SH3 and cysteine-rich protein 3 (STAC3), a small adapter protein originally identified as a core component of excitation-contraction coupling machinery, regulates the voltage-induced Ca2+ release in skeletal muscle. However, the possibility of additional, as yet unknown, non-muscle effects of STAC3 cannot be ruled out. Herein, we provide the evidence for the expression and functional involvement of STAC3 in spermatogenesis. STAC3 expression was localized in the testicular interstitium of rodent and human testes. By using the cytotoxic drug ethylene dimethane sulfonate (EDS), STAC3 expression was observed to be decreased sharply in rat testis after selective withdrawal of Leydig cells (LCs), and reappeared immediately after LCs repopulation, indicating that testicular expression of STAC3 mainly stems from LCs. From a functional standpoint, in vivo lentiviral vector-mediated suppression of STAC3 resulted in a significant decrease in testosterone production, and thereafter caused impairment of male fertility by inducing oligozoospermia and asthenospermia. The indispensible involvement of STAC3 in testicular steroidogenesis was validated using the in vivo knockdown model with isolated primary LCs as well as in vitro experiments with primary LCs. By generating the TM3Stac3-/- cells, we further revealed that STAC3 depletion attenuated mitochondrial membrane potential and StAR processing in db-cAMP-stimulated LCs. Thus, the inhibitory effect of STAC3 deficiency on testicular steroidogenesis may be ascribed to a disturbed mitochondrial homeostasis. Collectively, the present results strongly suggest that STAC3 may function as a novel regulator linking mitochondrial homeostasis and testicular steroidogenesis in LCs. Our data underscore an unexpected reproductive facet of this muscle-derived factor.

中文翻译：

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睾丸 STAC3 通过增强线粒体膜电位和 StAR 处理调节 Leydig 细胞类固醇生成

SH3 和富含半胱氨酸的蛋白 3 (STAC3)，一种最初被确定为兴奋-收缩耦合机制的核心成分的小衔接蛋白，可调节骨骼肌中电压诱导的 Ca2+ 释放。然而，不能排除 STAC3 的其他未知的非肌肉作用的可能性。在此，我们提供了 STAC3 在精子发生中的表达和功能参与的证据。STAC3 表达定位于啮齿动物和人类睾丸的睾丸间质。通过使用细胞毒性药物乙烯二甲磺酸盐（EDS），观察到在选择性撤除 Leydig 细胞（LCs）后大鼠睾丸中 STAC3 表达急剧下降，并在 LCs 重新增殖后立即重新出现，表明 STAC3 的睾丸表达主要来源于 LCs . 从功能上来说，体内慢病毒载体介导的 STAC3 抑制导致睾酮产生显着减少，然后通过诱导少精子症和弱精子症导致男性生育能力受损。STAC3 在睾丸类固醇生成中不可或缺的参与使用具有分离的初级 LC​​ 的体内敲低模型以及初级 LC​​ 的体外实验进行了验证。通过生成 TM3Stac3-/- 细胞，我们进一步揭示了 STAC3 耗竭减弱了 db-cAMP 刺激的 LC 中的线粒体膜电位和 StAR 处理。因此，STAC3 缺乏对睾丸类固醇生成的抑制作用可能归因于线粒体稳态失调。总的来说，目前的结果强烈表明，STAC3 可能作为一种新型调节剂，将 LC 中的线粒体稳态和睾丸类固醇生成联系起来。我们的数据强调了这种肌肉衍生因子的意外生殖方面。