A CCR2-V641 polymorphism affects stability of CCR2A isoform

Objective: A valine to isoleucine substitution at position 64 of CCR2 (CCR2-64l) is associated with a delay in progression to AIDS in HIV-1-infected individuals. The aim of the present study is to elucidate the molecular mechanism underlying the effect of this allele. Design: We analysed the effect of the 641 substitution on levels of expression of CCR2A and CCR2B, two CCR2 isoforms produced by alternative splicing. Methods: Sendai virus vector was used to express CCR2 molecules. Results: While CCR2B trafficked well to the cell surface, CCR2A, which differs from CCR2B only by the sequence of its C-terminal cytoplasmic tail, was detected predominantly in the cytoplasm. The level of expression of CCR2A-64l was significantly higher than that of CCR2A without the substitution. On the other hand, the 641 substitution did not affect levels of CCR2B expression. Pulse-chase experiments revealed that the 641 substitution increased the half-life of CCR2A in cells. When co-expressed with CCR5, CCR2A-64l interfered more severely with cell surface expression of CCR5 than did wild-type CCR2A. Furthermore, immunoprecipitation experiments showed that CCR2A co-precipitated with an immature form of CCR5. Conclusion: These results suggest that CCR2A hinds to CCR5 in the cytoplasm and down-modulates its surface expression. We propose that the increased ability of CCR2A-64l to down-modulate CCR5 expression might be a possible cause of a delay in HIV-1 disease progression in patients with this allele. (C) 2004 Lippincott Williams Wilkins.