Our hypothesis in the previous project period was that a pancreatic islet Ca2+ -independent phospholipase A2 (iPLA2B) is activated upon stimulation with secretagogues and that its products participate in B-cell signaling. We have now cloned iPLA2B from islet mRNA and determined the human iPLA2 gene structure and chromosomal location. Recombinant iPLA2B is inhibited by a bromoenol lactone (BEL) suicide substrate that also suppresses glucose-induced insulin secretion, and iPLA2B overexpression. amplifies insulinoma cell secretion and proliferation. We have also found that arachidonate-containing plasmalogens, which participate in membrane fusion and exocytosis, are abundant in B-cells, and these ether lipids are produced from peroxisome-derived intermediates. An iPLA2gamma isozyme targeted to peroxisomes is also expressed in islets and may participate in regulating complex lipid synthesis. Peroxisomal dysregulation could contribute to pathologic tissue lipid accumulation in diabetes. The recent success of human islet transplantation and the limited availability of donor organs highlights the need to identify genes and their products that affect B-cell secretion and survival to facilitate construction of engineered B-cell lines that might serve as an alternate source of transplantable B-cells. In the coming project period, we propose to further characterize roles of iPLA2 isozymes, complex lipids, and peroxisomes in B-cell function and to develop genetically modified mice with altered iPLA2B expression for in vivo studies.
Aim 1 is to characterize secretion, proliferation, and other responses of insulinoma cells and islets in which iPLA2B expression is manipulated by molecular biologic means.
Aim 2 is to characterize roles of complex lipids in B-cell function and of iPLA2 isozymes and peroxisomes in lipid formation.
Aim 3 is to characterize regulatory post-translational modifications of the iPLA2B protein.
Aim 4 is to conduct cell biologic studies of iPLA2B translocation among cellular compartments and interactions with other proteins.
Aim 5 is to develop genetically modified mice with altered iPLA2B expression for in vivo studies. We have prepared mouse embryonic stem cells in which an iPLA2B allele has been disrupted by homologous recombination as a step to generate mice that do not express the enzyme.
|Turk, John; White, Tayleur D; Nelson, Alexander J et al. (2018) iPLA2? and its role in male fertility, neurological disorders, metabolic disorders, and inflammation. Biochim Biophys Acta Mol Cell Biol Lipids :|
|Thimgan, Matthew S; Seugnet, Laurent; Turk, John et al. (2015) Identification of genes associated with resilience/vulnerability to sleep deprivation and starvation in Drosophila. Sleep 38:801-14|
|Tan, Chunyan; Day, Robert; Bao, Shunzhong et al. (2014) Group VIA phospholipase A2 mediates enhanced macrophage migration in diabetes mellitus by increasing expression of nicotinamide adenine dinucleotide phosphate oxidase 4. Arterioscler Thromb Vasc Biol 34:768-78|
|Blanchard, Helene; Taha, Ameer Y; Cheon, Yewon et al. (2014) iPLA2? knockout mouse, a genetic model for progressive human motor disorders, develops age-related neuropathology. Neurochem Res 39:1522-32|
|Lei, Xiaoyong; Bone, Robert N; Ali, Tomader et al. (2014) Evidence of contribution of iPLA2?-mediated events during islet ?-cell apoptosis due to proinflammatory cytokines suggests a role for iPLA2? in T1D development. Endocrinology 155:3352-64|
|Song, Haowei; Wohltmann, Mary; Tan, Min et al. (2014) Group VIA phospholipase A2 mitigates palmitate-induced ?-cell mitochondrial injury and apoptosis. J Biol Chem 289:14194-210|
|Lei, Xiaoyong; Bone, Robert N; Ali, Tomader et al. (2013) Genetic modulation of islet ?-cell iPLA?? expression provides evidence for its impact on ?-cell apoptosis and autophagy. Islets 5:29-44|
|Tatituri, Raju V V; Watts, Gerald F M; Bhowruth, Veemal et al. (2013) Recognition of microbial and mammalian phospholipid antigens by NKT cells with diverse TCRs. Proc Natl Acad Sci U S A 110:1827-32|
|Lodhi, Irfan J; Yin, Li; Jensen-Urstad, Anne P L et al. (2012) Inhibiting adipose tissue lipogenesis reprograms thermogenesis and PPAR? activation to decrease diet-induced obesity. Cell Metab 16:189-201|
|Liu, Shu; Xie, Zhongwen; Zhao, Qingwei et al. (2012) Smooth muscle-specific expression of calcium-independent phospholipase A2? (iPLA2?) participates in the initiation and early progression of vascular inflammation and neointima formation. J Biol Chem 287:24739-53|
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