Phospholipase A2 and Signal Transduction

Massachusetts General Hospital, Boston MA

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Abstract

Description (provided by applicant) Our proposed studies will focus on defining the roles played by group IVA cytosolic phospholipase A2 (cPLA2) and group IIa and V sPLA2 enzymes in mesangial cell signaling pathways important for growth regulation and inflammation. We will capitalize on the (cPLA2 /-, IIaPLA2-/-), (cPLA2-/-, IIaPLA2+/+) mice, as well as littermate control (cPLA2+/+, LA2-/-) and (cPLA2+/+, IIaPLA2+/+) mice which we have generated, the unique lines of mesangial cells derived from these mice, and reagents we have generated for PLIP and TRIP-Brl, two nuclear proteins which we have cloned. In Specific Aim 1 we will determine the role of cPLA2, the group IIa and V sPLAs, and the cPLA2-interacting protein, PLIP, in a mesangial cell PI-3kinase/Akt/GSK-3b/b-catenin signaling pathway which we propose regulates cyclin, cyclin-dependent kinase (cdk) and cyclin-dependent kinase inhibitors (cdkIs) and other proteins important for this cell's proliferative response to growth factors and inflammatory cytokines. The importance of nuclear translocation of components of the signaling pathway will be explored. The relative roles of cPLA2, groups IIa and V PLA2 and PLIP (and the alternatively spliced Tip60) on ERK activation, c-Myc expression, and TRIP-Br levels will be evaluated. We will also attempt to identify the effector of cPLA2-induced modulation of the PI3-kinase/Akt/GSK-3beta and cdkI/cyclin signaling systems, evaluating specifically the potential roles of noncyclooxygenase products of arachidonic acid and NADPH oxidase. In Specific Aim 2 we will determine the role of cPLA2 in TNFa- and IL-1beta-induced apoptosis and generation and secretion of inflammatory mediators and determine how the absence of cPLA2 and or group IIa PLA2 alters the response of the glomerulus in experimental models of glomerulonephritis, Cytokine signaling is important for inflammatory responses as well as proliferative ones. Effects of PLIP/Tip60 on cytokine-induced apoptosis will be evaluated. We will use our unique cell lines to dissect the role of arachidonic acid generated by PLA2 or group IIa or V sPLA2 on oxidant stress in the cell and evaluate the roles played by arachidonate and oxidants in eicosanoid production and NF-kB action. The effects of cPLA2, PLIP and groups IIa and V PLA2 on mesangial cell secretion of monocyte chemoattractant protein (MCP-1) and role of phospholipase D2 activity will in secretion of MCP-1 and group IIa PLA2 be explored.