Essential Role of Neuron-Enriched Diacylglycerol Kinase (DGK), DGKβ in Neurite Spine Formation, Contributing to Cognitive Function

BACKGROUND: Diacylglycerol (DG) kinase (DGK) phosphorylates DG to produce phosphatidic acid (PA). Of the 10 subtypes of mammalian DGKs, DGKbeta is a membrane-localized subtype and abundantly expressed in the cerebral cortex, hippocampus, and caudate-putamen. However, its physiological roles in neurons and higher brain function have not been elucidated. METHODOLOGY/PRINCIPAL FINDINGS: We, therefore, developed DGKbeta KO mice using the Sleeping Beauty transposon system, and found that its long-term potentiation in the hippocampal CA1 region was reduced, causing impairment of cognitive functions including spatial and long-term memories in Y-maze and Morris water-maze tests. The primary cultured hippocampal neurons from KO mice had less branches and spines compared to the wild type. This morphological impairment was rescued by overexpression of DGKbeta. In addition, overexpression of DGKbeta in SH-SY5Y cells or primary cultured mouse hippocampal neurons resulted in branch- and spine-formation, while a splice variant form of DGKbeta, which has kinase activity but loses membrane localization, did not induce branches and spines. In the cells overexpressing DGKbeta but not the splice variant form, DGK product, PA, was increased and the substrate, DG, was decreased on the plasma membrane. Importantly, lower spine density and abnormality of PA and DG contents in the CA1 region of the KO mice were confirmed. CONCLUSIONS/SIGNIFICANCE: These results demonstrate that membrane-localized DGKbeta regulates spine formation by regulation of lipids, contributing to the maintenance of neural networks in synaptic transmission of cognitive processes including memory

Diacylglycerol Kinase-α Mediates Hepatocyte Growth Factor-induced Epithelial Cell Scatter by Regulating Rac Activation and Membrane Ruffling

Diacylglycerol kinases (Dgk) phosphorylate diacylglycerol (DG) to phosphatidic acid (PA), thus turning off and on, respectively, DG-mediated and PA-mediated signaling pathways. We previously showed that hepatocyte growth factor (HGF), vascular endothelial growth factor, and anaplastic lymphoma kinase activate Dgkα in endothelial and leukemia cells through a Src-mediated mechanism and that activation of Dgkα is required for chemotactic, proliferative, and angiogenic signaling in vitro. Here, we investigate the downstream events and signaling pathways regulated by Dgkα, leading to cell scatter and migration upon HGF treatment and v-Src expression in epithelial cells. We report that specific inhibition of Dgkα, obtained either pharmacologically by R59949 treatment, or by expression of Dgkα dominant-negative mutant, or by small interfering RNA-mediated down-regulation of endogenous Dgkα, impairs 1) HGF- and v-Src-induced cell scatter and migration, without affecting the loss of intercellular adhesions; 2) HGF-induced cell spreading, lamellipodia formation, membrane ruffling, and focal adhesions remodeling; and 3) HGF-induced Rac activation and membrane targeting. In summary, we provide evidence that Dgkα, activated downstream of tyrosine kinase receptors and Src, regulates crucial steps directing Rac activation and Rac-dependent remodeling of actin cytoskeleton and focal contacts in migrating epithelial cells

Diacylglycerol kinase ζ controls diacylglycerol metabolism at the immunological synapse

DGKα and DGKζ negatively regulate the DAG/RasGRP1/Ras pathway in T cells. Study of the specific contribution of each isoform to DAG metabolism during immune synapse formation by use of a combination of RNAi and videomicroscopy techniques identifies DGKζ as mainly responsible for DAG consumption at the immunological synapse