MTORC1/C2 regulate spermatogenesis in Eriocheir sinensis via alterations in the actin filament network and cell junctions.

Abstract

Spermatogenesis is a finely regulated process of germ cell proliferation and differentiation that leads to the production of sperm in seminiferous tubules. Although the mammalian target of rapamycin (mTOR) signaling pathway is crucial for spermatogenesis in mammals, its functions and molecular mechanisms in spermatogenesis remain largely unknown in nonmammalian species, particularly in Crustacea. In this study, we first identified es-Raptor (the core component of mTOR complex 1) and es-Rictor (the core component of mTOR complex 2) from the testis of Eriocheir sinensis. Dynamic localization of es-Raptor and es-Rictor implied that these proteins were indispensable for the spermatogenesis of E. sinensis. Furthermore, es-Raptor and es-Rictor knockdown results showed that the mature sperm failed to be released, causing almost empty lumens in the testis. We investigated the reasons for these effects and found that the actin-based cytoskeleton was disrupted in the knockdown groups. In addition, the integrity of the testis barrier (similar to the blood-testis barrier in mammals) was impaired and affected the expression of cell junction proteins. Further study revealed that es-Raptor and es-Rictor may regulate spermatogenesis via both mTORC1- and mTORC2-dependent mechanisms that involve es-rpS6 and es-Akt/es-PKC, respectively. Moreover, to explore the testis barrier in E. sinensis, we established a cadmium chloride (CdCl2)-induced testis barrier damage model as a positive control. Morphological and immunofluorescence results were similar to those of the es-Raptor and es-Rictor knockdown groups. Altogether, es-Raptor and es-Rictor were important for spermatogenesis through maintenance of the actin filament network and cell junctions in E. sinensis.