前列腺跨膜蛋白TMEPAI在多种肿瘤细胞中高表达，并与TGF-β信号相关。我们前期研究表明：TMEPAI在细胞内定位于溶酶体和胞内体；TMEPAI与E3泛素连接酶Nedd4相互作用调控其在细胞内的定位；TMEPAI与细胞内微管运输相关的动力蛋白激活蛋白Dynactin6互作。本项目将在分子和细胞水平上深入研究和阐明TMEPAI在细胞内运输的调控机制和定位于溶酶体的功能，研究内容包括：1.鉴定TMEPAI泛素化位点和研究TMEPAI泛素化对其在细胞内运输和功能的作用；2.泛素结合蛋白对TMEPAI在细胞内运输的作用；3.鉴定TMEPAI与Dynactin复合体的结合位点和研究TMEPAI与Dynactin复合体互作对TMEPAI运输和囊泡运输的作用；4.TMEPAI对溶酶体通透性的影响和对细胞自噬的作用。本项目研究将有助于揭示TMEPAI调控TGF-β信号及其在肿瘤发生和发展中的作用机制。

TMEPAI (Transmembrane prostate androgen-induced protein) has been reported to be elevated in several cancers. TMEPAI expression is induced by TGF-β signaling, and in turn, expression of TMEPAI negatively regulates the TGF-β signaling, but the molecular mechanisms of TMEPAI induced TGF-β signaling inhibition are not well understood. Our preliminary studies indicated that TMEPAI is localized to the lysosome and late endosome; association of TMEPAI with the E3 ubiquitin ligase Nedd4 is required for its transport to the lysosome; TMEPAI interacts with the Dynactin pointed end complex subunit protein Dynactin6. This project will further study the regulatory mechanism of the intracellular transport of TMEPAI and its function in the lysosome, including: 1. Identification of the ubiquitination sites of TMEPAI, and study the role of ubiquitination of TMEPAI in regulating its intracellular transport and function; 2. The role of ubiquitin-binding proteins in regulating the intracellular transport of TMEPAI; 3. Identification of the binding domain between TMEPAI and Dynactin complex, and study the role of the TMEPAI-Dynactin interaction in regulating the intracellular transport of TMEPAI and vesicle trafficking; 4. The role of TMEPAI in regulating lysosomal membrane permeabilization and autophage. These studies will reveal a novel function for TMEPAI in regulating TGF-β signaling and tumorigenesis.