TY - THES A1 - De Lira, Maria Nathalia T1 - The regulation of T cell metabolism by neutral sphingomyelinase 2 T1 - Die Regulation des T-Zell-Metabolismus durch Neutrale Sphingomyelinase 2 N2 - T cells play an essential role in the immune system. Engaging the T cell receptor (TCR) initiates a cascade of signaling events that activates the T cells. Neutral sphingomyelinase (NSM) is a member of a superfamily of enzymes responsible for the hydrolysis of sphingomyelin into phosphocholine and ceramide. Sphingolipids are essential mediators in signaling cascades involved in apoptosis, proliferation, stress responses, necrosis, inflammation, autophagy, senescence, and differentiation. Upon specific ablation of NSM2, T cells proved to be hyper-responsive to CD3/CD28 co-stimulation, indicating that the enzyme acts to dampen early overshooting activation of these cells. It remained unclear whether a deregulated metabolic activity supports the hyper-reactivity of NSM2 deficient T cells. This work demonstrates that the ablation of NSM2 activity affects the metabolism of the quiescent CD4+ T cells. These accumulate ATP in mitochondria and increase basal glycolytic activity by increasing the basal glucose uptake and GLUT1 receptor expression, which, altogether, raises intracellular ATP levels and boosts cellular respiration. The increased basal metabolic activity is associated with rapid phosphorylation of S6, a mTORC1 target, as well as enhanced elevation total ATP levels within the first hour after CD3/CD28 costimulation. Increased metabolic activity in resting NSM2 deficient T cells does, however, not support sustained stimulated responses. While elevated under steady-state conditions and elevated early after co-stimulation in NSM2 deficient CD4+ T cells, the mTORC1 pathway regulating mitochondria size, oxidative phosphorylation, and ATP production is impaired after 24 hours of stimulation. Taken together, the absence of NSM2 promotes a hyperactive metabolic state in unstimulated CD4+ T cells yet fails to support sustained T cell responses upon antigenic stimulation without affecting T cell survival. N2 - T-Zellen spielen eine wesentliche Rolle im Immunsystem. Die Aktivierung des T-Zell-Rezeptors (TCR) löst eine Kaskade von Signalereignissen aus, die die T-Zellen aktivieren. Neutrale Sphingomyelinase (NSM) gehört zu einer Superfamilie von Enzymen, die für die Aufspaltung von Sphingomyelin in Phosphocholin und Ceramid verantwortlich sind. Sphingolipide sind wesentliche Mediatoren in Signalkaskaden, die an Apoptose, Proliferation, Stressreaktionen, Nekrose, Entzündung, Autophagie, Seneszenz und Differenzierung beteiligt sind. NSM2-depletierte T-Zellen erwiesen sich als hyper-reaktiv gegenüber CD3/CD28-Kostimulation, was darauf hinweist, dass das Enzym eine überschießende Aktivierung dieser Zellen dämpft. Es blieb unklar, ob die Hyperreaktivität NSM2-defizienter T-Zellen durch eine deregulierte Stoffwechselaktivität unterstützt wird. Diese Arbeit zeigt, dass NSM2-Insuffizienz den Metabolismus ruhender CD4+-T-Zellen beeinflusst: Diese akkumulieren ATP in Mitochondrien und zeigen eine erhöhte basale glykolytische Aktivität, die auf einer erhöhten Glukoseaufnahme und Expression des GLUT1-Rezeptors beruht und mit einer Erhöhung intrazellulärer ATP-Werte und gesteigerten Zellrespiration einhergeht. Aufgrund ihrer bereits erhöhten basalen metabolische Aktivität zeigen NSM2 defiziente T Zellen eine im Vergleich zu Kontrollzellen schnellere, effizientere Aktivierung nach Kostimulation, die sich in Phosphorylierung von S6, eines mTORC1 Targets, sowie erhöhtem ATP Spiegel manifestiert. Dies kann jedoch nicht aufrechterhalten werden:Die mTORC1-Aktivierung, die die Größe der Mitochondrien, die oxidative Phosphorylierung und die ATP-Produktion reguliert, unter stationären Bedingungen in NSM2-defizienten CD4+-T-Zellen erhöht ist, ist nach 24-stündiger Kostimulation beeinträchtigt. Insgesamt scheint die NSM2-Aktivität wesentlich für die Regulation der basalen metabolischen Aktivität ruhender T-Zellen und der Vermeidung überschiessender Antworten nach Kostimulation zu sein, jedoch ebenso wichtig für die dauerhafte Aufrechterhaltung des Aktivierungssignals zu sein. KW - T zellen KW - metabolism KW - t cell KW - NSM2 KW - mitochondria Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-215673 ER - TY - JOUR A1 - De Lira, Maria Nathalia A1 - Raman, Sudha Janaki A1 - Schulze, Almut A1 - Schneider-Schaulies, Sibylle A1 - Avota, Elita T1 - Neutral Sphingomyelinase-2 (NSM 2) Controls T Cell Metabolic Homeostasis and Reprogramming During Activation JF - Frontiers in Molecular Biosciences N2 - Neutral sphingomyelinase-2 (NSM2) is a member of a superfamily of enzymes responsible for conversion of sphingomyelin into phosphocholine and ceramide at the cytosolic leaflet of the plasma membrane. Upon specific ablation of NSM2, T cells proved to be hyper-responsive to CD3/CD28 co-stimulation, indicating that the enzyme acts to dampen early overshooting activation of these cells. It remained unclear whether hyper-reactivity of NSM2-deficient T cells is supported by a deregulated metabolic activity in these cells. Here, we demonstrate that ablation of NSM2 activity affects metabolism of the quiescent CD4\(^+\) T cells which accumulate ATP in mitochondria and increase basal glycolytic activity. This supports enhanced production of total ATP and metabolic switch early after TCR/CD28 stimulation. Most interestingly, increased metabolic activity in resting NSM2-deficient T cells does not support sustained response upon stimulation. While elevated under steady-state conditions in NSM2-deficient CD4\(^+\) T cells, the mTORC1 pathway regulating mitochondria size, oxidative phosphorylation, and ATP production is impaired after 24 h of stimulation. Taken together, the absence of NSM2 promotes a hyperactive metabolic state in unstimulated CD4\(^+\) T cells yet fails to support sustained T cell responses upon antigenic stimulation. KW - neutral sphingomyelinase-2 KW - T cell receptor KW - Seahorse XF KW - oxidative phosphorylation KW - ATP-adenosine triphosphate KW - Mitochondria Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-211311 SN - 2296-889X VL - 7 ER - TY - JOUR A1 - Avota, Elita A1 - de Lira, Maria Nathalia A1 - Schneider-Schaulies, Sibylle T1 - Sphingomyelin breakdown in T cells: role of membrane compartmentalization in T cell signaling and interference by a pathogen JF - Frontiers in Cell and Developmental Biology N2 - Sphingolipids are major components of cellular membranes, and at steady-state level, their metabolic fluxes are tightly controlled. On challenge by external signals, they undergo rapid turnover, which substantially affects the biophysical properties of membrane lipid and protein compartments and, consequently, signaling and morphodynamics. In T cells, external cues translate into formation of membrane microdomains where proximal signaling platforms essential for metabolic reprograming and cytoskeletal reorganization are organized. This review will focus on sphingomyelinases, which mediate sphingomyelin breakdown and ensuing ceramide release that have been implicated in T-cell viability and function. Acting at the sphingomyelin pool at the extrafacial or cytosolic leaflet of cellular membranes, acid and neutral sphingomyelinases organize ceramide-enriched membrane microdomains that regulate T-cell homeostatic activity and, upon stimulation, compartmentalize receptors, membrane proximal signaling complexes, and cytoskeletal dynamics as essential for initiating T-cell motility and interaction with endothelia and antigen-presenting cells. Prominent examples to be discussed in this review include death receptor family members, integrins, CD3, and CD28 and their associated signalosomes. Progress made with regard to experimental tools has greatly aided our understanding of the role of bioactive sphingolipids in T-cell biology at a molecular level and of targets explored by a model pathogen (measles virus) to specifically interfere with their physiological activity. KW - T cell KW - sphingomyelinase KW - activation KW - motility KW - measles virus Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199168 SN - 2296-634X VL - 7 IS - 152 ER -