Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON, Canada.
Department of Pharmaceutical Health Care and Sciences, Kyushu University, Fukuoka, Japan.
FASEB J. 2021 Jun;35(6):e21602. doi: 10.1096/fj.202100264R.
Diacylglycerol kinases catalyze the ATP-dependent phosphorylation of diacylglycerol (DAG) to produce phosphatidic acid (PA). In humans, the alpha isoform (DGKα) has emerged as a potential target in the treatment of cancer due to its anti-tumor and pro-immune responses. However, its mechanism of action at a molecular level is not fully understood. In this work, a systematic investigation of the role played by the membrane in the regulation of the enzymatic properties of human DGKα is presented. By using a cell-free system with purified DGKα and model membranes of variable physical and chemical properties, it is shown that membrane physical properties determine human DGKα substrate acyl chain specificity. In model membranes with a flat morphology; DGKα presents high enzymatic activity, but it is not able to differentiate DAG molecular species. Furthermore, DGKα enzymatic properties are insensitive to membrane intrinsic curvature. However, in the presence of model membranes with altered morphology, specifically the presence of physically curved membrane structures, DGKα bears substrate acyl chain specificity for palmitic acid-containing DAG. The present results identify changes in membrane morphology as one possible mechanism for the depletion of specific pools of DAG as well as the production of specific pools of PA by DGKα, adding an extra layer of regulation on the interconversion of these two potent lipid-signaling molecules. It is proposed that the interplay between membrane physical (shape) and chemical (lipid composition) properties guarantee a fine-tuned signal transduction system dependent on the levels and molecular species of DAG and PA.
二酰基甘油激酶催化二酰基甘油（DAG）与 ATP 的磷酸化反应，生成磷酸脂酸（PA）。在人类中，由于其抗肿瘤和促免疫反应，α 同工酶（DGKα）已成为癌症治疗的潜在靶点。然而，其在分子水平上的作用机制尚不完全清楚。在这项工作中，系统研究了膜在调节人 DGKα酶学特性中的作用。通过使用含有纯化 DGKα的无细胞系统和具有可变物理和化学性质的模型膜，表明膜物理性质决定了人 DGKα 底物酰基链特异性。在具有平面形态的模型膜中；DGKα表现出高酶活性，但不能区分 DAG 分子种类。此外，DGKα 的酶学性质对膜固有曲率不敏感。然而，在存在具有改变形态的模型膜的情况下，特别是存在物理弯曲的膜结构的情况下，DGKα对含有棕榈酸的 DAG 具有底物酰基链特异性。目前的结果表明，膜形态的变化可能是 DGKα耗尽特定 DAG 池以及产生特定 PA 池的一种机制，为这两种有效的脂质信号分子的相互转化增加了一层额外的调控。据推测，膜物理（形状）和化学（脂质组成）性质之间的相互作用保证了一个依赖于 DAG 和 PA 水平和分子种类的精细信号转导系统。
