GRK2 and GRK3 modulation of MCP-1 signaling mediated by the CCR2B receptor. (A) HEK293 cells were transiently transfected with pcDNA3 alone; with pcDNACCR2B with pcDNA3, pcDNAGRK2, or pCMVGRK3; or with pcDNACCR2B-IX and pcDNA3 or pcDNAGRK2 as indicated. Calcium was determined as described in the legend of Fig. 1. Data are given as a percentage of maximal MCP-1-induced response. Arrows indicate the time of MCP-1 addition. (B) Western blot analysis of the expression level of GRK2 and GRK3 in transiently cotransfected HEK293 cells. Recombinant GRK2 (lane 1) and lysates from CCR2B, CCR2B + GRK2, and CCR2B + GRK3 cells (lanes 2–4, respectively) were resolved by SDS/PAGE and transferred, and blots were developed simultaneously with anti-GRK2 AB9 and anti-GRK3 antibodies. (C) HEK293 cells cotransfected with the CCR2B receptor alone (lane 2) or with either GRK2 (lane 3) or GRK3 (lane 4) were lysed, and the cytosolic kinase activity was determined with rhodopsin as substrate. Recombinant GRK2 (10 nM) was used as a control (lane 1). A representative autoradiogram is shown. Results in all panels are representative of two independent experiments.