Zhang Li, Buhr Sebastian, Voigt Aaron, Methner Axel
University Medical Center, Institute for Molecular Medicine, Johannes Gutenberg University Mainz, Mainz, Germany.
Department of Neurology, RWTH Aachen University, Aachen, Germany.
Front Cell Dev Biol. 2021 Sep 3;9:666484. doi: 10.3389/fcell.2021.666484. eCollection 2021.
The mammalian Transmembrane BAX Inhibitor Motif (TMBIM) protein family consists of six evolutionarily conserved hydrophobic proteins that affect programmed cell death and the regulation of intracellular calcium levels. The bacterial ortholog BsYetJ is a pH-dependent calcium channel. We here identified seven TMBIM family members in and describe their expression levels in diverse tissues and developmental stages. A phylogenetic analysis revealed that CG30379 represents the ortholog of human TMBIM4 although these two proteins are much less related than TMBIM5 (CG2076 and CG1287/Mics1) and TMBIM6 (CG7188/Bi-1) to their respective orthologs. For TMBIM1-3 the assignment is more dubious because the fly and the human proteins cluster together. We conducted a functional analysis based on expression levels and the availability of RNAi lines. This revealed that the ubiquitous knockdown of CG3798/Nmda1 and CG3814/Lfg had no effect on development while knockdown of CG2076/dTmbim5 resulted in death at the pupa stage and knockdown of CG7188/dTmbim6 in death at the embryonic stage. Ubiquitous knockdown of the second TMBIM5 paralog CG1287/Mics1 ensued in male sterility. Knockdown of dTmbim5 and 6 in muscle and neural tissue also greatly reduced lifespan through different mechanisms. Knockdown of the mitochondrial family member dTmbim5 resulted in reduced ATP production and a pro-apoptotic expression profile while knockdown of the ER protein dTmbim6 increased the ER calcium levels similar to findings in mammalian cells. Our data demonstrate that dTmbim5 and 6 are essential for fly development and survival but affect cell survival through different mechanisms.
哺乳动物跨膜BAX抑制基序（TMBIM）蛋白家族由六种进化上保守的疏水蛋白组成，这些蛋白影响程序性细胞死亡和细胞内钙水平的调节。细菌直系同源物BsYetJ是一种pH依赖性钙通道。我们在此鉴定了七种TMBIM家族成员，并描述了它们在不同组织和发育阶段的表达水平。系统发育分析表明，CG30379代表人类TMBIM4的直系同源物，尽管这两种蛋白质与其各自的直系同源物相比，相关性远低于TMBIM5（CG2076和CG1287/Mics1）和TMBIM6（CG7188/Bi-1）。对于TMBIM1-3，由于果蝇和人类蛋白质聚集在一起，其归属更具不确定性。我们基于表达水平和RNAi品系的可用性进行了功能分析。结果表明，CG3798/Nmda1和CG3814/Lfg的普遍敲低对发育没有影响，而CG2076/dTmbim5的敲低导致蛹期死亡，CG7188/dTmbim6的敲低导致胚胎期死亡。第二个TMBIM5旁系同源物CG1287/Mics1的普遍敲低导致雄性不育。在肌肉和神经组织中敲低dTmbim5和6也通过不同机制大大缩短了寿命。线粒体家族成员dTmbim5的敲低导致ATP生成减少和促凋亡表达谱，而内质网蛋白dTmbim6的敲低增加了内质网钙水平，这与在哺乳动物细胞中的发现相似。我们的数据表明，dTmbim5和6对果蝇的发育和存活至关重要，但通过不同机制影响细胞存活。
