REGULATION OF PROTEIN-TYROSINE PHOSPHORYLATION DURING BOVINE SPERM CAPACITATION BY A CYCLIC ADENOSINE 3',5'-MONOPHOSPHATE-DEPENDENT PATHWAY

Citation
Hl. Galantinohomer et al., REGULATION OF PROTEIN-TYROSINE PHOSPHORYLATION DURING BOVINE SPERM CAPACITATION BY A CYCLIC ADENOSINE 3',5'-MONOPHOSPHATE-DEPENDENT PATHWAY, Biology of reproduction, 56(3), 1997, pp. 707-719
Citations number
65
Categorie Soggetti
Reproductive Biology
Journal title
ISSN journal
00063363
Volume
56
Issue
3
Year of publication
1997
Pages
707 - 719
Database
ISI
SICI code
0006-3363(1997)56:3<707:ROPPDB>2.0.ZU;2-6
Abstract
Mammalian sperm capacitation, defined as an obligatory maturational pr ocess leading to the development of the fertilization-competent state, results from a poorly understood series of morphological and molecula r events. We report here that ejaculated bovine sperm, incubated under conditions that support capacitation in vitro, display a reproducible pattern of protein tyrosine phosphorylations that are regulated by a cAMP-dependent pathway. The appearance of these tyrosine phosphorylate d proteins correlated temporally with the time course of capacitation induced by heparin, and these phosphorylations displayed a similar hep arin concentration dependence. Glucose, which inhibits capacitation, i nhibited these protein tyrosine phosphorylations in media containing h eparin. The biologically active cAMP analogues (dibutyryl cAMP [db-cAM P], 8-bromo cAMP, Sp-cAMPS) and the phosphodiesterase inhibitor 3-isob utyl-1-methylxanthine (IBMX) induced the same protein tyrosine phospho rylation patterns as seen with heparin. Moreover, these cAMP agonists could overcome the inhibition of the heparin-induced tyrosine phosphor ylations by glucose. In contrast, Rp-adenosine-3',5'-cyclic monophosph orothioate (Rp-cAMPS), a protein kinase A (PK-A) antagonist, blocked t he capacitation-associated increases in protein tyrosine phosphorylati on. This cAMP regulation of the protein tyrosine phosphorylation patte rn is mediated by PK-A since o)ethyl]-5-isoquinolinesulfonamide-dehydr ochloride (H89), another inhibitor of PK-A, inhibited the heparin-indu ced protein tyrosine phosphorylation pattern in a concentration-depend ent manner in either the absence or presence of db-cAMP, IBMX, and glu cose. These data support a model for sperm capacitation that includes protein tyrosine phosphorylation as an important regulatory pathway, a nd a role for cAMP/PK-A in the regulation of this pathway leading to c apacitation. These studies are the first to report a unique interrelat ionship between tyrosine kinase/ phosphatase and cAMP signaling pathwa ys at the level of PK-A in bovine sperm capacitation.