Effect of RAM.1 on adhesion of CHO-GPIb/IX cells containing progressive 11 amino acid deletions in the 535-590 intracellular domain of GPIbα.

CHO cells stably expressing GPIbβ/IX were transfected with GPIbα containing the deletions Δ535-568, Δ569-610, Δ535-545, Δ546-556, Δ557-568, Δ569-579, and Δ580-590. The cells were preincubated for 10 minutes with 10 μg/mL RAM.1 (■) or control rat IgG1 (▪) and perfused through microcapillaries coated with bovine VWF at a shear rate of 150 s^-1 for 10 minutes. Adherent cells were counted off-line at 10 minutes and results are expressed as the mean ± SEM of 4 separate experiments; *P < .05. Cells carrying mutant GPIbα displayed comparable levels of adhesion in the presence or absence of RAM.1, except those containing Δ569-579, which behaved like control cells and exhibited approximately 50% lower adhesion in the presence of RAM.1.