Genetic, structural, and chemical insights into the dual function of GRASP55 in germ cell Golgi remodeling and JAM-C polarized localization during spermatogenesis

PLoS Genet. 2017 Jun 15;13(6):e1006803. doi: 10.1371/journal.pgen.1006803. eCollection 2017 Jun.

Abstract

Spermatogenesis is a dynamic process that is regulated by adhesive interactions between germ and Sertoli cells. Germ cells express the Junctional Adhesion Molecule-C (JAM-C, encoded by Jam3), which localizes to germ/Sertoli cell contacts. JAM-C is involved in germ cell polarity and acrosome formation. Using a proteomic approach, we demonstrated that JAM-C interacted with the Golgi reassembly stacking protein of 55 kDa (GRASP55, encoded by Gorasp2) in developing germ cells. Generation and study of Gorasp2-/- mice revealed that knock-out mice suffered from spermatogenesis defects. Acrosome formation and polarized localization of JAM-C in spermatids were altered in Gorasp2-/- mice. In addition, Golgi morphology of spermatocytes was disturbed in Gorasp2-/- mice. Crystal structures of GRASP55 in complex with JAM-C or JAM-B revealed that GRASP55 interacted via PDZ-mediated interactions with JAMs and induced a conformational change in GRASP55 with respect of its free conformation. An in silico pharmacophore approach identified a chemical compound called Graspin that inhibited PDZ-mediated interactions of GRASP55 with JAMs. Treatment of mice with Graspin hampered the polarized localization of JAM-C in spermatids, induced the premature release of spermatids and affected the Golgi morphology of meiotic spermatocytes.

MeSH terms

  • Animals
  • Binding Sites
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Adhesion Molecules / metabolism*
  • Cells, Cultured
  • Golgi Apparatus / metabolism*
  • Golgi Apparatus / ultrastructure
  • Immunoglobulins / metabolism*
  • Intracellular Signaling Peptides and Proteins
  • Male
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Protein Binding
  • Protein Transport
  • Spermatogenesis*
  • Spermatogonia / cytology
  • Spermatogonia / metabolism*

Substances

  • Carrier Proteins
  • Cell Adhesion Molecules
  • Immunoglobulins
  • Intracellular Signaling Peptides and Proteins
  • Jam3 protein, mouse
  • Membrane Proteins
  • tamalin protein, mouse

Grants and funding

This work was supported by: to MAL, Agence Nationale de la recherche, BSV1 01902, http://www.agence-nationale-recherche.fr/; to MAL, AS, Fondation ARC pour la Recherche contre le Cancer, PJA20141201990 to MAL and PJA20131200238 to AS, http://www.recherche-cancer.net/; to ALB, Ligue Nationale contre le Cancer, TDQR15906, https://www.ligue-cancer.net/; to MAL, XM, JPB, AmiDex, ANR-11-IDEX-0001-02, http://fondation.univ-amu.fr/; to XS, Campus France, 26203WD, http://www.campusfrance.org/fr/; to JPB, Ligue Nationale contre le Cancer, Label2013, https://www.ligue-cancer.net/; to NS, National Natural Science Foundation of China, #31370738, http://www.nsfc.gov.cn/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.