Evidence that tubulobulbar complexes in the seminiferous epithelium are involved with internalization of adhesion junctions
Evidence that tubulobulbar complexes in the seminiferous epithelium are involved with internalization of adhesion junctions
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DOI：
10.1095/biolreprod.104.028803
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发表时间：
2004-08-01
影响因子：
3.6
通讯作者：
Vogl, AW
中科院分区：
文献类型：
--
作者：
Guttman, JA;Takai, Y;Vogl, AW
小管球复合体可能是精子释放过程中支持细胞内化细胞间黏附连接的部分机制。这些复合体发生在支持细胞通过细胞间黏附连接与相邻细胞连接的区域，称为胞外特化。在Sertoli细胞附着于精子细胞头部的部位，小管球复合体由精子细胞质膜的指状突起、相应的Sertoli细胞质膜内陷和周围修饰的Sertoli细胞质袖带组成。在复合体的末端出现一簇簇的囊泡。在这里，我们表明，小管球复合体发展在以前被胞外特化占据的区域，并且这些结构具有相似的分子组成。此外，分别在支持细胞和精子细胞质膜中发现的黏附分子Nectin 2和Nectin 3集中在小管球复合体的远端。我们还证明，双膜结合的小泡与小管球复合体的末端相连，并且Nectin 3存在于精子细胞上，但不存在于从上皮释放的精子中。这些结果与Sertoli细胞和精子细胞膜粘附域被小管球复合体内化的结论一致。PKCalpha是一种与其他系统中粘附域的内吞作用相关的激酶，它集中在小管球复合体中，抗内小体和溶酶体抗体(LAMP1，SGP1)标记与小管球复合体末端相关的小泡簇。我们的结果与这一结论是一致的，即小管球复合体参与了精子释放过程中胞外特化的解体和细胞间粘附域的内化。
Tubulobulbar complexes may be part of the mechanism by which intercellular adhesion junctions are internalized by Sertoli cells during sperm release. These complexes develop in regions where Sertoli cells are attached to adjacent cells by intercellular adhesion junctions termed ectoplasmic specializations. At sites where Sertoli cells are attached to spermatid heads, tubulobulbar complexes consist of fingerlike processes of the spermatid plasma membrane, corresponding invaginations of the Sertoli cell plasma membrane, and a surrounding cuff of modified Sertoli cell cytoplasm. At the terminal ends of the complexes occur clusters of vesicles. Here we show that tubulobulbar complexes develop in regions previously occupied by ectoplasmic specializations and that the structures share similar molecular components. In addition, the adhesion molecules nectin 2 and nectin 3, found in the Sertoli cell and spermatid plasma membranes, respectively, are concentrated at the distal ends of tubulobulbar complexes. We also demonstrate that double membrane bounded vesicles are associated with the ends of tubulobulbar complexes and nectin 3 is present on spermatids, but is absent from spermatozoa released from the epithelium. These results are consistent with the conclusion that Sertoli cell and spermatid membrane adhesion domains are internalized together by tubulobulbar complexes. PKCalpha, a kinase associated with endocytosis of adhesion domains in other systems, is concentrated at tubulobulbar complexes, and antibodies to endosomal and lysosomal (LAMP1, SGP1) markers label the cluster of vesicles associated with the ends of tubulobulbar complexes. Our results are consistent with the conclusion that tubulobulbar complexes are involved with the disassembly of ectoplasmic specializations and with the internalization of intercellular membrane adhesion domains during sperm release.