Activated H-Ras and Raf-1 suppress 4β1 integrin-mediated VCAM-1 ligand binding.

CHO-α4β1 cells were transiently transfected with cDNA encoding Tac-α5 or Tac-β1 alone or with a combination of Tac-α5 plus vector control DNA, H-Ras G12V, or RafBxB. After 48 hours, cells were analyzed for Tac expression and soluble VCAM-Ig binding by 2-color flow cytometry. 7 Ig-domain sVCAM-Ig binding was evaluated in low Tac-expressing cells, designated Tac(−) (□), and high Tac expressing cells, designated Tac(+) (▪). Percentage inhibition of VCAM-Ig binding was calculated relative to cells transfected with Tac-α5 cDNA alone. Results are the means ± SEM of 3 separate experiments.