Multiple PDZ domain protein regulates sperm motility through CatSper channel

Abstract

Multiple PDZ domain protein (MPDZ) is a component of the crumbs cell polarity complex and is ubiquitously expressed in mammalian tissues. In mouse sperm, MPDZ was identified as a regulator of the sperm acrosome reaction in the past two decades. Here, a relationship between MPDZ and sperm motility was discovered. During breeding, we found that MPDZ-null mice had smaller litter size. The Ca2+ signal in mouse sperm decreased. Computer-assisted semen analysis revealed that MPDZ-null males had reduced mouse sperm motility. In humans, MPDZ expression is positively associated with sperm motility. Considering the regulatory role of the CatSper channel in sperm motility and fertility, we identified the expression profile of CatSper subunits (CatSper1–4) and found a reduction at both the transcriptional and translational levels in MPDZ-null mouse spermatozoa. However, in vitro, only CatSper1/2 expression was upregulated in MPDZ-overexpressing GC2 cells. Meanwhile, we found an upregulated cell Ca2+ signal when MPDZ was overexpressed in GC2 cells. Mechanical analysis revealed that MPDZ bound to the signal transducer and activator of transcription 3 (Stat3) and promoted its phosphorylation at tyrosine 705 (Y705) to upregulate CatSper1/2 expression. Inhibition of Stat3 (Y705) phosphorylation or Stat3 expression attenuated the effect of MPDZ on CatSper1/2 expression. These results suggested that MPDZ was responsible for the transcriptional regulation of the CatSper channel, at least in part, to regulate Ca2+ signal and sperm motility. To the best of our knowledge, this is the first study to highlight the importance of MPDZ acting as a regulator of sperm motility.