Regulation of microtubule sliding by a 36-kDa phosphoprotein in hamster sperm flagella.
Cyclic AMP has been shown essential for activation of sperm motility. When immotile hamster caudal epididymal spermatozoa were suspended in a Ca2+-deficient solution, they showed a sluggish motility. Spermatozoa were demembranated and transferred to an ATP-containing reactivation solution. Demembranated spermatozoa did not exhibit reactivated flagellar movement unless cAMP was added. Conversely, when the immotile epididymal spermatozoa were suspended in a Ca2+-containing solution, they were immediately activated to display a vigorous motility; demembranated spermatozoa also exhibited reactivated flagellar movement in the reactivation solution without cAMP. Further investigation of microtubule sliding properties revealed that the effects of Ca2+ on live spermatozoa were identical with the effects of cAMP on demembranated spermatozoa both in microtubule sliding velocity and sliding disintegration pattern. Moreover, a 36-kDa flagellar protein was found to be phosphorylated in a cAMP-dependent manner and coupled to the motility activation. A polyclonal antibody against this protein was developed and showed specific immunolocalization and significant inhibitory effects on microtubule sliding disintegration. These results indicate that extracellular Ca2+ owes its effect to triggering intracellular cAMP production, and cAMP-dependent phosphorylation of a 36-kDa phosphoprotein activates hamster sperm motility through regulation of microtubule sliding properties.
Si
Y
Y
Department of Biology, College of Arts and Sciences, The University of Tokyo, Japan. ysi@nimbus.temple.edu
Okuno
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D008870:Microtubules / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism*; D013081:Sperm Motility; D013082:Sperm Tail / Q000378:metabolism* / Q000502:physiology
D010750:Phosphoproteins; D000242:Cyclic AMP; D002118:Calcium