Abstract
Abstract Regulation of lytic activity in CD8+ CTL remains incompletely understood despite the importance of this effector T cell function in immune response to intracellular pathogens and tumors. One important aspect involving the regulation of T cell effector function is the spatio-temporal regulation of DAG metabolism in T cells. Based on the involvement of phospholipase D (PLD) isoforms in DAG metabolism-related regulation of vesicular trafficking in other cells types, we reasoned that these enzymes might regulate lytic function in CD8+ T cells. By combining the use of pharmacological inhibitors and siRNA-mediated knockdown, we showed that PLD1 isoform modulates lytic function in primary mouse CD8+ CTL. Surprisingly, PLD1 knockdown in CTL lead to the enhancement of lytic activity despite its inhibitory effect on conjugate formation. The observed phenotype was not due to increased levels of expression of lytic molecules but was due to an increased release of lytic granule contents in response to TCR engagement. At the same time, overexpression of PLD1 in CTL resulted in the inhibition of lytic activity that coincided with an accumulation at the immunological synapse of both phosphatidic acid (PA), a byproduct of PLD1, and actin. Thus, PLD1 regulates the degree of lytic response in CD8+ CTL, potentially via PA-mediated induction of actin polymerization at the synapse, which could serve as a molecular gate that controls the extent of lytic granule release toward target cells.
Published Version
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