Membrane morphology determines diacylglycerol kinase α substrate acyl chain specificity

Diacylglycerol kinases catalyze the ATP-dependent phosphorylation of diacylglycerol (DAG) to produce phosphatidic acid (PA). In humans, the alpha isoform (DGK alpha) 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 DGK alpha is presented. By using a cell-free system with purified DGK alpha and model membranes of variable physical and chemical properties, it is shown that membrane physical properties determine human DGK alpha substrate acyl chain specificity. In model membranes with a flat morphology; DGK alpha presents high enzymatic activity, but it is not able to differentiate DAG molecular species. Furthermore, DGK alpha 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, DGK alpha 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 DGK alpha, 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.

Automated summary

The physical properties of membranes determine the substrate acyl chain specificity of human DGK alpha, affecting its enzymatic activity and ability to differentiate between DAG molecular species. Changes in membrane morphology, particularly the presence of physically curved membrane structures, impact the specificity of DGK alpha for certain DAG pools, adding a layer of regulation to the interconversion between DAG and PA. This suggests a fine-tuned signaling system dependent on the levels and molecular species of DAG and PA regulated by the interplay between membrane physical and chemical properties.