Maintenance of cellular proteostasis is achieved by a multi-layered quality control network, which counteracts the accumulation of misfolded proteins by refolding and degradation pathways. The organized sequestration of misfolded proteins, actively promoted by cellular sequestrases, represents a third strategy of quality control. Here we determine the role of sequestration within the proteostasis network in Saccharomyces cerevisiae and the mechanism by which it occurs. The Hsp42 and Btn2 sequestrases are functionally intertwined with the refolding activity of the Hsp70 system. Sequestration of misfolded proteins by Hsp42 and Btn2 prevents proteostasis collapse and viability loss in cells with limited Hsp70 capacity, likely by shielding Hsp70 from misfolded protein overload. Btn2 has chaperone and sequestrase activity and shares features with small heat shock proteins. During stress recovery Btn2 recruits the Hsp70-Hsp104 disaggregase by directly interacting with the Hsp70 co-chaperone Sis1, thereby shunting sequestered proteins to the refolding pathway.

• MeSH
• Proteostasis * MeSH
• HSP40 Heat-Shock Proteins metabolism   MeSH
• HSP70 Heat-Shock Proteins metabolism   MeSH
• Heat-Shock Proteins metabolism   MeSH
• Protein Refolding MeSH
• Saccharomyces cerevisiae Proteins metabolism   MeSH
• Saccharomyces cerevisiae metabolism   MeSH
• Amino Acid Transport Systems metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). Mouse AGR2 deletion increases intestinal inflammation and promotes the development of inflammatory bowel disease (IBD). Although these biological effects are well established, the underlying molecular mechanisms of AGR2 function toward inflammation remain poorly defined. Here, using a protein-protein interaction screen to identify cellular regulators of AGR2 dimerization, we unveiled specific enhancers, including TMED2, and inhibitors of AGR2 dimerization, that control AGR2 functions. We demonstrate that modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes, through either autophagy-dependent processes or secretion of AGR2, respectively. We also demonstrate that in IBD and specifically in Crohn's disease, the levels of AGR2 dimerization modulators are selectively deregulated, and this correlates with severity of disease. Our study demonstrates that AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. The latter might represent systemic alarm signals for pro-inflammatory responses.

• MeSH
• Endoplasmic Reticulum genetics   metabolism   MeSH
• HEK293 Cells MeSH
• Proteostasis * MeSH
• Humans MeSH
• Mucoproteins genetics   metabolism   MeSH
• Protein Multimerization * MeSH
• Mice MeSH
• Oncogene Proteins genetics   metabolism   MeSH
• Endoplasmic Reticulum Stress * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Východiska: Proteom eukaryotické buňky představuje komplexní systém, jehož složky jsou vystaveny nepříznivým vlivům vnitřního a vnějšího prostředí. Funkce buněčného proteomu je tudíž závislá na existenci kompenzačních mechanizmů udržujících vnitřní proteinovou homeostázu – proteostázu. K těmto mechanizmům náleží síť molekulárních chaperonů a transkripční program řídící jejich syntézu. Proces kancerogeneze je provázen výraznými změnami faktorů vnitřního prostředí nádorových buněk – teplota, pH, dostupnost živin. Tyto změny představují na jedné straně důsledek deregulovaného růstu nádorové tkáně a na straně druhé mohou být zdrojem selekčního tlaku, který umožňuje vznik rezistentních a agresivních populací nádorových buněk. Popis složek proteostatického aparátu a mechanizmus jejich zapojení ve vývoji nádorové tkáně jsou předmětem tohoto přehledového článku. Cíl: Tento přehledový článek se věnuje popisu dvou kauzálně propojených skupin proteostatických dějů, jejichž vzájemná koordinace je klíčová pro průběh odpovědi nádorové buňky a potažmo i celé nádorové tkáně na environmentální i vnitřní stresové faktory. První skupina těchto dějů je zastoupena „vykonavatelskou“ úlohou molekulárních chaperonů z rodiny HSP70, HSP90 a tzv. malých molekulárních chaperonů. Tyto proteiny se podílejí na udržování stability buněčných proteinů nezbytných pro regulaci proliferace, apoptózy, senescence, migrace a fenotypové plasticity nádorových buněk. K druhé skupině popisovaných dějů pak náleží posttranslační řízení „systémové“ úlohy transkripčního faktoru HSF1 při regulaci exprese genů pro molekulární chaperony a dalších genů specificky regulovaných tímto transkripčním faktorem v nádorových a stromálních buňkách.

Background: The proteome of eukaryotic cells represents a complex system. Its components are exposed to various intrinsic and extrinsic stresses. Therefore, the function of the cellular proteome is dependent on the existence of compensatory mechanisms balancing the inner protein homeostasis – proteostasis. These mechanisms involve the network of molecular chaperones and transcriptional program regulating their expression. The process of cancerogenesis is accompanied by significant changes in the intracellular milieu of cancer cells – temperature, pH, availability of nutrients. On the one hand, these changes represent a consequence of the deregulated growth of the tumor tissue; on the other hand, they can be a source of selection pressure, which allows the emergence of resistant and aggressive tumor cell populations. Description of the proteostatic apparatus components and the mechanism of their involvement in the tumor tissue development is provided in this review article. Aim: This review focuses on the description of two causally linked groups of proteostatic events; their mutual coordination is crucial to the process of tumor cell and by extension the entire tumor tissue response to environmental and internal stress factors. The first group of these processes is represented by the “executory” role of molecular chaperones from HSP70, HSP90 and so-called small molecular chaperone protein families. These proteins are involved in maintaining stability of cellular proteins essential for proliferation, apoptosis, senescence, migration and phenotypic plasticity of tumor cells. The second group of the described processes comprises the posttranslational control of the “systemic” role of the transcription factor HSF1 in regulating the gene expression of molecular chaperones and other genes specifically regulated by this transcription factor in the tumor and stromal cells.

• MeSH
• Humans MeSH
• Molecular Chaperones MeSH
• Neoplasms * pathology   MeSH
• Proteostasis Deficiencies MeSH
• Transcription Factors metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

• MeSH
• Amyloidosis MeSH
• Histiocytosis MeSH
• Humans MeSH
• Proteostasis Deficiencies MeSH
• Check Tag
• Humans MeSH

Stárnutí lze definovat jako progresivní, ireverzibilní ztrátu vitality a stoupající mortalitu nevyhnutelně přicházejícím s věkem. Jde o stochastický proces, nikoliv program. Biochemická podstata stárnutí spočívá v nemožnosti zabránit nahromadění náhodných chyb v důležitých biomolekulách, tj. v DNA a v bílkovinách. Svou roli v komplikovaném procesu stárnutí hrají reaktivní formy kyslíku, mitochondriální dysfunkce, reaktivní karbonyly, poškození genomové DNA včetně telomer, epigenetické alterace, buněčná senescence a selhání proteostázy. I když všechny tkáně lidského těla stárnou, biologické limity údržby a oprav nejvíce dopadají na buňky, které se nedělí. Jelikož klíčové orgány lidského organismu, mozek, srdce a kosterní sval jsou založeny na postmitotických buňkách, lidská bytost ve svém biologickém těle nesmrtelnosti nikdy dosáhnout nemůže. V rámci svých biologických limitů jsou organismy vybaveny důležitými adaptabilními mechanismy tělesné údržby a oprav, jako je stresem stimulovaná buněčná odolnost vůči stresu (hormeze), autofagie či reakce na poškození DNA. Vhled do těchto mechanismů poskytuje vysvětlení pro příznivé působení faktorů životního stylu, jako je kalorická restrikce a fyzická aktivita, a do budoucna může přinést i léky schopné stárnutí zpomalit.

Aging can be defined as progressive and irreversible loss of vitality and increasing mortality coming inescapably with age. It is a stochastic process, rather than a program. The biochemical essence of aging lies in impossibility to prevent accumulation of random errors in important biomolecules, such as DNA and proteins. In the complicated process of aging, there are roles for reactive oxygen species, mitochondrial dysfunction, reactive carbonyls, and damage to genomic DNA including telomeres, epigenetic alterations, cell senescence, and collapse of proteostasis. Although all tissues of human body age, the biological limits of maintenance and repair affect the non-dividing cells the most. As the key organs of human body, brain, heart, and skeletal muscle, are based on postmitotic cells, a human being in his biological body can never reach immortality. Within the biological limits, organisms are equipped with important adaptable mechanisms for body maintenance and repair, such as stress-induced cellular resistance to stress (hormesis), autophagy and DNA damage response. Insight into these mechanisms provides rationale for benefits of life style interventions, such as caloric restriction and physical exercise, and in future might even bring drugs that could slow aging.

• MeSH
• Proteostasis MeSH
• Humans MeSH
• Mitochondria MeSH
• DNA Damage MeSH
• Pyruvaldehyde MeSH
• Reactive Oxygen Species MeSH
• Aging * genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Research Support, Non-U.S. Gov't MeSH

V souvislosti se syndromem demence se v současnosti hovoří o tiché epidemii. V České republice trpí některou z demencí podle realistických odhadů asi 150 tisíc lidí, pesimisté hovoří až o 200 tisících nemocných. Není v silách jednoho medicínského oboru se o všechny tyto nemocné postarat a péče o ně se dělí zejména mezi neurologii, psychiatrii a geriatrii. Důležitá pro diagnostiku a včasnou léčbu je zejména primární péče. Autor článku se zaměřuje na klinický obraz, diagnostiku a léčbu nejčastějších demencí, se kterými se v běžné klinické praxi setkáváme. Jedná se o pohled gerontopsychiatra, je tedy kladen důraz i na psychopatologii, která jednotlivé onemocnění provází a je pro ně případně charakteristická.

In connection with dementia it is currently talked about a silent epidemic. In the Czech Republic there are currently according to some realistic estimates about 150 thousands people suffering from dementia, while the pessimists estimate up to about 200 thousand ill people. It is not within the power of a branch of medicine to take care for all these patients and the care of them is shared mainly with neurology, psychiatry and geriatrics. Particularly important for diagnostics and early treatment is the primary care. The author of the article focuses on the clinical picture, diagnostics and early treatment of the most common dementias, which are in routine clinical practice met. It is a gerontopsychiatrists view, so the emphasize is put also on psychopathology that accompanies the individual diseases and is pertinently characteristic for them.

• Keywords
• Alzheimerova choroba, neurodegenerativní demence, kognitivní funkce, dementní syndrom,
• MeSH
• Alzheimer Disease diagnosis   psychology   therapy   MeSH
• Dementia diagnosis   psychology   therapy   MeSH
• Cognition Disorders diagnosis   psychology   therapy   MeSH
• Humans MeSH
• Proteostasis Deficiencies diagnosis   psychology   therapy   MeSH
• Tauopathies diagnosis   psychology   therapy   MeSH
• Dementia, Vascular diagnosis   psychology   therapy   MeSH
• Check Tag
• Humans MeSH

Some pathological conditions affecting the human body can also disrupt metabolic pathways and thus alter the overall metabolic profile. Knowledge of metabolic disturbances in specific diseases could thus enable the differential diagnosis of otherwise similar conditions. This work therefore aimed to comprehensively characterize changes in tryptophan metabolism in selected neurodegenerative diseases. Levels of 18 tryptophan-related neuroactive substances were determined by high throughput and sensitive ultrahigh-performance liquid chromatography-tandem mass spectrometry in time-linked blood serum and cerebrospinal fluid samples from 100 age-matched participants belonging to five cohorts: healthy volunteers (n = 21) and patients with Lewy body disease (Parkinson's disease and dementia with Lewy bodies; n = 31), four-repeat tauopathy (progressive supranuclear palsy and corticobasal syndrome; n = 10), multiple system atrophy (n = 13), and Alzheimer's disease (n = 25). Although these conditions have different pathologies and clinical symptoms, the discovery of new biomarkers is still important. The most statistically significant differences (with p-values of ≤0.05 to ≤0.0001) between the study cohorts were observed for three tryptophan metabolites: l-kynurenine in cerebrospinal fluid and 3-hydroxy-l-kynurenine and 5-hydroxy-l-tryptophan in blood serum. This led to the discovery of distinctive correlation patterns between the profiled cerebrospinal fluid and serum metabolites that could provide a basis for the differential diagnosis of neurodegenerative tauopathies and synucleinopathies. However, further large-scale studies are needed to determine the direct involvement of these metabolites in the studied neuropathologies, their response to medication, and their potential therapeutic relevance.

• MeSH
• Alzheimer Disease * diagnosis   MeSH
• Biomarkers MeSH
• Kynurenine MeSH
• Humans MeSH
• Proteostasis Deficiencies * MeSH
• Serum MeSH
• Tauopathies * MeSH
• Tryptophan MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Classical homocystinuria is caused by mutations in the cystathionine β-synthase (CBS) gene. Previous experiments in bacterial and yeast cells showed that many mutant CBS enzymes misfold and that chemical chaperones enable proper folding of a number of mutations. In the present study, we tested the extent of misfolding of 27 CBS mutations previously tested in E. coli under the more folding-permissive conditions of mammalian CHO-K1 cells and the ability of chaperones to rescue the conformation of these mutations. Expression of mutations in mammalian cells increased the median activity 16-fold and the amount of tetramers 3.2-fold compared with expression in bacteria. Subsequently, we tested the responses of seven selected mutations to three compounds with chaperone-like activity. Aminooxyacetic acid and 4-phenylbutyric acid exhibited only a weak effect. In contrast, heme arginate substantially increased the formation of mutant CBS protein tetramers (up to sixfold) and rescued catalytic activity (up to ninefold) of five out of seven mutations (p.A114V, p.K102N, p.R125Q, p.R266K, and p.R369C). The greatest effect of heme arginate was observed for the mutation p.R125Q, which is non-responsive to in vivo treatment with vitamin B(6). Moreover, the heme responsiveness of the p.R125Q mutation was confirmed in fibroblasts derived from a patient homozygous for this genetic variant. Based on these data, we propose that a distinct group of heme-responsive CBS mutations may exist and that the heme pocket of CBS may become an important target for designing novel therapies for homocystinuria.

• MeSH
• Arginine pharmacology   MeSH
• CHO Cells MeSH
• Cricetulus MeSH
• Cystathionine beta-Synthase genetics   metabolism   MeSH
• Phenotype MeSH
• Fibroblasts drug effects   enzymology   MeSH
• Genetic Predisposition to Disease MeSH
• Heme pharmacology   MeSH
• Homocystinuria diagnosis   drug therapy   enzymology   genetics   MeSH
• Homozygote MeSH
• Catalytic Domain MeSH
• Protein Conformation MeSH
• Humans MeSH
• Molecular Chaperones pharmacology   MeSH
• Models, Molecular MeSH
• Mutation * MeSH
• Proteostasis Deficiencies diagnosis   drug therapy   enzymology   genetics   MeSH
• Protein Folding MeSH
• Substrate Specificity MeSH
• Transfection MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH
• Research Support, Non-U.S. Gov't MeSH

The integrated stress response (ISR) is a homeostatic mechanism induced by endoplasmic reticulum (ER) stress. In acute/transient ER stress, decreased global protein synthesis and increased uORF mRNA translation are followed by normalization of protein synthesis. Here, we report a dramatically different response during chronic ER stress. This chronic ISR program is characterized by persistently elevated uORF mRNA translation and concurrent gene expression reprogramming, which permits simultaneous stress sensing and proteostasis. The program includes PERK-dependent switching to an eIF3-dependent translation initiation mechanism, resulting in partial, but not complete, translational recovery, which, together with transcriptional reprogramming, selectively bolsters expression of proteins with ER functions. Coordination of transcriptional and translational reprogramming prevents ER dysfunction and inhibits "foamy cell" development, thus establishing a molecular basis for understanding human diseases associated with ER dysfunction.

• MeSH
• Time Factors MeSH
• Eukaryotic Initiation Factor-3 genetics   metabolism   MeSH
• Phenotype MeSH
• Fibroblasts metabolism   pathology   MeSH
• Transcription, Genetic * MeSH
• HEK293 Cells MeSH
• Proteostasis MeSH
• eIF-2 Kinase genetics   metabolism   MeSH
• Humans MeSH
• RNA, Messenger biosynthesis   genetics   MeSH
• Mice MeSH
• Open Reading Frames MeSH
• Cellular Reprogramming MeSH
• Protein Biosynthesis * MeSH
• RNA Interference MeSH
• Signal Transduction MeSH
• Endoplasmic Reticulum Stress * MeSH
• Transfection MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Severe progressive neurological paediatric disease mucopolysaccharidosis III type C is caused by mutations in the HGSNAT gene leading to deficiency of acetyl-CoA: α-glucosaminide N-acetyltransferase involved in the lysosomal catabolism of heparan sulphate. To understand the pathophysiology of the disease we generated a mouse model of mucopolysaccharidosis III type C by germline inactivation of the Hgsnat gene. At 6-8 months mice showed hyperactivity, and reduced anxiety. Cognitive memory decline was detected at 10 months and at 12-13 months mice showed signs of unbalanced hesitant walk and urinary retention. Lysosomal accumulation of heparan sulphate was observed in hepatocytes, splenic sinus endothelium, cerebral microglia, liver Kupffer cells, fibroblasts and pericytes. Starting from 5 months, brain neurons showed enlarged, structurally abnormal mitochondria, impaired mitochondrial energy metabolism, and storage of densely packed autofluorescent material, gangliosides, lysozyme, phosphorylated tau, and amyloid-β. Taken together, our data demonstrate for the first time that deficiency of acetyl-CoA: α-glucosaminide N-acetyltransferase causes lysosomal accumulation of heparan sulphate in microglial cells followed by their activation and cytokine release. They also show mitochondrial dysfunction in the neurons and neuronal loss explaining why mucopolysaccharidosis III type C manifests primarily as a neurodegenerative disease.

• MeSH
• Acetyltransferases deficiency   genetics   MeSH
• Behavior, Animal MeSH
• Energy Metabolism physiology   MeSH
• Gangliosides metabolism   MeSH
• Glycosaminoglycans metabolism   MeSH
• Mitochondrial Diseases etiology   pathology   MeSH
• Mucopolysaccharidosis III complications   pathology   psychology   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Neuritis etiology   pathology   MeSH
• Neurodegenerative Diseases etiology   pathology   psychology   MeSH
• Neurologic Examination MeSH
• Proteostasis Deficiencies pathology   MeSH
• Microtubule-Associated Proteins metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH