Effects of CC chemokine receptor 5 (CCR5) inhibitors on the dynamics of CCR5 and CC-chemokine-CCR5 interactions

Abstract

Background: This study aimed to examine how CC chemokine receptor 5 (CCR5) inhibitors (aplaviroc [APL], TAK779 and maraviroc [MVC]) interact with CCR5 and affect its dynamics and physiological CC-chemokine-CCR5 interactions.

Methods: A yellow fluorescent protein (YFP)-tagged CCR5-expressing U373-MAGI cell line was generated and a stable CCR5-expressing clonal population, (YFP)CCR5-UM16, was prepared. (YFP)CCR5-UM16 cells were exposed to RANTES, macrophage inflammatory protein (MIP)-1alpha or MIP-1beta (all 100 ng/ml) with or without CCR5 inhibitors and (YFP)CCR5 internalization was visualized with real-time by laser scanning confocal microscopy. The mobility of (YFP)CCR5 was also examined in the presence of CCR5 inhibitors with fluorescence recovery after photobleaching (FRAP) imaging.

Results: Following the addition of each CC chemokine, intracellular fluorescence intensity increased whereas membranous fluorescence decreased, signifying (YFP)CCR5 internalization. All three CCR5 inhibitors failed to induce (YFP)CCR5 internalization. All three CCR5 inhibitors blocked the CC-chemokine-induced internalization at a high concentration of 1 microM; however, the ratio of APL concentration that blocked RANTES-induced internalization by 50% over APL concentration that blocked HIV type-1 (HIV-1) replication by 50% was 16.4, indicating that APL permits CC-chemokine-induced internalization to a much greater extent compared with TAK779 and MVC, having ratios of 1.1 and 0.9, respectively. The examination of (YFP)CCR5 mobility with FRAP imaging revealed that (YFP)CCR5 continuously underwent rapid redistribution, which none of the three inhibitors blocked.

Conclusions: The finding that APL moderately blocked the RANTES-triggered (YFP)CCR5 internalization despite the highly potent anti-HIV-1 activity of APL strongly suggests that development of CCR5 inhibitors, which do not overly inhibit physiological CC-chemokine-CCR5 interactions, is practically feasible.

Figure 1

CCR5 expression and RANTES-induced ^YFP CCR5 internalization in ^YFPCCR5-UM16 cells

Figure 2

^YFPCCR5 internalization and calcium mobilization induced by RANTES in ^YFPCCR5-UM16 cells

Figure 3

Quantification of CC-chemokine-induced ^YFPCCR5 internalization and the effects of CCR5 inhibitors on this internalization

Figure 4

Influences of CCR5 inhibitors against the redistribution of ^YFPCCR5