Mitochondrial prohibitin and its ubiquitination during spermatogenesis of the swimming crab Charybdis japonica

It has been proposed that prohibitin (PHB) involved in multiple cellular functions, including cell proliferation, differentiation, apoptosis, senescence and carcinogenesis. Various cellular compartment location of PHB demonstrates its diverse roles. Based on the full-length sequence of PHB gene, we analyzed the deduced amino acid sequence and the predicted protein structure of this gene in the swimming crab Charybdis japonica. It shows that the structure and function of PHB are conservative. The expression level of PHB mRNA and protein in different tissues were analyzed by sqRT-PCR and western blot respectively, which showed its high expression in testis. We then traced PHB protein by immunofluorescence, and we found its diverse distribution in cytoplasm and mitochondria at different stages. We propose that PHB may participate actively in spermatogenic cell anti-apoptosis, cell nucleus distortion as well as acrosome morphogenesis during the spermatogenesis in Charybdis japonica. Furthermore, PHB was found to be ubiquitinated at different levels. Its signal was weak in spermatocytes and Stage 1 spermatids, stronger in stage 2-4 spermatids, and lowest in mature sperm. Our data shows that PHB may mediate the paternal mitochondrial material degradation by ubiquitination. We conclude that PHB is indispensable in the spermatogenesis of the swimming crab Charybdis japonica through different testis developmental stages.