Research ArticleReproductive Biology

Ca2+ Signaling Tools Acquired from Prostasomes Are Required for Progesterone-Induced Sperm Motility

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Sci. Signal.  17 May 2011:
Vol. 4, Issue 173, pp. ra31
DOI: 10.1126/scisignal.2001595

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Progesterone-induced calcium ion (Ca2+) signals in the neck region of sperm play a pivotal role in promoting sperm motility. Here, we show that a long-lasting Ca2+ signal required for sperm motility in response to progesterone depends on their pH-dependent fusion with prostasomes, which are small vesicles secreted by the prostate. We found that prostasome fusion led to the transfer of progesterone receptors, cyclic adenosine diphosphoribose (cADPR)–synthesizing enzymes, ryanodine receptors (RyRs), and other Ca2+ signaling tools from prostasomes to the sperm neck. Progesterone-induced sperm motility relied on cADPR-mediated Ca2+ mobilization through RyR located on acidic Ca2+ stores, followed by Ca2+ entry through store-operated channels. Treatment of prostasome-fused sperm with a cADPR antagonist or fusion with prostasomes in which type 2 RyR was depleted resulted in low fertilization rates, reduced sperm motility, or both. Thus, we conclude that sperm motility depends on the acquisition of Ca2+ signaling tools from prostasomes.

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