Sun Yizhe, Li Qi, Zhang Jingyu, Chen Zhongjiang, He Qihua, Liu Xi, Zhao Ning, Yin Ang, Huang He, He Minwei, Cao Lulu, Wang Lu
Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing 100700, China.
Cell Signal. 2017 Aug;36:34-41. doi: 10.1016/j.cellsig.2017.04.005. Epub 2017 Apr 13.
TMEM74 (Transmembrane protein 74), a lysosome transmembrane protein, induces cell autophagy. Knockdown of TMEM74 abolished EBSS-induced autophagy. BIK, belonging to BOP (BH3-only protein) protein family, has been reported to induce cell apoptosis. Autophagy and apoptosis, as different pathways regulated by extra- or intra-cellular signals precisely, both play a crucial role in processes of intra-cellular substrates degradation, energy metabolism and cell survival. However, the relationship between autophagy and apoptosis still remains elusive. To elucidate the putative new relationship and further identify the function of TMEM74, we performed the study mainly using co-immunoprecipitation, immunoblotting, fluorescent location and basic cell biologic experimental techniques. In the present study, for the first time, it is demonstrated that autophagy-related protein TMEM74 co-localizes with apoptosis-related protein BIK in subcellular organelles. The data indicated that TMEM74 associates with BIK via TM domains of TMEM74 and BH3 domain of BIK. Further investigations revealed that TMEM74 inhibits BIK-induced apoptosis by interacting with BIK, as evidenced by the results that autophagosome formation inhibitor could not block the inhibition effect completely. On the contrary, knockdown of TMEM74 and the TM domain-deficient mutant led to deprivation of the function. Overall, the results revealed the autophagy modulator TMEM74 interrelates with apoptosis inducer BIK and inhibits its function, which provides a novel crosstalk point between autophagy and apoptosis to enlarge our understanding of the programmed cell death.
跨膜蛋白74（TMEM74）是一种溶酶体跨膜蛋白，可诱导细胞自噬。敲低TMEM74可消除饥饿诱导的自噬。据报道，属于仅含BH3结构域蛋白（BOP）家族的BIK可诱导细胞凋亡。自噬和凋亡作为由细胞外或细胞内信号精确调控的不同途径，在细胞内底物降解、能量代谢和细胞存活过程中均起着关键作用。然而，自噬与凋亡之间的关系仍不清楚。为了阐明这种可能的新关系并进一步确定TMEM74的功能，我们主要使用免疫共沉淀、免疫印迹、荧光定位和基础细胞生物学实验技术进行了这项研究。在本研究中，首次证明自噬相关蛋白TMEM74与凋亡相关蛋白BIK在亚细胞器中共定位。数据表明，TMEM74通过其跨膜结构域与BIK的BH3结构域相互作用。进一步的研究表明，TMEM74通过与BIK相互作用抑制BIK诱导的凋亡，自噬体形成抑制剂不能完全阻断这种抑制作用的结果证明了这一点。相反，敲低TMEM74和跨膜结构域缺陷突变体导致功能丧失。总体而言，结果揭示了自噬调节因子TMEM74与凋亡诱导因子BIK相互关联并抑制其功能，这为自噬与凋亡之间提供了一个新的相互作用点，以加深我们对程序性细胞死亡的理解。
