PRESENCE OF PROTEIN PHOSPHATASE TYPE-1 AND ITS INVOLVEMENT IN TEMPERATURE-DEPENDENT FLAGELLAR MOVEMENT OF FOWL SPERMATOZOA

Even in the presence of ATP, the motility of demembranated fowl spermatozoa was negligible at the avian body temperature of 40 degrees C. Motility could be restored by the addition of calyculin A, okadaic acid, specific inhibitors of phosphatase type 1 (PP1) and PP-2A, and inhibitor 1 or inhibitor 2, which are specific inhibitors of protein phosphatase type 1 (PP1). Demembranated spermatozoa, stimulated by calyculin A or okadaic acid, lost their motility following the addition of 1 mM CaCl2, but this was restored gradually by the stepwise addition of EGTA. Immunoblotting of sperm extract using an antibody to PP1 revealed a major cross-reacting protein of 36-37 kDa, which corresponded to the molecular weight of the known catalytic subunit of PP1. These results suggest that PP1 present in the fowl sperm axoneme may be involved in the inhibition of fowl sperm motility at 40 degrees C via Ca2+-dependent regulatory systems.