Spectrin and plectin are present at apical tubulobulbar complexes in the seminiferous epithelium

Abstract

Tubulobulbar complexes (TBCs) are actin‐related double membrane structures that are suspected to internalize intercellular junctions, a process that is crucial for junction turnover and sperm release. At apical sites of adhesion between spermatids and Sertoli cells, each TBC consists of a tubulobulbar projection of the spermatid plasma membrane, the surrounding attached plasma membrane of the adjacent Sertoli cell, and an actin network cuff. In other systems, spectrin is part of the membrane skeleton that links actin filaments to the plasma membrane. Others previously have reported that the protein is present at differentiating germ cells and epididymal spermatozoa. Plectin links cytoskeletal elements to each other and to the plasma membrane. We probed the seminiferous epithelium for spectrin, plectin and actin on fixed frozen sections of rat testis and fixed epithelial fragments. Both in sections and in epithelial fragments, beta‐spectrin II and plectin are localized to apical actin‐related tubulobulbar. Neither protein is concentrated at actin‐related intercellular adhesion junctions (ectoplasmic specializations). Our results demonstrate that both spectrin and plectin are present in Sertoli cells at tubulobulbar complexes. Supported by an NSERC Discovery Grant to AWV.Grant Funding Source: NSERC