Participation of protein kinases and phosphatases in the progesterone‐induced acrosome reaction and calcium influx in human spermatozoa

Abstract

In human spermatozoa, protein kinases have a role in the acrosome reaction (AR) induced by a variety of stimuli. However, there is disagreement or a lack of information regarding the role of protein kinases and phosphatases in the progesterone (P)-induced increase in intracellular calcium concentration ([Ca ] ). In addition, there are no studies regarding the role of Ser/Thr and Tyr phosphatases and there are contradictory results regarding the role of Tyr kinases in the P-induced acrosome reaction. Here, we performed a simultaneous evaluation of the involvement of protein kinases and phosphatases in the P-induced acrosome reaction and in the P-induced calcium influx. Motile spermatozoa were capacitated for 18 h and different aliquots were allocated to treated or control groups and then evaluated for their ability to undergo the acrosome reaction and to increase [Ca ] in response to P. The acrosome reaction was evaluated using Pisum sativum agglutinin (PSA)-FITC, and [Ca ] was evaluated using fura 2AM. At all of the concentrations tested, PKA inhibitors significantly reduced the percentage of the P-induced acrosome reaction (p < 0.001). However, only the highest concentrations of PKA inhibitors reduced the P-induced calcium influx; lower concentrations of PKA inhibitors did not affect it. Similar results were apparent for PKC inhibitors and for tyrosine kinase inhibitors. None of the Ser/Thr phosphatase inhibitors affected the P-induced acrosome reaction or the P-induced calcium influx, except for the PP2B inhibitors that significantly reduced the P-induced acrosome reaction without affecting calcium influx. Finally, the protein tyrosine phosphatase inhibitors significantly blocked the P-induced acrosome reaction and reduced the amplitude of the P-induced calcium transient (p < 0.001) as well as the amplitude of the plateau phase (p < 0.01). The data suggest that protein kinases and possibly PP2B have a role on the acrosome reaction at some point downstream of calcium entry and that Tyr phosphatases have a role on the acrosome reaction upstream of calcium entry.

The Catsper channel and its roles in male fertility: a systematic review

“…Progesterone surrounds the egg in the female reproductive tract and is released by cumulus cells. Progesterone induces Ca 2+ entry into sperm through the Catsper channel and thus promotes the acrosome reaction [ 76 , 77 ]. How specifically progesterone regulates Ca 2+ concentration has been deeply investigated.…”

“…One study recorded the Catsper currents from human epididymal and testicular spermatozoa, and the results showed that the Catsper channel is sensitive to progesterone early in sperm development and this sensitivity increases gradually to a peak when spermatozoa are ultimately ejaculated [ 79 ]. Protein kinases and phosphatases participate in progesterone-induced Ca 2+ increases: the addition of PKA inhibitor or protein tyrosine phosphatase inhibitors reduced progesterone-induced Ca 2+ influx and progesterone-induced acrosome rections [ 77 ]. In 2010, two research groups proposed that as a progesterone receptor in fish sperm, the Catsper channel is functioning to increase intracellular Ca 2+ concentrations [ 80 , 81 ].…”

Occurrence and reproductive roles of hormones in seminal plasma

“…Vitamin D (VD) and its active metabolite 1,25-dihydroxycholecalciferol are among the major hormones responsible for calcium homeostasis. The influx of Ca 2+ participates in the acrosome reaction and calcium is present in remarkable concentrations in seminal plasma [ 17 ], the detailed mechanism was studied recently [ 18 ]. Human spermatozoa contain all the necessary machinery for its actions, including the VD receptor and VD metabolizing enzymes, the expression of which in human spermatozoa serve as positive predictive markers of sperm quality, with both genomic and non-genomic actions operating there [ 19 – 21 ].…”

Bbs5 functions as the docking compartment of Bbsome binding to Klc3 regulated by Bbs5-Ser246PKC-phosphorylation during mouse spermatogenesis

“…For the time being, there is still no data about the PKC phosphorylation sites of Bbs5. As an important role in various biological processes, PKC also takes part in spermatogenesis [17][18][19]. Bbs5 might be one potential target of which PKC gets involved in since BBS5 is the subunit of BBsome, an indispensable complex during ciliogenesis and spermatogenesis [20,21].…”