Natural proteolytic processing of hemofiltrate CC chemokine 1 generates a potent CC chemokine receptor (CCR)1 and CCR5 agonist with anti-HIV properties.
Bottom Line: Our results indicate that HCC-1 represents a nonfunctional precursor that can be rapidly converted to the active chemokine by proteolytic processing.This process represents an additional mechanism by which tumor cells might generate chemoattractant molecules and recruit inflammatory cells.It might also affect HIV-1 replication in infected individuals and play an important role in AIDS pathogenesis.
Affiliation: Euroscreen S.A., B-1070 Brussels, Belgium.
Hemofiltrate CC chemokine (HCC)-1 is a recently described human chemokine that is constitutively expressed in numerous tissues and is present at high concentrations in normal plasma. Using a cell line expressing CC chemokine receptor (CCR)5 as a bioassay, we isolated from human hemofiltrate an HCC-1 variant lacking the first eight amino acids. HCC-1[9-74] was a potent agonist of CCR1, CCR3, and CCR5 and promoted calcium flux and chemotaxis of T lymphoblasts, monocytes, and eosinophils. It also blocked entry of HIV-1 strains using CCR5 as coreceptor. Limited tryptic digestion of HCC-1 generated the active variant. Conditioned media from several tumor cell lines activated HCC-1 with a high efficiency, and this activity could be inhibited by serine protease inhibitors. Our results indicate that HCC-1 represents a nonfunctional precursor that can be rapidly converted to the active chemokine by proteolytic processing. This process represents an additional mechanism by which tumor cells might generate chemoattractant molecules and recruit inflammatory cells. It might also affect HIV-1 replication in infected individuals and play an important role in AIDS pathogenesis.
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Mentions: Given the role of CCR5 as the major coreceptor for macrophage-tropic strains of HIV 11121314 and the role ascribed to chemokines acting on CCR5 as entry inhibitors 15, we investigated the antiviral activity of HCC-1[9–74] in an infection inhibition assay. Both HCC-1[9–74] and RANTES inhibited infection by the macrophage-tropic strain YU2 (Fig. 4 a). RANTES reduced YU2 infection of P4-CCR5 cells by >95% at 3.2 μM and by 50% at 1.3 μM. HCC-1[9–74] was slightly more efficient, blocking YU2 infection by 50% at 0.5 μM. Similar results were obtained using the macrophage-tropic strain JR-CSF (not shown). No inhibitory effect on YU2 infection was observed with full-length HCC-1. None of the three chemokines inhibited the T-tropic strain NL4-3 (Fig. 4 b). In agreement with previously published results 33, RANTES enhanced infectivity of NL4-3 by ∼50% at concentrations over 0.6 μM. In contrast, no enhancing effect on infectivity was observed with HCC-1[9–74] (Fig. 4 b). We also tested whether HCC-1[9–74] could inhibit HIV-1 replication in human PBMCs. As shown in Fig. 4c and Fig. d, replication of the macrophage-tropic strain JR-CSF was blocked significantly by HCC-1[9–74] and RANTES at concentrations of 125 nM, whereas concentrations of 625 nM were necessary for the YU2 strain. No inhibition of NL4-3 replication was observed, and full size HCC-1 was ineffective for all strains (not shown).