scholarly journals Optineurin promotes aggregation of mutant huntingtin and mutant ataxin-3, and reduces cytotoxicity of aggregates

2020 ◽  
Author(s):  
Shivranjani C Moharir ◽  
Akhouri Kishore Raghawan ◽  
Ghanshyam Swarup
Keyword(s):  
Cell Death ◽  
Neurodegenerative Diseases ◽  
Protein Aggregation ◽  
Neuronal Cells ◽  
Protein Aggregates ◽  
Mutant Protein ◽  
Mutant Huntingtin ◽  
Aggregate Formation ◽  
Wild Type ◽  
Mutant Proteins

AbstractOptineurin (OPTN), a cytoplasmic adaptor protein involved in cargo selective autophagy of bacteria, damaged mitochondria and mutant protein aggregates, is frequently seen in pathological structures containing protein aggregates, associated with several neurodegenerative diseases. However, the function of OPTN in these protein aggregates is not known. Here, we have explored the role of OPTN in mutant protein aggregation and in cytoprotection from toxicity of mutant proteins. Mutant huntingtin (mHtt) and mutant ataxin-3 (mAtax-3) showed reduced formation of aggregates in Optn−/− mouse embryonic fibroblasts as compared with wild type cells. Co-expression of OPTN enhanced aggregate formation by mHtt and mAtax-3 in Optn−/− cells. C-terminal domain of OPTN (412-577 amino acids) was necessary and sufficient to promote aggregate formation by these mutant proteins. The E478G mutant of OPTN, defective in ubiquitin-binding and autophagy, was also able to promote aggregation of mHtt and mAtax-3. OPTN and its C-terminal domain form a complex with the chaperone HSP70 known to promote mutant protein aggregation. Overexpression of mHtt or mAtax-3 induced more cell death in Optn−/− cells compared with wild type cells. Importantly, compared to wild type cells, Optn-deficient cells having mHtt or mAtax-3 aggregates showed higher level of cell death in neuronal (N2A) and non-neuronal cells. Our results show that OPTN promotes formation of mutant huntingtin and mutant ataxin-3 aggregates, and this function of OPTN might be mediated through interaction with HSP70 chaperones. Our results also show that OPTN reduces cytotoxicity caused by these mutant protein aggregates.Significance statementThe hallmark of several neurodegenerative diseases like amyotrophic lateral sclerosis, Huntington’s disease, Parkinson’s disease, Alzheimer’s disease and Pick’s disease is the formation of pathological structures containing aggregated proteins, and OPTN is frequently observed in these structures. What role optineurin plays in those aggregates is not clear. Our results show that OPTN promotes aggregation of mutant huntingtin and mutant ataxin-3, and reduces cytotoxicity of aggregates in neuronal and non-neuronal cells. We suggest that OPTN provides cytoprotection in three different ways-by promoting mutant protein aggregation, by reducing cytotoxicity of aggregates and by autophagy-dependent clearance of aggregates reported earlier. These properties of OPTN provide a possible explanation for its association with various pathological structures containing protein aggregates seen in several neurodegenerative diseases.

scholarly journals Amitriptyline interferes with autophagy-mediated clearance of protein aggregates via inhibiting autophagosome maturation in neuronal cells

2020 ◽  
Vol 11 (10) ◽  
Author(s):  
Yoonjung Kwon ◽  
Yeojin Bang ◽  
Soung-Hee Moon ◽  
Aeri Kim ◽  
Hyun Jin Choi
Keyword(s):  
Neurodegenerative Diseases ◽  
Depressive Disorders ◽  
Neuronal Cells ◽  
Protein Aggregates ◽  
Underlying Mechanism ◽  
Tricyclic Antidepressant ◽  
Autophagic Flux ◽  
Autophagosome Maturation

Abstract Amitriptyline is a tricyclic antidepressant commonly prescribed for major depressive disorders, as well as depressive symptoms associated with various neurological disorders. A possible correlation between the use of tricyclic antidepressants and the occurrence of Parkinson’s disease has been reported, but its underlying mechanism remains unknown. The accumulation of misfolded protein aggregates has been suggested to cause cellular toxicity and has been implicated in the common pathogenesis of neurodegenerative diseases. Here, we examined the effect of amitriptyline on protein clearance and its relevant mechanisms in neuronal cells. Amitriptyline exacerbated the accumulation of abnormal aggregates in both in vitro neuronal cells and in vivo mice brain by interfering with the (1) formation of aggresome-like aggregates and (2) autophagy-mediated clearance of aggregates. Amitriptyline upregulated LC3B-II, but LC3B-II levels did not increase further in the presence of NH4Cl, which suggests that amitriptyline inhibited autophagic flux rather than autophagy induction. Amitriptyline interfered with the fusion of autophagosome and lysosome through the activation of PI3K/Akt/mTOR pathway and Beclin 1 acetylation, and regulated lysosome positioning by increasing the interaction between proteins Arl8, SKIP, and kinesin. To the best of our knowledge, we are the first to demonstrate that amitriptyline interferes with autophagic flux by regulating the autophagosome maturation during autophagy in neuronal cells. The present study could provide neurobiological clue for the possible correlation between the amitriptyline use and the risk of developing neurodegenerative diseases.

scholarly journals Aggregation of prion protein with insertion mutations is proportional to the number of inserts

2007 ◽  
Vol 403 (2) ◽  
pp. 343-351 ◽  
Author(s):  
Shuiliang Yu ◽  
Shaoman Yin ◽  
Chaoyang Li ◽  
Poki Wong ◽  
Binggong Chang ◽  
...  
Keyword(s):  
Prion Protein ◽  
Prion Diseases ◽  
Biochemical Properties ◽  
Mutant Protein ◽  
Insertion Mutant ◽  
Wild Type ◽  
Mutant Proteins ◽  
Severity Of The Disease ◽  
Α Helix ◽  
Insertion Mutations

Mutation in the prion gene, PRNP, accounts for approx. 10–15% of human prion diseases. However, little is known about the mechanisms by which a mutant prion protein (PrP) causes disease. We compared the biochemical properties of a wild-type human prion protein, rPrPC (recombinant wild-type PrP), which has five octapeptide-repeats, with two recombinant human prion proteins with insertion mutations, one with three more octapeptide repeats, rPrP8OR, and the other with five more octapeptide repeats, rPrP10OR. We found that the insertion mutant proteins are more prone to aggregate, and the degree and kinetics of aggregation are proportional to the number of inserts. The octapeptide-repeat and α-helix 1 regions are important in aggregate formation, because aggregation is inhibited with monoclonal antibodies that are specific for epitopes in these regions. We also showed that a small amount of mutant protein could enhance the formation of mixed aggregates that are composed of mutant protein and wild-type rPrPC. Accordingly, rPrP10OR is also more efficient in promoting the aggregation of rPrPC than rPrP8OR. These findings provide a biochemical explanation for the clinical observations that the severity of the disease in patients with insertion mutations is proportional to the number of inserts, and thus have implications for the pathogenesis of inherited human prion disease.

scholarly journals Aspartate 205 in the Catalytic Domain of Naphthalene Dioxygenase Is Essential for Activity

1999 ◽  
Vol 181 (6) ◽  
pp. 1831-1837 ◽  
Author(s):  
Rebecca E. Parales ◽  
Juanito V. Parales ◽  
David T. Gibson
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Catalytic Domain ◽  
Mutant Protein ◽  
Wild Type ◽  
Naphthalene Dioxygenase ◽  
Major Pathway ◽  
Α Subunit ◽  
Mutant Proteins ◽  
Mononuclear Iron

ABSTRACT The naphthalene dioxygenase enzyme system carries out the first step in the aerobic degradation of naphthalene byPseudomonas sp. strain NCIB 9816-4. The crystal structure of naphthalene dioxygenase (B. Kauppi, K. Lee, E. Carredano, R. E. Parales, D. T. Gibson, H. Eklund, and S. Ramaswamy, Structure 6:571–586, 1998) indicates that aspartate 205 may provide the most direct route of electron transfer between the Rieske [2Fe-2S] center of one α subunit and mononuclear iron in the adjacent α subunit. In this study, we constructed four site-directed mutations that changed aspartate 205 to alanine, glutamate, asparagine, or glutamine to test whether this residue is essential for naphthalene dioxygenase activity. The mutant proteins were very inefficient in oxidizing naphthalene tocis-naphthalene dihydrodiol, and oxygen uptake in the presence of naphthalene was below detectable levels. The purified mutant protein with glutamine in place of aspartate 205 had identical spectral properties to wild-type naphthalene dioxygenase and was reduced by NADH in the presence of catalytic amounts of ferredoxinNAP and reductaseNAP. Benzene, an effective uncoupler of oxygen consumption in purified naphthalene dioxygenase, did not elicit oxygen uptake by the mutant protein. These results indicate that electron transfer from NADH to the Rieske center in the mutant oxygenase is intact, a finding consistent with the proposal that aspartate 205 is a necessary residue in the major pathway of electron transfer to mononuclear iron at the active site.

scholarly journals Lipid Metabolism Influence on Neurodegenerative Disease Progression: Is the Vehicle as Important as the Cargo?

2021 ◽  
Vol 14 ◽  
Author(s):  
Raja Elizabeth Estes ◽  
Bernice Lin ◽  
Arnav Khera ◽  
Marie Ynez Davis
Keyword(s):  
Lipid Metabolism ◽  
Neurodegenerative Diseases ◽  
Protein Aggregation ◽  
Neurodegenerative Disease ◽  
Disease Progression ◽  
Protein Aggregates ◽  
Disease Etiology ◽  
Abnormal Protein ◽  
System A ◽  
Novel Therapeutic

Many neurodegenerative diseases are characterized by abnormal protein aggregates, including the two most common neurodegenerative diseases Alzheimer’s disease (AD) and Parkinson’s disease (PD). In the global search to prevent and treat diseases, most research has been focused on the early stages of the diseases, including how these pathogenic protein aggregates are initially formed. We argue, however, that an equally important aspect of disease etiology is the characteristic spread of protein aggregates throughout the nervous system, a key process in disease progression. Growing evidence suggests that both alterations in lipid metabolism and dysregulation of extracellular vesicles (EVs) accelerate the spread of protein aggregation and progression of neurodegeneration, both in neurons and potentially in surrounding glia. We will review how these two pathways are intertwined and accelerate the progression of AD and PD. Understanding how lipid metabolism, EV biogenesis, and EV uptake regulate the spread of pathogenic protein aggregation could reveal novel therapeutic targets to slow or halt neurodegenerative disease progression.

Nucleic Acid Therapeutics in Huntington’s Disease

2019 ◽  
Vol 13 (3) ◽  
pp. 187-206 ◽  
Author(s):  
Kuljit Singh ◽  
Ipsita Roy
Keyword(s):  
Nucleic Acid ◽  
Nucleic Acids ◽  
Protein Aggregation ◽  
Huntington's Disease ◽  
Antisense Oligonucleotides ◽  
Protein Misfolding ◽  
Mutant Protein ◽  
Mutant Huntingtin ◽  
Nucleic Acid Therapeutics ◽  
Delivery Techniques

Background: Protein misfolding is a critical factor in the progression of a large number of neurodegenerative diseases. The incorrectly folded protein is prone to aggregation, leading to aberrant interaction with other cellular proteins, elevated oxidative stress, impaired cellular machinery, finally resulting in cell death. Due to its monogenic origin, Huntington’s disease (HD) is a poster child of protein misfolding neurodegenerative disorders. The presence of neuronal inclusions of mutant huntingtin N-terminal fragments, mainly in the cortex and striatum, is a neuropathological hallmark of HD. Inhibition of protein misfolding and aggregation has been attempted using a variety of conventional protein stabilizers. Methods: This review describes how, in recent times, nucleic acid therapeutics has emerged as a selective tool to downregulate the aberrant transcript and reduce expression of mutant huntingtin, thereby alleviating protein aggregation. Different strategies of use of nucleic acids, including antisense oligonucleotides, short inhibitory RNA sequences and aptamers have been discussed. The following patent databases were consulted: European Patent Office (EPO), the United States Patent and Trademark Office (USPTO), Patent scope Search International and National Patent Collections (WIPO) and Google Patents. Results: Tools such as RNA interference (RNAi) and antisense oligonucleotides (ASOs) are potential therapeutic agents which target the post-transcriptional step, accelerating mRNA degradation and inhibiting the production of the mutant protein. These nucleic acid sequences not only target the elongated CAG triplet repeat translating to an expanded polyglutamine tract in the mutant protein, but have also been used to target single nucleotide polymorphisms associated with the mutant allele. The therapeutic sequences have been investigated in a number of cells and animal models of HD. One antisense sequence, with desirable safety properties, has recently shown downregulation of huntingtin protein in a limited clinical trial. RNA aptamers have also shown promising results in inhibiting protein aggregation in a yeast model of HD. Novel drug delivery techniques have been employed to overcome the blood brain barrier for the use of these therapeutic sequences. Conclusion: The selectivity and specificity imparted by nucleic acids, along with novel delivery techniques, make them hopeful candidates for the development of a curative strategy for HD.

GRP78 counteracts cell death and protein aggregation caused by mutant huntingtin proteins

2012 ◽  
Vol 516 (2) ◽  
pp. 182-187 ◽  
Author(s):  
Yufeng Jiang ◽  
Hailong Lv ◽  
Min Liao ◽  
Xiaoyuan Xu ◽  
Shanshan Huang ◽  
...  
Keyword(s):  
Cell Death ◽  
Protein Aggregation ◽  
Mutant Huntingtin

Dieckol, an edible seaweed polyphenol, retards rotenone-induced neurotoxicity and α-synuclein aggregation in human dopaminergic neuronal cells

RSC Advances ◽  
2016 ◽  
Vol 6 (111) ◽  
pp. 110040-110046 ◽  
Author(s):  
Seon-Heui Cha ◽  
Soo-Jin Heo ◽  
You-Jin Jeon ◽  
Sang Myun Park
Keyword(s):  
Oxidative Stress ◽  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Cell Death ◽  
Protein Aggregation ◽  
Dopaminergic Neurons ◽  
Neuronal Cells ◽  
Edible Seaweed

Dopaminergic neurons are particularly vulnerable to oxidative stress, which may initiate a cascade of intracellular toxic events that lead to protein aggregation and subsequent cell death, causing Parkinson's disease.

Huntington's disease: from pathology and genetics to potential therapies

2008 ◽  
Vol 412 (2) ◽  
pp. 191-209 ◽  
Author(s):  
Sara Imarisio ◽  
Jenny Carmichael ◽  
Viktor Korolchuk ◽  
Chien-Wen Chen ◽  
Shinji Saiki ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Trinucleotide Repeat ◽  
Mutant Protein ◽  
Mutant Huntingtin ◽  
Genetic Screens ◽  
Wild Type ◽  
Biological Studies ◽  
Polyglutamine Tract

Huntington's disease (HD) is a devastating autosomal dominant neurodegenerative disease caused by a CAG trinucleotide repeat expansion encoding an abnormally long polyglutamine tract in the huntingtin protein. Much has been learnt since the mutation was identified in 1993. We review the functions of wild-type huntingtin. Mutant huntingtin may cause toxicity via a range of different mechanisms. The primary consequence of the mutation is to confer a toxic gain of function on the mutant protein and this may be modified by certain normal activities that are impaired by the mutation. It is likely that the toxicity of mutant huntingtin is revealed after a series of cleavage events leading to the production of N-terminal huntingtin fragment(s) containing the expanded polyglutamine tract. Although aggregation of the mutant protein is a hallmark of the disease, the role of aggregation is complex and the arguments for protective roles of inclusions are discussed. Mutant huntingtin may mediate some of its toxicity in the nucleus by perturbing specific transcriptional pathways. HD may also inhibit mitochondrial function and proteasome activity. Importantly, not all of the effects of mutant huntingtin may be cell-autonomous, and it is possible that abnormalities in neighbouring neurons and glia may also have an impact on connected cells. It is likely that there is still much to learn about mutant huntingtin toxicity, and important insights have already come and may still come from chemical and genetic screens. Importantly, basic biological studies in HD have led to numerous potential therapeutic strategies.

scholarly journals Engineering of a Type III Rubisco from a Hyperthermophilic Archaeon in Order To Enhance Catalytic Performance in Mesophilic Host Cells

2007 ◽  
Vol 73 (19) ◽  
pp. 6254-6261 ◽  
Author(s):  
Shosuke Yoshida ◽  
Haruyuki Atomi ◽  
Tadayuki Imanaka
Keyword(s):  
Rhodopseudomonas Palustris ◽  
Host Cells ◽  
Mutant Protein ◽  
Wild Type ◽  
Turnover Number ◽  
Bisphosphate Carboxylase ◽  
Mutant Proteins ◽  
Hyperthermophilic Archaeon ◽  
Type Iii ◽  
Α Helix

ABSTRACT The hyperthermophilic archaeon Thermococcus kodakaraensis harbors a type III ribulose 1,5-bisphosphate carboxylase/oxygenase (RbcTk). It has previously been shown that RbcTk is capable of supporting photoautotrophic and photoheterotrophic growth in a mesophilic host cell, Rhodopseudomonas palustris Δ3, whose three native Rubisco genes had been disrupted. Here, we have examined the enzymatic properties of RbcTk at 25°C and have constructed mutant proteins in order to enhance its performance in mesophilic host cells. Initial sites for mutagenesis were selected by focusing on sequence differences in the loop 6 and α-helix 6 regions among RbcTk and the enzymes from spinach (mutant proteins SP1 to SP7), Galdieria partita (GP1 and GP2), and Rhodospirillum rubrum (RR1). Loop 6 of RbcTk is one residue longer than those found in the spinach and G. partita enzymes, and replacing RbcTk loop 6 with these regions led to dramatic decreases in activity. Six mutant enzymes retaining significant levels of Rubisco activity were selected, and their genes were introduced into R. palustris Δ3. Cells harboring mutant protein SP6 displayed a 31% increase in the specific growth rate under photoheterotrophic conditions compared to cells harboring wild-type RbcTk. SP6 corresponds to a complete substitution of the original α-helix 6 of RbcTk with that of the spinach enzyme. Compared to wild-type RbcTk, the purified SP6 mutant protein exhibited a 30% increase in turnover number (k cat) of the carboxylase activity and a 17% increase in the k cat/Km value. Based on these results, seven further mutant proteins were designed and examined. The results confirmed the importance of the length of loop 6 in RbcTk and also led to the identification of specific residue changes that resulted in an increase in the turnover number of RbcTk at ambient temperatures.

Sign in / Sign up

Export Citation Format

Share Document