Effects of βarr2 siRNA on CXCR4¹⁰¹³-mediated ERK1/2 activation. A0.01 T cells expressing CXCR4^wt or CXCR4¹⁰¹³ were nucleoporated with siRNA targeting βarr2 or control siRNA (NT). At 48 hours after transfection, cells were stimulated or not with 10 nM CXCL12 for 15 (B,C) or 2 minutes (C). Cell lysates were prepared, and 20 μg of proteins was used to visualize expression of βarr2 (A) and ERK1/2 phosphorylation (B,C). Representative results (n = 3) are shown in panels A and B. (C) ERK1/2 phosphorylation is expressed as a ratio of activated ERK1/2 over total ERK2, and ratios with βarr2 siRNA are compared with those from cells with control siRNA (arbitrarily set at 1). Results are means plus or minus SEM.