title: Roles of cAMP in regulating microtubule sliding and flagellar bending in demembranated hamster spermatozoa.
abstract: To understand the mechanism regulating spermatozoa motility, it is important to investigate the mechanism regulating the conversion of microtubule sliding into flagellar bending. Therefore, we analyzed microtubule sliding and its conversion into flagellar bending using a demembranated spermatozoa model in which microtubule sliding and flagellar bending could be analyzed separately by treating the demembranated spermatozoa with and without dithiothreitol, respectively. Using this model, we examined the roles of cAMP and its target molecules in regulating flagellar bending and microtubule sliding. Although flagellar bending did not occur in the absence of cAMP, microtubule extrusion occurred without it, suggesting that cAMP is necessary for the conversion of microtubule sliding into flagellar bending, but not for microtubule sliding itself. The target of cAMP for regulating flagellar bending was not cAMP-dependent protein kinase (PKA), since flagellar bending was still observed in the spermatozoa treated with a PKA-specific inhibitor. Alternatively, the Epac/Rap pathway may be the target. Epac2 and Rap2 were detected in hamster spermatozoa using immunoblotting. Since Rap2 is a GTPase, we investigated the flagellar bending of demembranated spermatozoa treated with GTPgammaS. The treatment markedly increased the beat frequency and bending rate. These results suggest that cAMP activates the Epac/Rap pathway to regulate the conversion of microtubule sliding into flagellar bending.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Shinryoiki-Seimei, Building 302, Kashiwa City, Chiba 277-8562, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kinukawa
authors.forename: Shoji
authors.initials: S
authors.lastname: Oda
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Shirakura
authors.forename: Masaki
authors.initials: M
authors.lastname: Okabe
authors.forename: Junko
authors.initials: J
authors.lastname: Ohmuro
authors.forename: Shoji A
authors.initials: SA
authors.lastname: Baba
authors.forename: Masao
authors.initials: M
authors.lastname: Nagata
authors.forename: Fugaku
authors.initials: F
authors.lastname: Aoki
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002465:Cell Movement; D006224:Cricetinae; D000242:Cyclic AMP / Q000502:physiology*; D005407:Flagella / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D008297:Male; D008870:Microtubules / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology*; D020668:rap GTP-Binding Proteins / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D000242:Cyclic AMP; D020668:rap GTP-Binding Proteins