The mechanism of androgen-dependent differentiation of the duct system in the submandibular gland

关于啮齿类动物颌下腺的分化，我们得到了以下结果：1）转录因子JunD在小鼠颌下腺中的表达定位于导管系统，且在雌性腺中的表达量明显高于雄性腺;在出生后发育和睾酮诱导的GCT细胞分化过程中，JunD在纹管细胞核中的表达被暂时诱导，并在它们分化为GCT细胞时消失（参考文献1）。2）menin（一种结合JunD的核蛋白）的表达和定位在小鼠SMG中显示出与JunD相同的模式，3）在去垂体大鼠SMG中，β-肾上腺素能激动剂异丙肾上腺素对蛋白酶抑制剂cystatin S的诱导作用明显低于对照组。给予一种垂体依赖性激素，即，睾酮、雌二醇、地塞米松和甲状腺素与异丙肾上腺素一起使用，可显著恢复半胱氨酸蛋白酶抑制剂S的表达（参考文献2）。这些结果表明，在啮齿动物SMG的分化中，多种信号传导途径（包括雄激素）之间的交互作用。SLAMP定位于内质网-高尔基体中间室（ERGIC）的膜上，表明其在粘蛋白糖蛋白的早期分泌途径中的作用。

In regard to the differentiation of rodent submandibular glands (SMG), we have obtained the following results :1)In the mouse SMG, the expression of the transcription factor JunD is localized to the duct system and much more abundant in the female than in the male gland. During the postnatal development and testosterone-induced GCT cell differentiation, JunD expression is temporarily induced in the nuclei of striated duct cells and dispappeares as they differentiated into GCT cells (Reference 1).2)The expression and localization of menin, a nuclear protein that binds JunD, showed the same pattern in the mouse SMG as that of JunD, suggesting that JunD-menin complex is responsible for the duct differentiation.3)In the SMG of hypophysectomized rats, the induction of the protease inhibitor cystatin S by the b-adrenergic agonist isoproterenol is much less than that in the control. Administration of one of the pituitary-dependent hormones, i.e., testosterone, estradiol, dexamethasone and thyroxine, together with isoproterenol results in marked recovery of cystatin S expression (Reference 2).These results suggest the role of cross-talks between multiple signaling pathways, including that of androgens, in the differentiation of rodent SMG.4)We have cloned a novel animal lectin specifically expressed in the rat sublingual gland and named it STAMP (sublingual gland acinar membrane protein). SLAMP is localized to the membrane of ER-Golgi intermediate compartment (ERGIC), suggesting its role in the early secretory pathway of mucin glycoproteins.