Human chemokine receptors CCR5, CCR3 and CCR2B share common polarity motif in the first extracellular loop with other human G‐protein coupled receptors

Abstract

Chemokine receptors (CRs) are 7-helix membrane proteins from the family of G-protein coupled receptors (GPCRs). A few human CRs act as cofactors for macrophage±tropic (M-tropic) human immunodeficiency virus type-1 (HIV-1) entry into cells, while others do not. In this study, we describe an application of molecular modeling techniques to delineate common molecular determinants that might be related to coreceptor activity, and the use of the data to identify other GPCRs as putative cofactors for M-tropic HIV-1 entry. Subsequently, the results were confirmed by an experimental approach. The sequences of extracellular domains (ECDs) of CRs were employed in a compatibility search against a database of environmental profiles derived for proteins with known spatial structure. The best-scoring sequence±profile alignments obtained for each ECD were compared in pairs to check for common patterns in residue environments, and consensus sequence±profile fits for ECDs were also derived. Similar hydrophobicity motifs were found in the first extracellular loops of the CRs CCR5, CCR3, and CCR2B, and are all used by M-tropic HIV-1 for cell entry. In contrast, other CRs did not reveal common motifs. However, the same environmental pattern was also delineated in the first extracellular loop of some human GPCRs showing either high (group 1) or low (group 2) degree of similarity of their polarity patterns with those in HIV-1 coreceptors. To address the question of whether the delineated molecular determinant plays a critical role in the receptor±virus binding, three of the identified GPCRs, bradykinin receptor (BRB2) and G-protein receptor (GPR)-CY6 from group 1, and GPR8 from group 2, were cloned and transfected into HeLa-CD4 cells, which are nonpermissive to M-tropic HIV-1 infection. We demonstrate that, similar to CCR5, the two selected GPCRs from group 1 were capable of mediating M-tropic HIV-1 entry, whereas GPR8 from group 2 did not serve as HIV-1 coreceptor. The potential biological significance of the identified structural motif shared by the human CCR5, CCR3, CCR2B and other GPCRs is discussed.

The role of chemokines in vertebrate physiology and disease: a concise review

“…CD4 is considered the primary receptor for HIV, where gp 120 and gp 41 (envelope proteins) mediate virus binding to the target cell membrane followed by consequent interaction with chemokine receptors CCR3 and 5 CCR2B or CXCR4 leading to merging of the host cell membrane and HIV membrane [63][64][65][66][67][68][69][70][71][72]. Other chemokines, CCR2, 3, 8 and 9, STRL33, Gpr15, Gpr1, APJ, ChemR23 and CX3CR1, are also used by HIV for host cell entry during in vitro infection [64,[73][74][75][76].…”

CCR6/CCL20 chemokine axis in human immunodeficiency virus immunity and pathogenesis

“…Using CCR6-CCR5 chimeras in which the ECDs of CCR5 were substituted for CCR6 ECDs in various combinations, one group found that replacement of one or more ECDs prevents the efficient binding of CCR6 to its CCL20 ligand [25]. Because HIV uses selected ECDs of CCR5 to gain cell entry [26,27], it is possible that CCR6 may permit entry in a similar manner. It is likely not dependent solely on static molecular structures, but requires a complex and subtle conformation of multiple aspects of the three-dimensional receptor structure.…”

HIV-1 Envelope Evolution and Vaccine Efficacy

“…Although several other chemokine receptors have been identified as potential entry factors [42][43][44][45][46], only CCR5 and CXCR4 appear to be important for infection by most clinical isolates of HIV-1 [47,48]. This observation is reflected in the current nomenclature for HIV-1 coreceptor use [49]; R5 for viruses that only use CCR5, X4 for viruses that only use CXCR4, and R5X4 for viruses that can use both receptors.…”