Neuronal loss is one of the striking causes of various central nervous system (CNS) disorders, including major neurodegenerative diseases, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and Amyotrophic lateral sclerosis (ALS). Although these diseases have different features and clinical manifestations, they share some common mechanisms of disease pathology. Progressive regional loss of neurons in patients is responsible for motor, memory, and cognitive dysfunctions, leading to disabilities and death. Neuronal cell death in neurodegenerative diseases is linked to various pathways and conditions. Protein misfolding and aggregation, mitochondrial dysfunction, generation of reactive oxygen species (ROS), and activation of the innate immune response are the most critical hallmarks of most common neurodegenerative diseases. Thus, endoplasmic reticulum (ER) stress, oxidative stress, and neuroinflammation are the major pathological factors of neuronal cell death. Even though the exact mechanisms are not fully discovered, the notable role of mentioned factors in neuronal loss is well known. On this basis, researchers have been prompted to investigate the neuroprotective effects of targeting underlying pathways to determine a promising therapeutic approach to disease treatment. This review provides an overview of the role of ER stress, oxidative stress, and neuroinflammation in neuronal cell death, mainly discussing the neuroprotective effects of targeting pathways or molecules involved in these pathological factors.

INTRODUCTION The most prevalent biological macromolecules in living systems are proteins, the building block of life, extremely dynamic in structure and functions. Due to several modifications, these proteins undergo misfolding, leading to aggregation and thereby developing neurodegenerative and systemic diseases. Understanding the pathology of these diseases and the techniques used to diagnosis them is therefore very crucial for the effective management of these diseases. There are several techniques, currently being in use to diagnose them and those will be discussed in this review. AIM/OBJECTIVES Current review aims to discuss an overview of protein aggregation and the underlying mechanisms linked to neurodegeneration and systemic diseases. Also, the review highlights protein misfolding disorders, their clinical diagnosis, and treatment strategies. METHODOLOGY Literature related to neurodegenerative and systemic diseases was retrieved through PubMed, Google Scholar, Scopus, and Medline databases. The keywords used for literature search and analysis are protein aggregation, neurodegenerative disorders, Alzheimer's disease, Parkinson's disease, systemic diseases, protein aggregation mechanisms, etc. DISCUSSION /CONCLUSION: This review summarises the pathogenesis of neurodegenerative and systemic disorders caused by protein misfolding and aggregation. The clinical diagnosis and therapeutic strategies adopted for the management of these diseases are also discussed to aid in a better understanding of protein misfolding disorders. Many significant concerns about the role, characteristics, and consequences of protein aggregates in neurodegenerative and systemic diseases are not clearly understood to date. Regardless of technological advancements, there are still great difficulties in the management and cure of these diseases. Therefore, for better understanding, diagnosis, and treatment of neurodegenerative and systemic diseases, more studies to identify novel drugs that may aid in their treatment and management are required.

Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease are characterized by progressive neuronal loss, driven mainly by the misfolding, aggregation, and accumulation of each disease’s specific proteins. These pathogenic aggregates, including tau, α-synuclein, TDP-43, and huntingtin, disrupt cellular proteostasis and initiate cascades of neuroinflammation, oxidative stress, mitochondrial dysfunction, and synaptic failure. While protein aggregation has been a long-recognized hallmark of these disorders, growing evidence points towards a more complex interplay of initial molecular pathways with defects in RNA processing, stress granule pathology, and cell-type-specific vulnerability. Notably, such events may manifest differentially with respect to sex and are further modulated by age-related loss of the protein quality control processes like the ubiquitin–proteasome pathway, autophagy–lysosome pathway, and molecular chaperones. This review synthesizes current insights into the structural and functional dynamics of protein aggregation and its significance for neuronal well-being. It highlights the role of post-translational modifications, prion-like transmission, and aggregation kinetics in the regulation of toxicity. The review further discusses promising therapeutic strategies centered on restoring proteostasis, including small molecules that inhibit aggregation, protein clearance pathway enhancers, immunotherapy, antioxidant therapy, and diagnostic prospects such as the identification of reliable molecular signatures in bodily fluids that can reflect pathological changes even before clinical symptoms emerge. Advancements in single-cell transcriptomics and multi-omics platforms, which are changing our understanding of disease onset and progression and opening avenues for precision medicine and personalized treatments, were also discussed. Ultimately, deciphering the molecular logic that distinguishes physiological from pathological protein assemblies and understanding how cellular systems fail to adapt under stress will be key to the development of effective, disease-modifying therapies for these debilitating disorders.

Multiple sclerosis (MS) is an inflammatory demyelinating and degenerative disease of the central nervous system (CNS). Although inflammatory responses are efficiently treated, therapies for progression are scarce and suboptimal, and biomarkers to predict the disease course are insufficient. Cure or preventive measures for MS require knowledge of core pathological events at the site of the tissue damage. Novelties in systems biology have emerged and paved the way for a more fine-grained understanding of key pathological pathways within the CNS, but they have also raised questions still without answers. Here, we systemically review the power of tissue and single-cell/nucleus CNS omics and discuss major gaps of integration into the clinical practice. Systemic search identified 49 transcriptome and 11 proteome studies of the CNS from 1997 till October 2021. Pioneering molecular discoveries indicate that MS affects the whole brain and all resident cell types. Despite inconsistency of results, studies imply increase in transcripts/proteins of semaphorins, heat shock proteins, myelin proteins, apolipoproteins and HLAs. Different lesions are characterized by distinct astrocytic and microglial polarization, altered oligodendrogenesis, and changes in specific neuronal subtypes. In all white matter lesion types, <i>CXCL12, SCD, CD163</i> are highly expressed, and STAT6- and TGFβ-signaling are increased. In the grey matter lesions, TNF-signaling seems to drive cell death, and especially <i>CUX2</i>-expressing neurons may be susceptible to neurodegeneration. The vast heterogeneity at both cellular and lesional levels may underlie the clinical heterogeneity of MS, and it may be more complex than the current disease phenotyping in the clinical practice. Systems biology has not solved the mystery of MS, but it has discovered multiple molecules and networks potentially contributing to the pathogenesis. However, these results are mostly descriptive; focused functional studies of the molecular changes may open up for a better interpretation. Guidelines for acceptable quality or awareness of results from low quality data, and standardized computational and biological pipelines may help to overcome limited tissue availability and the "snap shot" problem of omics. These may help in identifying core pathological events and point in directions for focus in clinical prevention.

Parkinson's Disease (PD) is a progressive neurodegenerative disorder marked by dopaminergic neuron degeneration, mitochondrial dysfunction, and Alpha-synuclein (α-synuclein) aggregation. Dynamin-related protein 1 (Drp1), a key regulator of mitochondrial fission, plays a critical role in PD. Overactivation of Drp1 causes excessive mitochondrial fragmentation, impairing mitochondrial function, increasing Reactive oxygen species (ROS) production, and exacerbating oxidative stress, neuroinflammation, and protein misfolding, all of which contribute to PD pathology. Targeting Drp1 with small molecule inhibitors and gene interventions has shown promise in preclinical models by reducing mitochondrial dysfunction, oxidative damage, and neuronal death. Combination therapies, integrating Drp1 inhibitors with antioxidants and anti-inflammatory agents, have demonstrated synergistic effects. Despite promising preclinical findings, clinical studies on Drp1-targeted therapies are still in early stages, with challenges like specificity and off-target effects. Future research will focus on refining Drp1-targeted therapies, including precision medicine, multi-target strategies, and clinical trials to assess efficacy, safety, and pharmacokinetics. This review highlights Drp1 as a promising therapeutic target for PD and discusses future clinical translation challenges.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory loss and cognitive decline. Its main pathological features are extracellular plaques composed of aggregated amyloid-β (Aβ) peptides and intracellular neurofibrillary tangles formed by hyperphosphorylated tau. The Aβ hypothesis proposes that Aβ accumulation is a key driver of AD, influencing tau pathology, neuroinflammation, and neurodegeneration. However, therapies that reduce Aβ have shown limited clinical benefits. This suggests that the mechanisms underlying peptide-mediated modulation of AD pathology are much more complex. Both Aβ and tau undergo various post-translational modifications (PTMs) that affect their structure, aggregation, and toxicity. In addition, these abnormal proteins are not efficiently cleared in AD, indicating dysfunction of the protein quality control (PQC) system that maintains proteostasis. Such abnormal PTMs and impaired PQC likely work together to drive disease progression, which may explain the limited success of Aβ-reduction therapies. In this review, we describe how major PTMs, including phosphorylation, ubiquitination, acetylation, glycosylation, and oxidation, regulate the pathological behavior of Aβ and tau. We also discuss the role of the PQC systems in the pathology of AD. We propose that dysregulation of PTMs and PQC constitutes a convergent mechanism underlying AD pathogenesis. Therapeutic strategies targeting these processes may provide more effective and sustained disease modification than approaches focused solely on Aβ reduction.

Parkinson’s disease (PD) pathology involves progressive degeneration and death of vulnerable dopamine neurons in the substantia nigra. Extensive axonal arborization and distinct functions make this type of neurons particularly sensitive to homeostatic perturbations, such as protein misfolding and Ca 2+ dysregulation. Endoplasmic reticulum (ER) is a cell compartment orchestrating protein synthesis and folding, as well as synthesis of lipids and maintenance of Ca 2+ homeostasis in eukaryotic cells. When misfolded proteins start to accumulate in ER lumen the unfolded protein response (UPR) is activated. UPR is an adaptive signaling machinery aimed at relieving of protein folding load in the ER. When UPR is chronic, it can either boost neurodegeneration and apoptosis or cause neuronal dysfunctions. We have recently discovered that mesencephalic astrocyte-derived neurotrophic factor (MANF) exerts its prosurvival action in dopamine neurons and in an animal model of PD through the direct binding to UPR sensor inositol-requiring protein 1 alpha (IRE1 α ) and attenuation of UPR. In line with this, UPR targeting resulted in neuroprotection and neurorestoration in various preclinical animal models of PD. Therefore, growth factors (GFs), possessing both neurorestorative activity and restoration of protein folding capacity are attractive as drug candidates for PD treatment especially their blood-brain barrier penetrating analogs and small molecule mimetics. In this review, we discuss ER s

Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease that is characterized by the loss of motor neurons, which results in progressive muscle atrophy. The pathology spreads from the initial site of onset to contiguous anatomic regions. Mutations in the gene encoding Cu/Zn-superoxide dismutase (SOD1) have been identified in a dominantly inherited form of ALS (ALS-SOD1). A major hallmark of ALS-SOD1 is the abnormal accumulation of conformationally aberrant SOD1 protein (i.e., misfolded SOD1) within motor neurons. Emerging experimental evidence has suggested that misfolded proteins associated with neurodegenerative diseases exhibit prion-like properties, i.e., misfolded proteins act as conformational templates that convert normal proteins into a pathogenic form. Possibly as a result of this prion-like self-propagation property, misfolded forms of pathological proteins are considered to accumulate in the central nervous system and cause neurodegeneration. In this article, we review recent evidence for the role of prion-like mechanisms in ALS-SOD1. In particular, we discuss the propensity of misfolded SOD1 to act as a pathological seed, spread between cells, and propagate neuroanatomically.

Protein misfolding is common across many neurodegenerative diseases, with misfolded proteins acting as seeds for "prion-like" conversion of normally folded protein to abnormal conformations. A central hypothesis is that misfolded protein accumulation, spread, and distribution are restricted to specific neuronal populations of the central nervous system and thus predict regions of neurodegeneration. We examined this hypothesis using a highly sensitive assay system for detection of misfolded protein seeds in a murine model of prion disease. Misfolded prion protein (PrP) seeds were observed wides

The absence of any histologic correlate for Alzheimer's disease despite its commonness and severe clinical sequelae may offers clues to its etiology. Recent evidence strongly suggests that the central event of this disease is the hyperphosphorylation of neuronal tau protein and not the beta amyloid precipitates. In each case, essential and soluble neuronal proteins derivatives form insoluble aggregates that can readily be detected by immunohistochemistry using antibodies specific for the misfolded proteins. Immunohistochemistry also demonstrates that neurons with hyperphosphorylated tau protein are viable. Experimental evidence using neuronal cell cultures suggests that the affected neurons in Alzheimer's disease may have undergone molecular changes that include accumulation of anti-apopotic proteins MCL1 and cFLIP that do not allow the cell to undergo programmed cell death but, rather, to "immortalize" and thus accumulate hyperphosphorylated tau protein in the neuronal cell body and beta amyloid in downstream dendrites. We describe a simplified protocol to demonstrate such changes based on tagged LNA modified microRNA/antimicroRNA oligomers and cell cultures. Co-expression showed that the tagged antimiR-512 strongly localized with the markedly up-regulated proteins MCL1 and cFLIP with concomitant accumulation of hyperphosphorylated tau protein. The data underscore to the anatomic pathologist that the diagnosis of Alzheimer's disease is best accomplished by simple immunohisto

Amyotrophic Lateral Sclerosis (ALS) is a fatal motor neuron disease presenting as sporadic (sALS) or familial (fALS) forms. Even if the list of the genes underlining ALS greatly expanded, defects in SOD1, encoding the copper/zinc superoxide dismutase 1, still remain a major cause of fALS and are likely involved also in apparently sporadic presentations. The pathogenesis of ALS is still unknown, but several lines of evidence indicate that the mitochondrial accumulation of mutant SOD1 is an important mechanism of mitochondrial dysfunction, leading to motor neuron pathology and death. The intramitochondrial localization of mutant SOD1 is debated. Mutant SOD1 might accumulate inside the intermembrane space (IMS), overriding the physiological retention regulated by its chaperone CCS. On the other hand, misfolded SOD1 might deposit onto the outer mitochondrial membrane (OMM), clumping the transport across mitochondrial membranes and engaging mitochondrial-dependent cell apoptosis. The elucidation of the mechanisms ruling SOD1 localization and misplacing might shed light on peculiar ALS features such as cell selectivity and late onset. More importantly, these studies might disclose novel targets for therapeutic intervention in familial ALS as well as non-genetic forms. Finally, pharmacological or genetic manipulation aimed to prevent or counteract the intracellular shifting of mutant SOD1 could be effective for other neurodegenerative disorders featuring the toxic accumulation of mi

Any prion-related disease.: #* {{quote-journal|en|author=Anderson, K.N.; Overcast, W.B.; Brosch, J.R.; Graner, B.D.; Veronesi, M.C.|title=Prionopathies and Prionlike Protein Aberrations in Neurodegenerative Diseases|journal=American Society of Neuroradiology|doi=10.3174/ng.2000035|date=2021-03-01|volume=11|number=2|pages=127-148|passage=The prionopathies are best known among the neurodegenerative diseases for their ability to misfold, self-propagate, and infect other organisms. In this review, we detail the role of a key protein aberration known to the various prion diseases, including sporadic, variant, and iatrogenic Creutzfeldt-Jakob disease; variably protease-sensitive prionopathy; Gerstmann-Straussler-Scheinker disease; fatal familial insomnia; and kuru.}}

responsible for prion diseases, which are fatal and transmissible neurodegenerative diseases affecting animals, including humans. These proteins can misfold sporadically A prion ( ) is a misfolded protein that induces folding problems in normal variants of the same protein, leading to cellular death. Prions are responsible for prion diseases, which are fatal and transmissible neurodegenerative diseases affecting animals, including humans. These proteins can misfold sporadically, due to genetic mutations, or through exposure to an already misfolded protein, leading A prion ( ) is a misfolded protein that induces folding problems in normal variants of the same protein, leading to cellular death. Prions are responsible for prion diseases, which are fatal and transmissible neurodegenerative diseases affecting animals, including humans. These proteins can misfold sporadically, due to genetic mutations, or through exposure to an already misfolded protein, leading to an abnormal three-dimensional structure that can propagate misfolding in other proteins. The term prion derives from "proteinaceous infectious particle". Unlike other infectious agents such as viruses, bacteria, and fungi, prions do not contain nucleic acids (DNA or RNA). Prions are primarily twisted isoforms of the major prion protein (PrP), a naturally occurring protein with an uncertain function. They are the hypothesized cause of various diseases, including scrapie in sheep, chronic wasting disease (CWD) in deer, bovine spongiform encephalopathy (BSE) in cattle (mad cow disease), and Creutzfeldt–Jakob disease (CJD) in humans. All known prion diseases in mammals affect the structure of the brain or other neural tissues. These diseases are progressive, have no known effective treatment, and are invariably fatal. Most prion diseases were thought to be caused by PrP until 2015 when a prion form of alpha-synuclein was linked to multiple system atrophy (MSA). Misfolded proteins are also linked to other neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS), which have been shown to originate and progress by a prion-like mechanism. Prions are a type of intrinsically disordered protein that continuously changes conformation unless bound to a specific partner, such as another protein. Once a prion binds to another in the same conformation, it stabilizes and can form a fibril, leading to abnormal protein aggregates called amyloids. These amyloids accumulate in infected tissue, causing damage and cell death. The structural stability of prions makes them resistant to denaturation by chemical or physical agents, complicating disposal and containment, and raising concerns about (physician caused) iatrogenic spread …

<h4>Introduction</h4>Protein Disulfide Isomerases (PDIs) and bacterial Dsb proteins are key members of the thioredoxin-fold superfamily, essential for oxidative protein folding in eukaryotic and prokaryotic systems, respectively. Despite their differences in cellular context, these proteins share a conserved thioredoxin domain architecture that enables catalysis of disulfide bond formation, isomerization, and reduction. This systematic review integrates biochemical, structural, and bioinformatic data to identify conserved features within the PDI and Dsb families that underline their catalytic functions.<h4>Methods</h4>Using a PRISMA-based methodology, we screened and analyzed 96 relevant articles and conducted a comparative structural analysis of 11 representative PDI proteins, most of which lack experimentally resolved structures. We leveraged AlphaFold models alongside crystal structures of canonical PDI (PDIA1), DsbC, and DsbG.<h4>Results</h4>We reveal conserved tertiary folds, catalytic motifs, and domain arrangements across species. These findings highlight the evolutionary conservation and structural versatility of thioredoxin-fold enzymes and underscore their biomedical relevance in diseases linked to protein misfolding, such as neurodegeneration, cancer, and infection.<h4>Discussion</h4>The results offer a foundation for future experimental studies and therapeutic exploration targeting redox-regulating thioredoxin-fold proteins.

where misfolded proteins convert normal ones into the same abnormal shape). Because PrP is continuously produced by a cell and the abnormal proteins stick Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a group of rare, progressive, incurable, and invariably fatal conditions that cause degeneration of the nervous system in humans and other animals, such as cattle and sheep. Prion diseases are caused by abnormally shaped proteins called prions, an idea once considered radical, but now well supported by evidence. Prions consis Tr…