| Title: | Constitutive activation of CCR5 and CCR2 induced by conformational changes in the conserved TXP motif in transmembrane helix 2 |
| Author(s): | Alvarez Arias D; Navenot JM; Zhang WB; Broach J; Peiper SC; |
| Address: | "Department of Pathology, Medical College of Georgia, Augusta, Georgia 30912, USA" |
| ISSN/ISBN: | 0021-9258 (Print) 0021-9258 (Linking) |
| Abstract: | "CCR5 is a G protein-coupled receptor for RANTES, MIP-1alpha, MIP-1beta, and MCP-2 that functions as the front line coreceptor for human immunodeficiency virus type 1 infection. To elucidate the mechanism for CCR5 activation, this coreceptor was expressed in yeast coupled to the pheromone response pathway and a constitutively active mutant (CAM) was derived by random mutagenesis. Conversion of Thr-82 in the highly conserved TXP motif in transmembrane helix 2 to Pro, His, Tyr, Arg, or Lys conferred autonomous signaling activity in yeast and mammalian cells. This substitution also imparted constitutive signaling to CCR2 in yeast and mammalian cells, but not CCR1, CCR3, CCR4, CXCR2, or CXCR4. The CCR5-CAM, but not the CCR2-CAM had a reduction in ligand binding affinity. Whereas the amplitude of calcium mobilization induced by RANTES stimulation was lower in the CCR5-CAM than the wild-type (WT) receptor, MCP-1 induced a higher signal in the CCR2-CAM than in CCR2-WT. The chemotactic response of CCR5-CAM(T82P) to RANTES was similar to that of CCR5-WT, but CCR5-CAM(T82K) was dramatically decreased. The chemotactic response of CCR2-WT and CCR2-CAM(T94K) were similar. These findings extend insight into the role of the TXP motif in the mechanism for CCR5 signaling. CCR2, the receptor most closely genetically related to CCR5, shared a similar signaling mechanism, but other receptors containing the TXP motif did not. The expression of CCR5 and CCR2 in yeast and the availability of variants with autonomous signaling represent critical tools for characterizing receptor antagonists and developing approaches to block their role in human diseases" |
| Keywords: | "Amino Acid Motifs Animals CHO Cells Cell Movement Chemokine CCL5/metabolism Chemotaxis Cricetinae Dose-Response Relationship, Drug Gene Library Genes, Reporter Guanosine 5'-O-(3-Thiotriphosphate)/metabolism Humans Ligands Mutation Open Reading Frames Plas;" |
| Notes: | "MedlineAlvarez Arias, Diana Navenot, Jean-Marc Zhang, Wen-Bo Broach, James Peiper, Stephen C eng R01 AI41346/AI/NIAID NIH HHS/ Research Support, U.S. Gov't, P.H.S. 2003/07/03 J Biol Chem. 2003 Sep 19; 278(38):36513-21. doi: 10.1074/jbc.M303739200. Epub 2003 Jul 1" |
