Amino-terminally modified RANTES analogues demonstrate differential effects on RANTES receptors

Modification of the amino terminus of regulated on activated normal T-cell expressed (RANTES) has been shown to have a significant effect on biologica l activity and produces proteins with antagonist properties. Two amino-term inally modified RANTES proteins, Met-RANTES and aminooxypentane-RANTES (AOP -RANTES), exhibit differential inhibitory properties on both monocyte and e osinophil chemotaxis, We have investigated their binding properties as well as their ability to activate the RANTES receptors CCR1, CCR3, and CCR5 in cell lines overexpressing these receptors, We show that Met-RANTES has weak activity in eliciting a calcium response in Chinese hamster ovary cells ex pressing CCR1, CCR3, and CCR5, whereas AOP-RANTES has full agonist activity on CCR5 but is less effective on CCR3 and CCR1, Their ability to induce ch emotaxis of the murine pre-B lymphoma cell line, L1.2, transfected with the same receptors, consolidates these results, Monocytes have detectable mRNA for CCR1, CCR2, CCR3, CCR4, and CCR5, and they respond to the ligands for these receptors in chemotaxis but not always in calcium mobilization, AOP-R ANTES does not induce calcium mobilization in circulating monocytes but is able to do so as these cells acquire the macrophage phenotype, which coinci des with a concomitant up-regulation of CCR5, We have also tested the abili ty of both modified proteins to induce chemotaxis of freshly isolated monoc ytes and eosinophils, Cells from most donors do not respond, but occasional ly cells from a particular donor do respond, particularly to AOP-RANTES, We therefore hypothesize that the occasional activity of AOP-RANTES to induce leukocyte chemotaxis is due to donor to donor variation of receptor expres sion.