Binding of R5- and X4-tropic HIV-1 gp120 to T-cell lines expressing the corresponding chemokine receptor stimulate phosphorylation of SAPK/JNK.

CD4⁻/CXCR4⁺ Jurkat cells (A), CD4⁻/CCR5⁺ Jurkat cells (B), or CD4⁻/CCR5⁺ CEM cells (C) were incubated with medium alone or in the presence of either 10 μg/mL gp120 (R5- or X4-tropic), MIP-1β (100 nM), SDF-1α (100 nM), anisomycin (500 ng/mL), gp120-CD4s complexes (molar ratio 1:20), or PMA (1 μM) for the indicated time period at 37°C. Cells were then lysed, proteins were separated by SDS-PAGE, and SAPK/JNK tyrosine phosphorylation was assessed. The immunoblot was stripped and reprobed with anti-JNK serum to verify equal loading and efficiency of protein transfer.