Cdc42 activity is necessary for the interplay between cAMP/PKA pathway and CatSper function

ROMAROWSKI A; DALOTTO-MORENO T; SCHIAVI-EHRENHAUS LJ; BUFFONE MG; LUQUE GM; GILIO N; JABLOÑSKI M; KRAPF D; STIVAL C; BALESTRINI PA; KRAPF D

Mar del Plata

Congreso; Reunión Anual de Sociedades de Biociencia. SAIC, SAFE, SAB, SAP, AACYTAL.; 2019

Sperm acquire the ability to fertilize in the female genital tract in a process called capacitation. During capacitation, sperm undergo changes in the motility pattern called hyperactivation, which depends on Ca2+ transport by the sperm-specific Ca2+ channel CatSper. CatSper is essential for fertilization and therefore, it is subjected to a complex regulation that is not fully understood. Recent reports found that mouse CatSper is upregulated by cAMP-dependent activation of protein kinase A (PKA). From a molecular point of view, bicarbonate stimulation of the soluble adenylyl cyclase (sAC) leads to an increase in cAMP, PKA activity and tyrosine phosphorylation of sperm proteins. It remains incompletely understood if PKA itself phosphorylates CatSper or if its activation relays on other intermediary events.By using super-resolution microscopy, we report that similar to CatSper, the small GTPase Cdc42 distribution in the principal piece is confined to four linear domains and this localization is disrupted in CatSper-null sperm. Cdc42 inhibition impaired CatSper opening, assessed by different approaches including analysis of downstream signaling events and membrane potential recordings. Consequently, Cdc42 inhibition abrogated the increase in intracellular Ca2+ and other Ca2+-associated events, resulting in a severe compromise of the sperm fertilizing potential: decreased percentage of sperm undergoing hyperactivation and in vitro fertilization. We also demonstrate that Cdc42 is essential for CatSper function by modulating cAMP production by sAC, providing a new regulatory mechanism for the upregulation of CatSper by the cAMP/PKA-dependent pathway. These results reveal a broad mechanistic insight into the regulation of Ca2+ in mammalian sperm, a matter of critical importance in male infertility as well as in contraception.