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HCC is the most frequent primary liver cancer with an extremely poor prognosis and often develops on preset of chronic liver diseases. Major risk factors for HCC include metabolic dysfunction-associated steatohepatitis, a complex multifactorial condition associated with abnormal endoplasmic reticulum (ER) proteostasis. To cope with ER stress, the unfolded protein response engages adaptive reactions to restore the secretory capacity of the cell. Recent advances revealed that ER stress signaling plays a critical role in HCC progression. Here, we propose that chronic ER stress is a common transversal factor contributing to the transition from liver disease (risk factor) to HCC. Interventional strategies to target the unfolded protein response in HCC, such as cancer therapy, are also discussed.
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Collagen is one the most abundant proteins and the main cargo of the secretory pathway, contributing to hepatic fibrosis and cirrhosis due to excessive deposition of extracellular matrix. Here we investigated the possible contribution of the unfolded protein response, the main adaptive pathway that monitors and adjusts the protein production capacity at the endoplasmic reticulum, to collagen biogenesis and liver disease. Genetic ablation of the ER stress sensor IRE1 reduced liver damage and diminished collagen deposition in models of liver fibrosis triggered by carbon tetrachloride (CCl 4 ) administration or by high fat diet. Proteomic and transcriptomic profiling identified the prolyl 4-hydroxylase (P4HB, also known as PDIA1), which is known to be critical for collagen maturation, as a major IRE1-induced gene. Cell culture studies demonstrated that IRE1 deficiency results in collagen retention at the ER and altered secretion, a phenotype rescued by P4HB overexpression. Taken together, our results collectively establish a role of the IRE1/P4HB axis in the regulation of collagen production and its significance in the pathogenesis of various disease states.
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Endoplasmic reticulum (ER) stress is a prominent cellular alteration of diseases impacting the nervous system that are associated to the accumulation of misfolded and aggregated protein species during aging. The unfolded protein response (UPR) is the main pathway mediating adaptation to ER stress, but it can also trigger deleterious cascades of inflammation and cell death leading to cell dysfunction and neurodegeneration. Genetic and pharmacological studies in experimental models shed light into molecular pathways possibly contributing to ER stress and the UPR activation in human neuropathies. Most of experimental models are, however, based on the overexpression of mutant proteins causing familial forms of these diseases or the administration of neurotoxins that induce pathology in young animals. Whether the mechanisms uncovered in these models are relevant for the etiology of the vast majority of age-related sporadic forms of neurodegenerative diseases is an open question. Here, we provide a systematic analysis of the current evidence linking ER stress to human pathology and the main mechanisms elucidated in experimental models. Furthermore, we highlight the recent association of metabolic syndrome to increased risk to undergo neurodegeneration, where ER stress arises as a common denominator in the pathogenic crosstalk between peripheral organs and the nervous system.
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Retículo Endoplasmático , Proteostase , Animais , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Estresse do Retículo Endoplasmático/genética , Humanos , Doenças Neurodegenerativas/genética , Proteostase/genética , Resposta a Proteínas não Dobradas/genéticaRESUMO
Alpha1-antitrypsin (α1AT) is an abundant serine-protease inhibitor in circulation. It has an important role in neutralizing the neutrophil elastase activity. Different pathogenic point mutations like Z(E342K)-α1AT have been implicated in the development of liver cirrhosis and Chronic Obstructive Pulmonary Disease (COPD), the latter being a cluster of progressive lung diseases including chronic bronchitis and emphysema. M3-α1AT (376Glu > Asp) is another variant of α1AT which so far is largely being considered as normal though increased frequency of the variant has been reported in many human diseases including COPD. We also observed increased frequency of M3-α1AT in COPD cases in Kashmiri population. The frequency of heterozygous (AC) genotype in cases and controls was 58.57% and 27.61% (odds-ratio 6.53 (2.27-15.21); p < 0.0001) respectively, while homozygous CC genotype was found to be 21.42% and 6.66% (odds-ratio 10.56 (3.63-18.64); p < 0.0001) respectively. Comparative in vitro investigations that include trypsinâantitrypsin assay, Circular Dichroism spectroscopy and dynamic light scattering performed on wild-type (M-α1AT), M3-α1AT, and Z-α1AT proteins along with the molecular dynamics simulations revealed that M3-α1AT has properties similar to Z-α1AT capable of forming aggregates of varied size. Our maiden observations suggest that M3-α1AT may contribute to the pathogenesis of COPD and other disorders by mechanisms that warrant further investigations.
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Substituição de Aminoácidos , Doença Pulmonar Obstrutiva Crônica/genética , alfa 1-Antitripsina/química , alfa 1-Antitripsina/genética , Estudos de Casos e Controles , Dicroísmo Circular , Difusão Dinâmica da Luz , Feminino , Genótipo , Humanos , Masculino , Simulação de Dinâmica Molecular , Agregados Proteicos , Tripsina/metabolismoRESUMO
The molecular connections between homeostatic systems that maintain both genome integrity and proteostasis are poorly understood. Here we identify the selective activation of the unfolded protein response transducer IRE1α under genotoxic stress to modulate repair programs and sustain cell survival. DNA damage engages IRE1α signaling in the absence of an endoplasmic reticulum (ER) stress signature, leading to the exclusive activation of regulated IRE1α-dependent decay (RIDD) without activating its canonical output mediated by the transcription factor XBP1. IRE1α endoribonuclease activity controls the stability of mRNAs involved in the DNA damage response, impacting DNA repair, cell cycle arrest and apoptosis. The activation of the c-Abl kinase by DNA damage triggers the oligomerization of IRE1α to catalyze RIDD. The protective role of IRE1α under genotoxic stress is conserved in fly and mouse. Altogether, our results uncover an important intersection between the molecular pathways that sustain genome stability and proteostasis.
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Sobrevivência Celular/genética , Reparo do DNA , Proteínas de Drosophila/metabolismo , Endorribonucleases/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Estabilidade de RNA/genética , Animais , Dano ao DNA , Proteínas de Drosophila/genética , Drosophila melanogaster , Endorribonucleases/genética , Feminino , Fibroblastos , Instabilidade Genômica , Células HEK293 , Humanos , Camundongos , Camundongos Knockout , Multimerização Proteica , Proteínas Serina-Treonina Quinases/genética , Proteostase/genética , Proteínas Proto-Oncogênicas c-abl/metabolismo , RNA Mensageiro/metabolismoRESUMO
Autophagy is an evolutionarily ancient process whereby eukaryotic cells eliminate disposable or potentially dangerous cytoplasmic material, to support bioenergetic metabolism and adapt to stress. Accumulating evidence indicates that autophagy operates as a critical quality control mechanism for the maintenance of hepatic homeostasis in both parenchymal (hepatocytes) and non-parenchymal (stellate cells, sinusoidal endothelial cells, Kupffer cells) compartments. In line with this notion, insufficient autophagy has been aetiologically involved in the pathogenesis of multiple liver disorders, including alpha-1-antitrypsin deficiency, Wilson disease, non-alcoholic steatohepatitis, liver fibrosis and hepatocellular carcinoma. Here, we critically discuss the importance of functional autophagy for hepatic physiology, as well as the mechanisms whereby defects in autophagy cause liver disease.
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Adaptação Fisiológica , Metabolismo Energético , Hepatopatias/metabolismo , Fígado/metabolismo , Macroautofagia , Mitofagia , Estresse Fisiológico , Animais , Retículo Endoplasmático/metabolismo , Homeostase , HumanosRESUMO
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Mitochondria-associated membranes (MAMs) are central microdomains that fine-tune bioenergetics by the local transfer of calcium from the endoplasmic reticulum to the mitochondrial matrix. Here, we report an unexpected function of the endoplasmic reticulum stress transducer IRE1α as a structural determinant of MAMs that controls mitochondrial calcium uptake. IRE1α deficiency resulted in marked alterations in mitochondrial physiology and energy metabolism under resting conditions. IRE1α determined the distribution of inositol-1,4,5-trisphosphate receptors at MAMs by operating as a scaffold. Using mutagenesis analysis, we separated the housekeeping activity of IRE1α at MAMs from its canonical role in the unfolded protein response. These observations were validated in vivo in the liver of IRE1α conditional knockout mice, revealing broad implications for cellular metabolism. Our results support an alternative function of IRE1α in orchestrating the communication between the endoplasmic reticulum and mitochondria to sustain bioenergetics.
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Retículo Endoplasmático/metabolismo , Endorribonucleases/genética , Metabolismo Energético , Mitocôndrias/metabolismo , Proteínas Serina-Treonina Quinases/genética , Animais , Cálcio/metabolismo , Sinalização do Cálcio/genética , Retículo Endoplasmático/genética , Receptores de Inositol 1,4,5-Trifosfato/genética , Camundongos , Camundongos Knockout , Mitocôndrias/genéticaRESUMO
In the version of this Article originally published, the competing interests statement was missing. The authors declare no competing interests; this statement has now been added in all online versions of the Article.
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Maintenance of endoplasmic reticulum (ER) proteostasis is controlled by a signalling network known as the unfolded protein response (UPR). Here, we identified filamin A as a major binding partner of the ER stress transducer IRE1α. Filamin A is an actin crosslinking factor involved in cytoskeleton remodelling. We show that IRE1α controls actin cytoskeleton dynamics and affects cell migration upstream of filamin A. The regulation of cytoskeleton dynamics by IRE1α is independent of its canonical role as a UPR mediator, serving instead as a scaffold that recruits and regulates filamin A. Targeting IRE1α expression in mice affected normal brain development, generating a phenotype resembling periventricular heterotopia, a disease linked to the loss of function of filamin A. IRE1α also modulated cell movement and cytoskeleton dynamics in fly and zebrafish models. This study unveils an unanticipated biological function of IRE1α in cell migration, whereby filamin A operates as an interphase between the UPR and the actin cytoskeleton.
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Citoesqueleto de Actina/metabolismo , Movimento Celular , Endorribonucleases/metabolismo , Fibroblastos/metabolismo , Filaminas/metabolismo , Neurônios/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Endorribonucleases/deficiência , Endorribonucleases/genética , Evolução Molecular , Feminino , Filaminas/genética , Células HEK293 , Humanos , Cinética , Masculino , Camundongos , Camundongos Knockout , Neurônios/patologia , Heterotopia Nodular Periventricular/genética , Heterotopia Nodular Periventricular/metabolismo , Heterotopia Nodular Periventricular/patologia , Fosforilação , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Proteínas Serina-Treonina Quinases/deficiência , Proteínas Serina-Treonina Quinases/genética , Transdução de Sinais , Resposta a Proteínas não Dobradas , Peixe-Zebra/genética , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
The global epidemic of obesity has been accompanied by a rising burden of non-alcoholic fatty liver disease (NAFLD), with manifestations ranging from simple steatosis to non-alcoholic steatohepatitis, potentially developing into hepatocellular carcinoma. Although much attention has focused on NAFLD, its pathogenesis remains largely obscure. The hallmark of NAFLD is the hepatic accumulation of lipids, which subsequently leads to cellular stress and hepatic injury, eventually resulting in chronic liver disease. Abnormal lipid accumulation often coincides with insulin resistance in steatotic livers and is associated with perturbed endoplasmic reticulum (ER) proteostasis in hepatocytes. In response to chronic ER stress, an adaptive signalling pathway known as the unfolded protein response is triggered to restore ER proteostasis. However, the unfolded protein response can cause inflammation, inflammasome activation and, in the case of non-resolvable ER stress, the death of hepatocytes. Experimental data suggest that the unfolded protein response influences hepatic tumour development, aggressiveness and response to treatment, offering novel therapeutic avenues. Herein, we provide an overview of the evidence linking ER stress to NAFLD and discuss possible points of intervention.
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Estresse do Retículo Endoplasmático/fisiologia , Hepatopatia Gordurosa não Alcoólica/etiologia , Transdução de Sinais/fisiologia , Fator 6 Ativador da Transcrição/fisiologia , Animais , Autofagia , Cálcio/metabolismo , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Terapia Genética , Humanos , Resistência à Insulina , Metabolismo dos Lipídeos , Hepatopatia Gordurosa não Alcoólica/terapia , Sulfonamidas/uso terapêutico , Tiofenos/uso terapêutico , Resposta a Proteínas não Dobradas/efeitos dos fármacosRESUMO
PURPOSE: Different mutations in coding and non-coding sequences of the SERPINA1 gene have been implicated in the pathogenesis of COPD. However, - 10T/C mutation in the hepatocyte-directed promoter region has not been associated with COPD pathogenesis so far. Here, we report an increased frequency of - 10C genotype that is associated with decreased levels of serum alpha1-antitrypsin (α1AT) in COPD patients. METHODS: The quantification of serum α1AT was done by ELISA, the phenol-chloroform method was used for DNA extraction, PCR products were directly sequenced. The IBM SPSS Statistics v21 software was used for statistical analyses of the data. RESULTS: The mean serum α1AT level was found to be 1.203+0.239 and 3.162+0.160 g/L in COPD cases and in control, respectively. The - 10C allele is associated with an increased risk of COPD [OR, 3.50 (95%CI, 1.86-6.58); p < 0.001]. The combined variant genotype (TT+CC) was significantly found associated with an increased risk of COPD [OR, 3.20 (95% CI, 1.47-6.96); p = 0.003]. A significant association of the family history with COPD (overall p value= 0.0331) suggests that genetics may play an important role in the pathogenesis of COPD. CONCLUSION: The polymorphism associated with hepatocyte-specific promoter region (- 10T/C) is likely to be associated with the pathogenesis of COPD. It is quite possible that the change of the base in the hepatocyte-specific promoter of the SERPINA1 gene can modulate its strength, thereby driving the reduced expression of α1AT.
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Hepatócitos/enzimologia , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas , Doença Pulmonar Obstrutiva Crônica/genética , alfa 1-Antitripsina/genética , Estudos de Casos e Controles , Feminino , Frequência do Gene , Estudos de Associação Genética , Predisposição Genética para Doença , Humanos , Índia/epidemiologia , Masculino , Fenótipo , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Doença Pulmonar Obstrutiva Crônica/enzimologia , Doença Pulmonar Obstrutiva Crônica/etnologia , Fatores de Risco , alfa 1-Antitripsina/sangueRESUMO
Maintenance of endoplasmic reticulum (ER) proteostasis is controlled by a dynamic signaling network known as the unfolded protein response (UPR). IRE1α is a major UPR transducer, determining cell fate under ER stress. We used an interactome screening to unveil several regulators of the UPR, highlighting the ER chaperone Hsp47 as the major hit. Cellular and biochemical analysis indicated that Hsp47 instigates IRE1α signaling through a physical interaction. Hsp47 directly binds to the ER luminal domain of IRE1α with high affinity, displacing the negative regulator BiP from the complex to facilitate IRE1α oligomerization. The regulation of IRE1α signaling by Hsp47 is evolutionarily conserved as validated using fly and mouse models of ER stress. Hsp47 deficiency sensitized cells and animals to experimental ER stress, revealing the significance of Hsp47 to global proteostasis maintenance. We conclude that Hsp47 adjusts IRE1α signaling by fine-tuning the threshold to engage an adaptive UPR.
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Endorribonucleases/metabolismo , Proteínas de Choque Térmico HSP47/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Células COS , Chlorocebus aethiops , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Retículo Endoplasmático/metabolismo , Estresse do Retículo Endoplasmático/fisiologia , Proteínas de Choque Térmico HSP47/fisiologia , Humanos , Camundongos , Chaperonas Moleculares/metabolismo , Transdução de Sinais , Estresse Fisiológico , Fatores de Transcrição/metabolismo , Resposta a Proteínas não DobradasRESUMO
Alpha-1-antitrypsin (AAT) is an acute phase secretory glycoprotein that inhibits neutrophil proteases like elastase and is considered as the archetype of a family of structurally related serine-protease inhibitors termed serpins. Serum AAT predominantly originates from liver and increases three to five fold during host response to tissue injury and inflammation. The AAT deficiency is unique among the protein-misfolding diseases in that it causes target organ injury by both loss-of-function and gain-of-toxic function mechanisms. Lack of its antiprotease activity is associated with premature development of pulmonary emphysema and loss-of-function due to accumulation of resultant aggregates in chronic obstructive pulmonary disease (COPD). This' in turn' markedly reduces the amount of AAT that is available to protect lungs against proteolytic attack by the enzyme neutrophil elastase. The coalescence of AAT deficiency, its reduced efficacy, and cigarette smoking or poor ventilation conditions have devastating effect on lung function. On the other hand, the accumulation of retained mutant proteins in the endoplasmic reticulum of hepatocytes in a polymerized form rather than secreted into the blood in its monomeric form is associated with chronic liver disease and predisposition to hepatocellular carcinoma (HCC) by gain- of- toxic function. Liver injury resulting from this gain-of-toxic function mechanism in which mutant AAT retained in the ER initiates a series of pathologic events, eventually culminating at liver cirrhosis and HCC. Here in this review, we underline the structural, genetic, polymorphic, biochemical and pathological advances made in the field of AAT deficiency and further comprehensively emphasize on the therapeutic interventions available for the patient.
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Polimorfismo de Nucleotídeo Único , Deficiência de alfa 1-Antitripsina/diagnóstico , Deficiência de alfa 1-Antitripsina/genética , Deficiência de alfa 1-Antitripsina/terapia , alfa 1-Antitripsina/genética , Animais , Modelos Animais de Doenças , Humanos , Fígado/metabolismo , Fígado/fisiopatologia , Hepatopatias/diagnóstico , Hepatopatias/etiologia , Hepatopatias/genética , Pulmão/metabolismo , Pulmão/fisiopatologia , Conformação Proteica , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Doença Pulmonar Obstrutiva Crônica/etiologia , Doença Pulmonar Obstrutiva Crônica/genética , Enfisema Pulmonar/diagnóstico , Enfisema Pulmonar/etiologia , Enfisema Pulmonar/genética , alfa 1-Antitripsina/metabolismo , Deficiência de alfa 1-Antitripsina/complicaçõesRESUMO
The p70ΔCT104 S6K is a 421 amino acid residue long truncated form of p70S6 kinase, with 104 amino acids residues cleaved from the carboxyl terminal end of the original protein. The p70ΔCT104 S6K was cloned in E. coli DH5α and successfully expressed in E. coli BL21 (DE3) strain. Western blot with rabbit polyclonal anti-GST antibody was used to follow the protein during expression and purification. The protein purification was achieved by affinity chromatography using Glutathione resin-agarose beads, followed by chromatography on a spin concentration column. The purified protein was confirmed by rabbit polyclonal anti-p70S6 kinase antibody. MALDI/MS Peptide mass fingerprinting confirmed identity of the expressed product.
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Escherichia coli/genética , Glutationa Transferase/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Quinases S6 Ribossômicas 70-kDa/genética , Proteínas Quinases S6 Ribossômicas 70-kDa/isolamento & purificação , Deleção de Sequência , Clonagem Molecular , Expressão Gênica , Modelos Moleculares , Conformação Proteica , Proteínas Recombinantes de Fusão/química , Proteínas Quinases S6 Ribossômicas 70-kDa/químicaRESUMO
A set of cellular response to counter any alteration in homeostasis of a cell originating at endoplasmic reticulum is collectively termed as unfolded protein response (UPR). It initially is adaptive in nature as to restore cellular normalcy failing in course often activates pro-apoptotic signaling pathway resulting in cell death. UPR has emerged as an essential adaptation mechanism that cross talk with various cellular processes for cancer pathogenesis. Interestingly, it plays diverse role in plethora of signaling pathways instrumental in transformation, cell invasion, cell migration, metastasis, neovascularization, proliferation, and maintenance of energy metabolism of cancerous cells. In cancerous cells, it is triggered by change in microenvironment of a cell usually driven by hypoxia, acidosis, and nutrient deprivation, which often leads to positive selection pressure involving the reprogramming of energy metabolism which promotes channelization of limited metabolites into the hexosamine biosynthetic pathway (HBP). Substantial evidences suggest the role of UPR in oncogene (Myc, mTOR, RAS, HER2) driven cancer transformation and progression. In this review, we have comprehensively underlined the role played by UPR in adaptation, transformation, proliferation, invasion, and metastasis of cancerous cells.
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Transformação Celular Neoplásica/patologia , Estresse do Retículo Endoplasmático/fisiologia , Invasividade Neoplásica/patologia , Neoplasias/patologia , Resposta a Proteínas não Dobradas/fisiologia , Proliferação de Células , Retículo Endoplasmático/patologia , Humanos , Metástase Neoplásica/patologia , Transdução de Sinais , Microambiente Tumoral/fisiologiaRESUMO
Alpha1-antitrypsin (AAT) is one of the major circulating anti-protease whose levels in circulation are raised during excessive amount of proteases, especially neutrophil elastase (NE) released during the course of inflammation. Proteolytic attack of NE on peripheral organs, more exclusively on lung parenchyma has severe consequence that may precipitate pulmonary emphysema. Normally, human body has its own molecular and physiological mechanisms to synthesize and regulate the production of anti-protease like AAT to mitigate the extent of inflammatory damage. AAT coded by serine-protease inhibitor (SERPINA1) is predominantly expressed in hepatocytes and to some extent by macrophages, monocytes, lung tissue etc. The observation that persons with AAT deficiency developed chronic obstructive pulmonary disease (COPD) and early-onset of emphysema proposed a role for pathways connecting AAT in pathogenesis. Extensive studies have been done till now to bridge a connection between numerous genetic polymorphisms of SERPINA1 gene and the early onset of COPD. Here in this review, we have comprehensively discussed some of the variants of SERPINA1 gene discovered till date and their association with the exacerbation of obstructive pulmonary disease.
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Doença Pulmonar Obstrutiva Crônica/genética , Deficiência de alfa 1-Antitripsina/genética , alfa 1-Antitripsina/genética , Adulto , Idoso , Progressão da Doença , Feminino , Humanos , Elastase de Leucócito/metabolismo , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único/genética , Doença Pulmonar Obstrutiva Crônica/complicações , Doença Pulmonar Obstrutiva Crônica/epidemiologia , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , alfa 1-Antitripsina/metabolismo , Deficiência de alfa 1-Antitripsina/complicações , Deficiência de alfa 1-Antitripsina/epidemiologia , Deficiência de alfa 1-Antitripsina/fisiopatologiaRESUMO
AIMS: Osmolytes are small organic molecules which play a significant role in maintaining functional homeostasis of proteins under extreme hostile stresses. Any imbalance to cell homeostasis leads to Endoplasmic Reticulum stress (ER-stress) to which a set of cellular responses both at transcriptional and translational level are initialed for restoration of cellular homeostasis called Unfolded Protein Response (UPR). In the present study we evaluated the role of Sarcosine, Betaine, Hydroxyectoine and Ectoine as potential modulators of UPR. ER-stress was induced by Tunicamycin, a prototypic experimental ER-stress inducer. MAIN METHODS: The endogenous cellular levels of UPR markers Glucose-Regulated Protein 78 (GRP78) and Activating Transcription Factor-4 (ATF-4) were evaluated in presence and absence of these osmolytes after inducing UPR with tunicamycin. As a prelude to this, IC50 values of these osmolytes were determined by using cell viability assays like MTT and Trypan Blue exclusion assay. KEY FINDINGS: We found that these osmolytes in a dose-dependent manner increased the rate of restoration of homeostasis as was evident by the decreased endogenous levels of GRP78 and ATF-4. SIGNIFICANCE: These natural osmolytes can thus be useful in therapeutic intervention to mitigate the pathophysiological state resulting from ER-stress.