A CCR2-V64I polymorphism affects stability of CCR2A isoform.
OBJECTIVE
A valine to isoleucine substitution at position 64 of CCR2 (CCR2-64I) 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.


METHODS
We analysed the effect of the 64I 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-64I was significantly higher than that of CCR2A without the substitution. On the other hand, the 64I substitution did not affect levels of CCR2B expression. Pulse-chase experiments revealed that the 64I substitution increased the half-life of CCR2A in cells. When co-expressed with CCR5, CCR2A-64I 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.


CONCLUSIONS
These results suggest that CCR2A binds to CCR5 in the cytoplasm and down-modulates its surface expression. We propose that the increased ability of CCR2A-64I to down-modulate CCR5 expression might be a possible cause of a delay in HIV-1 disease progression in patients with this allele.
Nakayama
Emi E
EE
Research Institute for Microbial diseases, Osaka University, Osaka, Japan.
Tanaka
Yuetsu
Y
Nagai
Yoshiyuki
Y
Iwamoto
Aikichi
A
Shioda
Tatsuo
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D018450:Disease Progression; D015870:Gene Expression; D005818:Genetic Engineering; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1; D006801:Humans; D019169:Jurkat Cells; D007668:Kidney / Q000821:virology; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D054390:Receptors, CCR2; D019713:Receptors, CCR5 / Q000378:metabolism; D019707:Receptors, Chemokine / Q000235:genetics* / Q000378:metabolism; D029082:Sendai virus / Q000235:genetics; D013601:T-Lymphocytes / Q000821:virology; D020298:U937 Cells; D014616:Vaccinia virus / Q000235:genetics; D014774:Virulence
C515334:CCR2 protein, human; D054390:Receptors, CCR2; D019713:Receptors, CCR5; D019707:Receptors, Chemokine