Grant: Discovery Grants Program - Individual

Mammalian cells tightly regulate the fatty acid composition of cellular phospholipids (PL). Enzymes including phospholipases, acyl-CoA synthetases and acyl-transferases can remodel PL generating new PL molecular species, including those containing polyunsaturated fatty acids (PUFA). This remodeling is largely responsible for the significant differences in the fatty acid composition, including PUFA, between different cell types or in cells under different activation states. Until recently, little information was available on the enzymes involved in generating this large diversity of PL molecular species. While several different isotypes of remodeling enzymes have been recently identified, the roles of individual isotypes in the generation of cellular PL diversity and on different cellular functions is largely unexplored. One outcome of PL remodeling is the capacity of cells to produce lipid mediators of inflammation, which are derived from PUFA. These mediators play important roles in initiating and terminating (resolving) inflammatory reactions. Macrophages are key immune cells that can be polarization into M1 and M2 cells. M1 cells produce lipid mediators that are primarily proinflammatory and M2 cells primarily produce pro-resolution lipid mediators. However, the impact of macrophage cell polarization on PL remodeling, including the expression of related genes/enzymes has not been evaluated, nor has the role of PL remodeling on lipid mediator synthesis been investigated in these cells. Therefore, the goals of AIM 1 of this proposal will be to characterize the molecular species of PL found in M1 and M2 cells, to identify potential remodeling genes/enzymes expressed in these cells, and to investigate the impact of gene silencing for targeted enzymes on PL profiles and lipid mediator production in these cells. T cells, like macrophages, are also key players in immunity. Upon stimulation, T cells begin to proliferate. We and others have shown that such stimulation of human T cells results in a significant modification of the fatty acid composition of cellular PL compared to non-proliferating T cells. While there is some evidence that aspects of PL remodeling are required for the maintenance of T cell proliferation, there is little information on the PL molecular species that are produced in response to the induction of T cell proliferation, nor on any associated changes in related gene and protein expression. Therefore, AIM 2 of this proposal will characterize the impact of T cell stimulation on changes in PL molecular species, and on changes in the expression of genes/enzymes potentially associated with PL remodeling. The impact of gene silencing of targeted enzymes on PL profiles and their role or requirement for appropriate cell proliferation will also be investigated. This research program will generate significant new information on the control of PL remodeling and the role that it plays in some important aspects of immune responses.