Testin secreted by Sertoli cells is associated with the cell surface, and its expression correlates with the disruption of Sertoli-germ cell junctions but not the inter-Sertoli tight junction
Testin secreted by Sertoli cells is associated with the cell surface, and its expression correlates with the disruption of Sertoli-germ cell junctions but not the inter-Sertoli tight junction
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DOI：
10.1074/jbc.273.33.21040
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发表时间：
1998-08-14
影响因子：
4.8
通讯作者：
Cheng, CY
中科院分区：
文献类型：
--
作者：
Grima, J;Wong, CCS;Cheng, CY
Testin 是一种睾酮反应性支持细胞分泌产物。在本研究中，我们证明支持细胞在体外分泌的测试蛋白量与其他几种支持细胞分泌产物相当。然而，当细胞间连接事先没有被破坏时，在睾丸和附睾的腔液和胞质中几乎没有发现睾丸激素，这表明分泌的睾丸激素可能在体内被睾丸细胞重吸收。使用具有和不具有细胞表面交联剂和放射性碘标记结合免疫沉淀的支持细胞进行的研究表明，存在两种 28 和 45 kDa 的多肽，它们构成了将 testin 锚定到细胞表面上的结合蛋白复合物。28-和 45-kDa 肽似乎分别驻留在细胞表面上和内部。免疫金电镜研究表明，睾丸素大量定位于围绕发育中精子细胞的胞质特化（一种改良的粘附连接）的支持细胞一侧。相比之下，在支持细胞间紧密连接处发现了很少的测试素金颗粒。当支持间紧密连接形成或破坏时，测试蛋白表达没有显着变化。这与支持细胞-生殖细胞连接的破坏形成鲜明对比，后者伴随着睾丸素表达的激增。这些结果证明了 testin 在检查支持细胞-生殖细胞相互作用中的有用性。
Testin is a testosterone-responsive Sertoli cell secretory product. In the present study, we demonstrated that the amount of testin secreted by Sertoli cells in vitro was comparable with several other Sertoli cell secretory products. However, virtually no testin was found in the luminal fluid and cytosols of the testis and epididymis when the intercellular junctions were not previously disrupted, suggesting that secreted testin may be reabsorbed by testicular cells in vivo. Studies using Sertoli cells with and without a cell surface cross-inker and radioiodination in conjunction with immunoprecipitation illustrated the presence of two polypeptides of 28 and 45 kDa, which constitute a binding protein complex that anchors testin onto the cell surface, The 28- and 45-kDa peptide appear to be residing on and inside the cell surface, respectively. Immunogold EM studies illustrated testin was abundantly localized on the Sertoli cell side of the ectoplasmic specialization (a modified adherens junction) surrounding developing spermatids. In contrast, very few testin gold particles were found at the site of inter-Sertoli tight junctions. When the inter-Sertoli tight junctions were formed or disrupted, no significant change in testin expression was noted. This is in sharp contrast to the disruption of Sertoli-germ cell junctions, which is accompanied by a surge in testin expression. These results demonstrate the usefulness of testin in examining Sertoli-germ cell interactions.