gp120-induced MAPK activation in the transformed Jurkat T-cell line does not correlate with surface CD4 expression.
(A) Surface expression of CXCR4 and CD4 was analyzed on a FACScan using PE-conjugated monoclonal antibodies. The expression profiles of these 2 proteins in the 77-6.8 and E6.1 Jurkat clones (open histograms) are indicated. The respective immunoglobulin isotype controls (filled histograms) are shown. (B) The 77-6.8 and E6.1 Jurkat clones were either incubated in medium alone (−) or stimulated with gp120 (1 μg), SDF-1 (100 ng), an αCD3 mAb (0.25 μg) or an αCD4 mAb (1 μg). Total cell lysates (1 × 106 cell equivalents) were fractionated on an SDS gel. Membranes were immunoblotted with a polyclonal Ab that recognizes the dually phosphorylated forms of Erk1 and Erk2. The positions of phosphorylated Erk1 (p-Erk1) and Erk2 (p-Erk2) are indicated. Blots were reprobed with an αZAP-70 mAb to assure that expression of a T-cell–specific protein was equivalent in each lane. Results are representative of data obtained in 4 independent experiments.
