Activation of Ciona sperm motility: phosphorylation of dynein polypeptides and effects of a tyrosine kinase inhibitor

Abstract

A high molecular mass dynein ATPase polypeptide and a 18–20 kDa dynein light chain of Ciona sperm flagella are phosphorylated during in vivo activation of motility or in vitro activation of motility by incubation with cyclic AMP. A similar level of phosphorylation of these proteins is obtained by incubation of washed, demembranated spermatozoa with catalytic subunit of cyclic AMP-dependent protein kinase, under conditions where there is no activation of motility until a supernatant component is added. Therefore, phosphorylation of these dynein polypeptides is not sufficient for activation of motility. Activation of motility in vitro by incubation with cyclic AMP can be completely inhibited by a random copolymer of glutamate and tyrosine that inhibits tyrosine kinase activity. Under these conditions, much of the protein phosphorylation associated with activation of motility is also inhibited. These new results suggest that regulation of motility of these spermatozoa may involve a multicomponent kinase cascade rather than a simple phosphorylation of a protein ‘switch’ by the cyclic AMP-dependent kinase. A 53 kDa axonemal phosphoprotein band, identified as band M1, shows the strongest correlation with activation of motility in these experiments.