Disease relevance of DGKA

• DAGK with an I110P or I110R mutation in the third transmembrane helix could not be purified because its expression was toxic to the E. coli host, most likely because of severe folding defects [1].
• These results provide strong and detailed evidence that d-alpha-tocopherol can prevent hyperglycemia induced DAG-PKC activation by enhancing DAG kinase activity, probably through an antioxidant effect [2].
• Survival trees for analyzing clinical outcome in lung adenocarcinomas based on gene expression profiles: identification of neogenin and diacylglycerol kinase alpha expression as critical factors [3].

High impact information on DGKA

• T cell anergy is reversed by active Ras and is regulated by diacylglycerol kinase-alpha [4].
• Both anergy and DGK-alpha overexpression were associated with defective translocation of the Ras guanine nucleotide-exchange factor RasGRP1 to the plasma membrane [4].
• We also determined in the same system that, when utilizing the DAGK assay, increased phosphorylation of substrates that comigrated with ceramide standards was apparent but that this effect was due to an enhancement of DAGK activity rather than increases in levels of cellular ceramides as substrates per se [5].
• Induced changes in cellular levels of such sphingosine-based ceramides are normally extrapolated from measurements of sphingomyelinase activity or following their conversion to ceramide phosphate by treatment of cellular lipid extracts with bacterial diacylglycerol kinase (DAGK) [5].
• Diacylglycerol (DAG) acts as an allosteric activator of protein kinase C (PKC) and is converted to phosphatidic acid by DAG kinase (DGK) [6].

Chemical compound and disease context of DGKA

• Escherichia coli diacylglycerol kinase (DAGK) is a homotrimeric helical integral membrane protein in which a number of single-site mutations to cysteine are known to promote misfolding [1].

Biological context of DGKA

• Here we studied the role of DGKalpha on activation-induced cell death on a T cell line and primary T lymphoblasts [7].
• On the contrary, the overactivation of the DGKalpha pathway inhibits exosome secretion and subsequent apoptosis [7].
• DAG kinase activity was monitored by DAG phosphorylation and individual DAG molecular species were quantified using liquid chromatography and tandem mass spectrometry-based lipidomics [8].
• Assignment of the gene for diacylglycerol kinase (DAGK) to human chromosome 12 [9].
• Interestingly, the kinetics of DGKA using physiologically relevant long-chain DAGs was dependent on substrate surface concentration and the detergent that was used [10].

Anatomical context of DGKA

• DGKalpha was found associated with the trans-Golgi network and late endosomal compartments [7].
• When transfected with a truncated version of this cDNA, COS-7 cells had a marked increase in DAG kinase activity, which demonstrated clear selectivity for arachidonoyl-containing species of diacylglycerol [11].
• Our study thus demonstrates that the mitogenic activity of 15- and 12-HETE on endothelial cells may be mediated via DAG kinase inhibition with the concomitant accumulation of cellular DAG [12].
• As we had previously shown that Src-mediated activation of diacylglycerol kinase-alpha (Dgk-alpha) is required for hepatocytes growth factor-stimulated cell migration, we asked whether Dgk-alpha is involved in the transduction of angiogenic signaling [13].
• In PAE-KDR cells, an endothelial-derived cell line expressing VEGFR-2, VEGF-A165, stimulates the enzymatic activity of Dgk-alpha: activation is inhibited by R59949, an isoform-specific Dgk inhibitor, and is dependent on Src tyrosine kinase, with which Dgk-alpha forms a complex [13].

Associations of DGKA with chemical compounds

• Finally, we show the catalytic activity of DGKA was significantly enhanced by phosphatidylserine (PS) and phosphatidic acid (PA) [10].
• In contrast, DGKA displayed sigmoidal kinetics with respect to bulk substrate concentrations at all surface concentrations in Triton X-100 mixed micelles [10].
• DGKA displayed Michaelis-Menten kinetics with respect to bulk substrate concentration (1,2-dioleoyl-sn-glycerol) in octyl glucoside mixed micelles when the surface substrate concentration was at or below 3.5 mol % [10].
• In vitro assays revealed that both 1,2-diacylglycerol and 1-O-alkyl-2-acylglycerol were substrates for 1,2-diacylglycerol kinase alpha, the major isoform in CTLL-2 cells, and that the lipid kinase activity was almost totally inhibited by R59949 [14].
• Three immediate metabolites of DiC8, monooctanoylglycerol, octanoate, and glycerol, did not evoke any change in [Ca2+]i. Monooleoylglycerol and R59022, which induce increases in endogenous diacylglycerol (DAG) by inhibiting DAG kinase, evoked increases in [Ca2+]i. DiC8 did not cause any change in inositol 1,4,5-trisphosphate levels [15].
• We show that DGKalpha is tyrosine phosphorylated, and identify tyrosine 335 (Y335), at the hinge between the atypical C1 domains and the catalytic region, as essential for membrane localization [16].

Regulatory relationships of DGKA

• Diacylglycerol kinase alpha regulates the secretion of lethal exosomes bearing Fas ligand during activation-induced cell death of T lymphocytes [7].

Other interactions of DGKA

• A new role of diacylglycerol kinase alpha on the secretion of lethal exosomes bearing Fas ligand during activation-induced cell death of T lymphocytes [17].
• Recently, a protein that is significantly similar to human DGK-theta, DGKA, was identified in Dictyostelium discoideum [10].
• Activation of diacylglycerol kinase alpha is required for VEGF-induced angiogenic signaling in vitro [13].
• The metabolic fates for DAG include 1) ATP-dependent phosphorylation to form phosphatidic acid (DAG kinase), 2) hydrolysis to release fatty acids and glycerol (DAG and monoacylglycerol lipases), 3) synthesis of triacylglycerol (DAG acyltransferase), and 4) synthesis of PC (choline phosphotransferase) [18].

Analytical, diagnostic and therapeutic context of DGKA

• Assignment of the human diacylglycerol kinase gene (DAGK) to 12q13.3 using fluorescence in situ hybridization analysis [19].
• In cells transfected with the DGKiota cDNA, we detected an approximately 130-kDa protein by immunoassay, and activity assays demonstrated that it encodes a functional DAG kinase [20].
• Western blots of various DAG kinase isoforms were not changed by d-alpha-tocopherol treatment [2].

References