Hidden kinetic traps in multidomain folding highlight the presence of a misfolded but functionally competent intermediate

Although more than 75% of the proteome is composed of multidomain proteins, current knowledge of protein folding is based primarily on studies of isolated domains. In this work, we describe the folding mechanism of a multidomain tandem construct comprising two distinct covalently bound PDZ domains belonging to a protein called Whirlin, a scaffolding protein of the hearing apparatus. In particular, via a synergy between NMR and kinetic experiments, we demonstrate the presence of a misfolded intermediate that competes with productive folding. In agreement with the view that tandem domain swapping is a potential source of transient misfolding, we demonstrate that such a kinetic trap retains native-like functional activity, as shown by the preserved ability to bind its physiological ligand. Thus, despite the general knowledge that protein misfolding is intimately associated with dysfunction and diseases, we provide a direct example of a functionally competent misfolded state. Remarkably, a bioinformatics analysis of the amino acidic sequence of Whirlin from different species suggests that the tendency to perform tandem domain swapping between PDZ1 and PDZ2 is highly conserved, as demonstrated by their unexpectedly high sequence identity. On the basis of these observations, we discuss on a possible physiological role of such misfolded intermediate.

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Role of Mitochondrial Cytochrome P450 2E1 in Healthy and Diseased Liver

Cells ◽

10.3390/cells11020288 ◽

2022 ◽

Vol 11 (2) ◽

pp. 288

Author(s):

Julie Massart ◽

Karima Begriche ◽

Jessica H. Hartman ◽

Bernard Fromenty

Keyword(s):

Oxidative Stress ◽

Cytochrome P450 ◽

Liver Disease ◽

Fatty Liver ◽

Current Knowledge ◽

Physiological Role ◽

Experimental Investigations ◽

Rat Liver Mitochondria ◽

Cytochrome P450 2E1

Cytochrome P450 2E1 (CYP2E1) is pivotal in hepatotoxicity induced by alcohol abuse and different xenobiotics. In this setting, CYP2E1 generates reactive metabolites inducing oxidative stress, mitochondrial dysfunction and cell death. In addition, this enzyme appears to play a role in the progression of obesity-related fatty liver to nonalcoholic steatohepatitis. Indeed, increased CYP2E1 activity in nonalcoholic fatty liver disease (NAFLD) is deemed to induce reactive oxygen species overproduction, which in turn triggers oxidative stress, necroinflammation and fibrosis. In 1997, Avadhani’s group reported for the first time the presence of CYP2E1 in rat liver mitochondria, and subsequent investigations by other groups confirmed that mitochondrial CYP2E1 (mtCYP2E1) could be found in different experimental models. In this review, we first recall the main features of CYP2E1 including its role in the biotransformation of endogenous and exogenous molecules, the regulation of its expression and activity and its involvement in different liver diseases. Then, we present the current knowledge on the physiological role of mtCYP2E1, its contribution to xenobiotic biotransformation as well as the mechanism and regulation of CYP2E1 targeting to mitochondria. Finally, we discuss experimental investigations suggesting that mtCYP2E1 could have a role in alcohol-associated liver disease, xenobiotic-induced hepatotoxicity and NAFLD.

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Ammonium transport: unifying concepts and unique aspects

Functional Plant Biology ◽

10.1071/pp01070 ◽

2001 ◽

Vol 28 (9) ◽

pp. 959 ◽

Cited By ~ 1

Author(s):

Anne van Dommelen ◽

René de Mot ◽

Jos Vanderleyden

Keyword(s):

Current Knowledge ◽

Natural Habitat ◽

Physiological Role ◽

Ammonium Uptake ◽

Ammonium Transport ◽

Symbiotic Interaction ◽

Ammonium Transporters ◽

Operating Current ◽

Living Organisms

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Ammonium uptake by cells has been studied for more than a century, but only recently a family of ammonium transporters (Mep/Amt) with 10–12 transmembrane domains has been defined. These proteins are probably ubiquitous, since homologues have been found in the major kingdoms of living organisms. Plants as well as yeast and some archaebacteria have multiple Mep/Amt paralogues, which can be distinguished by their affinity for ammonium and the ammonium analogue methylammonium. Most ammonium transporters are induced in nitrogen-starving conditions, both in prokaryotes and plants. In Saccharomyces cerevisiae, Escherichia coli and Azospirillum brasilense Mep/Amt proteins where shown to be necessary for growth when the external concentration of the diffusive ammonium form (NH3) becomes limiting. Ammonium transporters also play an important role in pseudohyphal differentiation in yeast and efficient symbiotic interaction between Rhizobium etli and its host plant. In most bacteria, NH4+ transport appears to be a uniport mechanism driven by the membrane potential, but, depending on the organism, a different mode of ammonium uptake may be operating. Current knowledge offers the basis to investigate further the physiological role of ammonium transporters in the natural habitat of organisms and their importance in plant–bacteria interactions.

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Bicarbonate Transport in Cystic Fibrosis and Pancreatitis

Cells ◽

10.3390/cells11010054 ◽

2021 ◽

Vol 11 (1) ◽

pp. 54

Author(s):

Dora Angyal ◽

Marcel J. C. Bijvelds ◽

Marco J. Bruno ◽

Maikel P. Peppelenbosch ◽

Hugo R. de Jonge

Keyword(s):

Cystic Fibrosis ◽

Current Knowledge ◽

Pancreatic Insufficiency ◽

Anion Channel ◽

Exocrine Pancreatic Insufficiency ◽

Scaffolding Protein ◽

Bicarbonate Transport ◽

Human Pancreas ◽

Ductal Cells

CFTR, the cystic fibrosis (CF) gene-encoded epithelial anion channel, has a prominent role in driving chloride, bicarbonate and fluid secretion in the ductal cells of the exocrine pancreas. Whereas severe mutations in CFTR cause fibrosis of the pancreas in utero, CFTR mutants with residual function, or CFTR variants with a normal chloride but defective bicarbonate permeability (CFTRBD), are associated with an enhanced risk of pancreatitis. Recent studies indicate that CFTR function is not only compromised in genetic but also in selected patients with an acquired form of pancreatitis induced by alcohol, bile salts or smoking. In this review, we summarize recent insights into the mechanism and regulation of CFTR-mediated and modulated bicarbonate secretion in the pancreatic duct, including the role of the osmotic stress/chloride sensor WNK1 and the scaffolding protein IRBIT, and current knowledge about the role of CFTR in genetic and acquired forms of pancreatitis. Furthermore, we discuss the perspectives for CFTR modulator therapy in the treatment of exocrine pancreatic insufficiency and pancreatitis and introduce pancreatic organoids as a promising model system to study CFTR function in the human pancreas, its role in the pathology of pancreatitis and its sensitivity to CFTR modulators on a personalized basis.

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C-Cbl-PI3K Interaction Is Important for Platelet Outside-In Signaling

Blood ◽

10.1182/blood.v116.21.2014.2014 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2014-2014

Author(s):

Claudia Lorena Buitrago ◽

Satya P. Kunapuli ◽

Archana Sanjay

Keyword(s):

Actin Cytoskeleton ◽

Protein Interactions ◽

Conflicts Of Interest ◽

Physiological Role ◽

Human Platelets ◽

Scaffolding Protein ◽

Protein Protein Interactions ◽

Clot Retraction ◽

Knock Out

Abstract Abstract 2014 Platelet activation by outside-in signaling is initiated by the binding of fibrinogen to alphaIIbbeta3, an integrin only expressed in platelets and megakaryocytes. Signals transduced by alphaIIbbeta3 regulate actin cytoskeleton resulting in filopodia and lamellipodia formation, cell spreading and retraction. c-Cbl protein is abundantly expressed in platelets and functions as E3 ubiquitin ligase and scaffolding protein to mediate protein-protein interactions. Importantly, c-Cbl tyrosine 731 has been shown to interact with p85 subunit of phosphotidylinositol 3-kinase (PI3K) modulating the actin cytoskeleton. Although previous reports showed c-Cbl activation downstream of alphaIIbbeta3, the mechanisms and implications of this activation or the downstream targets remain to be elucidated. We have studied the role of c-Cbl in platelet outside-in signaling: Using human platelets we have demonstrated that c-Cbl Y700, Y731 and Y774 residues undergoes tyrosine phosphorylation upon platelet adhesion to immobilized fibrinogen. These phosphorylation events are completely inhibited in the presence of the pan Src Family Kinases (SFKs) inhibitor (PP2) suggesting that c-Cbl is phosphorylated downstream of SFKs. Spleen tyrosine kinase (Syk) is also involved in this signaling pathway since its inhibition significantly reduce c-Cbl phosphorylation at residues Y774 and Y700; interestingly, tyrosine 731 phosphorylation, which allows the interaction with the p85-subunit of PI3K, is not affected by Syk inhibition. The physiological role of c-Cbl in platelet outside-in signaling was studied using c-Cbl knock-out mice. We found that in contrast to WT platelets, c-Cbl KO platelets had a significantly reduced spreading over a fibrinogen-coated surface. Furthermore, clot retraction analysis demonstrated that c-Cbl KO platelets retraction time was delayed when compared to WT platelets, suggesting a retraction defect. To further elucidate the physiological role of c-Cbl-PI3K interaction we used a knock-in mouse in which the c-Cbl residue Y 731 was substituted with phenylalanine (Y731F) thereby abolishing the PI3K binding site on c-Cbl. Importantly, platelets from Y731F mice showed spreading and clot retraction defect that were comparable with the c-Cbl KO. These result indicates that in large part, the role of c-Cbl in platelets outside-in signaling is determined by its interaction with PI3K. In conclusion, we have demonstrated that c-Cbl plays an important role in platelet outside-in signaling, and its interaction with PI3K through tyrosine 731 is of pivotal importance in platelet spreading and retraction. Disclosures: No relevant conflicts of interest to declare.

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Toward Understanding the Role of Aryl Hydrocarbon Receptor in the Immune System: Current Progress and Future Trends

BioMed Research International ◽

10.1155/2014/520763 ◽

2014 ◽

Vol 2014 ◽

pp. 1-14 ◽

Cited By ~ 38

Author(s):

Hamza Hanieh

Keyword(s):

Immune System ◽

Aryl Hydrocarbon Receptor ◽

Immune Cells ◽

Immune Cell ◽

Current Knowledge ◽

Physiological Role ◽

Clinical Practices ◽

Aryl Hydrocarbon ◽

Active Research

The immune system is regulated by distinct signaling pathways that control the development and function of the immune cells. Accumulating evidence suggest that ligation of aryl hydrocarbon receptor (Ahr), an environmentally responsive transcription factor, results in multiple cross talks that are capable of modulating these pathways and their downstream responsive genes. Most of the immune cells respond to such modulation, and many inflammatory response-related genes contain multiple xenobiotic-responsive elements (XREs) boxes upstream. Active research efforts have investigated the physiological role of Ahr in inflammation and autoimmunity using different animal models. Recently formed paradigm has shown that activation of Ahr by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 3,3′-diindolylmethane (DIM) prompts the differentiation of CD4+Foxp3+regulatory T cells (Tregs) and inhibits T helper (Th)-17 suggesting that Ahr is an innovative therapeutic strategy for autoimmune inflammation. These promising findings generate a basis for future clinical practices in humans. This review addresses the current knowledge on the role of Ahr in different immune cell compartments, with a particular focus on inflammation and autoimmunity.

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The Role of Autophagy in Immunity and Autoimmune Diseases / Uloga Autofagije U Imunskom Odgovoru I Autoimunskim Bolestima

Serbian Journal of Experimental and Clinical Research ◽

10.2478/sjecr-2014-0028 ◽

2014 ◽

Vol 15 (4) ◽

pp. 223-229

Author(s):

Bojana Simovic Markovic ◽

Ljubica Vucicevic ◽

Sanja Bojic ◽

Vladislav Volarevic

Keyword(s):

Autoimmune Diseases ◽

Potential Role ◽

Current Knowledge ◽

Inflammatory Diseases ◽

Physiological Role ◽

Immune Functions ◽

Complex Relationships ◽

Cellular Components ◽

Chaperone Mediated Autophagy

ABSTRACT Autophagy is a catabolic mechanism in the cell that involves the degradation of unnecessary or dysfunctional cellular components by the lysosomal machinery. Recent studies have indicated that autophagy is a source of autoantigens, thus highlighting its potential role in the pathogenesis of autoimmunity. There are at least three different forms of autophagy: macroautophagy, microautophagy and chaperone-mediated autophagy (CMA). The physiological role of autophagy is to maintain cellular homeostasis by removing long-lived, damaged proteins and dysfunctional organelles and by providing energy. Aberrant autophagy may contribute to chronic inflammatory diseases and autoimmune diseases. An understanding of the complex relationships between autophagy and autophagy-related genes in each autoimmune disease creates the possibility of developing more specific and effective therapeutic strategies. Given the importance of autophagy in immune functions, this review article summarises current knowledge about the role of autophagy in the pathogenesis of autoimmune diseases.

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The BPI-like/PLUNC family proteins in cattle

Biochemical Society Transactions ◽

10.1042/bst0391006 ◽

2011 ◽

Vol 39 (4) ◽

pp. 1006-1011 ◽

Cited By ~ 12

Author(s):

Thomas T. Wheeler ◽

Brendan J. Haigh ◽

Marita K. Broadhurst ◽

Kylie A. Hood ◽

Nauman J. Maqbool

Keyword(s):

Protein Gene ◽

Current Knowledge ◽

Physiological Role ◽

Secretory Protein ◽

Salivary Protein ◽

Ancestral Gene ◽

Bacterial Aggregation ◽

Parotid Secretory Protein ◽

Pathogen Exposure

Members of the protein family having similarity to BPI (bactericidal/permeability increasing protein) (the BPI-like proteins), also known as the PLUNC (palate, lung and nasal epithelium clone) family, have been found in a range of mammals; however, those in species other than human or mouse have been relatively little characterized. Analysis of the BPI-like proteins in cattle presents unique opportunities to investigate the function of these proteins, as well as address their evolution and contribution to the distinct physiology of ruminants. The present review summarizes the current understanding of the nature of the BPI-like locus in cattle, including the duplications giving rise to the multiple BSP30 (bovine salivary protein 30 kDa) genes from an ancestral gene in common with the single PSP (parotid secretory protein) gene found in monogastric species. Current knowledge of the expression of the BPI-like proteins in cattle is also presented, including their pattern of expression among tissues, which illustrate their independent regulation at sites of high pathogen exposure, and the abundance of the BSP30 proteins in saliva and salivary tissues. Finally, investigations of the function of the BSP30 proteins are presented, including their antimicrobial, lipopolysaccharide-binding and bacterial aggregation activities. These results are discussed in relation to hypotheses regarding the physiological role of the BPI-like proteins in cattle, including the role they may play in host defence and the unique aspects of digestion in ruminants.

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Role of Protein Misfolding and Proteostasis Deficiency in Protein Misfolding Diseases and Aging

International Journal of Cell Biology ◽

10.1155/2013/638083 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 75

Author(s):

Karina Cuanalo-Contreras ◽

Abhisek Mukherjee ◽

Claudio Soto

Keyword(s):

Protein Misfolding ◽

Current Knowledge ◽

Ubiquitin Proteasome System ◽

Unfolded Protein ◽

Natural Defense ◽

Dependent Protein ◽

The Unfolded Protein Response ◽

Misfolding Diseases ◽

Protein Response

The misfolding, aggregation, and tissue accumulation of proteins are common events in diverse chronic diseases, known as protein misfolding disorders. Many of these diseases are associated with aging, but the mechanism for this connection is unknown. Recent evidence has shown that the formation and accumulation of protein aggregates may be a process frequently occurring during normal aging, but it is unknown whether protein misfolding is a cause or a consequence of aging. To combat the formation of these misfolded aggregates cells have developed complex and complementary pathways aiming to maintain protein homeostasis. These protective pathways include the unfolded protein response, the ubiquitin proteasome system, autophagy, and the encapsulation of damaged proteins in aggresomes. In this paper we review the current knowledge on the role of protein misfolding in disease and aging as well as the implication of deficiencies in the proteostasis cellular pathways in these processes. It is likely that further understanding of the mechanisms involved in protein misfolding and the natural defense pathways may lead to novel strategies for treatment of age-dependent protein misfolding disorders and perhaps aging itself.

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GDNF and protection of adult central catecholaminergic neurons

Journal of Molecular Endocrinology ◽

10.1530/jme-10-0125 ◽

2011 ◽

Vol 46 (3) ◽

pp. R83-R92 ◽

Cited By ~ 40

Author(s):

Alberto Pascual ◽

María Hidalgo-Figueroa ◽

Raquel Gómez-Díaz ◽

José López-Barneo

Keyword(s):

Current Knowledge ◽

Physiological Role ◽

Adult Brain ◽

Peripheral Neurons ◽

Central Neurons ◽

Small Proteins ◽

Therapeutic Tools ◽

And Function ◽

Catecholaminergic Cells

Neurotrophic factors are small proteins necessary for neuron survival and maintenance of phenotype. They are considered as promising therapeutic tools for neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF) protects catecholaminergic cells from toxic insults; thus, its potential therapeutic applicability in Parkinson's disease has been intensely investigated. In recent years, there have been major advances in the analysis of GDNF signaling pathways in peripheral neurons and embryonic dopamine mesencephalic cells. However, the actual physiological role of GDNF in maintaining catecholaminergic central neurons during adulthood is only starting to be unraveled, and the mechanisms whereby GDNF protects central brain neurons are poorly known. In this study, we review the current knowledge of GDNF expression, signaling, and function in adult brain, with special emphasis on the genetic animal models with deficiency in the GDNF-dependent pathways.

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Vitamin C in critical conditions: from bench to bedside (part 2)

EMERGENCY MEDICINE ◽

10.22141/2224-0586.17.1.2021.225708 ◽

2021 ◽

Vol 17 (1) ◽

pp. 6-13

Author(s):

S.M. Chuklin ◽

S.S. Chuklin

Keyword(s):

Ascorbic Acid ◽

Vitamin C ◽

Key Words ◽

Current Knowledge ◽

Physiological Role ◽

Surgical Patients ◽

Critical Conditions ◽

Metabolic Functions ◽

Critically Ill Surgical Patients

Vitamin C (ascorbic acid) plays an important physiological role in numerous metabolic functions. It is also a cofactor in the synthesis of important substances, in particular catecholamines and vasopressin. A decrease in the level of ascorbic acid has been noted in various diseases, often accompanying the severity of the patient’s state. The aim of this article is to review the current knowledge on the physiological role of vitamin C and the experimental evidences of its use in critically ill surgical patients. Medline database on the PubMed platform was used to search for the literature sources with key words: vitamin C, sepsis, shock, trauma, burns.

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