Diacylglycerol kinase control of protein kinase C

The diacylglycerol kinases (DGK) are lipid kinases that transform diacylglycerol (DAG) into phosphatidic acid (PA) in a reaction that terminates DAG-based signals. DGK provide negative regulation to conventional and novel protein kinase C (PKC) enzymes, limiting local DAG availability in a tissue-and subcellular-restricted manner. Defects in the expression/activity of certain DGK isoforms contribute substantially to cognitive impairment and mental disorders. Abnormal DGK overexpression in tumors facilitates invasion and resistance to chemotherapy preventing tumor immune destruction by tumor-infiltrating lymphocytes. Effective translation of these findings into therapeutic approaches demands a better knowledge of the physical and functional interactions between the DGK and PKC families. DGK zeta is abundantly expressed in the nervous and immune system, where physically and functionally interacts with PKC alpha. The latest discoveries suggest that PDZ-mediated interaction facilitates spatial restriction of PKC alpha by DGK zeta at the cell-cell contact sites in a mechanism where the two enzymes regulate each other. In T lymphocytes, DGK zeta interaction with Sorting Nexin 27 (SNX27) guarantees the basal control of PKC alpha activation. SNX27 is a trafficking component required for normal brain function whose deficit has been linked to Alzheimer's disease (AD) pathogenesis. The enhanced PKC alpha activation as the result of SNX27 silencing in T lymphocytes aligns with the recent correlation found between gain-of-function PKC alpha mutations and AD and suggests that disruption of the mechanisms that provides a correct spatial organization of DGK zeta and PKC alpha may lie at the basis of immune and neuronal synapse impairment.