TNF-α-mediated reduction in inhibitory neurotransmission precedes sporadic Alzheimer's disease pathology in young Trem2R47H rats

Roles of Cytokines in Alzheimer's Disease

The neuroimmune system is a collection of immune cells, cytokines, and the glymphatic system that plays a pivotal role in the pathogenesis and progression of Alzheimer's disease (AD). Of particular focus are cytokines, a group of immune signaling molecules that facilitate communication among immune cells and contribute to inflammation in AD. Extensive research has shown that the dysregulated secretion of certain cytokines (IL-1β, IL-17, IL-12, IL-23, IL-6, and TNF-α) promotes neuroinflammation and exacerbates neuronal damage in AD. However, anti-inflammatory cytokines (IL-2, IL-3, IL-33, and IL-35) are also secreted during AD onset and progression, thereby preventing neuroinflammation. This review summarizes the involvement of pro- and anti-inflammatory cytokines in AD pathology and discusses their therapeutic potential.

Luteolin ameliorates pentetrazole-induced seizures through the inhibition of the TLR4/NF-κB signaling pathway

Epilepsy represents a prevalent neurological disorder in the population, and the existing antiepileptic drugs (AEDs) often fail to adequately control seizures. Inflammation is recognized as a pivotal factor in the pathophysiology of epilepsy. Luteolin, a natural flavonoid extract, possesses anti-inflammatory properties and exhibits promising neuroprotective activity. Nevertheless, the precise molecular mechanisms underlying the antiepileptic effects of luteolin remain elusive. In this study, we established a rat model of epilepsy using pentylenetetrazole (PTZ) to induce seizures. A series of behavioral experiments were conducted to assess behavioral abilities and cognitive function. Histological techniques, including HE staining, Nissl staining, and TUNEL staining, were employed to assess hippocampal neuronal damage. Additionally, Western blotting, RT-qPCR, and ELISA were utilized to analyze the expression levels of proteins involved in the TLR4/IκBα/NF-κB signaling pathway, transcription levels of apoptotic factors, and levels of inflammatory cytokines, respectively. Luteolin exhibited a dose-dependent reduction in seizure severity, prolonged the latency period of seizures, and shortened seizure duration. Furthermore, luteolin prevented hippocampal neuronal damage in PTZ-induced epileptic rats and partially restored behavioral function and learning and memory abilities. Lastly, PTZ kindling activated the TLR4/IκBα/NF-κB pathway, leading to elevated levels of the cytokines TNF-α, IL-6 and IL-1β, which were attenuated by luteolin. Luteolin exerted anticonvulsant and neuroprotective activities in the PTZ-induced epileptic model. Its mechanism was associated with the inhibition of the TLR4/IκBα/NF-κB pathway, alleviating the immune-inflammatory response in the post-epileptic hippocampus.

Epilepsy and epileptiform activity in late-onset Alzheimer disease: clinical and pathophysiological advances, gaps and conundrums

A growing body of evidence has demonstrated a link between Alzheimer disease (AD) and epilepsy. Late-onset epilepsy and epileptiform activity can precede cognitive deterioration in AD by years, and its presence has been shown to predict a faster disease course. In animal models of AD, amyloid and tau pathology are linked to cortical network hyperexcitability that precedes the first signs of memory decline. Thus, detection of epileptiform activity in AD has substantial clinical importance as a potential novel modifiable risk factor for dementia. In this Review, we summarize the epidemiological evidence for the complex bidirectional relationship between AD and epilepsy, examine the effect of epileptiform activity and seizures on cognition in people with AD, and discuss the precision medicine treatment strategies based on the latest research in human and animal models. Finally, we outline some of the unresolved questions of the field that should be addressed by rigorous research, including whether particular clinicopathological subtypes of AD have a stronger association with epilepsy, and the sequence of events between epileptiform activity and amyloid and tau pathology.

The brain cytokine orchestra in multiple sclerosis: from neuroinflammation to synaptopathology

The central nervous system (CNS) is finely protected by the blood-brain barrier (BBB). Immune soluble factors such as cytokines (CKs) are normally produced in the CNS, contributing to physiological immunosurveillance and homeostatic synaptic scaling. CKs are peptide, pleiotropic molecules involved in a broad range of cellular functions, with a pivotal role in resolving the inflammation and promoting tissue healing. However, pro-inflammatory CKs can exert a detrimental effect in pathological conditions, spreading the damage. In the inflamed CNS, CKs recruit immune cells, stimulate the local production of other inflammatory mediators, and promote synaptic dysfunction. Our understanding of neuroinflammation in humans owes much to the study of multiple sclerosis (MS), the most common autoimmune and demyelinating disease, in which autoreactive T cells migrate from the periphery to the CNS after the encounter with a still unknown antigen. CNS-infiltrating T cells produce pro-inflammatory CKs that aggravate local demyelination and neurodegeneration. This review aims to recapitulate the state of the art about CKs role in the healthy and inflamed CNS, with focus on recent advances bridging the study of adaptive immune system and neurophysiology.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

Cytokines as emerging regulators of central nervous system synapses

Cytokines are key messengers by which immune cells communicate, and they drive many physiological processes, including immune and inflammatory responses. Early discoveries demonstrated that cytokines, such as the interleukin family members and TNF-α, regulate synaptic scaling and plasticity. Still, we continue to learn more about how these traditional immune system cytokines affect neuronal structure and function. Different cytokines shape synaptic function on multiple levels ranging from fine-tuning neurotransmission, to regulating synapse number, to impacting global neuronal networks and complex behavior. These recent findings have cultivated an exciting and growing field centered on the importance of immune system cytokines for regulating synapse and neural network structure and function. Here, we highlight the latest findings related to cytokines in the central nervous system and their regulation of synapse structure and function. Moreover, we explore how these mechanisms are becoming increasingly important to consider in diseases-especially those with a large neuroinflammatory component.

The role of genetic risk factors of Alzheimer's disease in synaptic dysfunction

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive deterioration of cognitive functions. Due to the extended global life expectancy, the prevalence of AD is increasing among aging populations worldwide. While AD is a multifactorial disease, synaptic dysfunction is one of the major neuropathological changes that occur early in AD, before clinical symptoms appear, and is associated with the progression of cognitive deterioration. However, the underlying pathological mechanisms leading to this synaptic dysfunction remains unclear. Recent large-scale genomic analyses have identified more than 40 genetic risk factors that are associated with AD. In this review, we discuss the functional roles of these genes in synaptogenesis and synaptic functions under physiological conditions, and how their functions are dysregulated in AD. This will provide insights into the contributions of these encoded proteins to synaptic dysfunction during AD pathogenesis.

Inflammatory Processes in Alzheimer's Disease-Pathomechanism, Diagnosis and Treatment: A Review

Alzheimer's disease is one of the most commonly diagnosed cases of senile dementia in the world. It is an incurable process, most often leading to death. This disease is multifactorial, and one factor of this is inflammation. Numerous mediators secreted by inflammatory cells can cause neuronal degeneration. Neuritis may coexist with other mechanisms of Alzheimer's disease, contributing to disease progression, and may also directly underlie AD. Although much has been established about the inflammatory processes in the pathogenesis of AD, many aspects remain unexplained. The work is devoted in particular to the pathomechanism of inflammation and its role in diagnosis and treatment. An in-depth and detailed understanding of the pathomechanism of neuroinflammation in Alzheimer's disease may help in the development of diagnostic methods for early diagnosis and may contribute to the development of new therapeutic strategies for the disease.

Late-long-term potentiation magnitude, but not Aβ levels and amyloid pathology, is associated with behavioral performance in a rat knock-in model of Alzheimer disease

Cleavage of Amyloid precursor protein by β- and γ-secretases lead to Aβ formation. The widely accepted pathogenic model states that these mutations cause AD via an increase in Aβ formation and accumulation of Aβ in Amyloid plaques. APP mutations cause early onset familial forms of Alzheimer's disease (FAD) in humans. We generated App-Swedish (Apps ) knock-in rats, which carry a pathogenic APP mutation in the endogenous rat App gene. This mutation increases β-secretase processing of APP leading to both augmented Aβ production and facilitation of glutamate release in Apps/s rats, via a β-secretase and APP-dependent glutamate release mechanism. Here, we studied 11 to 14-month-old male and female Apps/s rats. To determine whether the Swedish App mutation leads to behavioral deficits, Apps/s knock-in rats were subjected to behavioral analysis using the IntelliCage platform, an automated behavioral testing system. This system allows behavioral assessment in socially housed animals reflecting a more natural, less stress-inducing environment and eliminates experimenter error and bias while increasing precision of measurements. Surprisingly, a spatial discrimination and flexibility task that can reveal deficits in higher order brain function showed that Apps/s females, but not Apps/s male rats, performed significantly worse than same sex controls. Moreover, female control rats performed significantly better than control and Apps/s male rats. The Swedish mutation causes a significant increase in Aβ production in 14-month-old animals of both sexes. Yet, male and female Apps/s rats showed no evidence of AD-related amyloid pathology. Finally, Apps/s rats did not show signs of significant neuroinflammation. Given that the APP Swedish mutation causes alterations in glutamate release, we analyzed Long-term potentiation (LTP), a long-lasting form of synaptic plasticity that is a cellular basis for learning and memory. Strikingly, LTP was significantly increased in Apps/s control females compared to both Apps/s sexes and control males. In conclusion, this study shows that behavioral performances are sex and App-genotype dependent. In addition, they are associated with LTP values and not Aβ or AD-related pathology. These data, and the failures of anti-Aβ therapies in humans, suggest that alternative pathways, such as those leading to LTP dysfunction, should be targeted for disease-modifying AD therapy.

NK-cell dysfunction of acute myeloid leukemia in relation to the renin–angiotensin system and neurotransmitter genes

Acute myeloid leukemia (AML) is the most heterogeneous hematological disorder and blast cells need to fight against immune system. Natural killer (NK) cells can elicit fast anti-tumor responses in response to surface receptors of tumor cells. NK-cell activity is often impaired in the disease, and there is a risk of insufficient tumor suppression and progression. The aim of this study is to assess the dysfunction of NK cells in AML patients via focusing on two important pathways. We obtained single-cell RNA-sequencing data from NK cells obtained from healthy donors and AML patients. The data were used to perform a wide variety of approaches, including DESeq2 (version 3.9), limma (version 3.26.8) power differential expression analyses, hierarchical clustering, gene set enrichment, and pathway analysis. ATP6AP2, LNPEP, PREP, IGF2R, CTSA, and THOP1 genes were found to be related to the renin–angiotensin system (RAS) family, while DPP3, GLRA3, CRCP, CHRNA5, CHRNE, and CHRNB1 genes were associated with the neurotransmitter pathways. The determined genes are expressed within different patterns in the AML and healthy groups. The relevant molecular pathways and clusters of genes were identified, as well. The cross-talks of NK-cell dysfunction in relation to the RAS and neurotransmitters seem to be important in the genesis of AML.

Influence of methadone on the anticonvulsant efficacy of valproate sodium gabapentin against maximal electroshock seizure in mice by regulation of brain MDA TNF-α

Methadone is the most frequently used opioid therapy worldwide, with controversial effects on oxidative stress homeostasis. This study investigated the effects of intraperitoneal (i.p.) co-administration of methadone (0.1, 0.3, 1, and 3 mg/kg) and valproate sodium (300 mg/kg) or gabapentin (50 mg/kg) in the mice maximal electroshock (MES)-induced seizure model. The adverse effect of drugs was assessed using the chimney test. The levels of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) contents were measured in mice brains after a single seizure. Administration of methadone alone resulted in a significant reduction in the duration of hind limb extension (HLE) than that in the control group. Methadone pretreatment at doses of 0.1 and 0.3 mg/kg i.p. decreased, and at doses of 1 and 3 mg/kg i.p. had an increasing effect on anticonvulsant efficacy of gabapentin. Pretreatment with all doses of methadone significantly decreased the valproate anticonvulsive efficacy. At doses of 1 and 3 mg/kg i.p. methadone per se increased brain MDA levels after MES-induced seizure. Administration of methadone (0.3 mg/kg i.p.) enhanced and at 3 mg/kg decreased gabapentin effect on brain MDA level, but their co-treatment did not lead to further increase in MDA. Methadone at 0.3–3 mg/kg enhanced the effect of sodium valproate on MDA levels in the brain, but at all doses significantly potentiated its effect on brain TNF-α levels. The drugs did not produce any side effects on motor coordination in experimental animals. In conclusion, methadone showed different effects on anticonvulsant actions of gabapentin and valproate through regulation of brain levels of MDA and TNF-α.

Synovial Fluid-Derived Extracellular Vesicles of Patients with Arthritides Contribute to Hippocampal Synaptic Dysfunctions and Increase with Mood Disorders Severity in Humans

Arthritides are a highly heterogeneous group of disorders that include two major clinical entities, localized joint disorders such as osteoarthritis (OA) and systemic autoimmune-driven diseases such as rheumatoid arthritis (RA). Arthritides are characterized by chronic debilitating musculoskeletal conditions and systemic chronic inflammation. Poor mental health is also one of the most common comorbidities of arthritides. Depressive symptoms which are most prevalent, negatively impact patient global assessment diminishing the probability of achieving the target of clinical remission. Here, we investigated new insights into mechanisms that link different joint disorders to poor mental health, and to this issue, we explored the action of the synovial fluid-derived extracellular vesicles (EVs) on neuronal function. Our data show that the exposure of neurons to different concentrations of EVs derived from both RA and OA synovial fluids (RA-EVs and OA-EVs) leads to increased excitatory synaptic transmission but acts on specific modifications on excitatory or inhibitory synapses, as evidenced by electrophysiological and confocal experiments carried out in hippocampal cultures. The treatment of neurons with EVs membrane is also responsible for generating similar effects to those found with intact EVs suggesting that changes in neuronal ability arise upon EVs membrane molecules′ interactions with neurons. In humans with arthritides, we found that nearly half of patients (37.5%) showed clinically significant psychiatric symptoms (CGIs score ≥ 3), and at least mild anxiety (HAM-A ≥ 7) or depression (MADRS and HAM-D ≥ 7); interestingly, these individuals revealed an increased concentration of synovial EVs. In conclusion, our data showing opposite changes at the excitatory and inhibitory levels in neurons treated with OA- and RA-EVs, lay the scientific basis for personalized medicine in OA and RA patients, and identify EVs as new potential actionable biomarkers in patients with OA/RA with poor mental health.

Reducing PDK1/Akt Activity: An Effective Therapeutic Target in the Treatment of Alzheimer's Disease

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease that leads to memory loss and cognitive function damage due to intracerebral neurofibrillary tangles (NFTs) and amyloid-β (Aβ) protein deposition. The phosphoinositide-dependent protein kinase (PDK1)/protein kinase B (Akt) signaling pathway plays a significant role in neuronal differentiation, synaptic plasticity, neuronal survival, and neurotransmission via the axon–dendrite axis. The phosphorylation of PDK1 and Akt rises in the brain, resulting in phosphorylation of the TNF-α-converting enzyme (TACE) at its cytoplasmic tail (the C-terminal end), changing its internalization as well as its trafficking. The current review aimed to explain the mechanisms of the PDK1/Akt/TACE signaling axis that exerts its modulatory effect on AD physiopathology. We provide an overview of the neuropathological features, genetics, Aβ aggregation, Tau protein hyperphosphorylation, neuroinflammation, and aging in the AD brain. Additionally, we summarized the phosphoinositide 3-kinase (PI3K)/PDK1/Akt pathway-related features and its molecular mechanism that is dependent on TACE in the pathogenesis of AD. This study reviewed the relationship between the PDK1/Akt signaling pathway and AD, and discussed the role of PDK1/Akt in resisting neuronal toxicity by suppressing TACE expression in the cell membrane. This work also provides a perspective for developing new therapeutics targeting PDK1/Akt and TACE for the treatment of AD.

Microglia as a Hub for Suicide Neuropathology: Future Investigation and Prevention Targets

Suicide is a complex public health challenge associated worldwide with one death every 40 s. Research advances in the neuropathology of suicidal behaviors (SB) have defined discrete brain changes which may hold the key to suicide prevention. Physiological differences in microglia, the resident immune cells of the brain, are present in post-mortem tissue samples of individuals who died by suicide. Furthermore, microglia are mechanistically implicated in the outcomes of important risk factors for SB, including early-life adversity, stressful life events, and psychiatric disorders. SB risk factors result in inflammatory and oxidative stress activities which could converge to microglial synaptic remodeling affecting susceptibility or resistance to SB. To push further this perspective, in this Review we summarize current areas of opportunity that could untangle the functional participation of microglia in the context of suicide. Our discussion centers around microglial state diversity in respect to morphology, gene and protein expression, as well as function, depending on various factors, namely brain region, age, and sex.

Initial assessment of the spatial learning, reversal, and sequencing task capabilities of knock-in rats with humanizing mutations in the Aβ-coding region of App

Model organisms mimicking the pathogenesis of human diseases are useful for identifying pathogenic mechanisms and testing therapeutic efficacy of compounds targeting them. Models of Alzheimer's disease (AD) and related dementias (ADRD) aim to reproduce the brain pathology associated with these neurodegenerative disorders. Transgenic models, which involve random insertion of disease-causing genes under the control of artificial promoters, are efficient means of doing so. There are confounding factors associated with transgenic approaches, however, including target gene overexpression, dysregulation of endogenous gene expression at transgenes' integration sites, and limitations in mimicking loss-of-function mechanisms. Furthermore, the choice of species is important, and there are anatomical, physiological, and cognitive reasons for favoring the rat over the mouse, which has been the standard for models of neurodegeneration and dementia. We report an initial assessment of the spatial learning, reversal, and sequencing task capabilities of knock-in (KI) Long-Evans rats with humanizing mutations in the Aβ-coding region of App, which encodes amyloid precursor protein (Apph/h rats), using the IntelliCage, an automated operant social home cage system, at 6-8 weeks of age, then again at 4-5 months of age. These rats were previously generated as control organisms for studies on neurodegeneration involving other knock-in rat models from our lab. Apph/h rats of either sex can acquire place learning and reversal tasks. They can also acquire a diagonal sequencing task by 6-8 weeks of age, but not a more advanced serial reversal task involving alternating diagonals, even by 4-5 months of age. Thus, longitudinal behavioral analysis with the IntelliCage system can be useful to determine, in follow-up studies, whether KI rat models of Familial AD (FAD), sporadic late onset AD (LOAD), and of ADRD develop aging-dependent learning and memory deficits.

Deciphering the contributions of neuroinflammation to neurodegeneration: lessons from antibody-mediated encephalitis and coronavirus disease 2019

PURPOSE OF REVIEW

Does neuroinflammation promote neurodegeneration? Does neurodegeneration promote neuroinflammation? Or, is the answer to both questions, yes? These questions have proven challenging to answer in patients with typical age-related neurodegenerative diseases in whom the onset of neuroinflammation and neurodegeneration are largely unknown. Patients recovering from diseases associated with abrupt-onset neuroinflammation, including rare forms of antibody-mediated encephalitis (AME) and common complications of novel coronavirus disease 2019 (COVID-19), provide a unique opportunity to untangle the relationship between neuroinflammation and neurodegeneration. This review explores the lessons learned from patients with AME and COVID-19.

RECENT FINDINGS

Persistent cognitive impairment is increasingly recognized in patients recovering from AME or COVID-19, yet the drivers of impairment remain largely unknown. Clinical observations, neuroimaging and biofluid biomarkers, and pathological studies imply a link between the severity of acute neuroinflammation, subsequent neurodegeneration, and disease-associated morbidity.

SUMMARY

Data from patients with AME and COVID-19 inform key hypotheses that may be evaluated through future studies incorporating longitudinal biomarkers of neuroinflammation and neurodegeneration in larger numbers of recovering patients. The results of these studies may inform the contributors to cognitive impairment in patients with AME and COVID-19, with potential diagnostic and therapeutic applications in patients with age-related neurodegenerative diseases.

The role of the integral type II transmembrane protein BRI2 in health and disease

BRI2 is a type II transmembrane protein ubiquitously expressed whose physiological function remains poorly understood. Although several recent important advances have substantially impacted on our understanding of BRI2 biology and function, providing valuable information for further studies on BRI2. These findings have contributed to a better understanding of BRI2 biology and the underlying signaling pathways involved. In turn, these might provide novel insights with respect to neurodegeneration processes inherent to BRI2-related pathologies, namely Familial British and Danish dementias, Alzheimer's disease, ITM2B-related retinal dystrophy, and multiple sclerosis. In this review, we provided a state-of-the-art outline of BRI2 biology, both in physiological and pathological conditions, and discuss the proposed molecular underlying mechanisms. Overall, the BRI2 knowledge here reviewed is of extreme importance and may contribute to propose BRI2 and/or BRI2 proteolytic fragments as novel therapeutic targets for neurodegenerative diseases, such as Alzheimer's disease.

A familial Danish dementia rat shows impaired presynaptic and postsynaptic glutamatergic transmission

Familial British dementia and familial Danish dementia are neurodegenerative disorders caused by mutations in the gene integral membrane protein 2B (ITM2b) encoding BRI2, which tunes excitatory synaptic transmission at both presynaptic and postsynaptic termini. In addition, BRI2 interacts with and modulates proteolytic processing of amyloid-β precursor protein (APP), whose mutations cause familial forms of Alzheimer's disease (AD) (familial AD). To study the pathogenic mechanisms triggered by the Danish mutation, we generated rats carrying the Danish mutation in the rat Itm2b gene (Itm2b^D rats). Given the BRI2/APP interaction and the widely accepted relevance of human amyloid β (Aβ), a proteolytic product of APP, to AD, Itm2b^D rats were engineered to express two humanized App alleles and produce human Aβ. Here, we studied young Itm2b^D rats to investigate early pathogenic changes in these diseases. We found that periadolescent Itm2b^D rats not only present subtle changes in human Aβ levels along with decreased spontaneous glutamate release and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor–mediated responses but also had increased short-term synaptic facilitation in the hippocampal Schaeffer-collateral pathway. These alterations in excitatory interneuronal communication can impair learning and memory processes and were akin to those observed in adult mice producing rodent Aβ and carrying either the Danish or British mutations in the mouse Itm2b gene. Collectively, the data show that the pathogenic Danish mutation alters the physiological function of BRI2 at glutamatergic synapses across species and early in life. Future studies will determine whether this phenomenon represents an early pathogenic event in human dementia.

A Review of APOE Genotype-Dependent Autophagic Flux Regulation in Alzheimer's Disease

Autophagy is a basic physiological process maintaining cell renewal, the degradation of dysfunctional organelles, and the clearance of abnormal proteins and has recently been identified as a main mechanism underlying the onset and progression of Alzheimer's disease (AD). The APOE ɛ4 genotype is the strongest genetic determinant of AD pathogenesis and initiates autophagic flux at different times. This review synthesizes the current knowledge about the potential pathogenic effects of ApoE4 on autophagy and describes its associations with the biological hallmarks of autophagy and AD from a novel perspective. Via a remarkable variety of widely accepted signaling pathway markers, such as mTOR, TFEB, SIRT1, LC3, p62, LAMP1, LAMP2, CTSD, Rabs, and V-ATPase, ApoE isoforms differentially modulate autophagy initiation; membrane expansion, recruitment, and enclosure; autophagosome and lysosome fusion; and lysosomal degradation. Although the precise pathogenic mechanism varies for different genes and proteins, the dysregulation of autophagic flux is a key mechanism on which multiple pathogenic processes converge.