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

• DOI: 10.1371/journal.pgen.1006803
• Publication Date: 2017-06-15T20:36:25Z
• Authors: Amandine Cartier-...; Anne-Laure Bailly; Stéphane Betzi; Xiaoli Shi; Jean-Claude Lissi...; Ana Zarubica; Arnauld Sergé; Philippe Roche; Adrien Lugari; Véronique Hamon; Florence Bardin; Carine Derviaux; Frédérique Lembo; Stéphane Audebert; Sylvie Marchetto; Bénédicte Durand; Jean-Paul Borg; Ning Shi; Xavier Morelli; Michel Aurrand-Lions
• Keywords: Male; 0301 basic medicine; [SDV]Life Sciences [q-bio]; Golgi Apparatus; Immunoglobulins; [SDV.BC]Life Sciences [q-bio]/Cellular Biology; QH426-470; Mice; 03 medical and health sciences; Spermatocytes; Germ cells; Acrosomes; Genetics; Animals; Testes; Spermatogenesis; Cells, Cultured; Binding Sites; DAPI staining; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Spermatids; Spermatogonia; Mice, Inbred C57BL; Protein Transport; Seminiferous tubules; Carrier Proteins; Cell Adhesion Molecules; Research Article; Protein Binding

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.