Accumulation Of Misfolded Proteins Research Articles

Misfolded protein deposits in Parkinson’s disease and Parkinson’s disease-related cognitive impairment, a [11C]PBB3 study

Parkinson’s disease (PD) is associated with aggregation of misfolded α-synuclein and other proteins, including tau. We designed a cross-sectional study to quantify the brain binding of [11C]PBB3 (a ligand known to bind to misfolded tau and possibly α-synuclein) as a proxy of misfolded protein aggregation in Parkinson’s disease (PD) subjects with and without cognitive impairment and healthy controls (HC). In this cross-sectional study, nineteen cognitively normal PD subjects (CN-PD), thirteen cognitively impaired PD subjects (CI-PD) and ten HC underwent [11C]PBB3 PET. A subset of the PD subjects also underwent PET imaging with [11C](+)DTBZ to assess dopaminergic denervation and [11C]PBR28 to assess neuroinflammation. Compared to HC, PD subjects showed higher [11C]PBB3 binding in the posterior putamen but not the substantia nigra. There was no relationship across subjects between [11C]PBB3 and [11C]PBR28 binding in nigrostriatal regions. [11C]PBB3 binding was increased in the anterior cingulate in CI-PD compared to CN-PD and HC, and there was an inverse correlation between cognitive scores and [11C]PBB3 binding in this region across all PD subjects. Our results support a primary role of abnormal protein deposition localized to the posterior putamen in PD. This suggests that striatal axonal terminals are preferentially involved in the pathophysiology of PD. Furthermore, our findings suggest that anterior cingulate pathology might represent a significant in vivo marker of cognitive impairment in PD, in agreement with previous neuropathological studies.

The role of labile iron on brain proteostasis; could it be an early event of neurodegenerative disease?

Iron deposits in the brain are a natural consequence of aging. Iron accumulation, especially in the form of labile iron, can trigger a cascade of adverse effects, eventually leading to neurodegeneration and cognitive decline. Aging also increases the dysfunction of cellular proteostasis. The question of whether iron alters proteostasis is now being pondered. Herein, we investigated the effect of ferric citrate, considered as labile iron, on various aspects of proteostasis of neuronal cell lines, and also established an animal model having a labile iron diet in order to evaluate proteostasis alteration in the brain along with behavioral effects. According to an in vitro study, labile iron was found to activate lysosome formation but inhibits lysosomal clearance function. Furthermore, the presence of labile iron can alter autophagic flux and can also induce the accumulation of protein aggregates. RNA-sequencing analysis further reveals the upregulation of various terms related to proteostasis along with neurodegenerative disease-related terms. According to an in vivo study, a labile iron-rich diet does not induce iron overload conditions and was not detrimental to the behavior of male Wistar rats. However, an iron-rich diet can promote iron accumulation in a region-dependent manner. By staining for autophagic markers and misfolding proteins in the cerebral cortex and hippocampus, an iron-rich diet was actually found to alter autophagy and induce an accumulation of misfolding proteins. These findings emphasize the importance of labile iron on brain cell proteostasis, which could be implicated in developing of neurological diseases.

Raman microspectroscopy for label‐free diagnosis of amyloid light‐chain amyloidosis in various organs

AbstractSystemic amyloidosis is a group of diseases in which misfolded proteins aggregate as fibrous amyloid proteins with a β‐sheet structure and deposit in organs, resulting in organ failure. Most types of amyloidosis have a poor prognosis, and prompt diagnosis is essential for treatment. Systemic immunoglobulin light‐chain (AL) amyloidosis is a type of amyloidosis that occurs when abnormal immunoglobulin light‐chain proteins are deposited in various organs and tissues. The deposition of amyloid proteins in tissues has traditionally been confirmed using Congo red staining and polarised light microscopy, which show apple‐green birefringence. In this study, we aimed to verify whether amyloid deposition in the heart, kidney, rectum, duodenum and skin can be detected using Raman microspectroscopy. Serial sections were prepared from formalin‐fixed paraffin‐embedded tissue biopsy samples obtained from patients with systemic amyloidosis. One of the serial sections was stained with Congo red to confirm the deposition of amyloid proteins using polarised light microscopy, whereas the other was left unstained for Raman microspectroscopy. A characteristic peak at Raman shift of 1665–1680 cm−1, which may represent a β‐sheet structure of amyloid proteins, was recorded in the area where the amyloid deposition had been confirmed by Congo red staining. Based on the peak at 1640–1680 cm−1, a colour map was obtained to detect amyloid protein‐positive regions. Thus, amyloid protein detection using Raman microspectroscopy may be useful for rapid diagnosis of amyloidosis.

Glitches in the brain: the dangerous relationship between radiotherapy and brain fog.

Up to approximately 70% of cancer survivors report persistent deficits in memory, attention, speed of information processing, multi-tasking, and mental health functioning, a series of symptoms known as "brain fog." The severity and duration of such effects can vary depending on age, cancer type, and treatment regimens. In particular, every year, hundreds of thousands of patients worldwide undergo radiotherapy (RT) for primary brain tumors and brain metastases originating from extracranial tumors. Besides its potential benefits in the control of tumor progression, recent studies indicate that RT reprograms the brain tumor microenvironment inducing increased activation of microglia and astrocytes and a consequent general condition of neuroinflammation that in case it becomes chronic could lead to a cognitive decline. Furthermore, radiation can induce endothelium reticulum (ER) stress directly or indirectly by generating reactive oxygen species (ROS) activating compensatory survival signaling pathways in the RT-surviving fraction of healthy neuronal and glial cells. In particular, the anomalous accumulation of misfolding proteins in neuronal cells exposed to radiation as a consequence of excessive activation of unfolded protein response (UPR) could pave the way to neurodegenerative disorders. Moreover, exposure of cells to ionizing radiation was also shown to affect the normal proteasome activity, slowing the degradation rate of misfolded proteins, and further exacerbating ER-stress conditions. This compromises several neuronal functions, with neuronal accumulation of ubiquitinated proteins with a consequent switch from proteasome to immunoproteasome that increases neuroinflammation, a crucial risk factor for neurodegeneration. The etiology of brain fog remains elusive and can arise not only during treatment but can also persist for an extended period after the end of RT. In this review, we will focus on the molecular pathways triggered by radiation therapy affecting cognitive functions and potentially at the origin of so-called "brain fog" symptomatology, with the aim to define novel therapeutic strategies to preserve healthy brain tissue from cognitive decline.

Aggresome formation promotes ASK1/JNK signaling activation and stemness maintenance in ovarian cancer

Aggresomes are the product of misfolded protein aggregation, and the presence of aggresomes has been correlated with poor prognosis in cancer patients. However, the exact role of aggresomes in tumorigenesis and cancer progression remains largely unknown. Herein, the multiomics screening reveal that OTUD1 protein plays an important role in retaining ovarian cancer stem cell (OCSC) properties. Mechanistically, the elevated OTUD1 protein levels lead to the formation of OTUD1-based cytoplasmic aggresomes, which is mediated by a short peptide located in the intrinsically disordered OTUD1 N-terminal region. Furthermore, OTUD1-based aggresomes recruit ASK1 via protein-protein interactions, which in turn stabilize ASK1 in a deubiquitinase-independent manner and activate the downstream JNK signaling pathway for OCSC maintenance. Notably, the disruption of OTUD1-based aggresomes or treatment with ASK1/JNK inhibitors, including ibrutinib, an FDA-approved drug that was recently identified as an MKK7 inhibitor, effectively reduced OCSC stemness (OSCS) of OTUD1high ovarian cancer cells. In summary, our work suggests that aggresome formation in tumor cells could function as a signaling hub and that aggresome-based therapy has translational potential for patients with OTUD1high ovarian cancer.

Mitochondrial stress: a key role of neuroinflammation in stroke.

Stroke is a clinical syndrome characterized by an acute, focal neurological deficit, primarily caused by the occlusion or rupture of cerebral blood vessels. In stroke, neuroinflammation emerges as a pivotal event contributing to neuronal cell death. The occurrence and progression of neuroinflammation entail intricate processes, prominently featuring mitochondrial dysfunction and adaptive responses. Mitochondria, a double membrane-bound organelle are recognized as the "energy workshop" of the body. Brain is particularly vulnerable to mitochondrial disturbances due to its high energy demands from mitochondria-related energy production. The interplay between mitochondria and neuroinflammation plays a significant role in the pathogenesis of stroke. The biological and pathological consequences resulting from mitochondrial stress have substantial implications for cerebral function. Mitochondrial stress serves as an adaptive mechanism aimed at mitigating the stress induced by the import of misfolded proteins, which occurs in response to stroke. This adaptive response involves a reduction in misfolded protein accumulation and overall protein synthesis. The influence of mitochondrial stress on the pathological state of stroke is underscored by its capacity to interact with neuroinflammation. The impact of mitochondrial stress on neuroinflammation varies according to its severity. Moderate mitochondrial stress can bolster cellular adaptive defenses, enabling cells to better withstand detrimental stressors. In contrast, sustained and excessive mitochondrial stress detrimentally affects cellular and tissue integrity. The relationship between neuroinflammation and mitochondrial stress depends on the degree of mitochondrial stress present. Understanding its role in stroke pathogenesis is instrumental in excavating the novel treatment of stroke. This review aims to provide the evaluation of the cross-talk between mitochondrial stress and neuroinflammation within the context of stroke. We aim to reveal how mitochondrial stress affects neuroinflammation environment in stroke.

Application of Nanocomposites and Nanoparticles in Treating Neurodegenerative Disorders.

Neurodegenerative diseases represent a formidable global health challenge, affecting millions and imposing substantial burdens on healthcare systems worldwide. Conditions, like Alzheimer's, Parkinson's, and Huntington's diseases, among others, share common characteristics, such as neuronal loss, misfolded protein aggregation, and nervous system dysfunction. One of the major obstacles in treating these diseases is the presence of the blood-brain barrier, limiting the delivery of therapeutic agents to the central nervous system. Nanotechnology offers promising solutions to overcome these challenges. In Alzheimer's disease, NPs loaded with various compounds have shown remarkable promise in preventing amyloid-beta (Aβ) aggregation and reducing neurotoxicity. Parkinson's disease benefits from improved dopamine delivery and neuroprotection. Huntington's disease poses its own set of challenges, but nanotechnology continues to offer innovative solutions. The promising developments in nanoparticle-based interventions for neurodegenerative diseases, like amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), have offered new avenues for effective treatment. Nanotechnology represents a promising frontier in biomedical research, offering tailored solutions to the complex challenges posed by neurodegenerative diseases. While much progress has been made, ongoing research is essential to optimize nanomaterial designs, improve targeting, and ensure biocompatibility and safety. Nanomaterials possess unique properties that make them excellent candidates for targeted drug delivery and neuroprotection. They can effectively bypass the blood-brain barrier, opening doors to precise drug delivery strategies. This review explores the extensive research on nanoparticles (NPs) and nanocomposites in diagnosing and treating neurodegenerative disorders. These nanomaterials exhibit exceptional abilities to target neurodegenerative processes and halt disease progression.

Simulation and Computational Study of RING Domain Mutants of BRCA1 and Ube2k in AD/PD Pathophysiology.

Lysine-based post-translational modification (PTM) such as acylation, acetylation, deamination, methylation, SUMOylation, and ubiquitination has proven to be a major regulator of gene expression, chromatin structure, protein stability, protein-protein interaction, protein degradation, and cellular localization. However, besides all the PTMs, ubiquitination stands as the second most common PTM after phosphorylation that is involved in the etiology of neurodegenerative diseases (NDDs) namely, Alzheimer's disease (AD) and Parkinson's disease (PD). NDDs are characterized by the accumulation of misfolded protein aggregates in the brain that lead to disease-related gene mutation and irregular protein homeostasis. The ubiquitin-proteasome system (UPS) is in charge of degrading these misfolded proteins, which involve an interplay of E1, E2, E3, and deubiquitinase enzymes. Impaired UPS has been commonly observed in NDDs and E3 ligases are the key members of the UPS, thus, dysfunction of the same can accelerate the neurodegeneration process. Therefore, the aim of this study is firstly, to find E3 ligases that are common in both AD and PD through data mining. Secondly, to study the impact of mutation on its structure and function. The study deciphered 74 E3 ligases that were common in both AD and PD. Later, 10 hub genes were calculated of which protein-protein interaction, pathway enrichment, lysine site prediction, domain, and motif analysis were performed. The results predicted BRCA1, PML, and TRIM33 as the top three putative lysine-modified E3 ligases involved in AD and PD pathogenesis. However, based on structural characterization, BRCA1 was taken further to study RING domain mutation that inferred K32Y, K32L, K32C, K45V, K45Y, and K45G as potential mutants that alter the structural and functional ability of BRCA1 to interact with Ube2k, E2-conjugating enzyme. The most probable mutant observed after molecular dynamics simulation of 50 ns is K32L. Therefore, our study concludes BRCA1, a potential E3 ligase common in AD and PD, and RING domain mutation at sites K32 and K45 possibly disturbs its interaction with its E2, Ube2k. Graphical representation of all the steps involved to study mutation in the RING domain of BRCA1 which is a common E3 ligase observed in Alzheimer's disease and Parkinson's disease.

Interaction of Tau with G-Protein-Coupled Purinergic P2Y12 Receptor by Molecular Docking and Molecular Dynamic Simulation.

Alzheimer's disease, a progressive neurological disorder, is characterized by the accumulation of neurofibrillary tangles and senile plaques by Tau and amyloid-β, respectively, in the brain microenvironment. The misfolded protein aggregates interact with several components of neuronal and glial cells such as membrane lipids, receptors, transporters, enzymes, cytoskeletal proteins, etc. Under pathological conditions, Tau interacts with several G-protein-coupled receptors (GPCRs), which undergoes either receptor signaling or desensitization followed by internalization of the protein complex. The purinergic GPCR, P2Y12 which is expressed in microglial cells, plays a key role in its activation and migration. Microglial cells sense and migrate to the site of injury aided by P2Y12 receptor that interacts with ADP released from damaged cells. P2Y12 receptor also interacts with misfolded Tau accumulated at the extracellular space and promotes receptor-mediated internalization. Immunocolocalization and co-immunoprecipitation studies demonstrated the interaction of Tau species with the P2Y12 receptor. Later, in-silico analyses were carried out with the repeat domain of Tau (TauRD), which has been identified as the interacting partner of P2Y12 receptor by in-vitro studies. Molecular docking and molecular dynamics simulation studies show the stability and the type of interaction in TauRD-receptor complex. Tau interaction with P2Y12 receptor plays a significant role in maintaining the active state of microglia which could lead to neuroinflammation and neuronal damage in AD brain. Hence, blocking P2Y12-Tau interaction and P2Y12-mediated Tau internalization in microglial cells could be possible therapeutic strategies in downregulating the severity of neuroinflammation in AD.

Development of fluorophores for the detection of oligomeric aggregates of amyloidogenic proteins found in neurodegenerative diseases.

Alzheimer's disease and Parkinson's disease are the two most common neurodegenerative diseases globally. These neurodegenerative diseases have characteristic late-stage symptoms allowing for differential diagnosis; however, they both share the presence of misfolded protein aggregates which appear years before clinical manifestation. Historically, research has focused on the detection of higher-ordered aggregates (or amyloids); however, recent evidence has shown that the oligomeric state of these protein aggregates plays a greater role in disease pathology, resulting in increased efforts to detect oligomers to aid in disease diagnosis. In this review, we summarize some of the exciting new developments towards the development of fluorescent probes that can detect oligomeric aggregates of amyloidogenic proteins present in Alzheimer's and Parkinson's disease patients.

Mitophagy biomarkers are changed in the continuum of Alzheimer’s disease

AbstractBackgroundAutophagy is a cellular self “garbage clearance ”system through which cells eliminate and recycle dysfunctional cytoplasmatic components, such as defective organelles and misfolded protein aggregates. Mitophagy is the sub‐type of autophagy that recognizes and degrades damaged or superfluous mitochondria to maintain cellular homeostasis. Emerging evidence demonstrates that autophagy and mitophagy are impaired in Alzheimer’s disease (AD); its upregulation ameliorates Aß pathology and slows down the cognitive decline in animal models of AD, thus representing a potentially treatable target. The change in the mitophagy biomarkers in individuals with AD needs to be clarified. We aimed to explore the changes of mitophagy biomarkers in biomarkers‐defined individuals in various stages of AD and compare them to cognitively unimpaired individuals (CU).MethodWe included 228 biomarker‐defined individuals from the Czech Brain Aging Study:98 AD dementia (ADD), 88 mild cognitive impairment due to AD (MCI‐AD), and 42 CU individuals. They underwent clinical examination, complex neuropsychological assessment, and brain MRI. Commercial ELISA kits were used to measure standard AD biomarkers in CSF (Aß42, Aß40, pTau, tTau), a biomarker of neurodegeneration (neurofilament light chain – NfL), synaptic dysfunction (neurogranin, Ng), and mitophagy biomarkers in CSF (PINK1‐ mitochondrial kinase crucial for mitophagy) and in serum (BNIP3L‐ mitophagy receptor, TFEB‐ transcription factor critical for lysosomal degradation).ResultWe found a significant increase in PINK1 CSF and BNIP3L serum levels in ADD compared to MCI‐AD and CU (ps<.001). TFEB serum levels were decreased in ADD compared to MCI‐AD and CU (ps<.05). Additionally, in ADD, PINK1 correlated with NfL (r = 0.27) and Ng (r = 0.47). In MCI‐AD, there was a correlation between PINK1 and Ng (r = 0.51), but not with NfL. There was no correlation in CU individuals with NfL or Ng.ConclusionWe identified candidate proteins of mitophagy that are changed in various cognitive stages of AD. In the ADD stage, there is an upregulation of the mitophagy inducers, PINK1 and BNIP3L, together with decreased levels of TFEB, a master regulator of lysosomal biogenesis. One of the possible explanations is that these findings reflect impairment in the final stage of autophagy–lysosomal degradation. Further research is needed to clarify its pathophysiological importance in the AD cascade.

Safety and Efficacy of Subcutaneous Daratumumab in Systemic AL Amyloidosis.

Systemic AL amyloidosis, a plasma cell dyscrasia, is characterized by the production of misfolded immunoglobulin light chain. These misfolded proteins aggregate into amyloid fibrils and deposit throughout the body, resulting in widespread organ dysfunction and ultimately death. Achieving rapid and maximal elimination of the plasma cell clone is crucial to long-term survival. Daratumumab, an anti-CD38 monoclonal antibody delivered intravenously, has been swiftly incorporated into standard first-line treatment regimens. A novel formulation of daratumumab has been developed that can be injected subcutaneously. As a retrospective qualitative review of prior publications involving daratumumab, this work briefly summarizes the existing data regarding the safety and efficacy of subcutaneous (SC) daratumumab, compared to intravenous (IV) daratumumab. SC daratumumab appears to deliver the same disease benefit as IV daratumumab to patients with decreased infusion-related reactions (IRRs), decreased time for administration, and similar rates of adverse events (AEs) intrinsically related to daratumumab. SC daratumumab is preferred over IV daratumumab, but the clinical situation ultimately should determine route of administration. Further investigation into cost-effectiveness benefit is warranted.

T‐cell population and PD‐1 expression in Alzheimer’s disease patients do not follow the age trend of normal individuals

AbstractBackgroundDestruction of cerebral neurons may relate to atypical immune responses. These intracerebral immune responses were induced by various antigens, such as viral DNA fragments or misfolded proteins. Aging is the major risk factor for Alzheimer’s disease (AD). Throughout the aging process, people experienced repetitive microbial infections and misfolded protein accumulation. But not every individual developed AD during aging. Immune regulation may contribute to determining whether the brain could clean unfavorable misfolded proteins and maintain homeostasis. T cell populations and programmed death 1 (PD‐1) are involved in immune pathology. In our study, we examined T cells and PD‐1 between normal aging and AD individuals to elucidate the role of immune regulation in aging‐related AD.MethodSixteen normal aging individuals (age range between 65‐91 years old) and 16 AD patients (age range 69‐88 years old) participated in this study. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood. Antibodies against T cells and PD‐1 molecules were used to classify PBMC with flow cytometry.Result(1) T cell population is different between normal and AD individualsThe normal aging group had significantly fewer adaptive immune T cells and fewer helper T cells (TH). However, these immune features were not present in AD patients.(2) PD‐1 pattern in PBMC is different between normal and AD individualsNatural killer T (NKT) cells with CD56 (neural cell adhesion molecule) had increased PD‐1 expression with normal aging. But AD patients did not show this trend of regulatory changes. These trends of suppressive phenotypic changes were absent in AD patients.ConclusionOur study demonstrated that the T‐cell population was shrinking progressively with normal aging. Nerve‐adherent NKT cells exhibited a higher inhibitory receptor (PD‐1). These findings suggested that T‐cell immune population tended to be suppressed with normal aging. However, these characteristic transitions of immune cells were not present in AD patients, suggesting that T cells were prone to activate in older AD patients. These distinctive immunomodulatory features of AD might be potential biomarkers of late‐onset AD, and predictive factors for developing AD in normal aging individuals.

The APOE4 Allele Exacerbates Pathology in a Mouse Model of Prion Disease

AbstractBackgroundThe APOE4 allele is the strongest genetic risk factor in sporadic Alzheimer’s disease (AD). In allele‐dose dependent manner APOE4 increases AD risk, lowers age of onset, and accelerates the rate of dementia progression. Like AD, prionoses are conformational neurodegenerative disorders, which neuropathological hallmarks include accumulation of disease specific misfolded protein(s) and presence of reactive astrocytes and microglia. Accumulation of PrPSc, a toxic conformer of the cellular prion protein‐PrPC, is the initial culprit in prion pathogenesis. PrPSc buildup is associated with the presence of A1 neurotoxic astrocytes and neurodegenerative phenotype microglia (MGnD), which proinflammatory character contributes importantly to neurodegeneration in prionoses. Despite similarities between AD and prionoses, and established effects of APOE4 on misfolded protein accumulation and MGnD activation in AD, effects of the APOE genotype on prion pathology remain uninvestigated.MethodAPOE2, APOE3, and APOE4 targeted replacement mice were inoculated with 22L mouse adapted scrapie strain or normal brain homogenate (NBH) and subjected to repetitive behavioral testing. They were sacrificed at 15 or 23 weeks post inoculation (WPI), when they remained presymptomatic or showed overt neurological symptoms. Neuropathological and biochemical analyses were performed at either timepoint, while NanoStringTM analysis of microglia and astrocyte transcriptomic markers was done at 23WPI.ResultAPOE4 mice feature significantly shorter incubation period and more severe burden of neurological symptoms following prion inoculation than APOE2 and APOE3 mice. Neuropathological analysis reveals significantly higher burden of spongiforms changes in the brain cortex and greater load of reactive astrocytes and microglia in APOE4 mice compared to other APOE genotypes. APOE4 mice also show the highest level of total PrP and PrPSc and insoluble/soluble PrP index. Transcriptomic analysis reveals prion inoculation effects marked elevation of PAN and A1 reactive astrocyte markers, MGnD markers, and in pro‐inflammatory chemokines and cytokine receptors transcripts across all APOE genotypes but the NBH‐relative increase is the highest in APOE4 mice.ConclusionThe APOE4 allele promotes prion neurodegeneration through two separate mechanisms. It is associated with greater PrPSc accumulation and toxicity suggesting its role in the PrPSc metabolism and clearance. It also promotes acquisition of A1 and MGnD neurotoxic phenotypes by astrocytes and microglia, respectively.

Expression of SARS-CoV-2 Nonstructural Proteins 3 and 4 Can Tune the Unfolded Protein Response in Cell Culture.

Coronaviruses (CoV), including SARS-CoV-2, modulate host proteostasis through the activation of stress-responsive signaling pathways such as the Unfolded Protein Response (UPR), which remedies misfolded protein accumulation by attenuating translation and increasing protein folding capacity. While CoV nonstructural proteins (nsps) are essential for infection, little is known about the role of nsps in modulating the UPR. We characterized the impact of overexpression of SARS-CoV-2 nsp4, a key driver of replication, on the UPR in cell culture using quantitative proteomics to sensitively detect pathway-wide upregulation of effector proteins. We find that nsp4 preferentially activates the ATF6 and PERK branches of the UPR. Previously, we found that an N-terminal truncation of nsp3 (nsp3.1) can suppress pharmacological ATF6 activation. To determine how nsp3.1 and nsp4 tune the UPR, their coexpression demonstrated that nsp3.1 suppresses nsp4-mediated PERK, but not ATF6 activation. Reanalysis of SARS-CoV-2 infection proteomics data revealed time-dependent activation of PERK targets early in infection, which subsequently fades. This temporal regulation suggests a role for nsp3 and nsp4 in tuning the PERK pathway to attenuate host translation beneficial for viral replication while avoiding later apoptotic signaling caused by chronic activation. This work furthers our understanding of CoV-host proteostasis interactions and highlights the power of proteomic methods for systems-level analysis of the UPR.

Lanosterol elevates cytoprotective response through induced-proteasomal degradation of aberrant proteins

Efficient protein synthesis is a basic requirement of our cells to replace the old or defective proteins from the intrinsic crowded biomolecular environment. The interconnection among synthesis, folding, and degradation of proteins represents central paradigm to proteostasis. Failure of protein quality control (PQC) mechanisms results in the disturbance and inadequate functions of proteome. The consequent misfolded protein accumulation can form the basis of neurodegeneration onset and largely represents imperfect aging. Understanding how cells improve the function of deregulated PQC mechanisms to establish and maintain proteostasis against the unwanted sequestration of normal proteins with misfolded proteinaceous inclusions is a major challenge. Here we show that treatment of Lanosterol, a cholesterol synthesis pathway intermediate, induces Proteasome proteolytic activities and, therefore, supports the PQC mechanism for the elimination of intracellular aberrant proteins. The exposure of Lanosterol not only promotes Proteasome catalytic functions but also elevates the removal of both bona fide and neurodegenerative diseases associated toxic proteins. Our current study suggests that increasing Proteasome functions with the help of small molecules such as Lanosterol could serve as a cytoprotective therapeutic approach against abnormal protein accumulation. Cumulatively, based on findings in this study, we can understand the critical importance of small molecules and their potential therapeutic influence in re-establishing disturbed proteostasis linked with neurodegeneration.

The Role of the Proteasome in Limiting Cellular Stress Associated with Protein Accumulation

AbstractThe proteasome is comprised of multiple subunits that catalyze the degradation of proteins to maintain cellular homeostasis. The proteasome targets protein substrates by two different pathways. The ubiquitin‐dependent pathway requires proteins to be labeled with a ubiquitin tag to signal for degradation by the 26S isoform of the proteasome. Protein degradation through this pathway declines during age progression. The ubiquitin‐independent pathway utilizes the 20S proteasome isoform. It can degrade misfolded and intrinsically disordered proteins to decrease cellular stress. Age‐related protein accumulation and aggregation can occur due to the decreased activity and expression of the proteasome. Protein accumulation causes increased cellular stress which can contribute to disease progression. Increasing proteasome activity could serve as a solution to eliminating and preventing protein accumulation. Studies have shown the value of the proteasome as a therapeutic entity to mitigate cellular stress. This perspective explores the link between proteasome activity and cellular stress caused by age‐related misfolded protein accumulation.

HRS mediates tumor immune evasion by regulating proteostasis-associated interferon pathway activation

By sorting receptor tyrosine kinases into endolysosomes, the endosomal sorting complexes required for transport (ESCRTs) are thought to attenuate oncogenic signaling in tumor cells. Paradoxically, ESCRT members are upregulated in tumors. Here, we show that disruption of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a pivotal ESCRT component, inhibited tumor growth by promoting CD8+ Tcell infiltration in melanoma and colon cancer mouse models. HRS ablation led to misfolded protein accumulation and triggered endoplasmic reticulum (ER) stress, resulting in the activation of the type I interferon pathway in an inositol-requiring enzyme-1α (IRE1α)/X-box binding protein 1 (XBP1)-dependent manner. HRS was upregulated in tumor cells with high tumor mutational burden (TMB). HRS expression associates with the response to PD-L1/PD-1 blockade therapy in melanoma patients with high TMB tumors. HRS ablation sensitized anti-PD-1 treatment in mouse melanoma models. Our study shows a mechanism by which tumor cells with high TMB evade immune surveillance and suggests HRS as a promising target to improve immunotherapy.

Inhibition of SQSTM1 S403 phosphorylation facilitates the aggresome formation of ubiquitinated proteins during proteasome dysfunction

BackgroundUbiquitin–proteasome-system-mediated clearance of misfolded proteins is essential for cells to maintain proteostasis and reduce the proteotoxicity caused by these aberrant proteins. When proteasome activity is inadequate, ubiquitinated proteins are sorted into perinuclear aggresomes, which is a significant defense mechanism employed by cells to combat insufficient proteasome activity, hence mitigating the proteotoxic crisis. It has been demonstrated that phosphorylation of SQSTM1 is crucial in regulating misfolded protein aggregation and autophagic degradation. Although SQSTM1 S403 phosphorylation is essential for the autophagic degradation of ubiquitinated proteins, its significance in proteasome inhibition-induced aggresome formation is yet unknown. Herein, we investigated the influence of SQSTM1 S403 phosphorylation on the aggresome production of ubiquitinated proteins during proteasome suppression.MethodsWe examined the phosphorylation levels of SQSTM1 S403 or T269/S272 in cells after treated with proteasome inhibitors or/and autophagy inhibitors, by western blot and immunofluorescence. We detected the accumulation and aggresome formation of ubiquitinated misfolded proteins in cells treated with proteasome inhibition by western blot and immunofluorescence. Furthermore, we used SQSTM1 phosphorylation-associated kinase inhibitors and mutant constructs to confirm the regulation of different SQSTM1 phosphorylation in aggresome formation. We examined the cell viability using CCK-8 assay.ResultsHerein, we ascertained that phosphorylation of SQSTM1 S403 did not enhance the autophagic degradation of ubiquitinated proteins during proteasome inhibition. Proteasome inhibition suppresses the phosphorylation of SQSTM1 S403, which facilitated the aggresome production of polyubiquitinated proteins. Interestingly, we found proteasome inhibition-induced SQSTM1 T269/S272 phosphorylation inhibits the S403 phosphorylation. Suppressing S403 phosphorylation rescues the defective aggresome formation and protects cells from cell death caused by unphosphorylated SQSTM1 (T269/S272).ConclusionsThis study shows that inhibition of SQSTM1 S403 phosphorylation facilitates the aggresome formation of ubiquitinated proteins during proteasome dysfunction. SQSTM1 T269/S272 phosphorylation inhibits the S403 phosphorylation, boosting the aggresome formation of ubiquitinated protein and shielding cells from proteotoxic crisis.

MANF stimulates autophagy and restores mitochondrial homeostasis to treat autosomal dominant tubulointerstitial kidney disease in mice

Misfolded protein aggregates may cause toxic proteinopathy, including autosomal dominant tubulointerstitial kidney disease due to uromodulin mutations (ADTKD-UMOD), a leading hereditary kidney disease. There are no targeted therapies. In our generated mouse model recapitulating human ADTKD-UMOD carrying a leading UMOD mutation, we show that autophagy/mitophagy and mitochondrial biogenesis are impaired, leading to cGAS-STING activation and tubular injury. Moreover, we demonstrate that inducible tubular overexpression of mesencephalic astrocyte-derived neurotrophic factor (MANF), a secreted endoplasmic reticulum protein, after the onset of disease stimulates autophagy/mitophagy, clears mutant UMOD, and promotes mitochondrial biogenesis through p-AMPK enhancement, thus protecting kidney function in our ADTKD mouse model. Conversely, genetic ablation of MANF in the mutant thick ascending limb tubular cells worsens autophagy suppression and kidney fibrosis. Together, we have discovered MANF as a biotherapeutic protein and elucidated previously unknown mechanisms of MANF in the regulation of organelle homeostasis, which may have broad therapeutic applications to treat various proteinopathies.