Protein kinase C is an important signaling mediator associated with motility of intact sea urchin spermatozoa
Daniel White*,
Eve de Lamirande, and
Claude Gagnon
Urology Research Laboratory, Royal Victoria Hospital, McGill
University Health Center and Faculty of Medicine, McGill University,
Montréal, H3A 1A1, Canada
*
Author for correspondence (e-mail:
dan7white{at}yahoo.ca)
Accepted for publication 4 September 2007.
Abstract:
Numerous kinases and phosphatases are most likely implicated in sperm
motility initiation and maintenance. Data on these signaling molecules were
mostly obtained from studies conducted on in vitro
demembranated–reactivated sperm models but are not necessarily
representative of the in vivo situation. We therefore investigated
the effect of a variety of cell-permeable chemicals, mostly kinase inhibitors,
on the motility initiation and maintenance of intact sea urchin spermatozoa.
Among the 20 substances tested, the protein kinase C (PKC) inhibitor
chelerythrine was the most potent, arresting motility at concentrations
starting from 1.5–2 µmol l–1. Motility was also
inhibited by two other PKC inhibitors as well as staurosporine. Furthermore,
these inhibitors prevented the motility-associated increase in phosphorylation
of at least four PKC substrates. These phospho-PKC target proteins, as
assessed with an antibody specific to phosphorylated motifs of PKC substrates,
were found to be associated with the flagellum, either in the Triton X-100
soluble portion or the axoneme (Triton X-100 insoluble). A phosphorylated
PKC-like enzyme was also detected by immunoblotting in the flagellum, as well
as a significant 50 kDa PKC cleavage product. Taken together, the data
strongly indicate for the first time that, in vivo, which means on
intact spermatozoa, PKC is a key signaling mediator associated with the
maintenance of sea urchin sperm motility.
Key Words: sperm motility • kinase inhibitors • protein kinase C • protein kinase M • protein phosphorylation • axoneme • sea urchin • Lytechinus pictus
