Activation of the p44/42 MAP kinase by SDF-1α is not required for the up-regulation of VLA-4–mediated cell adhesion.

(A) NCI-H929 cells were pre-incubated in the absence or in the presence of PD98059 before the addition of SDF-1α (100 ng/mL) for the indicated times. Cells were solubilized and subjected to immunoblotting using an anti-phospho–p44/42 antibody. After stripping and blocking, the same blots were reprobed with anti-p44/42 antibodies to check for total p44/42 protein content. Blots were developed by a chemiluminescence reaction and exposed to radiographic film. (B) Cells were labeled with BCECF-AM and treated for 30 minutes in adhesion medium without (Nil) or with PD98059 (50 μM). SDF-1α (100 ng/mL, 1 minute) was added, and cells were allowed to adhere to FN-H89– or sVCAM-1–coated wells for 2 minutes. Adhesions were quantified in a fluorescence analyzer. Adhesion data represent the mean ± SD of triplicate samples from one representative result of 4 independent experiments.