title: Differential effects of c-Src and c-Yes on the endocytic vesicle-mediated trafficking events at the Sertoli cell blood-testis barrier: an in vitro study.
abstract: The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the mammalian body. However, it undergoes cyclic restructuring during the epithelial cycle of spermatogenesis in which the "old" BTB located above the preleptotene spermatocytes being transported across the immunological barrier is "disassembled," whereas the "new" BTB found behind these germ cells is rapidly "reassembled," i.e., mediated by endocytic vesicle-mediated protein trafficking events. Thus, the immunological barrier is maintained when preleptotene spermatocytes connected in clones via intercellular bridges are transported across the BTB. Yet the underlying mechanism(s) in particular the involving regulatory molecules that coordinate these events remains unknown. We hypothesized that c-Src and c-Yes might work in contrasting roles in endocytic vesicle-mediated trafficking, serving as molecular switches, to effectively disassemble and reassemble the old and the new BTB, respectively, to facilitate preleptotene spermatocyte transport across the BTB. Following siRNA-mediated specific knockdown of c-Src or c-Yes in Sertoli cells, we utilized biochemical assays to assess the changes in protein endocytosis, recycling, degradation and phagocytosis. c-Yes was found to promote endocytosed integral membrane BTB proteins to the pathway of transcytosis and recycling so that internalized proteins could be effectively used to assemble new BTB from the disassembling old BTB, whereas c-Src promotes endocytosed Sertoli cell BTB proteins to endosome-mediated protein degradation for the degeneration of the old BTB. By using fluorescence beads mimicking apoptotic germ cells, Sertoli cells were found to engulf beads via c-Src-mediated phagocytosis. A hypothetical model that serves as the framework for future investigation is thus proposed.
authors.affiliation: Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York;
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York;
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
authors.affiliation: Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York;
authors.forename: Elissa W P
authors.initials: EW
authors.lastname: Wong
authors.affiliation: School of Biological Sciences, University of Hong Kong, Hong Kong, China;
authors.forename: Will M
authors.initials: WM
authors.lastname: Lee
authors.affiliation: Department of Cell Biology, School of Basic Medicine, Institute of Basic Medical Sciences, Peking Union Medical College, Beijing, China; and.
authors.forename: Daishu
authors.initials: D
authors.lastname: Han
authors.affiliation: Department of Biology, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Chris K C
authors.initials: CK
authors.lastname: Wong
authors.affiliation: Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, New York; y-cheng@popcbr.rockefeller.edu.
authors.forename: C Yan
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001814:Blood-Testis Barrier / Q000378:metabolism*; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology; D055785:Gene Knockdown Techniques; D016391:Genes, src / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology; D051575:Proto-Oncogene Proteins c-yes / Q000235:genetics / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology*; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; D051575:Proto-Oncogene Proteins c-yes; D016392:Proto-Oncogene Proteins pp60(c-src)
keywords: blood-testis barrier; c-Src; c-Yes; ectoplasmic specialization; endosome; recycling; seminiferous epithelial cycle; spermatogenesis; testis; tight junction; transcytosis