Protein Kinase C δ Regulates the Depletion of Actin at the Immunological Synapse Required for Polarized Exosome Secretion by T Cells.

Multivesicular bodies (MVB) are endocytic compartments that enclose intraluminal vesicles (ILVs) formed by inward budding from the limiting membrane of endosomes. In T lymphocytes, ILVs are secreted as Fas ligand-bearing, pro-apoptotic exosomes following T cell receptor (TCR)-induced fusion of MVB with the plasma membrane at the immune synapse (IS). In this study we show that protein kinase C δ a novel isotype activated by diacylglycerol (DAG), regulates TCR-controlled MVB polarization toward the IS and exosome secretion. Concomitantly, we demonstrate that T lymphocytes are defective in activation-induced cell death. Using a DAG sensor based on the C1 DAG-binding domain of and a chimera, we reveal that T lymphocyte activation enhances DAG levels at the MVB endomembranes which mediates the association of duanyu1531δ to MVB. Spatiotemporal reorganization of F-actin at the IS is inhibited in duanyu1531δ-interfered T lymphocytes. Therefore, we propose duanyu1531δ as a DAG effector that regulates the actin reorganization necessary for MVB traffic and exosome secretion.

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