Rictor Regulates Spermatogenesis by Controlling Sertoli Cell Cytoskeletal Organization and Cell Polarity in the Mouse Testis

Endocrinology. 2015 Nov;156(11):4244-56. doi: 10.1210/en.2015-1217. Epub 2015 Sep 11.

Abstract

Maintenance of cell polarity is essential for Sertoli cell and blood-testis barrier (BTB) function and spermatogenesis; however, the signaling mechanisms that regulate the integrity of the cytoskeleton and polarity of Sertoli cells are not fully understood. Here, we demonstrate that rapamycin-insensitive component of target of rapamycin (TOR) (Rictor), a core component of mechanistic TOR complex 2 (mTORC2), was expressed in the seminiferous epithelium during testicular development, and was down-regulated in a cadmium chloride-induced BTB damage model. We then conditionally deleted the Rictor gene in Sertoli cells and mutant mice exhibited azoospermia and were sterile as early as 3 months old. Further study revealed that Rictor may regulate actin organization via both mTORC2-dependent and mTORC2-independent mechanisms, in which the small GTPase, ras-related C3 botulinum toxin substrate 1, and phosphorylation of the actin filament regulatory protein, Paxillin, are involved, respectively. Loss of Rictor in Sertoli cells perturbed actin dynamics and caused microtubule disarrangement, both of which accumulatively disrupted Sertoli cell polarity and BTB integrity, accompanied by testicular developmental defects, spermiogenic arrest and excessive germ cell loss in mutant mice. Together, these findings establish the importance of Rictor/mTORC2 signaling in Sertoli cell function and spermatogenesis through the maintenance of Sertoli cell cytoskeletal dynamics, BTB integrity, and cell polarity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Azoospermia / genetics
  • Azoospermia / metabolism
  • Blood-Testis Barrier / metabolism
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Polarity / physiology*
  • Cytoskeleton / metabolism*
  • Male
  • Mechanistic Target of Rapamycin Complex 2
  • Mice
  • Mice, Transgenic
  • Multiprotein Complexes / metabolism
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Seminiferous Epithelium / metabolism
  • Sertoli Cells / cytology
  • Sertoli Cells / metabolism*
  • Signal Transduction / physiology
  • Spermatogenesis / physiology*
  • TOR Serine-Threonine Kinases / metabolism
  • Testis / cytology
  • Testis / metabolism*

Substances

  • Carrier Proteins
  • Multiprotein Complexes
  • Rapamycin-Insensitive Companion of mTOR Protein
  • rictor protein, mouse
  • Mechanistic Target of Rapamycin Complex 2
  • TOR Serine-Threonine Kinases