CDB15:0000192 CCL13 — CCR5
Experimentally validated in Human; Orthology-inferred in Frog, Zebrafish, Chicken, Macaque, Pig, Dog, Cow, Chimp, Horse, Marmoset
Title
Journal:; Year Published:
Abstract
CCR5 binds multiple CC-chemokines: MCP-3 acts as a natural antagonist.
Blood, 1999; PubMed, Homo sapiens CCL13 — Homo sapiens CCR5
ABSTRACT: CCR5 was first characterized as a receptor for MIP-1alpha, MIP-1beta, and RANTES, and was rapidly shown to be the main coreceptor for M-tropic human immunodeficiency virus (HIV)-1 strains and simian immunodeficiency virus (SIV). Chemokines constitute a rapidly growing family of proteins and receptor-chemokine interactions are known to be promiscuous and redundant. We have therefore tested whether other CC-chemokines could bind to and activate CCR5. All CC-chemokines currently available were tested for their ability to compete with [(125)I]-MIP-1beta binding on a stable cell line expressing recombinant CCR5, and/or to induce a functional response in these cells. We found that in addition to MIP-1beta, MIP-1alpha, and RANTES, five other CC-chemokines could compete for [(125)I]-MIP-1beta binding: MCP-2, MCP-3, MCP-4, MCP-1, and eotaxin binding was characterized by IC(50) values of 0.22, 2.14, 5.89, 29.9, and 21.7 nmol/L, respectively. Among these ligands, MCP-3 had the remarkable property of binding CCR5 with high affinity without eliciting a functional response, MCP-3 could also inhibit the activation of CCR5 by MIP-1beta and may therefore be considered as a natural antagonist for CCR5. It was unable to induce significant endocytosis of the receptor. Chemokines that could compete with high affinity for MIP-1beta binding could also compete for monomeric gp120 binding, although with variable potencies; maximal gp120 binding inhibition was 80% for MCP-2, but only 30% for MIP-1beta. MCP-3 could compete efficiently for gp120 binding but was, however, found to be a weak inhibitor of HIV infection, probably as a consequence of its inability to downregulate the receptor.
CCR5 has an expanded ligand-binding repertoire and is the primary receptor used by MCP-2 on activated T cells.
Cellular immunology, 1998; PubMed, Homo sapiens CCL13 — Homo sapiens CCR5
ABSTRACT: CCR5 is a chemokine receptor expressed by T cells and macrophages, which also functions as the principal coreceptor for macrophage (M)-tropic HIV-1 strains to enter the host cells. In this study, we aim to better understand the ligand-binding profiles of CCR5 and the chemokine-receptor usage on leukocyte cells. We found that MCP-2 could bind to CCR5 transfectants with high affinity and cross-compete effectively with RANTES, MIP-1alpha, and MIP-1beta. MCP-2 is a true agonist for CCR5, eliciting a robust chemotactic response in CCR5 transfectants similar to that of the three known CCR5 ligands and exhibiting cross-desensitization with RANTES in the Ca2+ flux response. MCP-4 also bound to CCR5 with high affinity and was efficiently displaced by other CCR5 ligands. However, MCP-4 only partially displaced the binding of radiolabeled MIP-1alpha and caused a chemotactic response only at high concentrations. Furthermore, MCP-2 inhibited the binding of the M-tropic HIV-1 gp120 envelope glycoprotein to CCR5 and HIV-1 infection of peripheral blood mononuclear cells. More importantly, we found that MCP-2 could bind and elicit chemotaxis in CD3-activated and IL-2-maintained T cells, and most of these functions could be specifically inhibited by the anti-CCR5 mAb 2D7, whereas the responses mediated by MIP-1alpha or MCP-4 were only partially inhibited by 2D7. Thus, although MCP-2 can bind to and signal through CCR1, CCR2b, and CCR5, among which both CCR2 and CCR5 are expressed at high levels on activated T cells, it appears to preferably utilize CCR5 on these cells. In contrast, MIP-1alpha and MCP-4 seem to activate multiple receptors on the same cells.