardiovascular Disease, the§Department of Medicine, and the ‡Daiichi Research Center, University of California, San Francisco, California 94141-9100
Abstract
To investigate the role of the carboxyl-terminal region (52 amino acids) of the monocyte chemoattractant protein 1 receptor (CCR2B) in chemotaxis, we created a series of mutants and expressed them in a murine pre-B lymphocyte cell line. Truncation of the cytoplasmic carboxyl tail to 20 amino acids had little or no effect on chemotaxis or signal transduction, but further truncation resulted in marked functional defects. Upon incubation with monocyte chemoattractant protein 1, CCR2B underwent rapid and extensive internalization, and this was impaired progressively as the carboxyl tail was truncated from 52 to 8 amino acids. Mutation of all of the serine and threonine residues in the carboxyl tail to alanine also resulted in markedly impaired receptor internalization but did not affect signaling or chemotaxis. We conclude that the membrane-proximal portion of the cytoplasmic carboxyl tail of CCR2B is critically involved in chemotaxis and signal transduction, but neither phosphorylation of carboxyl serines or threonines nor internalization of the receptor is required for robust chemotaxis.
Footnotes
-
↵* This work was supported in part by National Institutes of Health Grant HL52773 (to I. F. C.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵¶ To whom correspondence should be addressed: Gladstone Institute of Cardiovascular Disease, P.O. Box 419100, San Francisco, CA 94141-9100. Tel.: 415-826-7500; Fax: 415-285-5632; E-mail:izzy_charo.gicd{at}quickmail.ucsf.edu.
-
↵1 The abbreviations used are: MCP-1, monocyte chemoattractant protein 1; CCR, C-C chemokine receptor; HEK, human embryo kidney; FACS, fluorescence-activated cell sorter; PBS, phosphate-buffered saline; BSA, bovine serum albumin; ERK, extracellular signal-regulated kinase.
-
- Received March 18, 1997.
- Revision received July 22, 1997.
