Identification of the functional domains in an orphan G protein-coupled receptor, GPR1, which acts as a coreceptor for the brain-derived cell tropism of HIV-1, HIV-2, and SIV

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【Aim】 Pericytes located around the brain blood vessels constitute the blood-brain barrier with endothelial cells. The infection of the cells with human immunodeficiency virus type-1 (HIV-1) is thought to be a causative factor to develop acquired immune deficiency syndrome (AIDS)-related encephalitis. An orphan G protein-coupled receptor, GPR1, acts as a coreceptor for HIV-1 strains which infect the brain vessels-derived pericytes. The aim of this study was to identify the important domain of GPR1 for its coreceptor activity. 【Methods】 (1) The amino-terminal domain (NTR) and three extracellular loops (ECLs) interact with HIV-1. Therefore, the DNA fragments of GPR1 coding four extracellular domains were prepared by polymerase chain reaction (PCR) and recombined with CCR5 which acts as a coreceptor for macrophage tropic HIV-1 strains. (2) Some nucleotide changes were introduced into GPR1 gene by PCR to make the amino acid deletion or substitution mutants of the NTR. (3) The chimeras betwe … More en GPR1 and CCR5 and the GPR1 mutants of the NTR were introduced into a glioma-derived cell line NP-2/CD4 which is strictly resistant to the infection with HIV-1, HIV type-2 (HIV-2), and simian immunodeficiency virus (SIV) even though the expression of CD4 is detected. Susceptibility of the established cells to various HIV-1, HIV-2, and SIV strains were detected. 【Results】 (1) All of ELC chimeras lost its coreceptor activities. (2) The NTR chimeras acted as the coreceptor. (3) The amino acid mutant of GPR1 in which the first tyrosine in the NTR was substituted with alanine lost the coreceptor function. On the other hand, the substitutions of the second, the third, and the fourth tyrosine with alanine had no effects on the function. (4) The deletion of the amino-terminal 11 amino acids of the NTR had no effects on the coreceptor activity of GPR1. 【Conclusion】 The NTR is important for the coreceptor function of GPR1. The region containing four tyrosine residues in the NTR is important for its coreceptor functions. These results are available to know the mechanisms of the HIV-1 infection to the brain vessels pericytes and applicable to the development of anti-HIV-1 drugs. Less