Protein folding and misfolding in the neurodegenerative disorders: A review (original) (raw)

Autophagy and misfolded proteins in neurodegeneration

Experimental Neurology, 2012

The accumulation of misfolded proteins in insoluble aggregates within the neuronal cytoplasm is one of the common pathological hallmarks of most adult-onset human neurodegenerative diseases. The clearance of these misfolded proteins may represent a promising therapeutic strategy in these diseases. The two main routes for intracellular protein degradation are the ubiquitin-proteasome and the autophagy-lysosome pathways. In this review, we will focus on the autophagic pathway, by providing some examples of how impairment at different steps in this degradation pathway is related to different neurodegenerative diseases. We will also consider that upregulating autophagy may be useful in the treatment of some of these diseases. Finally, we discuss how antioxidants, which have been considered to be beneficial in neurodegenerative diseases, can block autophagy, thus potentially compromising their therapeutic potential.

Protein aggregation and degradation mechanisms in neurodegenerative diseases

American Journal of Neurodegenerative Disease, 2013

Neurodegenerative diseases are characterized by selective neuronal vulnerability and neurodegeneration in specific brain regions. The pathogenesis of these disorders centrally involves abnormal accumulation and aggregation of specific proteins, which are deposited in intracellular inclusions or extracellular aggregates that are characteristic for each disease. Increasing evidence suggests that genetic mutations or environmental factors can instigate protein misfolding and aggregation in these diseases. Consequently, neurodegenerative diseases are often considered as conformational diseases. This idea is further supported by studies implicating that impairment of the protein quality control (PQC) and clearance systems, such as the ubiquitin-proteasome system and autophagosome-lysosome pathway, may lead to the abnormal accumulation of disease-specific proteins. This suggests that similar pathological mechanisms may underlie the pathogenesis of the different neurodegenerative disorders. Interestingly, several proteins that are known to associate with neurodegenerative diseases have been identified as important regulators of PQC and clearance systems. In this review, we summarize the central features of abnormal protein accumulation in different common neurodegenerative diseases and discuss some aspects of specific disease-associated proteins regulating the PQC and clearance mechanisms, such as ubiquilin-1.

Removing Protein Aggregates: The Role of Proteolysis in Neurodegeneration

Current Medicinal Chemistry, 2011

A common characteristic of neurodegenerative diseases like Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) is the accumulation of protein aggregates. This reflects a severe disturbance of protein homeostasis, the proteostasis. Here, we review the involvement of the two major proteolytic machineries, the ubiquitin proteasome system (UPS) and the autophagy/lysosomal system, in the pathogenesis of neurodegenerative diseases. These proteolytic systems cooperate to maintain the proteostasis, as is indicated by intricate cross talk. In addition, the UPS and autophagy are regulated by stress pathways that are activated by disturbed proteostasis, like the unfolded protein response (UPR). We will specifically discuss how these proteolytic pathways are affected in neurodegenerative diseases. We will show that there is a differential involvement of the UPS and autophagy in different neurodegenerative disorders. In addition, the proteolytic impairment may be primary or secondary to the pathology. These differences have important implications for the design of therapeutic strategies. The opportunities and caveats of targeting the UPS and autophagy/lysosomal system as a therapeutic strategy in neurodegeneration will be discussed.

Editorial: Protein misfolding, altered mechanisms and neurodegeneration

Frontiers in Molecular Neuroscience

Editorial on the Research Topic Protein misfolding, altered mechanisms and neurodegeneration Neurodegenerative diseases (NDs) like Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), Frontotemporal lobe degeneration (FTLD), Polyglutamine diseases such as Huntington's disease (HD), Spinocerebellar ataxias (SCAs) etc., are a group of debilitating disorders that affects millions of people worldwide and have no cure to-date. Despite the advancement in our understanding of molecular and genetic mechanisms underlying these NDs, only a limited symptom-based treatment options are available. As the life expectancy increases there is an increase in the number of ND patients, which will seriously challenge the availability of resources and will impact a nation's economy. There is an urgent need to develop an affordable healthcare system and find effective treatment options to provide better clinical regimens to cure these diseases. NDs affect neurons, neuronal connections associated with memory, cognition, thinking, strength, sensation, movements, learning, coordination , and other abilities. Although the causative factors of NDs varies from one to another and the differences in the disease symptoms could be many, these diseases share some common features. One of the common pathological hallmarks among the most NDs is aggregation or deposition of misfolded proteins. Compelling evidence from neuropathological, genetic, animal models studies, and other approaches have strongly supported the fact that accumulation of misfolded protein aggregates triggers a series of detrimental events, which results in synaptic alterations, neuronal cell loss, and significantly contributes toward disease pathogenesis. This Research Topic highlights the new approaches employed to develop therapeutics, which can effectively block or slow down the onset or progression of these fatal NDs. This manuscripts collection highlights the current advances in the field of neurodegenerative disorders, which may help in addressing some of the unanswered questions pertaining to this Research Topic. This collection of manuscripts is divided into three vital categories: (1) Disease mechanisms, (2) Therapeutic perspectives, and (3) Animal model(s). We hope that this topic may help discern the gaps, connect the missing links, improve our current understanding, knowledge related to this topic and open new avenues of research focuses to improve current treatments options against these deadly yet incurable disorders.

Protein misfolding in neurodegenerative diseases

Neuropathology and Applied Neurobiology, 2004

A common pathogenic mechanism shared by diverse neurodegenerative disorders, like Alzheimer's disease, Parkinson's disease, Huntington's disease and transmissible spongiform encephalopathies, may be altered protein homeostasis leading to protein misfolding and aggregation of a wide variety of different proteins in the form of insoluble fibrils. Mutations in the genes encoding protein constituents of these aggregates have been linked to the corresponding diseases, thus a reasonable scenario of pathogenesis was based on misfolding of a neurone-specific protein that forms insoluble fibrils that subsequently kill neuronal cells. However, during the past 5 years accumulating evidence has revealed the neurotoxic role of prefibrillar intermediate forms (soluble oligomers and protofibrils) produced during fibril formation. Many think these may be the predominant neurotoxic species, whereas microscopically visible fibrillar aggregates may not be toxic. Large protein aggregates may rather be simply inactive, or even represent a protective state that sequesters and inactivates toxic oligomers and protofibrils. Further understanding of the biochemical mechanisms involved in protein misfolding and fibrillization may optimize the planning of common therapeutic approaches for neurodegenerative diseases, directed towards reversal of protein misfolding, blockade of protein oligomerization and interference with the action of toxic proteins.

Editorial: Protein Misfolding and Spreading Pathology in Neurodegenerative Diseases

Frontiers in Molecular Neuroscience

Editorial on the Research Topic Protein Misfolding and Spreading Pathology in Neurodegenerative Diseases A common pathological hallmark among different neurodegenerative diseases is the accumulation of aggregated proteins that might cause cellular dysfunction and, eventually, lead to cell death. Amyloid-beta, Tau, alpha-synuclein, TDP-43, or the prion protein, are just a few examples of proteins that can aggregate and contribute to the pathogenesis of neurodegenerative diseases with diverse clinical manifestations (Alzheimer's disease, frontotemporal lobar degeneration, Pick's disease, Parkinson's disease, Lewy body dementia, multiple system atrophy, amyotrophic lateral sclerosis among the most common). Emerging evidence suggests that the progression of symptoms in patients affected by such disorders correlates with the spreading of pathology through the brain, but the molecular mechanisms underlying aggregation and propagation of protein aggregates are still obscure. This Research Topic focuses on the structural and molecular characteristics of aggregation-prone proteins and resumes new aspects of pathology spreading. A series of 10 articles provides an exciting up-to-date overview of core biological features of prion and prion-like neurodegenerative disorders. Protein aggregation is a common feature among numerous neurodegenerative diseases, and is thought to culminate with detrimental effects for the cells where the proteins accumulate. Despite the commonalities of protein aggregation and cell dysfunction, the pathobiological bases of these diseases may differ. For example, the two characteristic protein deposits in Alzheimer's disease (AD) are the extracellular senile plaques, whose main constituent are amyloid-β (Aβ) fibrils, and intraneuronal neurofibrillary tangles (NFT), composed of hyperphosphorylated Tau protein (

Quality control of the proteins associated with neurodegenerative diseases

Acta biochimica et biophysica Sinica, 2008

Most neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease and other polyglutamine diseases are associated with degeneration and death of specific neuronal populations due to misfolding or aggregation of certain proteins. These aggregates often contain ubiquitin that is the signal for proteolysis by the ubiquitin-proteasome system, and chaperone proteins that are involved in the assistance of protein folding. Here we review the role of protein quality control systems in the pathogenesis of neurodegenerative diseases, and aim to learn more from the cooperation between molecular chaperones and ubiquitin-proteasome system responding to cellular protein aggregates, in order to find molecular targets for therapeutic intervention.

Protein misfolding in Alzheimer’s and Parkinson’s disease: genetics and molecular mechanisms

Neurobiology of Aging, 2002

The accumulation of altered proteins is a common pathogenic mechanism in several neurodegenerative disorders. A causal role of protein aggregation was originally proposed in Alzheimer's disease (AD) where extracellular deposition of ␤-amyloid (A␤) is the main neuropathological feature. It is now believed that intracellular deposition of aggregated proteins may be relevant in Parkinson's disease (PD), amyotrophic lateral sclerosis and polyglutamine disorders. An impairment of ubiquitin-proteasome system (UPS) appears directly involved in these disorders. We reviewed the results on the role of protein misfolding in AD and PD and the influence of mutations associated with these diseases on the expression of amyloidogenic proteins. Results of genetic screening of familial cases of AD and PD are summarized. In the familial AD population (70 subjects) we found several mutations of the presenilin 1 (PS1) gene with a frequency of 12.8% and one mutation in the gene encoding the protein precursor of amyloid (APP) (1.4%). One mutation of Parkin in the homozygous form and two in the heterozygous form were identified in our PD population. We also reported data obtained with synthetic peptides and other experimental models, for evaluation of the pathogenic role of mutations in terms of protein misfolding.

Protein degradation, aggregation, and misfolding

Movement Disorders, 2010

The cellular surveillance systems guarantee proper removal of altered components from inside cells. Alterations of these systems in neurons have been proposed to be involved in the pathogenesis of different neurodegenerative disorders. In this review, we comment on the advances in our current understanding of how changes in the intracellular proteolytic systems, the main components of the cellular quality control system, contribute to neurodegeneration, with special emphasis on Parkinson's disease.