Abstract
The sperm of Eriocheir sinensis has a cup-shaped nucleus that contains several mitochondria embedded at the opening of the cup. The acrosome vesicle also contains derivants of mitochondria. The mitochondria distribution pattern involves a decrease in the number and changes in the structure and transportation of these organelles. The decreased number of sperm mitochondria is achieved through autophagy or the ubiquitination pathway. Prohibitin (PHB), the mitochondria inner membrane protein, is an evolutionarily highly conserved protein, is closely associated with spermatogenesis and sperm quality control and is also a potential substrate of ubiquitination. However, whether PHB protein mediates the ubiquitination pathway of sperm mitochondria in crustacean animals remains poorly understood. In the present study, we revealed that PHB, a substrate of ubiquitin, participates in the ubiquitination and degradation of mitochondria during spermiogenesis in E. sinensis. To confirm this finding, we used shRNA interference to reduce PHB expression and an overexpression technique to increase PHB expression in vitro. The interference experiment showed that the reduced PHB expression directly affected the polyubiquitination level and mitochondria status, whereas PHB overexpression markedly increased the polyubiquitination level. In vitro experiments also showed that PHB and its ubiquitination decide the fate of mitochondria.
Highlights
Spermiogenesis is the last stage of spermatogenesis, which includes acrosome formation, nuclear shaping and flagellation in mammals
We explored one of the physiological mechanisms of spermiogenesis in E. sinensis, which was that PHB located on the mitochondrial inner membrane participates in mitochondrial ubiquitination during spermiogenesis of E. sinensis
Our results show that PHB and its ubiquitination decide the fate of mitochondria during spermiogenesis of E. sinensis
Summary
Spermiogenesis is the last stage of spermatogenesis, which includes acrosome formation, nuclear shaping and flagellation in mammals. For crustacean sperm, which have no flagellum, spermiogenesis only involves acrosome formation and nuclear shaping [1,2,3]. Whereas in non-flagellated sperm, including the vast majority of crustaceans, shrimp and crabs, mitochondria are embedded in a nuclear cup, or as a derivative integrated into the lamellar structure of the acrosome vesicle; or together with lysosomes and Golgi bodies to form lamellar complexes (LCx) involved in acrosome formation [1,2,3]. Sperm cells need to discard the vast majority of organelles and cytoplasm, including certain www.impactjournals.com/oncotarget mitochondria, to form concentrated spermatid [4]. Studies have shown that mitochondria are ubiquitinated during mammalian spermiogenesis, and ubiquitin mitochondria are degraded by mitochondrial membrane protein PHB as a substrate [11]
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