An autocrine axis in the testis that coordinates spermiation and blood-testis barrier restructuring during spermatogenesis
Yan,Helen H.N.; Mruk,Dolores D.; Wong,Elissa W.P.; Lee,Will M.; Cheng,Chuen-yan
Proceedings of the National Academy of Sciences of the United States of America 105(26): 8950-8955
Publication date: 2008
The mechanism(s) that regulate and coordinate the events of spermiation and blood-testis barrier (BTB) restructuring in the seminiferous epithelium that occur concurrently at stage VIII of the seminiferous epithelial cycle of spermatogenesis are unknown. In this report, fragments derived from the laminin complex composed of laminin a3, ß3, and ?3 chains (laminin-333) at the apical ectoplasmic specialization (apical ES) were shown to modulate BTB dynamics directly and/or indirectly via hemidesmosome. Experiments were performed using cultured Sertoli cells with functional tight junction (TJ) barrier and the ultrastructural features of the BTB but not apical ES. Recombinant protein fragments of laminin ß3 and ?3 chains were shown to reduce the protein levels of occludin and ß1-integrin dose dependently at the Sertoli-Sertoli and Sertoli-basement membrane interface, respectively, thereby destabilizing the BTB permeability function. These results were corroborated by transient overexpression of laminin fragments in Sertoli cells. To further assess the role of ß1-integrin in hemidesmosome, knockdown of ß1-integrin in Sertoli cells by RNAi was found to associate with occludin redistribution at the Sertoli-Sertoli cell interface, wherein occludin moved away from the cell surface and became associated with endosomes, thereby destabilizing the BTB. In short, an apical ES-BTB-hemidesmosome autocrine regulatory axis was identified in testes, coordinating the events of spermiation and BTB restructuring that occur at the opposite ends of the seminiferous epithelium during spermatogenesis.