Latrepirdine improves cognition and arrests progression of neuropathology in an Alzheimer's mouse model

Latrepirdine (Dimebon) is a pro-neurogenic, antihistaminic compound that has yielded mixed results in clinical trials of mild to moderate Alzheimer's disease, with a dramatically positive outcome in a Russian clinical trial that was unconfirmed in a replication trial in the United States. We sought to determine whether latrepirdine (LAT)-stimulated amyloid precursor protein (APP) catabolism is at least partially attributable to regulation of macroautophagy, a highly conserved protein catabolism pathway that is known to be impaired in brains of patients with Alzheimer's disease (AD). We utilized several mammalian cellular models to determine whether LAT regulates mammalian target of rapamycin (mTOR) and Atg5-dependent autophagy. Male TgCRND8 mice were chronically administered LAT prior to behavior analysis in the cued and contextual fear conditioning paradigm, as well as immunohistological and biochemical analysis of AD-related neuropathology. Treatment of cultured mammalian cells with LAT led to enhanced mTOR- and Atg5-dependent autophagy. Latrepirdine treatment of TgCRND8 transgenic mice was associated with improved learning behavior and with a reduction in accumulation of Aβ42 and α-synuclein. We conclude that LAT possesses pro-autophagic properties in addition to the previously reported pro-neurogenic properties, both of which are potentially relevant to the treatment and/or prevention of neurodegenerative diseases. We suggest that elucidation of the molecular mechanism(s) underlying LAT effects on neurogenesis, autophagy and behavior might warranty the further study of LAT as a potentially viable lead compound that might yield more consistent clinical benefit following the optimization of its pro-neurogenic, pro-autophagic and/or pro-cognitive activities.

What is new in the pathology of pancreatic neuroendocrine tumors?

The diagnostics of pancreatic neuroendocrine tumors (PanNEN) have changed in recent years especially concerning the World Health Organization (WHO) classification, TNM staging and grading. Furthermore, some new prognostic and predictive immunohistochemical markers have been introduced. Most progress, however, has been made in the molecular pathogenesis of these neoplasms. Using next generation sequencing techniques, the mammalian target of rapamycin (mTOR) pathway, hypoxia and epigenetic changes were identified as key players in tumorigenesis. In this article the most important developments of morphological as well as immunohistochemical diagnostics together with the molecular background of PanNEN are summarized.

Rapamycin impairs endothelial cell function in human internal thoracic arteries.

BACKGROUND Definitive fate of the coronary endothelium after implantation of a drug-eluting stent remains unclear, but evidence has accumulated that treatment with rapamycin-eluting stents impairs endothelial function in human coronary arteries. The aim of our study was to demonstrate this phenomenon on functional, morphological and biochemical level in human internal thoracic arteries (ITA) serving as coronary artery model. METHODS After exposure to rapamycin for 20 h, functional activity of ITA rings was investigated using the organ bath technique. Morphological analysis was performed by scanning electron microscopy and evaluated by two independent observers in blinded fashion. For measurement of endothelial nitric oxide synthase (eNOS) release, mammalian target of rapamycin (mTOR) and protein kinase B (PKB) (Akt) activation, Western blotting on human mammary epithelial cells-1 and on ITA homogenates was performed. RESULTS Comparison of the acetylcholine-induced relaxation revealed a significant concentration-dependent decrease to 66 ± 7 % and 36 ± 7 % (mean ± SEM) after 20-h incubation with 1 and 10 μM rapamycin. Electron microscopic evaluation of the endothelial layer showed no differences between controls and samples exposed to 10 μM rapamycin. Western blots after 20-h incubation with rapamycin (10 nM-1 μM) revealed a significant and concentration-dependent reduction of p (Ser 1177)-eNOS (down to 38 ± 8 %) in human mammary epithelial cells (Hmec)-1. Furthermore, 1 μM rapamycin significantly reduced activation of p (Ser2481)-mTOR (58 ± 11 %), p (Ser2481)-mTOR (23 ± 4 %) and p (Ser473)-Akt (38 ± 6 %) in ITA homogenates leaving Akt protein levels unchanged. CONCLUSIONS The present data suggests that 20-h exposure of ITA rings to rapamycin reduces endothelium-mediated relaxation through down-regulation of Akt-phosphorylation via the mTOR signalling axis within the ITA tissue without injuring the endothelial cell layer.

Caffeine affects the biological responses of human hematopoietic cells of myeloid lineage via downregulation of the mTOR pathway and xanthine oxidase activity.

Correction of human myeloid cell function is crucial for the prevention of inflammatory and allergic reactions as well as leukaemia progression. Caffeine, a naturally occurring food component, is known to display anti-inflammatory effects which have previously been ascribed largely to its inhibitory actions on phosphodiesterase. However, more recent studies suggest an additional role in affecting the activity of the mammalian target of rapamycin (mTOR), a master regulator of myeloid cell translational pathways, although detailed molecular events underlying its mode of action have not been elucidated. Here, we report the cellular uptake of caffeine, without metabolisation, by healthy and malignant hematopoietic myeloid cells including monocytes, basophils and primary acute myeloid leukaemia mononuclear blasts. Unmodified caffeine downregulated mTOR signalling, which affected glycolysis and the release of pro-inflammatory/pro-angiogenic cytokines as well as other inflammatory mediators. In monocytes, the effects of caffeine were potentiated by its ability to inhibit xanthine oxidase, an enzyme which plays a central role in human purine catabolism by generating uric acid. In basophils, caffeine also increased intracellular cyclic adenosine monophosphate (cAMP) levels which further enhanced its inhibitory action on mTOR. These results demonstrate an important mode of pharmacological action of caffeine with potentially wide-ranging therapeutic impact for treating non-infectious disorders of the human immune system, where it could be applied directly to inflammatory cells.

Effect of thiazolidinedione, a class of anti-diabetic drugs, on the mouse skin tumorigenesis

Thiazolidinediones (TZDs), a novel class of anti-diabetic drugs, have been known as ligands of peroxisome proliferator-activated receptor γ (PPARγ), a transcription factor that belongs to the nuclear receptor superfamily. These synthetic compounds improve insulin sensitivity in patients with type II diabetes likely through activating PAPRγ. Interestingly, they were also shown to inhibit cell growth and proliferation in a wide variety of tumor cell lines. The aim of this study is to assess the potential use of TZDs in the prevention of carcinogenesis using mouse skin as a model. ^ We found that troglitazone, one of TZD drugs, strongly inhibited cultured mouse skin keratinocyte proliferation as demonstrated by [3H]thymidine incorporation assay. It also induced a cell cycle G1 phase arrest and inhibited expression of cell cycle proteins, including cyclin D1, cdk2 and cdk4. Further experiments showed that PPARγ expression in keratinocytes was surprisingly undetectable in vitro or in vivo. Consistent with this, no endogenous PPARγ function in keratinocytes was found, suggesting that the inhibition of troglitazone on keratinocyte proliferation and cell cycle was PPARγ-independent. We further found that troglitazone inhibited insulin/insulin growth factor I (IGF-1) mitogenic signaling, which may explains, at least partly, its inhibitory effect on keratinocyte proliferation. We showed that troglitazone rapidly inhibited IGF-1 induced phosphorylation of p70S6K by mammalian target of rapamycin (mTOR). However, troglitazone did not directly inhibit mTOR kinase activity as shown by in vitro kinase assay. The inhibition of p70S6K is likely to be the result of strong activation of AMP activated protein kinase (AMPK) by TZDs. Stable expression of a dominant negative AMPK in keratinocytes blocked the inhibitory effect of troglitazone on IGF-1 induced phosphorylation of p70S6K. ^ Finally, we found that dietary TZDs inhibited by up to 73% mouse skin tumor development promoted by elevated IGF-1 signaling in BK5-IGF-1 transgenic mice, while they had no or little effect on skin tumor development promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA) or ultraviolet (UV). Since IGF-1 signaling is frequently found to be elevated in patients with insulin resistance and in many human tumors, our data suggest that TZDs may provide tumor preventive benefit particularly to these patients. ^

Mechanism of attenuation of skeletal muscle atrophy by zinc-α2-glycoprotein

The mechanism by which the adipokine zinc-a2-glycoprotein (ZAG) increases the mass of gastrocnemius, but not soleus muscle of diabetic mice, has been evaluated both in vivo and in vitro. There was an increased phosphorylation of both double-stranded RNA-dependent protein kinase and its substrate, eukaryotic initiation factor-2a, which was attenuated by about two-thirds in gastrocnemius but not soleus muscle of ob/ob mice treated with ZAG (50 µg, iv daily) for 5 d. ZAG also reduced the expression of the phospho forms of p38MAPK and phospholipase A2, as well as expression of the ubiquitin ligases (E3) muscle atrophy F-box/atrogin-1 and muscle RING finger protein, and the increased activity of both caspase-3 and casapse-8 to values found in nonobese controls. ZAG also increased the levels of phospho serine-threonine kinase and mammalian target of rapamycin in gastrocnemius muscle and reduced the phosphorylation of insulin receptor substrate-1 (Ser307) associated with insulin resistance. Similar changes were seen with ZAG when murine myotubes were incubated with high glucose concentrations (10 and 25 mm), showing that the effect of ZAG was direct. ZAG produced an increase in cAMP in murine myotubes, and the effects of ZAG on protein synthesis and degradation in vitro could be replicated by dibutyryl cAMP. ZAG increased cAMP levels of gastrocnemius but not soleus muscle. These results suggest that protein accretion in skeletal muscle in response to ZAG may be due to changes in intracellular cAMP and also that ZAG may have a therapeutic application in the treatment of muscle wasting conditions.

Attenuation of depression of muscle protein synthesis induced by lipopolysaccharide, tumor necrosis factor, and angiotensin II by beta-hydroxy-beta-methylbutyrate

beta-Hydroxy-beta-methylbutyrate (HMB; 50 microM) has been shown to attenuate the depression in protein synthesis in murine myotubes in response to lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) with or without interferon-gamma (IFN-gamma), and angiotensin II (ANG II). The mechanism for the depression of protein synthesis by all three agents was the same and was attributed to activation of double-stranded RNA-dependent protein kinase (PKR) with the subsequent phosphorylation of eukaryotic initiation factor 2 (eIF2) on the alpha-subunit as well as increased phosphorylation of the elongation factor (eEF2). Myotubes expressing a catalytically inactive PKR variant, PKRDelta6, showed no depression of protein synthesis in response to either LPS or TNF-alpha, confirming the importance of PKR in this process. There was no effect of any of the agents on phosphorylation of mammalian target of rapamycin (mTOR) or initiation factor 4E-binding protein (4E-BP1), and thus no change in the amount of eIF4E bound to 4E-BP1 or the concentration of the active eIF4E.eIF4G complex. HMB attenuated phosphorylation of eEF2, possibly by increasing phosphorylation of mTOR, and also attenuated phosphorylation of eIF2alpha by preventing activation of PKR. These results suggest that HMB may be effective in attenuating muscle atrophy in a range of catabolic conditions.

Involvement of phosphoinositide 3-kinase and Akt in the induction of muscle protein degradation by proteolysis-inducing factor

In the present study the role of Akt/PKB (protein kinase B) in PIF- (proteolysis-inducing factor) induced protein degradation has been investigated in murine myotubes. PIF induced transient phosphorylation of Akt at Ser(473) within 30 min, which was attenuated by the PI3K (phosphoinositide 3-kinase) inhibitor LY294002 and the tyrosine kinase inhibitor genistein. Protein degradation was attenuated in myotubes expressing a dominant-negative mutant of Akt (termed DNAkt), compared with the wild-type variant, whereas it was enhanced in myotubes containing a constitutively active Akt construct (termed MyrAkt). A similar effect was observed on the induction of the ubiquitin-proteasome pathway. Phosphorylation of Akt has been linked to up-regulation of the ubiquitin-proteasome pathway through activation of NF-kappaB (nuclear factor kappaB) in a PI3K-dependent process. Protein degradation was attenuated by rapamycin, a specific inhibitor of mTOR (mammalian target of rapamycin), when added before, or up to 30 min after, addition of PIF. PIF induced transient phosphorylation of mTOR and the 70 kDa ribosomal protein S6 kinase. These results suggest that transient activation of Akt results in an increased protein degradation through activation of NF-kappaB and that this also allows for a specific synthesis of proteasome subunits.

Protein quality and distribution determines anabolic signaling, cellular energetics, and body composition

Building and maintaining muscle is critical to the quality of life for adults and elderly. Physical activity and nutrition are important factors for long-term muscle health. In particular, dietary protein – including protein distribution and quality – are under-appreciated determinants of muscle health for adults. The most unequivocal evidence for the benefit of optimal dietary protein at individual meals is derived from studies of weight management. During the catabolic condition of weight loss, higher protein diets attenuate loss of lean tissue and partition weight loss to body fat when compared with commonly recommended high carbohydrate, low protein diets. Muscle protein turnover is a continuous process in which proteins are degraded, and replaced by newly synthesized proteins. Muscle growth occurs when protein synthesis exceeds protein degradation. Regulation of protein synthesis is complex, with multiple signals influencing this process. The mammalian target of rapamycin (mTORC1) pathway has been identified as a particularly important regulator of protein synthesis, via stimulation of translation initiation. Key regulatory points of translation initiation effected by mTORC1 include assembly of the eukaryotic initiation factor 4F (eIF4F) complex and phosphorylation of the 70 kilodalton ribosomal protein S6 kinase (S6K1). Assembly of the eIF4F initiation complex involves phosphorylation of the inhibitory eIF4E binding protein-1 (4E-BP1), which releases the initiation factor eIF4E and allows it to bind with eIF4G. Binding of eIF4E with eIF4G promotes preparation of the mRNA for binding to the 43S pre-initiation complex. Consumption of the amino acid leucine (Leu) is a key factor determining the anabolic response of muscle protein synthesis (MPS) and mTORC1 signaling to a meal. Research from this dissertation demonstrates that the peak activation of MPS following a complete meal is proportional to the Leu content of a meal and its ability to elevate plasma Leu. Leu has also been implicated as an inhibitor of muscle protein degradation (MPD). In particular, there is evidence suggesting that in muscle wasting conditions Leu supplementation attenuates expression of the ubiquitin-proteosome pathway, which is the primary mode of intracellular protein degradation. However, this is untested in healthy, physiological feeding models. Therefore, an experiment was performed to see if feeding isonitrogenous protein sources with different Leu contents to healthy adult rats would differentially impact ubiquitin-proteosome (protein degradation) outcomes; and if these outcomes are related to the meal responses of plasma Leu. Results showed that higher Leu diets were able to attenuate total proteasome content but had no effect on ubiquitin proteins. This research shows that dietary Leu determines postprandial muscle anabolism. In a parallel line of research, the effects of dietary Leu on changes in muscle mass overtime were investigated. Animals consuming higher Leu diets had larger gastrocnemius muscle weights; furthermore, gastrocnemius muscle weights were correlated with postprandial changes in MPS (r=0.471, P<0.01) and plasma Leu (r=0.400, P=0.01). These results show that the effect of Leu on ubiquitin-proteosome pathways is minimal for healthy adult rats consuming adequate diets. Thus, long-term changes in muscle mass observed in adult rats are likely due to the differences in MPS, rather than MPD. Factors determining the duration of Leu-stimulated MPS were further investigated. Despite continued elevations in plasma Leu and associated translation initiation factors (e.g., S6K1 and 4E-BP1), MPS returned to basal levels ~3 hours after a meal. However, administration of additional nutrients in the form of carbohydrate, Leu, or both ~2 hours after a meal was able to extend the elevation of MPS, in a time and dose dependent manner. This effect led to a novel discovery that decreases in translation elongation activity was associated with increases in activity of AMP kinase, a key cellular energy sensor. This research shows that the Leu density of dietary protein determines anabolic signaling, thereby affecting cellular energetics and body composition.

Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise

Background: Ingestion of whey or casein yields divergent patterns of aminoacidemia that influence whole-body and skeletal muscle myofibrillar protein synthesis (MPS) after exercise. Direct comparisons of the effects of contrasting absorption rates exhibited by these proteins are confounded by their differing amino acid contents. Objective: Our objective was to determine the effect of divergent aminoacidemia by manipulating ingestion patterns of whey protein alone on MPS and anabolic signaling after resistance exercise. Design: In separate trials, 8 healthy men consumed whey protein either as a single bolus (BOLUS; 25-g dose) or as repeated, small, "pulsed" drinks (PULSE; ten 2.5-g drinks every 20 min) to mimic a more slowly digested protein. MPS and phosphorylation of signaling proteins involved in protein synthesis were measured at rest and after resistance exercise. Results: BOLUS increased blood essential amino acid (EAA) concentrations above those of PULSE (162% compared with 53%, P < 0.001) 60 min after exercise, whereas PULSE resulted in a smaller but sustained increase in aminoacidemia that remained elevated above BOLUS amounts later (180-220 min after exercise, P < 0.05). Despite an identical net area under the EAA curve, MPS was elevated to a greater extent after BOLUS than after PULSE early (1-3 h: 95% compared with 42%) and later (3-5 h: 193% compared with 121%) (both P < 0.05). There were greater changes in the phosphorylation of the Akt-mammalian target of rapamycin pathway after BOLUS than after PULSE. Conclusions: Rapid aminoacidemia in the postexercise period enhances MPS and anabolic signaling to a greater extent than an identical amount of protein fed in small pulses that mimic a more slowly digested protein. A pronounced peak aminoacidemia after exercise enhances protein synthesis.

mTOR function in skeletal muscle : a focal point for overnutrition and exercise

The mammalian target of rapamycin (mTOR) is a highly conserved atypical serine-threonine kinase that controls numerous functions essential for cell homeostasis and adaptation in mammalian cells via 2 distinct protein complex formations. Moreover, mTOR is a key regulatory protein in the insulin signalling cascade and has also been characterized as an insulin-independent nutrient sensor that may represent a critical mediator in obesity-related impairments of insulin action in skeletal muscle. Exercise characterizes a remedial modality that enhances mTOR activity and subsequently promotes beneficial metabolic adaptation in skeletal muscle. Thus, the metabolic effects of nutrients and exercise have the capacity to converge at the mTOR protein complexes and subsequently modify mTOR function. Accordingly, the aim of the present review is to highlight the role of mTOR in the regulation of insulin action in response to overnutrition and the capacity for exercise to enhance mTOR activity in skeletal muscle.

Simian Virus 40 Small T Antigen Activates AMPK and Triggers Autophagy To Protect Cancer Cells from Nutrient Deprivation

As tumors grow larger, they often experience an insufficient supply of oxygen and nutrients. Hence, cancer cells must develop mechanisms to overcome these stresses. Using an in vitro transformation model where the presence of the simian virus 40 (SV40) small T (ST) antigen has been shown to be critical for tumorigenic transformation, we investigated whether the ST antigen has a role to play in regulating the energy homeostasis of cancer cells. We find that cells expressing the SV40 ST antigen (+ST cells) are more resistant to glucose deprivation-induced cell death than cells lacking the SV40 ST antigen (-ST cells). Mechanistically, we find that the ST antigen mediates this effect by activating a nutrient-sensing kinase, AMP-activated protein kinase (AMPK). The basal level of active, phosphorylated AMPK was higher in +ST cells than in -ST cells, and these levels increased further in response to glucose deprivation. Additionally, inhibition of AMPK in +ST cells increased the rate of cell death, while activation of AMPK in -ST cells decreased the rate of cell death, under conditions of glucose deprivation. We further show that AMPK mediates its effects, at least in part, by inhibiting mTOR (mammalian target of rapamycin), thereby shutting down protein translation. Finally, we show that +ST cells exhibit a higher percentage of autophagy than -ST cells upon glucose deprivation. Thus, we demonstrate a novel role for the SV40 ST antigen in cancers, where it functions to maintain energy homeostasis during glucose deprivation by activating AMPK, inhibiting mTOR, and inducing autophagy as an alternate energy source.

Role of T cells in malnutrition and obesity.

Nutritional status is critically important for immune cell function. While obesity is characterized by inflammation that promotes metabolic syndrome including cardiovascular disease and insulin resistance, malnutrition can result in immune cell defects and increased risk of mortality from infectious diseases. T cells play an important role in the immune adaptation to both obesity and malnutrition. T cells in obesity have been shown to have an early and critical role in inducing inflammation, accompanying the accumulation of inflammatory macrophages in obese adipose tissue, which are known to promote insulin resistance. How T cells are recruited to adipose tissue and activated in obesity is a topic of considerable interest. Conversely, T cell number is decreased in malnourished individuals, and T cells in the setting of malnutrition have decreased effector function and proliferative capacity. The adipokine leptin, which is secreted in proportion to adipocyte mass, may have a key role in mediating adipocyte-T cell interactions in both obesity and malnutrition, and has been shown to promote effector T cell function and metabolism while inhibiting regulatory T cell proliferation. Additionally, key molecular signals are involved in T cell metabolic adaptation during nutrient stress; among them, the metabolic regulator AMP kinase and the mammalian target of rapamycin have critical roles in regulating T cell number, function, and metabolism. In summary, understanding how T cell number and function are altered in obesity and malnutrition will lead to better understanding of and treatment for diseases where nutritional status determines clinical outcome.

La Rapamycine inhibe l’expression de l’ARNm de l’ADAMTS-4 induit par les cytokines dans les chondrocytes articulaires

Introduction: Durant la pathogenèse d’ostéoarthrose (OA), les cytokines pro-inflammatoires IL-1β (Interleukin-1 beta) et TNF-α (Tumor necrosis factor alpha) stimulent la dégradation des agrécanes par l’aggrécanase-1 ou ADAMTS-4 (a disintegrin and metalloproteinase with thrombospondin motif). Ces cytokines peuvent stimuler plusieurs voies de signalisation conduisant ainsi à l’augmentation de l’expression des ADAMTS dans les chondrocytes humains. Les TIMPs (tissue inhibitor of metalloproteinases) présentent des inhibiteurs endogènes de l’ADAMTS. Nous avons démontré que la Rapamycine (un immunosuppresseur et un inhibiteur du mamalian target of Rapamycin (mTOR)) peut avoir des effets bénéfiques dans cette pathologie. Notre étude examine l’effet de la Rapamycine sur l’expression de l’ADAMTS-4 induit par les cytokines, son implication dans certaines voies de signalisation, et son effet sur l’expression du TIMP-3. Méthodes: Des chondrocytes normaux sont traités avec la Rapamycine seule ou stimulés aussi avec l’IL-1β et le TNF-α. Les effets de la Rapamycine sur l’expression de l’ADAMTS-4 et du TIMP-3 ont été étudiés par l’analyse RT-PCR et l’activité enzymatique a été étudiée par la technique d’ELISA. Les effets de la Rapamycine sur certaines voies de signalisation ont été étudiés par le Western blot. Résultats: Nous avons trouvé que la Rapamycine inhibe l’expression de l’ARNm de l’ADAMTS-4 induit par les cytokines pro-inflammatoires dans les chondrocytes humains. L’activité enzymatique de l’ADAMTS-4 induit par l’IL-1β a été légèrement diminuée par la Rapamycine. En plus, cette dernière a montré de différents effets sur plusieurs voies de signalisation stimulées par l’IL-1β et le TNF-α telles que les voies des MAPKs (Mitogen activated protein kinase), de l’AKT, et de la p70 S6 kinase. La Rapamycine a inhibé partiellement l’activation de la phosphorylation de l’ERK1/2 MAPK (extracellular signal-regulated protein kinase MAPK) en présence du TNF-α seulement. En outre, la Rapamycine a inhibé la phosphorylation des protéines p38 MAPK, JNK (c-Jun N-terminal kinase), et AKT activée par l’IL-1β seulement. En plus, la phosphorylation de la protéine p70 S6K stimulée par l’IL-1β et le TNF-α a été inhibée par la Rapamycine. D’autre part, nous avons démontré que le niveau du TIMP-3 a été augmenté en présence de la Rapamycine. Conclusion: Ces résultats suggèrent que la Rapamycine peut bloquer l’action de l’ADAMTS-4 via l’inhibition de l’activation des MAPKs, de l’AKT, et de la p70 S6K. La Rapamycine pourrait ainsi être considérée pour la prévention de la perte du cartilage chez les patients ostéoarthritiques.

Genèse de l’immunopeptidome du CMH de classe I

La différentiation entre le « soi » et le « non-soi » est un processus biologique essentiel à la vie. Les peptides endogènes présentés par les complexes majeurs d’histocompatibilité de classe I (CMH I) représentent le fondement du « soi » pour les lymphocytes T CD8+. On donne le nom d’immunopeptidome à l’ensemble des peptides présentés à la surface cellulaire par les molécules du CMH I. Nos connaissances concernant l’origine, la composition et la plasticité de l’immunopeptidome restent très limitées. Dans le cadre de cette thèse, nous avons développé une nouvelle approche par spectrométrie de masse permettant de définir avec précision : la nature et l’abondance relative de l’ensemble des peptides composant l’immunopeptidome. Nous avons trouvé que l’immunopeptidome, et par conséquent la nature du « soi » immun, est surreprésenté en peptides provenant de transcrits fortement abondants en plus de dissimuler une signature tissu-spécifique. Nous avons par la suite démontré que l’immunopeptidome est plastique et modulé par l’activité métabolique de la cellule. Nous avons en effet constaté que les modifications du métabolisme cellulaire par l’inhibition de mTOR (de l’anglais mammalian Target Of Rapamycin) provoquent des changements dynamiques dans la composition de l’immunopeptidome. Nous fournissons également la première preuve dans l’étude des systèmes que l’immunopeptidome communique à la surface cellulaire l’activité de certains réseaux biochimiques ainsi que de multiples événements métaboliques régulés à plusieurs niveaux à l’intérieur de la cellule. Nos découvertes ouvrent de nouveaux horizons dans les domaines de la biologie des systèmes et de l’immunologie. En effet, notre travail de recherche suggère que la composition de l’immunopeptidome est modulée dans l’espace et le temps. Il est par conséquent très important de poursuivre le développement de méthodes quantitatives au niveau des systèmes qui nous permettront de modéliser la plasticité de l’immunopeptidome. La simulation et la prédiction des variations dans l’immunopeptidome en réponse à différents facteurs cellulaires intrinsèques et extrinsèques seraient hautement pertinentes pour la conception de traitements immunothérapeutiques.