Recombinant calcium transport inhibitor: role in capacitation and emergent biotechnological tool?

CESARI A

Ciudad Autónoma de Buenos Aires

Jornada; Jornadas de la Sociedad Argentina de Andrología (SAA): Oocitos y Espermatozoides: Otras miradas para el estudio de la fecundación; 2017

Sociedad Argentina de Andrología (SAA):

We studied the mechanism by which BSA induces intracellular calcium increase in mouse sperm, its regulation by a low molecular weight protein from male tract -Serine protease inhibitor Kazal 3 (SPINK3)- and the influence of this protein on downstream events of the capacitation signaling cascade. The addition of BSA produced an intracellular Ca2+ increase after 20 seconds; a decrease was caused by SPINK3 and two different antagonists of store-operated calcium (SOC) channels (YM-58483 and SKF-96365), shown both in the percentage of responding cells and in the intensity of the calcium signal. Moreover, SPINK3 and the same antagonists decreased the proportion of cells showing tyrosine phosphorylated proteins upon BSA stimulus. Consequently, SPINK3 reduced acrosomal reaction percentages but its effect was specifically targeted at intracellular Ca2+ increase linked to capacitation rather than at acrosome reaction itself, as shown by the evaluation of AR after SPINK3 addition at the beginning or at the end of capacitation. The co- occurrence of SPINK3 and an extracellular domain of ORAI-1 over the acrosome and the midpiece of spermatozoa suggests some kind of interaction between both proteins. We propose SPINK3 as a protein that down-regulates intracellular calcium uptake, probably through interaction with a SOC channel during early stages of capacitation stimulated by BSA. While SPINK3 remains attached to spermatozoa, it avoids premature capacitation and subsequent acrosome reaction, until it detaches from sperm surface in response to oviductal physiological signals.