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 (PKCδ), a novel PKC isotype activated by diacylglycerol (DAG), regulates TCR-controlled MVB polarization toward the IS and exosome secretion. Concomitantly, we demonstrate that PKCδ-interfered T lymphocytes are defective in activation-induced cell death. Using a DAG sensor based on the C1 DAG-binding domain of PKCδ and a GFP-PKCδ chimera, we reveal that T lymphocyte activation enhances DAG levels at the MVB endomembranes which mediates the association of PKCδ to MVB. Spatiotemporal reorganization of F-actin at the IS is inhibited in PKCδ-interfered T lymphocytes. Therefore, we propose PKCδ as a DAG effector that regulates the actin reorganization necessary for MVB traffic and exosome secretion.

Childhood cancer patients are at risk of developing important adverse effects, mortality and disease relapse after treatments, which has a substantial economic impact on healthcare systems. The objective of this study was to determine the effects of supervised inhospital exercise on clinical endpoints during childhood cancer treatment.169 children with a new diagnosis of cancer were divided into an exercise intervention (n = 68, 11 ± 4 years) or a control group (n = 101, 11 ± 3 years). The cohort was followed up from the start of treatment for up to five years. Supervised inhospital exercise intervention was performed during the neoadjuvant (for solid tumors) or intensive chemotherapy treatment period (for leukemias). The median duration of the intervention was 22 (interquartile range, 14-28) weeks. We assessed survival, risk of disease relapse or metastasis, and days of hospitalization (primary outcomes), and cardiovascular function, anthropometry and blood variables (secondary outcomes).No exercise-related adverse events were noted. The exercise group had significantly less days of hospitalization than the control group (P = .031), resulting in a lower (~−17%) mean total economic cost of hospitalization in the former. Moreover, echocardiography-determined left ventricular function (ejection fraction and fractional shortening) was significantly impaired in the control group after treatment compared with baseline, whereas it was maintained in the exercise group (P = .024 and .021 for the between-group differences, respectively). In conclusion, supervised inhospital exercise intervention is safe and plays a cardioprotective role, at least in the short term, in children with cancer, also reducing hospitalization time, and therefore alleviating the economic burden.

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We recently uncovered a regulatory pathway of the muscle isoform of glycogen phosphorylase (PYGM) that plays an important role in regulating immune function in T cells. Here, using various enzymatic, pulldown, and immunoprecipitation assays, we describe signaling cross-talk between the small GTPases RAS and RAP1A, member of RAS oncogene family (RAP1) in human Kit 225 lymphoid cells, which, in turn, is regulated by the epidermal growth factor receptor (EGFR). We found that this communication bridge is essential for glycogen phosphorylase (PYG) activation through the canonical pathway because this enzyme is inactive in the absence of adenylyl cyclase type 6 (ADCY6). PYG activation required stimulation of both exchange protein directly activated by cAMP 2 (EPAC2) and RAP1 via RAS and ADCY6 phosphorylation, with the latter being mediated by Raf-1 proto-oncogene, Ser/ Thr kinase (RAF1). Consistent with this model, PYG activation was EGFR-dependent and may be initiated by the constitutively active form of RAS. Consequently, PYG activation in Kit 225 T cells could be blocked with specific inhibitors of RAS, EPAC, RAP1, RAF1, ADCY6, and cAMP-dependent protein kinase. Our results establish a new paradigm for the mechanism of PYG activation, which depends on the type of receptor involved.