Mitochondrial Glycerol-3-Phosphate Acyltransferase-Dependent Phospholipid Synthesis Modulates Phospholipid Mass and...

Changes in glycerophospholipid metabolism with age and disease can have a profound effect on immune cell activation and effector function. We previously demonstrated that glycerol-3-phosphate acyltransferase-1, the first and rate limiting step in de novo glycerophospholipid synthesis, plays a role in modulating murine T cell function. The resultant phenotype is characterized by decreased IL-2 production, increased propensity toward apoptosis, and altered membrane glycerophospholipid mass similar to that of an aged T cell. Since T cells in previous experiments were harvested from GPAT-1(-/-) mice, questions remained as to what extent the macro environment of the model influenced the observed cellular phenotype. Therefore, we generated and phenotypically characterized a mitochondrial glycerol-3-phosphate acyltransferase (GPAM) deficient Jurkat T cell. Furthermore, this line was used to probe possible mechanisms by which GPAT-1/GPAM regulates T cell function. We report here that many of the key dysfunctional characteristics of murine GPAT-1(-/-) T cells are recapitulated in the GPAMKD Jurkat T cell. We found striking decreased IL-2 production along with altered phospholipid mass and increased incidence of apoptosis. Since PtdOH is an indirect downstream product of GPAM, we attempted to rescue IL-2 production with PtdOH supplementation; however, this addition did not return IL-2 production to normal levels. Interestingly, we did find significantly decreased Zap-70 phosphorylation following stimulation, suggesting that GPAM deficiency may alter membrane based stimulatory signaling. These data show for the first time that GPAM deficiency results in an inherent defect in Jurkat T cell function and glycerophospholipid composition and that this defect cannot be rescued by addition of exogenous PtdOH.