scholarly journals Morphology, clearing efficacy, and mTOR dependency of the organelle autophagoproteasome

2021 ◽  
Vol 65 (s1) ◽  
Author(s):  
Fiona Limanaqi ◽  
Francesca Biagioni ◽  
Alessandra Salvetti ◽  
Stefano Puglisi-Allegra ◽  
Paola Lenzi ◽  
...  
Keyword(s):  
Target Of Rapamycin ◽  
Catabolic Pathway ◽  
Cell Protection ◽  
Mtor Inhibition ◽  
Biochemical Evidence ◽  
Mechanistic Target Of Rapamycin ◽  
Ubiquitin Proteasome ◽  
Baseline Conditions

The interplay between autophagy (ATG) and ubiquitin proteasome (UP) cell-clearing systems was recently evidenced at biochemical and morphological levels, where subunits belonging to both pathways co-localize within a novel organelle named autophagoproteasome (APP). We previously documented that APP occurs at baseline conditions, while it is hindered by neurotoxicant administration. This is bound to the activity of the mechanistic target of rapamycin (mTOR), since APP is stimulated by mTOR inhibition, which in turn, is correlated with cell protection. In this brief report, we provide novel, morphological and biochemical evidence on APP, suggesting the presence of active UP subunits within ATG vacuoles. Although a stream of interpretation considers such a merging as a catabolic pathway to clear inactive UP subunits, our data further indicate that UP-ATG merging may rather provide an empowered catalytic organelle.

scholarly journals Selective Deletion of the Mechanistic Target of Rapamycin From the Renal Collecting Duct Principal Cell in Mice Down-Regulates the Epithelial Sodium Channel

2022 ◽  
Vol 12 ◽  
Author(s):  
Bruce Chen ◽  
Maurice B. Fluitt ◽  
Aaron L. Brown ◽  
Samantha Scott ◽  
Anirudh Gadicherla ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Principal Cell ◽  
Target Of Rapamycin ◽  
Mtor Inhibition ◽  
Sodium Homeostasis ◽  
Mechanistic Target Of Rapamycin ◽  
Data Support ◽  
Body Sodium

The mechanistic target of rapamycin (mTOR), a serine-threonine-specific kinase, is a cellular energy sensor, integrating growth factor and nutrient signaling. In the collecting duct (CD) of the kidney, the epithelial sodium channel (ENaC) essential in the determination of final urine Na+ losses, has been demonstrated to be upregulated by mTOR, using cell culture and mTOR inhibition in ex vivo preparations. We tested whether CD-principal cell (PC) targeted deletion of mTOR using Cre-lox recombination would affect whole-body sodium homeostasis, blood pressure, and ENaC regulation in mice. Male and female CD-PC mTOR knockout (KO) mice and wild-type (WT) littermates (Cre-negative) were generated using aquaporin-2 (AQP2) promoter to drive Cre-recombinase. Under basal conditions, KO mice showed a reduced (∼30%) natriuretic response to benzamil (ENaC) antagonist, suggesting reduced in vivo ENaC activity. WT and KO mice were fed normal sodium (NS, 0.45% Na+) or a very low Na+ (LS, <0.02%) diet for 7-days. Switching from NS to LS resulted in significantly higher urine sodium losses (relative to WT) in the KO with adaptation occurring by day 2. Blood pressures were modestly (∼5–10 mm Hg) but significantly lower in KO mice under both diets. Western blotting showed KO mice had 20–40% reduced protein levels of all three subunits of ENaC under LS or NS diet. Immunohistochemistry (IHC) of kidney showed enhanced apical-vs.-cellular localization of all three subunits with LS, but a reduction in this ratio for γ-ENaC in the KO. Furthermore, the KO kidneys showed increased ubiquitination of α-ENaC and reduced phosphorylation of the serum and glucocorticoid regulated kinase, type 1 [serum glucocorticoid regulated kinase (SGK1)] on serine 422 (mTOR phosphorylation site). Taken together this suggests enhanced degradation as a consequence of reduced mTOR kinase activity and downstream upregulation of ubiquitination may have accounted for the reduction at least in α-ENaC. Overall, our data support a role for mTOR in ENaC activity likely via regulation of SGK1, ubiquitination, ENaC channel turnover and apical membrane residency. These data support a role for mTOR in the collecting duct in the maintenance of body sodium homeostasis.

scholarly journals Fructose leads to hepatic steatosis in zebrafish that is reversed by mechanistic target of rapamycin (mTOR) inhibition

Hepatology ◽  
2014 ◽  
Vol 60 (5) ◽  
pp. 1581-1592 ◽  
Author(s):  
Valerie Sapp ◽  
Leah Gaffney ◽  
Steven F. EauClaire ◽  
Randolph P. Matthews
Keyword(s):  
Hepatic Steatosis ◽  
Target Of Rapamycin ◽  
Mtor Inhibition ◽  
Mechanistic Target Of Rapamycin

scholarly journals Inhibition of mTOR protects the blood-brain barrier in models of Alzheimer’s disease and vascular cognitive impairment

2018 ◽  
Vol 314 (4) ◽  
pp. H693-H703 ◽  
Author(s):  
Candice E. Van Skike ◽  
Jordan B. Jahrling ◽  
Angela B. Olson ◽  
Naomi L. Sayre ◽  
Stacy A. Hussong ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Blood Brain Barrier ◽  
Vascular Cognitive Impairment ◽  
Brain Barrier ◽  
Target Of Rapamycin ◽  
Mtor Inhibition ◽  
Mechanistic Target Of Rapamycin ◽  
Blood Brain

An intact blood-brain barrier (BBB) limits entry of proinflammatory and neurotoxic blood-derived factors into the brain parenchyma. The BBB is damaged in Alzheimer’s disease (AD), which contributes significantly to the progression of AD pathologies and cognitive decline. However, the mechanisms underlying BBB breakdown in AD remain elusive, and no interventions are available for treatment or prevention. We and others recently established that inhibition of the mammalian/mechanistic target of rapamycin (mTOR) pathway with rapamycin yields significant neuroprotective effects, improving cerebrovascular and cognitive function in mouse models of AD. To test whether mTOR inhibition protects the BBB in neurological diseases of aging, we treated hAPP(J20) mice modeling AD and low-density lipoprotein receptor-null (LDLR−/−) mice modeling vascular cognitive impairment with rapamycin. We found that inhibition of mTOR abrogates BBB breakdown in hAPP(J20) and LDLR−/− mice. Experiments using an in vitro BBB model indicated that mTOR attenuation preserves BBB integrity through upregulation of specific tight junction proteins and downregulation of matrix metalloproteinase-9 activity. Together, our data establish mTOR activity as a critical mediator of BBB breakdown in AD and, potentially, vascular cognitive impairment and suggest that rapamycin and/or rapalogs could be used for the restoration of BBB integrity. NEW & NOTEWORTHY This report establishes mammalian/mechanistic target of rapamycin as a critical mediator of blood-brain barrier breakdown in models of Alzheimer's disease and vascular cognitive impairment and suggests that drugs targeting the target of rapamycin pathway could be used for the restoration of blood-brain barrier integrity in disease states.

scholarly journals mTOR Inhibition: From Aging to Autism and Beyond

Scientifica ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Matt Kaeberlein
Keyword(s):  
Mtor Inhibitors ◽  
Cellular Level ◽  
Mtor Signaling ◽  
Target Of Rapamycin ◽  
Mtor Inhibition ◽  
Pharmacological Modulation ◽  
Related Disease ◽  
Mechanistic Target Of Rapamycin ◽  
Age Related ◽  
Growing Body

The mechanistic target of rapamycin (mTOR) is a highly conserved protein that regulates growth and proliferation in response to environmental and hormonal cues. Broadly speaking, organisms are constantly faced with the challenge of interpreting their environment and making a decision between “grow or do not grow.” mTOR is a major component of the network that makes this decision at the cellular level and, to some extent, the tissue and organismal level as well. Although overly simplistic, this framework can be useful when considering the myriad functions ascribed to mTOR and the pleiotropic phenotypes associated with genetic or pharmacological modulation of mTOR signaling. In this review, I will consider mTOR function in this context and attempt to summarize and interpret the growing body of literature demonstrating interesting and varied effects of mTOR inhibitors. These include robust effects on a multitude of age-related parameters and pathologies, as well as several other processes not obviously linked to aging or age-related disease.

scholarly journals Sirolimus and Other Mechanistic Target of Rapamycin Inhibitors Directly Activate Latent Pathogenic Human Polyomavirus Replication

2020 ◽  
Author(s):  
Jennifer Alvarez Orellana ◽  
Hyun Jin Kwun ◽  
Sara Artusi ◽  
Yuan Chang ◽  
Patrick S Moore
Keyword(s):  
Dna Replication ◽  
Jc Virus ◽  
Mtor Inhibitors ◽  
Bk Virus ◽  
Target Of Rapamycin ◽  
Human Polyomavirus ◽  
Merkel Cell ◽  
Mtor Inhibition ◽  
Mechanistic Target Of Rapamycin ◽  
Transplant Patients

Abstract Background Human polyomaviruses can reactivate in transplant patients, causing nephropathy, progressive multifocal leukoencephalopathy, Merkel cell carcinoma, pruritic, rash or trichodysplasia spinulosa. Sirolimus and related mechanistic target of rapamycin (mTOR) inhibitors are transplant immunosuppressants. It is unknown if they directly reactivate polyomavirus replication from latency beyond their general effects on immunosuppression. Methods In vitro expression and turnover of large T (LT) proteins from BK virus, JC virus (JCV), Merkel cell polyomavirus (MCV), human polyomavirus 7 (HPyV7), and trichodysplasia spinulosa polyomavirus (TSV) after drug treatment were determined by immunoblotting, proximity ligation, replicon DNA replication, and whole virus immunofluorescence assays. Results mTOR inhibition increased LT protein expression for all 5 pathogenic polyomaviruses tested. This correlated with LT stabilization, decrease in the S-phase kinase-associated protein 2 (Skp2) E3 ligase targeting these LT proteins for degradation, and increase in virus replication for JCV, MCV, TSV, and HPyV7. Treatment with sirolimus, but not the calcineurin inhibitor tacrolimus, at levels routinely achieved in patients, resulted in a dose-dependent increase in viral DNA replication for BKV, MCV, and HPyV7. Conclusions mTOR inhibitors, at therapeutic levels, directly activate polyomavirus replication through a Skp2-dependent mechanism, revealing a proteostatic latency mechanism common to polyomaviruses. Modifying existing drug regimens for transplant patients with polyomavirus-associated diseases may reduce symptomatic polyomavirus replication while maintaining allograft-sparing immunosuppression.

scholarly journals Lysosomes, Autophagy, and Hormesis in Cell Physiology, Pathology, and Age-Related Disease

Dose-Response ◽  
2020 ◽  
Vol 18 (3) ◽  
pp. 155932582093422 ◽  
Author(s):  
Michael N. Moore
Keyword(s):  
Intracellular Signaling ◽  
Adenosine Monophosphate ◽  
Target Of Rapamycin ◽  
Cell Physiology ◽  
Mechanistic Target Of Rapamycin ◽  
Age Related ◽  
Mechanistic Basis ◽  
The Many ◽  
Mtor Complex 1

Autophagy has been strongly linked with hormesis, however, it is only relatively recently that the mechanistic basis underlying this association has begun to emerge. Lysosomal autophagy is a group of processes that degrade proteins, protein aggregates, membranes, organelles, segregated regions of cytoplasm, and even parts of the nucleus in eukaryotic cells. These degradative processes are evolutionarily very ancient and provide a survival capability for cells that are stressed or injured. Autophagy and autophagic dysfunction have been linked with many aspects of cell physiology and pathology in disease processes; and there is now intense interest in identifying various therapeutic strategies involving its regulation. The main regulatory pathway for augmented autophagy is the mechanistic target of rapamycin (mTOR) cell signaling, although other pathways can be involved, such as 5′-adenosine monophosphate-activated protein kinase. Mechanistic target of rapamycin is a key player in the many highly interconnected intracellular signaling pathways and is responsible for the control of cell growth among other processes. Inhibition of mTOR (specifically dephosphorylation of mTOR complex 1) triggers augmented autophagy and the search is on the find inhibitors that can induce hormetic responses that may be suitable for treating many diseases, including many cancers, type 2 diabetes, and age-related neurodegenerative conditions.

Infektionen unter Immunsuppression nach Nierentransplantation

2020 ◽  
Vol 24 (08) ◽  
pp. 309-318
Author(s):  
Stephan Kemmner ◽  
Ulf Schönermarck
Keyword(s):  
Mtor Inhibitor ◽  
Pneumocystis Jirovecii ◽  
Target Of Rapamycin ◽  
Virale Infektionen ◽  
Mechanistic Target Of Rapamycin ◽  
Nach Transplantation ◽  
Polyomavirus Bk ◽  
Prophylaktische Therapie

ZUSAMMENFASSUNGUnter immunsuppressiver Therapie besteht ein deutlich erhöhtes Infektionsrisiko nach Nierentransplantation (NTx), insbesondere für virale Infektionen. Bereits vor einer geplanten NTx sollte auf einen aktuellen Impfstatus geachtet werden, da nach einer Transplantation unter immunsuppressiver Therapie einerseits Lebendimpfstoffe nicht mehr gegeben werden dürfen und andererseits eine adäquate Impfantwort schwieriger zu erreichen ist. Die saisonale Influenzaimpfung kann bereits einen Monat nach Transplantation gegeben werden, für alle anderen Impfungen wird ein Abwarten von 3–6 Monaten empfohlen. Eine prophylaktische Therapie kann das Auftreten bestimmter Infektionen effektiv verhindern. Nach NTx sollte für die ersten 6 Monate eine PjP-Prophylaxe (PjP: Pneumocystis-jirovecii-Pneumonie) mit Trimethoprim/Sulfamethoxazol verabreicht werden. Eine CMV-Prophylaxe (CMV: Zytomegalievirus) mit Valganciclovir erfolgt in Abhängigkeit vom Sero-Status von Empfänger und Spender i. d. R. für 3 bzw. 6 Monate. Im Falle einer Infektion kann in Abhängigkeit vom Schweregrad der Antimetabolit (meist MMF: Mycophenolatmofetil) dosishalbiert oder pausiert werden, jedoch ist dies mit einem erhöhten Rejektionsrisiko verbunden. Insbesondere bei Infektionen mit CMV und BKV (Polyomavirus BK) kann anstelle von MMF ein mTOR-Inhibitor (mTOR: „mechanistic target of rapamycin“) eingesetzt werden in Kombination mit einem niedrigdosierten Calcineurininhibitor (CNI). Bei einer COVID-19-Erkrankung (COVID-19: Coronavirus Disease 2019) nach NTx sollte wie bei anderen Infektionen in einer Kombinationstherapie zunächst der Antimetabolit bzw. der mTOR-Inhibitor dosisreduziert oder pausiert werden. Ein Absetzen des CNIs bei COVID-19 erscheint aus unserer Sicht nicht regelhaft indiziert, sondern bleibt schweren Verläufen im Einzelfall vorbehalten. Im Falle einer antiviralen Therapie bei COVID-19 muss immer an mögliche Interaktionen mit den Immunsuppressiva (v. a. mit CNI und mTOR-Inhibitoren) gedacht werden.

scholarly journals Mammalian target of rapamycin signaling activation patterns in neuroendocrine tumors of the lung

2010 ◽  
Vol 17 (4) ◽  
pp. 977-987 ◽  
Author(s):  
Luisella Righi ◽  
Marco Volante ◽  
Ida Rapa ◽  
Veronica Tavaglione ◽  
Frediano Inzani ◽  
...  
Keyword(s):  
Neuroendocrine Tumors ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Pathway ◽  
Differential Sensitivity ◽  
Initiation Factor ◽  
Target Of Rapamycin ◽  
Low Grade ◽  
Mtor Inhibition ◽  
Signaling Activation ◽  
Activation Status

Among alternative therapeutic strategies in clinically aggressive neuroendocrine tumors (NETs) of the lung, promising results have been obtained in experimental clinical trials with mammalian target of rapamycin (mTOR) inhibitors, though in the absence of a proven mTOR signaling activation status. This study analyzed the expression of phosphorylated mTOR (p-mTOR) and its major targets, the ribosomal p70S6-kinase (S6K) and the eukaryotic initiation factor 4E-binding protein 1 (4EBP1) in a large series of 218 surgically resected, malignant lung NETs, including 24 metastasizing typical carcinoids, 73 atypical carcinoids, 60 large cell neuroendocrine carcinomas (LCNECs), and 61 small cell carcinomas (SCLCs). By immunohistochemistry, low-to-intermediate-grade tumors as compared with high-grade tumors showed higher levels of p-mTOR and phosphorylated S6K (p-S6K) (P<0.001), at variance with phosphorylated 4EBP1 (p-4EBP1), which was mainly expressed in LCNECs and SCLCs (P<0.001). The activated status of mTOR pathway was proved by the strong correlation of p-mTOR with p-S6K and somatostatin receptor(s). Western blot analysis of NET tumor samples confirmed such findings, and differential sensitivity to mTOR inhibition according to mTOR pathway activation characteristics was determined in two lung carcinoid cell lines in vitro. None of the investigated molecules had an impact on survival. However, in low-grade tumors, low p-mTOR expression correlated with lymph node metastases (P=0.016), recurrent disease, and survival (P=0.005). In conclusion, these data demonstrate a differential mTOR activation status in the spectrum of pulmonary NETs, possibly suggesting that mTOR pathway profiling might play a predictive role in candidate patients for mTOR-targeted therapies.

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