Binding of gp120 JRFL to CCR5 does not involve activation of the ERK1/ERK2 MAPK pathway.

Cell surface expression of CCR5 on CD4⁻ CEM cells was analyzed by flow cytometry (A), after staining of the cells with an isotype-matched control MAb (i) or the anti-CCR5 182 MAb (ii). CD4⁻/CCR5⁺ CEM cells were preincubated in medium alone or in the presence of gp120 JRFL (10 μg/mL), MIP-1β (100 nM), recombinant soluble CD4 (10 μg/mL), or PMA (1 μM) for 1 hour on ice. Stimulations were then performed at 37°C for the indicated time periods before lysis (B). ERK1/ERK2 activation was assessed by using a polyclonal anti–active MAPK antibody. The immunoblot was then stripped and reblotted with ERK1/ERK2 antibodies detecting total level of these kinases.