Lan Yu-Jing, Cheng Chu-Chun, Chu Shu-Chi, Chiang Yun-Wei
Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan.
Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan.
Biochim Biophys Acta Biomembr. 2023 Jun;1865(5):184153. doi: 10.1016/j.bbamem.2023.184153. Epub 2023 Mar 21.
The transmembrane BAX inhibitor-1-containing motif 6 (TMBIM6) is suggested to modulate apoptosis by regulating calcium homeostasis in the endoplasmic reticulum (ER). However, the precise molecular mechanism underlying this calcium regulation remains poorly understood. To shed light on this issue, we investigated all negatively charged residues in BsYetJ, a bacterial homolog of TMBIM6, using mutagenesis and fluorescence-based functional assays. We reconstituted BsYetJ in membrane vesicles with a lipid composition similar to that of the ER. Our results show that the charged residues E49 and R205 work together as a major gate, regulating calcium conductance in these ER-like lipid vesicles. However, these residues become largely inactive when reconstituted in other lipid environments. In addition, we found that D195 acts as a minor filter compared to the E49-R205 dyad. Our study uncovers a previously unknown function of BsYetJ/TMBIM6 in the calcium-dependent inactivation of BsYetJ, providing a framework for the development of a lipid-dependent mechanistic model of BsYetJ that will facilitate our understanding of calcium-dependent apoptosis.
跨膜含BAX抑制因子1基序6（TMBIM6）被认为可通过调节内质网（ER）中的钙稳态来调控细胞凋亡。然而，这种钙调节的精确分子机制仍知之甚少。为阐明这一问题，我们利用诱变和基于荧光的功能测定法，研究了TMBIM6的细菌同源物BsYetJ中的所有带负电荷残基。我们在脂质组成与内质网相似的膜泡中重组了BsYetJ。我们的结果表明，带电荷残基E49和R205共同作为一个主要闸门，调节这些内质网样脂质泡中的钙电导。然而，当在其他脂质环境中重组时，这些残基基本上失去活性。此外，我们发现与E49-R205二元组相比，D195起到次要过滤器的作用。我们的研究揭示了BsYetJ/TMBIM6在BsYetJ钙依赖性失活中的一个此前未知的功能，为构建BsYetJ的脂质依赖性机制模型提供了一个框架，这将有助于我们理解钙依赖性细胞凋亡。
