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Abstract

Testin secreted by Sertoli cells is associated with cell surface and its expression correlates with the disruption of Sertoli-germ cell junctions but not the inter-Sertoli tight junction protein complex in the testis (PDF) (HTML) 
Grima,Josephine; Wong,Connie C.S.; Zhu,Li-Ji; Zong,Shudong; Cheng,Chuen-yan
Journal of Biological Chemistry 273(33): 21040-21053
Publication date: 1998

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Testin is a testosterone-responsive Sertoli cell secretory product. In the present study, we demonstrated that the amountof testin secreted by Sertoli cells in vitro was comparable withseveral other Sertoli cell secretory products. However, virtuallyno testin was found in the luminal fluid and cytosols of the testisand epididymis when the intercellular junctions were not previouslydisrupted, suggesting that secreted testin may be reabsorbed bytesticular cells in vivo. Studies using Sertoli cells with andwithout a cell surface cross-linker and radioiodination in conjunctionwith immunoprecipitation illustrated the presence of two polypeptidesof 28 and 45 kDa, which constitute a binding protein complex thatanchors testin onto the cell surface. The 28- and 45-kDa peptideappear to be residing on and inside the cell surface, respectively.Immunogold EM studies illustrated testin was abundantly localizedon the Sertoli cell side of the ectoplasmic specialization (amodified adherens junction) surrounding developing spermatids.In contrast, very few testin gold particles were found at thesite of inter-Sertoli tight junctions. When the inter-Sertolitight junctions were formed or disrupted, no significant changein testin expression was noted. This is in sharp contrast to thedisruption of Sertoli-germ cell junctions, which is accompaniedby a surge in testin expression. These results demonstrate theusefulness of testin in examining Sertoli-germ cell interactions.

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