The sCD38-induced tyrosine phosphorylation of sperm protein is mediated by ERK pathway.

(A) CD31 activation of human sperm by sCD38 stimulated tyrosine phosphorylation of sperm protein mediated by ERK1/2. Human sperm were incubated in capacitating medium supplemented with sCD38 as time-dependent manner. Following incubation, sperm were solubilized in lysis buffer and prepared for immunoblotting with anti-phospho-ERK1/2 and anti-phospho-p38. Total ERK and p38 was detected as a control for sample loading. (B) Sperm were preincubated with inhibitors (50 μM SU6656, 3 μM FTI-277 and 50 μM PD98059) for 30 min, then treated with (+) or without (-) 600 ng/ml sCD38 for 0 or 60 minutes, sperm proteins were immunoblotted with the anti-phospho-ERK1/2 antibody and total ERK1/2.