A Becn1 mutation mediates hyperactive autophagic sequestration of amyloid oligomers and improved cognition in Alzheimer's disease

The plasma peptides of Alzheimer's disease

Background

A practical strategy to discover proteins specific to Alzheimer’s dementia (AD) may be to compare the plasma peptides and proteins from patients with dementia to normal controls and patients with neurological conditions like multiple sclerosis or other diseases. The aim was a proof of principle for a method to discover proteins and/or peptides of plasma that show greater observation frequency and/or precursor intensity in AD. The endogenous tryptic peptides of Alzheimer’s were compared to normals, multiple sclerosis, ovarian cancer, breast cancer, female normal, sepsis, ICU Control, heart attack, along with their institution-matched controls, and normal samples collected directly onto ice.

Methods

Endogenous tryptic peptides were extracted from blinded, individual AD and control EDTA plasma samples in a step gradient of acetonitrile for random and independent sampling by LC–ESI–MS/MS with a set of robust and sensitive linear quadrupole ion traps. The MS/MS spectra were fit to fully tryptic peptides within proteins identified using the X!TANDEM algorithm. Observation frequency of the identified proteins was counted using SEQUEST algorithm. The proteins with apparently increased observation frequency in AD versus AD Control were revealed graphically and subsequently tested by Chi Square analysis. The proteins specific to AD plasma by Chi Square with FDR correction were analyzed by the STRING algorithm. The average protein or peptide log₁₀ precursor intensity was compared across disease and control treatments by ANOVA in the R statistical system.

Results

Peptides and/or phosphopeptides of common plasma proteins such as complement C2, C7, and C1QBP among others showed increased observation frequency by Chi Square and/or precursor intensity in AD. Cellular gene symbols with large Chi Square values (χ2 ≥ 25, p ≤ 0.001) from tryptic peptides included KIF12, DISC1, OR8B12, ZC3H12A, TNF, TBC1D8B, GALNT3, EME2, CD1B, BAG1, CPSF2, MMP15, DNAJC2, PHACTR4, OR8B3, GCK, EXOSC7, HMGA1 and NT5C3A among others. Similarly, increased frequency of tryptic phosphopeptides were observed from MOK, SMIM19, NXNL1, SLC24A2, Nbla10317, AHRR, C10orf90, MAEA, SRSF8, TBATA, TNIK, UBE2G1, PDE4C, PCGF2, KIR3DP1, TJP2, CPNE8, and NGF amongst others. STRING analysis showed an increase in cytoplasmic proteins and proteins associated with alternate splicing, exocytosis of luminal proteins, and proteins involved in the regulation of the cell cycle, mitochondrial functions or metabolism and apoptosis. Increases in mean precursor intensity of peptides from common plasma proteins such as DISC1, EXOSC5, UBE2G1, SMIM19, NXNL1, PANO, EIF4G1, KIR3DP1, MED25, MGRN1, OR8B3, MGC24039, POLR1A, SYTL4, RNF111, IREB2, ANKMY2, SGKL, SLC25A5, CHMP3 among others were associated with AD. Tryptic peptides from the highly conserved C-terminus of DISC1 within the sequence MPGGGPQGAPAAAGGGGVSHRAGSRDCLPPAACFR and ARQCGLDSR showed a higher frequency and highest intensity in AD compared to all other disease and controls.

Conclusion

Proteins apparently expressed in the brain that were directly related to Alzheimer’s including Nerve Growth Factor (NFG), Sphingomyelin Phosphodiesterase, Disrupted in Schizophrenia 1 (DISC1), the cell death regulator retinitis pigmentosa (NXNl1) that governs the loss of nerve cells in the retina and the cell death regulator ZC3H12A showed much higher observation frequency in AD plasma vs the matched control. There was a striking agreement between the proteins known to be mutated or dis-regulated in the brains of AD patients with the proteins observed in the plasma of AD patients from endogenous peptides including NBN, BAG1, NOX1, PDCD5, SGK3, UBE2G1, SMPD3 neuronal proteins associated with synapse function such as KSYTL4, VTI1B and brain specific proteins such as TBATA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09320-2.

Vitamin K2 Holds Promise for Alzheimer's Prevention and Treatment

Recent studies have highlighted the importance of vitamin K2 (VK2) in human health. However, there have been no clinical studies investigating the role of VK2 in the prevention or treatment of Alzheimer's disease (AD), a debilitating disease for which currently there is no cure. In reviewing basic science research and clinical studies that have connected VK2 to factors involved in AD pathogenesis, we have found a growing body of evidence demonstrating that VK2 has the potential to slow the progression of AD and contribute to its prevention. In our review, we consider the antiapoptotic and antioxidant effects of VK2 and its impact on neuroinflammation, mitochondrial dysfunction, cognition, cardiovascular health, and comorbidities in AD. We also examine the link between dysbiosis and VK2 in the context of the microbiome's role in AD pathogenesis. Our review is the first to consider the physiological roles of VK2 in the context of AD, and, given the recent shift in AD research toward nonpharmacological interventions, our findings emphasize the timeliness and need for clinical studies involving VK2.

BECLIN1: Protein Structure, Function and Regulation

BECLIN1 is a well-established regulator of autophagy, a process essential for mammalian survival. It functions in conjunction with other proteins to form Class III Phosphoinositide 3-Kinase (PI3K) complexes to generate phosphorylated phosphatidylinositol (PtdIns), lipids essential for not only autophagy but other membrane trafficking processes. Over the years, studies have elucidated the structural, biophysical, and biochemical properties of BECLIN1, which have shed light on how this protein functions to allosterically regulate these critical processes of autophagy and membrane trafficking. Here, we review these findings and how BECLIN1’s diverse protein interactome regulates it, as well as its impact on organismal physiology.

Enhanced autophagy in Becn1F121A/F121A knockin mice counteracts aging-related neural stem cell exhaustion and dysfunction

Macroautophagy/autophagy is emerging as a major pathway that regulates both aging and stem cell function. Previous studies have demonstrated a positive correlation of autophagy with longevity; however, these studies did not directly address the consequence of altered autophagy in stem cells during aging. In this study, we used Becn1^F121A/F121A knockin mice (designated as Becn1 KI mice) with the F121A allele in the autophagy gene Becn1 to investigate the consequences of enhanced autophagy in postnatal neural stem cells (NSCs) during aging. We found that increased autophagy protected NSCs from exhaustion and promoted neurogenesis in old (≥18-months-old) mice compared with age-matched wild-type (WT) mice, although it did not affect NSCs in young (3-months-old) mice. After pharmacologically-induced elimination of proliferative cells in the subventricular zone (SVZ), there was enhanced re-activation of quiescent NSCs in old Becn1 KI mice as compared to those in WT mice, with more efficient exit from quiescent status to generate proliferative cells and neuroblasts. Moreover, there was also improved maintenance and increased neuronal differentiation of NSCs isolated from the SVZ of old Becn1 KI mice in in vitro assays. Lastly, the increased neurogenesis in Becn1 KI mice was associated with better olfactory function in aged animals. Together, our results suggest a protective role of increased autophagy in aging NSCs, which may help the development of novel strategies to treat age-related neurodegeneration.

Carbon monoxide alleviates senescence in diabetic nephropathy by improving autophagy

OBJECTIVES

Senescence, characterized by permanent cycle arrest, plays an important role in diabetic nephropathy (DN). However, the mechanism of renal senescence is still unclear, and the treatment targeting it remains to be further explored.

MATERIALS AND METHODS

The DN mice were induced by HFD and STZ, and 3 types of renal cells were treated with high glucose (HG) to establish in vitro model. Senescence-related and autophagy-related markers were detected by qRT-PCR and Western blot. Further, autophagy inhibitors and co-immunoprecipitation were used to clarify the mechanism of CO. Additionally, the specific relationship between autophagy and senescence was explored by immunofluorescence triple co-localization and ELISA.

RESULTS

We unravelled that senescence occurred in vivo and in vitro, which could be reversed by CO. Mechanistically, we demonstrated that CO inhibited the dysfunction of autophagy in DN mice partly through dissociating Beclin-1-Bcl-2 complex. Further results showed that autophagy inhibitors blocked the improvement of CO on senescence. In addition, the data revealed that autophagy regulated the degradation of senescence-related secretory phenotype (SASP) including Il-1β, Il-6, Tgf-β and Vegf.

CONCLUSIONS

These results suggested that CO protects DN mice from renal senescence and function loss via improving autophagy partly mediated by dissociating Beclin-1-Bcl-2 complex, which is possibly ascribed to the degradation of SASP. These findings bring new ideas for the prevention and treatment of DN and the regulation of senescence.

The autophagy protein Becn1 improves insulin sensitivity by promoting adiponectin secretion via exocyst binding

Autophagy dysregulation is implicated in metabolic diseases, including type 2 diabetes. However, the mechanism by which the autophagy machinery regulates metabolism is largely unknown. Autophagy is generally considered a degradation process via lysosomes. Here, we unveil a metabolically important non-cell-autonomous, non-degradative mechanism regulated by the essential autophagy protein Becn1 in adipose tissue. Upon high-fat diet challenge, autophagy-hyperactive Becn1F121A mice show systemically improved insulin sensitivity and enhanced activation of AMP-activated protein kinase (AMPK), a central regulator of energy homeostasis, via a non-cell-autonomous mechanism mediated by adiponectin, an adipose-derived metabolic hormone. Adipose-specific Becn1F121A expression is sufficient to activate AMPK in non-adipose tissues and improve systemic insulin sensitivity by increasing adiponectin secretion. Further, Becn1 enhances adiponectin secretion by interacting with components of the exocyst complex via the coiled-coil domain. Together, our study demonstrates that Becn1 improves insulin sensitivity by facilitating adiponectin secretion through binding the exocyst in adipose tissue.

Vitamin K2 protects against Aβ42-induced neurotoxicity by activating autophagy and improving mitochondrial function in Drosophila

OBJECTIVE

Alzheimer disease is characterized by progressive decline in cognitive function due to neurodegeneration induced by accumulation of Aβ and hyperphosphorylated tau protein. This study was conducted to explore the protective effect of vitamin K2 against Aβ42-induced neurotoxicity.

METHODS

Alzheimer disease transgenic Drosophila model used in this study was amyloid beta with the arctic mutation expressed in neurons. Alzheimer disease flies were treated with vitamin K2 for 28 days after eclosion. Aβ42 level in brain was detected by ELISA. Autophagy-related genes and NDUFS3, the core subunit of mitochondrial complex I, were examined using real-Time PCR (RT-PCR) and western blot analysis.

RESULTS

Vitamin K2 improved climbing ability (P = 0.0105), prolonged lifespan (P < 0.0001) and decreased Aβ42 levels (P = 0.0267), upregulated the expression of LC3 and Beclin1(P = 0.0012 and P = 0.0175, respectively), increased the conversion of LC3I to LC3II (P = 0.0206) and decreased p62 level (P =0.0115) in Alzheimer disease flies. In addition, vitamin K2 upregulated the expression of NDUFS3 (P = 0.001) and increased ATP production (P = 0.0033) in Alzheimer disease flies.

CONCLUSION

It seems that vitamin K2 protect against Aβ42-induced neurotoxicity by activation of autophagy and rescue mitochondrial dysfunction, which suggests that it may be a potential valuable therapeutic approach for Alzheimer disease.

Activation of CREB-mediated autophagy by thioperamide ameliorates β-amyloid pathology and cognition in Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease, and the imbalance between production and clearance of β-amyloid (Aβ) is involved in its pathogenesis. Autophagy is an intracellular degradation pathway whereby leads to removal of aggregated proteins, up-regulation of which may be a plausible therapeutic strategy for the treatment of AD. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Our previous study showed that thioperamide, as an antagonist of H3R, enhances autophagy and protects against ischemic injury. However, the effect of thioperamide on autophagic function and Aβ pathology in AD remains unknown. In this study, we found that thioperamide promoted cognitive function, ameliorated neuronal loss, and Aβ pathology in APP/PS1 transgenic (Tg) mice. Interestingly, thioperamide up-regulated autophagic level and lysosomal function both in APP/PS1 Tg mice and in primary neurons under Aβ-induced injury. The neuroprotection by thioperamide against AD was reversed by 3-MA, inhibitor of autophagy, and siRNA of Atg7, key autophagic-related gene. Furthermore, inhibition of activity of CREB, H3R downstream signaling, by H89 reversed the effect of thioperamide on promoted cell viability, activated autophagic flux, and increased autophagic-lysosomal proteins expression, including Atg7, TFEB, and LAMP1, suggesting a CREB-dependent autophagic activation by thioperamide in AD. Taken together, these results suggested that H3R antagonist thioperamide improved cognitive impairment in APP/PS1 Tg mice via modulation of the CREB-mediated autophagy and lysosomal pathway, which contributed to Aβ clearance. This study uncovered a novel mechanism involving autophagic regulating behind the therapeutic effect of thioperamide in AD.

Mitochondria-associated endoplasmic reticulum membranes: At the crossroad between familiar and sporadic Alzheimer's disease

Alzheimer's disease (AD) is the leading cause of dementia and is incurable. The widely accepted amyloid hypothesis failed to produce efficient clinical therapies. In contrast, there is increasing evidence suggesting that the disruption of mitochondria-associated endoplasmic reticulum (ER) membranes (MAM) is a critical upstream event of AD pathogenesis. Here, we review MAM's role in some AD symptoms such as plaque formation, tau hyperphosphorylation, synaptic loss, aberrant lipid synthesis, disturbed calcium homeostasis, and abnormal autophagy. At last, we proposed that MAM plays a central role in familial AD (FAD) and sporadic AD (SAD).

FNDC5/Irisin System in Neuroinflammation and Neurodegenerative Diseases: Update and Novel Perspective

Irisin, the circulating peptide originating from fibronectin type III domain-containing protein 5 (FNDC5), is mainly expressed by muscle fibers under peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) control during exercise. In addition to several beneficial effects on health, physical activity positively affects nervous system functioning, particularly the hippocampus, resulting in amelioration of cognition impairments. Recently, FNDC5/irisin detection in hippocampal neurons and the presence of irisin in the cerebrospinal fluid opened a new intriguing chapter in irisin history. Interestingly, in the hippocampus of mice, exercise increases FNDC5 levels and upregulates brain-derived neurotrophic factor (BDNF) expression. BDNF, displaying neuroprotection and anti-inflammatory effects, is mainly produced by microglia and astrocytes. In this review, we discuss how these glial cells can morphologically and functionally switch during neuroinflammation by modulating the expression of a plethora of neuroprotective or neurotoxic factors. We also focus on studies investigating the irisin role in neurodegenerative diseases (ND). The emerging involvement of irisin as a mediator of the multiple positive effects of exercise on the brain needs further studies to better deepen this issue and the potential use in therapeutic approaches for neuroinflammation and ND.

Beclin-1-mediated activation of autophagy improves proximal and distal urea cycle disorders

Urea cycle disorders (UCD) are inherited defects in clearance of waste nitrogen with high morbidity and mortality. Novel and more effective therapies for UCD are needed. Studies in mice with constitutive activation of autophagy unravelled Beclin-1 as druggable candidate for therapy of hyperammonemia. Next, we investigated efficacy of cell-penetrating autophagy-inducing Tat-Beclin-1 (TB-1) peptide for therapy of the two most common UCD, namely ornithine transcarbamylase (OTC) and argininosuccinate lyase (ASL) deficiencies. TB-1 reduced urinary orotic acid and improved survival under protein-rich diet in spf-ash mice, a model of OTC deficiency (proximal UCD). In AslNeo/Neo mice, a model of ASL deficiency (distal UCD), TB-1 increased ureagenesis, reduced argininosuccinate, and improved survival. Moreover, it alleviated hepatocellular injury and decreased both cytoplasmic and nuclear glycogen accumulation in AslNeo/Neo mice. In conclusion, Beclin-1-dependent activation of autophagy improved biochemical and clinical phenotypes of proximal and distal defects of the urea cycle.

Programmable DNA Nanodevices for Applications in Neuroscience

The broad area of neuroscience has witnessed an increasing exploitation of a variety of synthetic biomaterials with controlled nanosized features. Different bionanomaterials offer very peculiar physicochemical and biochemcial properties contributing to the development of novel imaging devices toward imaging the brain, or as smartly functionalized scaffolds, or diverse tools contributing toward a better understanding of nervous tissue and its functions. DNA nanotechnology-based devices and scaffolds have emerged as ideal materials for cellular and tissue engineering due to their very biocompatible properties, robust adaptation with diverse biological systems, and biosafety in terms of reduced immune response triggering. Here we present technologies with respect to DNA nanodevices that are designed to better interact with nervous systems like neural cells, advanced molecular imaging technologies for imaging brain, biomaterials in neural regeneration, neuroprotection, and targeted delivery of drugs and small molecules across the blood-brain barrier. Along with comments regarding the progress of DNA nanotechnology in neuroscience, we also present a perspective on challenges and opportunities for applying DNA nanotechnology in applications pertaining to neurosciences.

An autophagy-related protein Becn2 regulates cocaine reward behaviors in the dopaminergic system

Drug abuse is a foremost public health problem. Cocaine is a widely abused drug worldwide that produces various reward-related behaviors. The mechanisms that underlie cocaine-induced disorders are unresolved, and effective treatments are lacking. Here, we found that an autophagy-related protein Becn2 is a previously unidentified regulator of cocaine reward behaviors. Becn2 deletion protects mice from cocaine-stimulated locomotion and reward behaviors, as well as cocaine-induced dopamine accumulation and signaling, by increasing presynaptic dopamine receptor 2 (D2R) autoreceptors in dopamine neurons. Becn2 regulates D2R endolysosomal trafficking, degradation, and cocaine-induced behaviors via interacting with a D2R-bound adaptor GASP1. Inactivating Becn2 by upstream autophagy inhibitors stabilizes striatal presynaptic D2R, reduces dopamine release and signaling, and prevents cocaine reward in normal mice. Thus, the autophagy protein Becn2 is essential for cocaine psychomotor stimulation and reward through regulating dopamine neurotransmission, and targeting Becn2 by autophagy inhibitors is a potential strategy to prevent cocaine-induced behaviors.

Brain Permeable AMP-Activated Protein Kinase Activator R481 Raises Glycaemia by Autonomic Nervous System Activation and Amplifies the Counterregulatory Response to Hypoglycaemia in Rats

AIM

We evaluated the efficacy of a novel brain permeable "metformin-like" AMP-activated protein kinase activator, R481, in regulating glucose homeostasis.

MATERIALS AND METHODS

We used glucose sensing hypothalamic GT1-7 neuronal cells and pancreatic αTC1.9 α-cells to examine the effect of R481 on AMPK pathway activation and cellular metabolism. Glucose tolerance tests and hyperinsulinemic-euglycemic and hypoglycemic clamps were used in Sprague-Dawley rats to assess insulin sensitivity and hypoglycemia counterregulation, respectively.

RESULTS

In vitro, we demonstrate that R481 increased AMPK phosphorylation in GT1-7 and αTC1.9 cells. In Sprague-Dawley rats, R481 increased peak glucose levels during a glucose tolerance test, without altering insulin levels or glucose clearance. The effect of R481 to raise peak glucose levels was attenuated by allosteric brain permeable AMPK inhibitor SBI-0206965. This effect was also completely abolished by blockade of the autonomic nervous system using hexamethonium. During hypoglycemic clamp studies, R481 treated animals had a significantly lower glucose infusion rate compared to vehicle treated controls. Peak plasma glucagon levels were significantly higher in R481 treated rats with no change to plasma adrenaline levels. In vitro, R481 did not alter glucagon release from αTC1.9 cells, but increased glycolysis. Non brain permeable AMPK activator R419 enhanced AMPK activity in vitro in neuronal cells but did not alter glucose excursion in vivo.

CONCLUSIONS

These data demonstrate that peripheral administration of the brain permeable "metformin-like" AMPK activator R481 increases blood glucose by activation of the autonomic nervous system and amplifies the glucagon response to hypoglycemia in rats. Taken together, our data suggest that R481 amplifies the counterregulatory response to hypoglycemia by a central rather than a direct effect on the pancreatic α-cell. These data provide proof-of-concept that central AMPK could be a target for future drug development for prevention of hypoglycemia in diabetes.

Dysfunctional Autophagy and Endolysosomal System in Neurodegenerative Diseases: Relevance and Therapeutic Options

Autophagy and endolysosomal trafficking are crucial in neuronal development, function and survival. These processes ensure efficient removal of misfolded aggregation-prone proteins and damaged organelles, such as dysfunctional mitochondria, thus allowing the maintenance of proper cellular homeostasis. Beside this, emerging evidence has pointed to their involvement in the regulation of the synaptic proteome needed to guarantee an efficient neurotransmitter release and synaptic plasticity. Along this line, an intimate interplay between the molecular machinery regulating synaptic vesicle endocytosis and synaptic autophagy is emerging, suggesting that synaptic quality control mechanisms need to be tightly coupled to neurosecretion to secure release accuracy. Defects in autophagy and endolysosomal pathway have been associated with neuronal dysfunction and extensively reported in Alzheimer's, Parkinson's, Huntington's and amyotrophic lateral sclerosis among other neurodegenerative diseases, with common features and emerging genetic bases. In this review, we focus on the multiple roles of autophagy and endolysosomal system in neuronal homeostasis and highlight how their defects probably contribute to synaptic default and neurodegeneration in the above-mentioned diseases, discussing the most recent options explored for therapeutic interventions.

GLIPR2 is a negative regulator of autophagy and the BECN1-ATG14-containing phosphatidylinositol 3-kinase complex

A key mediator of macroautophagy/autophagy induction is the class III phosphatidylinositol 3-kinase complex I (PtdIns3K-C1) consisting of PIK3C3/VPS34, PIK3R4/VPS15, BECN1, and ATG14. Although several proteins are known to enhance or decrease PtdIns3K-C1 activity, our understanding of the molecular regulation of PtdIns3K-C1 is still incomplete. Previously, we identified a Golgi-associated protein, GLIPR2, in a screen for proteins that interact with amino acids 267–284 of BECN1, a region of BECN1 sufficient to induce autophagy when fused to a cell penetrating leader sequence. In this study, we used CRISPR-Cas9-mediated depletion of GLIPR2 in cells and mice to investigate the role of GLIPR2 in the regulation of autophagy and PtdIns3K-C1 activity. Depletion of GLIPR2 in HeLa cells increased autelophagic flux and generation of phosphatidylinositol 3-phosphate (PtdIns3P). GLIPR2 knockout resulted in less compact Golgi structures, which was also observed in autophagy-inducing conditions such as amino acid starvation or Tat-BECN1 peptide treatment. Importantly, the binding of GLIPR2 to purified PtdIns3K-C1 inhibited the in vitro lipid kinase activity of PtdIns3K-C1. Moreover, the tissues of glipr2 knockout mice had increased basal autophagic flux as well as increased recruitment of the PtdIns3P-binding protein, WIPI2. Taken together, our findings demonstrate that GLIPR2 is a negative regulator of PtdIns3K-C1 activity and basal autophagy.

Abbreviations: ATG14: autophagy related 14; Baf A1: bafilomycin A₁; BARA: β-α repeated, autophagy-specific; CQ: chloroquine; GFP: green fluorescent protein; GLIPR2: GLI pathogenesis related 2; HBSS: Hanks’ balanced salt solution; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PBS: phosphate-buffered saline; PtdIns3K-C1: phosphatidylinositol 3-kinase complex I; PtdIns3P: phosphatidylinositol-3-phosphate; SEM: standard error of the mean; WIPI2: WD repeat domain, phosphoinositide interacting 2

Network Simulations Reveal Molecular Signatures of Vulnerability to Age-Dependent Stress and Tau Accumulation

Alzheimer’s disease (AD) is the leading cause of dementia and one of the most common causes of death worldwide. As an age-dependent multifactorial disease, the causative triggers of AD are rooted in spontaneous declines in cellular function and metabolic capacity with increases in protein stressors such as the tau protein. This multitude of age-related processes that cause neurons to change from healthy states to ones vulnerable to the damage seen in AD are difficult to simultaneously investigate and even more difficult to quantify. Here we aimed to diminish these gaps in our understanding of neuronal vulnerability in AD development by using simulation methods to theoretically quantify an array of cellular stress responses and signaling molecules. This temporally-descriptive molecular signature was produced using a novel multimethod simulation approach pioneered by our laboratory for biological research; this methodology combines hierarchical agent-based processes and continuous equation-based modeling in the same interface, all while maintaining intrinsic distributions that emulate natural biological stochasticity. The molecular signature was validated for a normal organismal aging trajectory using experimental longitudinal data from Caenorhabditis elegans and rodent studies. In addition, we have further predicted this aging molecular signature for cells impacted by the pathogenic tau protein, giving rise to distinct stress response conditions needed for cytoprotective aging. Interestingly, our simulation experiments showed that oxidative stress signaling (via daf-16 and skn-1 activities) does not substantially protect cells from all the early stressors of aging, but that it is essential in preventing a late-life degenerative cellular phenotype. Together, our simulation experiments aid in elucidating neurodegenerative triggers in the onset of AD for different genetic conditions. The long-term goal of this work is to provide more detailed diagnostic and prognostic tools for AD development and progression, and to provide more comprehensive preventative measures for this disease.

Comprehensive autophagy evaluation in cardiac disease models

Autophagy is a highly conserved recycling mechanism essential for maintaining cellular homeostasis. The pathophysiological role of autophagy has been explored since its discovery 50 years ago, but interest in autophagy has grown exponentially over the last years. Many researchers around the globe have found that autophagy is a critical pathway involved in the pathogenesis of cardiac diseases. Several groups have created novel and powerful tools for gaining deeper insights into the role of autophagy in the aetiology and development of pathologies affecting the heart. Here, we discuss how established and emerging methods to study autophagy can be used to unravel the precise function of this central recycling mechanism in the cardiac system.

Mechanisms by which autophagy regulates memory capacity in ageing

Autophagy agonists have been proposed to slow down neurodegeneration. Spermidine, a polyamine that acts as an autophagy agonist, is currently under clinical trial for the treatment of age‐related memory decline. How Spermidine and other autophagy agonists regulate memory and synaptic plasticity is under investigation. We set up a novel mouse model of mild cognitive impairment (MCI), in which middle‐aged (12‐month‐old) mice exhibit impaired memory capacity, lysosomes engulfed with amyloid fibrils (β‐amyloid and α‐synuclein) and impaired task‐induced GluA1 hippocampal post‐translation modifications. Subchronic treatment with Spermidine as well as the autophagy agonist TAT‐Beclin 1 rescued memory capacity and GluA1 post‐translational modifications by favouring the autophagy/lysosomal‐mediated degradation of amyloid fibrils. These findings provide new mechanistic evidence on the therapeutic relevance of autophagy enhancers which, by improving the degradation of misfolded proteins, slow down age‐related memory decline.

Possible Neuroprotective Mechanisms of Physical Exercise in Neurodegeneration

Physical exercise (PE) improves physical performance, mental status, general health, and well-being. It does so by affecting many mechanisms at the cellular and molecular level. PE is beneficial for people suffering from neuro-degenerative diseases because it improves the production of neurotrophic factors, neurotransmitters, and hormones. PE promotes neuronal survival and neuroplasticity and also optimizes neuroendocrine and physiological responses to psychosocial and physical stress. PE sensitizes the parasympathetic nervous system (PNS), Autonomic Nervous System (ANS) and central nervous system (CNS) by promoting many processes such as synaptic plasticity, neurogenesis, angiogenesis, and autophagy. Overall, it carries out many protective and preventive activities such as improvements in memory, cognition, sleep and mood; growth of new blood vessels in nervous system; and the reduction of stress, anxiety, neuro-inflammation, and insulin resistance. In the present work, the protective effects of PE were overviewed. Suitable examples from the current research work in this context are also given in the article.

Role of tau protein in Alzheimer's disease: The prime pathological player

Alzheimer's disease (AD) is a prevalently found tauopathy characterized by memory loss and cognitive insufficiency. AD is an age-related neurodegenerative disease with two major hallmarks which includes extracellular amyloid plaques made of amyloid-β (Aβ) and intracellular neurofibrillary tangles of hyperphosphorylated tau. With population aging worldwide, there is an indispensable need for treatment strategies that can potentially manage this developing dementia. Despite broad researches on targeting Aβ in the past two decades, research findings on Aβ targeted therapeutics failed to prove efficacy in the treatment of AD. Tau protein with its extensive pathological role in several neurodegenerative diseases can be considered as a promising target candidate for developing therapeutic interventions. The abnormal hyperphosphorylation of tau plays detrimental pathological functions which ultimately lead to neurodegeneration. This review will divulge the importance of tau in AD pathogenesis, the interplay of Aβ and tau, the pathological functions of tau, and potential therapeutic strategies for an effective management of neuronal disorders.

ALDH2 contributes to melatonin-induced protection against APP/PS1 mutation-prompted cardiac anomalies through cGAS-STING-TBK1-mediated regulation of mitophagy

Ample clinical evidence suggests a high incidence of cardiovascular events in Alzheimer's disease (AD), although neither precise etiology nor effective treatment is available. This study was designed to evaluate cardiac function in AD patients and APP/PS1 mutant mice, along with circulating levels of melatonin, mitochondrial aldehyde dehydrogenase (ALDH2) and autophagy. AD patients and APP/PS1 mice displayed cognitive and myocardial deficits, low levels of circulating melatonin, ALDH2 activity, and autophagy, ultrastructural, geometric (cardiac atrophy and interstitial fibrosis) and functional (reduced fractional shortening and cardiomyocyte contraction) anomalies, mitochondrial injury, cytosolic mtDNA buildup, apoptosis, and suppressed autophagy and mitophagy. APP/PS1 mutation downregulated cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) levels and TBK1 phosphorylation, while promoting Aβ accumulation. Treatment with melatonin overtly ameliorated unfavorable APP/PS1-induced changes in cardiac geometry and function, apoptosis, mitochondrial integrity, cytosolic mtDNA accumulation (using both immunocytochemistry and qPCR), mitophagy, and cGAS-STING-TBK1 signaling, although these benefits were absent in APP/PS1/ALDH2-/- mice. In vitro evidence indicated that melatonin attenuated APP/PS1-induced suppression of mitophagy and cardiomyocyte function, and the effect was negated by the nonselective melatonin receptor blocker luzindole, inhibitors or RNA interference of cGAS, STING, TBK1, and autophagy. Our data collectively established a correlation among cardiac dysfunction, low levels of melatonin, ALDH2 activity, and autophagy in AD patients, with compelling support in APP/PS1 mice, in which melatonin rescued myopathic changes by promoting cGAS-STING-TBK1 signaling and mitophagy via an ALDH2-dependent mechanism.

Beclin1 Binds to Enterovirus 71 3D Protein to Promote the Virus Replication

Enterovirus 71 (EV71) is the main pathogen causing hand-foot-mouth disease (HFMD) in infants and children, which can also lead to severe neurological diseases and even death. Therefore, understanding the replication mechanism of EV71 is of great significance for the prevention and control of EV71-induced diseases. Beclin1 (BECN1, a mammalian homologue of ATG6 in yeast) is an important core protein for the initiation and the normal process of autophagy in cells. In addition to its involvement in autophagy, Beclin1 has also been reported to play an important role in cancer and innate immune signaling pathways. However, the role of Beclin1 in EV71 replication remains elusive. Here, we primarily found that Beclin1 facilitates EV71 replication in human rhabdomyosarcoma (RD) cells and the autophagy was actually induced, but Beclin1 was not significantly affected at either mRNA level or protein level during early EV71 infection. Further studies discovered that Beclin1 could interacts with EV71 non-structural protein 3D mainly through its evolutionary conserved domain (ECD) and coiled-coiled domain (CCD), thus promoting the replication of EV71 in human rhabdomyosarcoma (RD) cells and human astroglioma (U251) cells. Collectively, we reveal a novel regulatory mechanism associated with Beclin1 to promote EV71 replication, thus providing a potential therapeutic target for the prevention and control of EV71-associated diseases.

Progress and Challenges in The Use of MAP1LC3 as a Legitimate Marker for Measuring Dynamic Autophagy In Vivo

Tremendous efforts have been made these last decades to increase our knowledge of intracellular degradative systems, especially in the field of autophagy. The role of autophagy in the maintenance of cell homeostasis is well documented and the existence of defects in the autophagic machinery has been largely described in diseases and aging. Determining the alterations occurring in the many forms of autophagy that coexist in cells and tissues remains complicated, as this cellular process is highly dynamic in nature and can vary from organ to organ in the same individual. Although autophagy is extensively studied, its functioning in different tissues and its links with other biological processes is still poorly understood. Several assays have been developed to monitor autophagy activity in vitro, ex vivo, and in vivo, based on different markers, the use of various inhibitors and activators, and distinct techniques. This review emphasizes the methods applied to measure (macro-)autophagy in tissue samples and in vivo via a protein, which centrally intervenes in the autophagy pathway, the microtubule-associated protein 1A/1B-light chain 3 (MAP1LC3), which is the most widely used marker and the first identified to associate with autophagosomal structures. These approaches are presented and discussed in terms of pros and cons. Some recommendations are provided to improve the reliability of the interpretation of results.

The beclin 1 interactome: Modification and roles in the pathology of autophagy-related disorders

Beclin 1 a yeast Atg6/VPS30 orthologue has a significant role in autophagy process (Macroautophagy) and protein sorting. The function of beclin 1 depends on the interaction with several autophagy-related genes (Atgs) and other proteins during the autophagy process. The role mediated by beclin 1 is controlled by various conditions and factors. Beclin 1 is regulated at the gene and protein levels by different factors. These regulations could subsequently alter the beclin 1 induced autophagy process. Therefore, it is important to study the components of beclin 1 interactome and factors affecting its expression. Expression of this gene is differentially regulated under different conditions in different cells or tissues. So, the regulation part is important to study as beclin 1 is one of the candidate genes involved in diseases related to autophagy dysfunction. This review focuses on the functions of beclin 1, its interacting partners, regulations at gene and protein level, and the role of beclin 1 interactome in relation to various diseases along with the recent developments in the field.

Beclin 1/Bcl-2 complex-dependent autophagy activity modulates renal susceptibility to ischemia-reperfusion injury and mediates renoprotection by Klotho

Klotho- and beclin 1-driven autophagy extends life. We examined the role of beclin 1 in modifying acute kidney injury (AKI) and whether beclin 1 mediates Klotho's known renoprotective action in AKI. AKI was induced by ischemia-reperfusion injury in mice with different levels of autophagy activity by genetic manipulation: wild-type (WT) mice with normal beclin 1 expression and function, mice with normal beclin 1 levels but high activity through knockin of gain-of-function mutant beclin 1 (Becn1F121A), mice with low beclin 1 levels and activity caused by heterozygous global deletion of beclin 1 (Becn1+/-), or mice with extremely low beclin 1 activity from knockin of the mutant constitutively active beclin 1 inhibitor Bcl-2 (Bcl2AAA). Klotho was increased by transgenic overexpression (Tg-Kl) or recombinant Klotho protein administration. After ischemia-reperfusion injury, Becn1F121A mice (high autophagy) had milder AKI and Becn1+/- and Bcl2AAA mice (low autophagy) had more severe AKI than WT mice. Tg-Kl mice had milder AKI, but its renoprotection was partially attenuated in Becn1+/-;Tg-Kl mice and was significantly reduced, although not completely abolished, in Bcl2AAA;Tg-Kl mice. Recombinant Klotho protein conferred more renoprotection from AKI in WT mice than in Becn1+/- or Bcl2AAA mice. Klotho reduced beclin 1/Bcl-2 protein complexes and increased autophagy activity, but this effect was less prominent in mice or cells with Bcl2AAA. Transfected Bcl2AAA or Becn1F123A decreased or increased autophagy activity and rendered cells more susceptible or more resistant to oxidative cytotoxicity, respectively. In conclusion, beclin 1 confers renoprotection by activating autophagy. Klotho protects the kidney partially via disruption of beclin 1/Bcl-2 interactions and enhancement of autophagy activity.

Protein Kinase C Isozymes and Autophagy during Neurodegenerative Disease Progression

Protein kinase C (PKC) isozymes are members of the Serine/Threonine kinase family regulating cellular events following activation of membrane bound phospholipids. The breakdown of the downstream signaling pathways of PKC relates to several disease pathogeneses particularly neurodegeneration. PKC isozymes play a critical role in cell death and survival mechanisms, as well as autophagy. Numerous studies have reported that neurodegenerative disease formation is caused by failure of the autophagy mechanism. This review outlines PKC signaling in autophagy and neurodegenerative disease development and introduces some polyphenols as effectors of PKC isozymes for disease therapy.

Pharmacological Tools to Modulate Autophagy in Neurodegenerative Diseases

Considerable evidences suggest a link between autophagy dysfunction, protein aggregation, and neurodegenerative diseases. Given that autophagy is a conserved intracellular housekeeping process, modulation of autophagy flux in various model organisms have highlighted its importance for maintaining proteostasis. In postmitotic cells such as neurons, compromised autophagy is sufficient to cause accumulation of ubiquitinated aggregates, neuronal dysfunction, degeneration, and loss of motor coordination-all hallmarks of neurodegenerative diseases. Reciprocally, enhanced autophagy flux augments cellular and organismal health, in addition to extending life span. These genetic studies not-withstanding a plethora of small molecule modulators of autophagy flux have been reported that alleviate disease symptoms in models of neurodegenerative diseases. This review summarizes the potential of such molecules to be, perhaps, one of the first autophagy drugs for treating these currently incurable diseases.

The tripartite interaction of phosphate, autophagy, and αKlotho in health maintenance

Aging-related organ degeneration is driven by multiple factors including the cell maintenance mechanisms of autophagy, the cytoprotective protein αKlotho, and the lesser known effects of excess phosphate (Pi), or phosphotoxicity. To examine the interplay between Pi, autophagy, and αKlotho, we used the BK/BK mouse (homozygous for mutant Becn1F121A ) with increased autophagic flux, and αKlotho-hypomorphic mouse (kl/kl) with impaired urinary Pi excretion, low autophagy, and premature organ dysfunction. BK/BK mice live longer than WT littermates, and have heightened phosphaturia from downregulation of two key NaPi cotransporters in the kidney. The multi-organ failure in kl/kl mice was rescued in the double-mutant BK/BK;kl/kl mice exhibiting lower plasma Pi, improved weight gain, restored plasma and renal αKlotho levels, decreased pathology of multiple organs, and improved fertility compared to kl/kl mice. The beneficial effects of heightened autophagy from Becn1F121A was abolished by chronic high-Pi diet which also shortened life span in the BK/BK;kl/kl mice. Pi promoted beclin 1 binding to its negative regulator BCL2, which impairs autophagy flux. Pi downregulated αKlotho, which also independently impaired autophagy. In conclusion, Pi, αKlotho, and autophagy interact intricately to affect each other. Both autophagy and αKlotho antagonizes phosphotoxicity. In concert, this tripartite system jointly determines longevity and life span.

Schizandrol A protects against Aβ1-42-induced autophagy via activation of PI3K/AKT/mTOR pathway in SH-SY5Y cells and primary hippocampal neurons

Autophagy, a lysosomal degradative pathway, is crucial for the pathogenesis of Alzheimer's disease (AD). Schizandrol A (SchA) shows multiple pharmacological effects. However, the potential effects and mechanisms of SchA on amyloid-β (Aβ)-induced autophagy remain unclear. In this study, differentiated SH-SY5Y cells or primary hippocampal neurons were pretreated with SchA (2 μg/ml) for 1 h before subjected to Aβ_1-42 (10 μM) for 24 h to test its effects on cell viability, apoptosis, oxidative stress, and autophagy. Then an mTOR inhibitor (rapamycin) and a PI3K inhibitor (LY294002) were employed to explore the role of PI3K/AKT/mTOR pathway. The results showed that SchA significantly inhibited Aβ_1-42-triggered reduction of viable cells, increases of apoptotic cell number and pro-apoptotic protein expressions, as well as alterations of oxidative stress markers. In addition, the increases of LC3-II/LC3-I and Beclin-1 and decrease of p62 were suppressed by SchA. At the molecular level, we found that the inactivation of PI3K/AKT/mTOR pathway was ameliorated by SchA. Inhibition of PI3K/AKT/mTOR pathway deteriorated the protective effects of SchA against Aβ_1-42-induced autophagy activation, cell death, and apoptosis. In conclusion, we demonstrate that SchA attenuates Aβ_1-42-induced autophagy through activating PI3K/AKT/mTOR signaling pathway. SchA may be a novel drug for the prevention and treatment of AD.

Molecular Mechanism of Autophagy: Its Role in the Therapy of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder of progressive dementia that is characterized by the accumulation of beta-amyloid (Aβ)-containing neuritic plaques and intracellular Tau protein tangles. This distinctive pathology indicates that the protein quality control is compromised in AD. Autophagy functions as a "neuronal housekeeper" that eliminates aberrant protein aggregates by wrapping then into autophagosomes and delivering them to lysosomes for degradation. Several studies have suggested that autophagy deficits in autophagy participate in the accumulation and propagation of misfolded proteins (including Aβ and Tau). In this review, we summarize current knowledge of autophagy in the pathogenesis of AD, as well as some pathways targeting the restoration of autophagy. Moreover, we discuss how these aspects can contribute to the development of disease-modifying therapies in AD.

Neuroprotective effects of ZL006 in Aβ1-42-treated neuronal cells

Amyloid beta (Aβ)-induced neurotoxicity and oxidative stress plays an important role in the pathogenesis of Alzheimer’s disease (AD). ZL006 is shown to reduce over-produced nitric oxide and oxidative stress in ischemic stroke by interrupting the interaction of neuronal nitric oxide synthase and postsynaptic density protein 95. However, few studies are reported on the role of ZL006 in AD. To investigate whether ZL006 exerted neuroprotective effects in AD, we used Aβ_1–42 to treat primary cortical neurons and N2a neuroblastoma cells as an in vitro model of AD. Cortical neurons were incubated with ZL006 or dimethyl sulfoxide for 2 hours and treated with Aβ_1–42 or NH₃•H₂O for another 24 hours. The results of cell counting Kit-8 (CCK-8) assay and calcein-acetoxymethylester/propidium iodide staining showed that ZL006 pretreatment rescued the neuronal death induced by Aβ_1–42. Fluorescence and western blot assay were used to detect oxidative stress and apoptosis-related proteins in each group of cells. Results showed that ZL006 pretreatment decreased neuronal apoptosis and oxidative stress induced by Aβ_1–42. The results of CCK8 assay showed that inhibition of Akt or NF-E2-related factor 2 (Nrf2) in cortical neurons abolished the protective effects of ZL006. Moreover, similar results were also observed in N2a neuroblastoma cells. ZL006 inhibited N2a cell death and oxidative stress induced by Aβ_1–42, while inhibition of Akt or Nrf2 abolished the protective effect of ZL006. These results demonstrated that ZL006 reduced Aβ_1–42-induced neuronal damage and oxidative stress, and the mechanisms might be associated with the activation of Akt/Nrf2/heme oxygenase-1 signaling pathways.

Autophagy Induction as a Therapeutic Strategy for Neurodegenerative Diseases

Autophagy is a major, conserved cellular pathway by which cells deliver cytoplasmic contents to lysosomes for degradation. Genetic studies have revealed extensive links between autophagy and neurodegenerative disease, and disruptions to autophagy may contribute to pathology in some cases. Autophagy degrades many of the toxic, aggregate-prone proteins responsible for such diseases, including mutant huntingtin (mHTT), alpha-synuclein (α-syn), tau, and others, raising the possibility that autophagy upregulation may help to reduce levels of toxic protein species, and thereby alleviate disease. This review examines autophagy induction as a potential therapy in several neurodegenerative diseases-Alzheimer's disease, Parkinson's disease, polyglutamine diseases, and amyotrophic lateral sclerosis (ALS). Evidence in cells and in vivo demonstrates promising results in many disease models, in which autophagy upregulation is able to reduce the levels of toxic proteins, ameliorate signs of disease, and delay disease progression. However, the effective therapeutic use of autophagy induction requires detailed knowledge of how the disease affects the autophagy-lysosome pathway, as activating autophagy when the pathway cannot go to completion (e.g., when lysosomal degradation is impaired) may instead exacerbate disease in some cases. Investigating the interactions between autophagy and disease pathogenesis is thus a critical area for further research.

Biological Functions of Autophagy Genes: A Disease Perspective

The lysosomal degradation pathway of autophagy plays a fundamental role in cellular, tissue, and organismal homeostasis and is mediated by evolutionarily conserved autophagy-related (ATG) genes. Definitive etiological links exist between mutations in genes that control autophagy and human disease, especially neurodegenerative, inflammatory disorders and cancer. Autophagy selectively targets dysfunctional organelles, intracellular microbes, and pathogenic proteins, and deficiencies in these processes may lead to disease. Moreover, ATG genes have diverse physiologically important roles in other membrane-trafficking and signaling pathways. This Review discusses the biological functions of autophagy genes from the perspective of understanding-and potentially reversing-the pathophysiology of human disease and aging.

Targeting Autophagy for the Treatment of Alzheimer's Disease: Challenges and Opportunities

Alzheimer's disease (AD) is the most common type of dementia which characterized by a progressive loss of memory and cognitive function due to degeneration of synapses and axons. Currently, there is no cure for AD. Deposition of extracellular amyloid-β (Aβ) plaques and intracellular tau neurofibrillary tangles (NFTs) are two hallmark pathologic changes in the brains of Alzheimer's patients. Autophagy is the major mechanism in cells responsible for removing protein aggregates. Accumulation of immature autophagic vacuoles (AVs) in dystrophic neurites of Alzheimer patients' brains suggests that autophagy process is disrupted. Till now, it is far from clear what role autophagy plays in AD, a causative role, a protective role, or just a consequence of the disease process itself. To design more effective therapeutic strategies towards this devastating disorder, it is essential to understand the exact role of autophagy played during different stages of AD.

Age-related dysfunction of the autophago-lysosomal pathway in human endothelial cells

Senescent cells, which are cells in a post-proliferative state, show an increased number of dysfunctional mitochondria and oxidatively damaged and aggregated proteins. The mitochondrial-lysosomal axis theory of aging proposes that the autophago-lysosomal system is unable to cope with the rising amount of damaged organelles and proteins. We used human umbilical vein endothelial cells (HUVEC) as in vitro model system to determine which part/s of the autophago-lysosomal pathway become deficient by aging. Senescent HUVEC contained a much larger population of autophagosomes and lysosomes compared to young cells. Transcriptome analysis comparing young and old cells demonstrated several age-related changes of autophagy gene expression. One reason for the observed increase of autophagosomes was an impairment of the autophagic flux in senescent cells due to reduced V-ATPase activity required for acidification of the lysosomes and thus functionality of lysosomal hydrolases. The hypothesis that reduced mitochondrial ATP production underlies low V-ATPase activity was supported by addition of exogenous ATP. This procedure rescued the lysosomal acidification and restored the autophagic flux. Thus, we propose impaired lysosomal acidification due to ATP shortage which may result from mitochondrial dysfunction as a mechanism underlying the accumulation of dysfunctional cellular constituents during aging.

The Amyloid-β Oligomer Hypothesis: Beginning of the Third Decade

The amyloid-β oligomer (AβO) hypothesis was introduced in 1998. It proposed that the brain damage leading to Alzheimer’s disease (AD) was instigated by soluble, ligand-like AβOs. This hypothesis was based on the discovery that fibril-free synthetic preparations of AβOs were potent CNS neurotoxins that rapidly inhibited long-term potentiation and, with time, caused selective nerve cell death (Lambert et al., 1998). The mechanism was attributed to disrupted signaling involving the tyrosine-protein kinase Fyn, mediated by an unknown toxin receptor. Over 4,000 articles concerning AβOs have been published since then, including more than 400 reviews. AβOs have been shown to accumulate in an AD-dependent manner in human and animal model brain tissue and, experimentally, to impair learning and memory and instigate major facets of AD neuropathology, including tau pathology, synapse deterioration and loss, inflammation, and oxidative damage. As reviewed by Hayden and Teplow in 2013, the AβO hypothesis “has all but supplanted the amyloid cascade.” Despite the emerging understanding of the role played by AβOs in AD pathogenesis, AβOs have not yet received the clinical attention given to amyloid plaques, which have been at the core of major attempts at therapeutics and diagnostics but are no longer regarded as the most pathogenic form of Aβ. However, if the momentum of AβO research continues, particularly efforts to elucidate key aspects of structure, a clear path to a successful disease modifying therapy can be envisioned. Ensuring that lessons learned from recent, late-stage clinical failures are applied appropriately throughout therapeutic development will further enable the likelihood of a successful therapy in the near-term.

Insulin and Autophagy in Neurodegeneration

Crosstalk in the pathophysiological processes underpinning metabolic diseases and neurodegenerative disorders have been the subject of extensive investigation, in which insulin signaling and autophagy impairment demonstrate to be a common factor in both conditions. Although it is still somewhat conflicting, pharmacological and genetic strategies that regulate these pathways may be a promising approach for aggregate protein clearancing and consequently the delaying of onset or progression of the disease. However, as the response due to this modulation seems to be time-dependent, finding the right regulation of autophagy may be a potential target for drug development for neurodegenerative diseases. In this way, this review focuses on the role of insulin signaling/resistance and autophagy in some neurodegenerative diseases, discussing pharmacological and non-pharmacological interventions in these diseases.

Distinct functional roles of Vps41-mediated neuroprotection in Alzheimer's and Parkinson's disease models of neurodegeneration

Commonalities and, in some cases, pathological overlap between neurodegenerative diseases have led to speculation that targeting of underlying mechanisms might be of potentially shared therapeutic benefit. Alzheimer's disease is characterized by the formation of plaques, composed primarily of the amyloid-β 1-42 (Aβ) peptide in the brain, resulting in neurodegeneration. Previously, we have shown that overexpression of the lysosomal-trafficking protein, human Vps41 (hVps41), is neuroprotective in a transgenic worm model of Parkinson's disease, wherein progressive dopaminergic neurodegeneration is induced by α-synuclein overexpression. Here, we report the results of a systematic comparison of hVps41-mediated neuroprotection between α-synuclein and Aβ in transgenic nematode models of Caenorhabditis elegans. Our results indicate that an ARF-like GTPase gene product, ARL-8, mitigates endocytic Aβ neurodegeneration in a VPS-41-dependent manner, rather than through RAB-7 and AP3 as with α-synuclein. Furthermore, the neuroprotective effect of ARL-8 or hVps41 appears to be dependent on their colocalization and the activity of ARL-8. Additionally, we demonstrate that the LC3 orthologue, LGG-2, plays a critical role in Aβ toxicity with ARL-8. Further analysis of functional effectors of Aβ protein processing via the lysosomal pathway will assist in the elucidation of the underlying mechanism involving VPS-41-mediated neuroprotection. These results reveal functional distinctions in the intracellular management of neurotoxic proteins that serve to better inform the path for development of therapeutic interventions to halt neurodegeneration.

The effects of treadmill exercise on autophagy in hippocampus of APP/PS1 transgenic mice

The β-amyloid (Aβ) deposition is one of the major pathological hallmark of Alzheimer’s disease. Dysfunction in autophagy has been reported to lead to the Aβ deposition. The current study aimed to investigate the effects of treadmill exercise on autophagy activity and the Aβ deposition and to demonstrate whether exercise-induced reduction in the Aβ deposition was associated with changes in autophagy activity. APP/PS1 transgenic mice were divided into transgenic sedentary (TG-SED, n=12) and transgenic exercise (TG-EXE, n=12) groups. Wild-type mice were also divided into sedentary (WT-SED, n=12) and exercise (WT-EXE, n=12) groups. The WT-EXE and TG-EXE mice were subjected to treadmill exercise for 12 weeks. The levels of Aβ plaques and soluble forms of Aβ, autophagy markers light chain 3 and P62, and lysosomal marker lysosome-associated membrane protein 1 (Lamp1) were measured in the hippocampus. Both Aβ plaques and soluble forms of Aβ (Aβ40 and Aβ42) were significantly increased in TG-SED mice compared with WT-SED mice, whereas exercise reduced Aβ deposition in APP/PS1 transgenic mice. Coincidentally, TG-SED mice displayed a decrease in autophagy activity as evidenced by a significant increase in the levels of light chain 3-II and P62, as well as an accumulation of lysosome as evidenced by a significant over-expression of Lamp1. Interestingly, exercise increased autophagy activity as evidenced by a significant reduction in the levels of P62 and Lamp1 in TG-EXE mice. These findings suggest that treadmill exercise is efficient in decreasing Aβ deposition by enhancing autophagy–lysosomal activity in APP/PS1 transgenic mice, demonstrating a possible approach in Alzheimer’s disease prevention and treatment.

Autophagy in Alzheimer's disease and promising modulatory effects of herbal medicine

Alzheimer's disease (AD) is a progressive and unremitting neurodegenerative disorder characterized by memory loss and cognitive impairment. It affects the quality of life of victims severely. The prevalence of AD has been increasing in recent years. Therefore, it is of great importance to elucidate the pathogenesis of AD and find out effective therapeutic approaches. Autophagy, a primary intracellular way of degrading aggregated proteins and damaged organelles, has been discovered to be involved in the pathological changes of AD. In the last few years, much progress has been made in finding autophagy regulators from natural products, providing new insights to develop treatment strategy for AD by targeting autophagy. In the present review, we provided an overview of the recent research progress regarding the function role of autophagy in AD, the regulation mechanisms of autophagy-lysosomal pathway as well as therapeutic potential of herbal medicine on AD by targeting autophagy.

Beclin 1, Bcl-2 and Autophagy

Beclin 1 is the first mammalian autophagy protein identified as a novel Bcl-2-interacting protein. Subsequent studies have demonstrated that this landmark protein is essential for autophagy. By investigating the interaction between Bcl-2 and Beclin 1, key molecular mechanisms of mammalian autophagy regulation have been discovered. In this chapter, we will first review the discovery of Beclin 1 and then focus on the mechanisms of Bcl-2 and Beclin 1 regulation and their effect on autophagy regulation. Finally, we summarize the evidence related to the interaction of Bcl-2 and Beclin 1 and the involvement of these proteins in human diseases such as cancers, neurodegenerative diseases and infectious diseases.

Proteolytic cleavage of Beclin 1 exacerbates neurodegeneration

Background

Neuronal cell loss contributes to the pathology of acute and chronic neurodegenerative diseases, including Alzheimer’s disease (AD). It remains crucial to identify molecular mechanisms sensitizing neurons to various insults and cell death. To date, the multifunctional, autophagy-related protein Beclin 1 has been shown to be both necessary and sufficient for neuronal integrity in neurodegenerative models associated with protein aggregation. Interestingly, besides its role in cellular homeostasis, Beclin 1 has also been ascribed a role in apoptosis. This makes it critical to elucidate whether Beclin 1 regulates neuronal death and survival across neurodegenerative conditions independent of protein clearance. Here, we provide experimental evidence for a direct functional link between proteolytic cleavage of Beclin 1 and apoptotic neuronal cell loss in two independent models of neurodegeneration in vivo.

Methods

Proteolytic cleavage of Beclin 1 was characterized in lysates of human AD brain samples. We developed viral tools allowing for the selective neuronal expression of the various Beclin 1 forms, including Beclin 1 cleavage products as well as a cleavage-resistant form. The effect of these Beclin 1 forms on survival and integrity of neurons was examined in models of acute and chronic neurodegeneration in vitro and in vivo. Markers of neuronal integrity, neurodegeneration and inflammation were further assessed in a Kainic acid-based mouse model of acute excitotoxic neurodegeneration and in a hAPP-transgenic mouse model of AD following perturbation of Beclin 1 in the susceptible CA1 region of the hippocampus.

Results

We find a significant increase in caspase-mediated Beclin 1 cleavage fragments in brain lysates of human AD patients and mimic this phenotype in vivo using both an excitotoxic and hAPP-transgenic mouse model of neurodegeneration. Surprisingly, overexpression of the C-terminal cleavage-fragment exacerbated neurodegeneration in two distinct models of degeneration. Local inhibition of caspase activity ameliorated neurodegeneration after excitotoxic insult and prevented Beclin 1 cleavage. Furthermore, overexpression of a cleavage-resistant form of Beclin 1 in hippocampal neurons conferred neuroprotection against excitotoxic and Amyloid beta-associated insults in vivo.

Conclusions

Together, these findings indicate that the cleavage state of Beclin 1 determines its functional involvement in both neurodegeneration and neuroprotection. Hence, manipulating the cleavage state of Beclin 1 may represent a therapeutic strategy for preventing neuronal cell loss across multiple forms of neurodegeneration.

Electronic supplementary material

The online version of this article (10.1186/s13024-018-0302-4) contains supplementary material, which is available to authorized users.

Post-translational modifications of Beclin 1 provide multiple strategies for autophagy regulation

Autophagy is a conserved intracellular degradation pathway essential for protein homeostasis, survival and development. Defects in autophagic pathways have been connected to a variety of human diseases, including cancer and neurodegeneration. In the process of macroautophagy, cytoplasmic cargo is enclosed in a double-membrane structure and fused to the lysosome to allow for digestion and recycling of material. Autophagosome formation is primed by the ULK complex, which enables the downstream production of PI(3)P, a key lipid signalling molecule, on the phagophore membrane. The PI(3)P is generated by the PI3 kinase (PI3K) complex, consisting of the core components VPS34, VPS15 and Beclin 1. Beclin 1 is a central player in autophagy and constitutes a molecular platform for the regulation of autophagosome formation and maturation. Post-translational modifications of Beclin 1 affect its stability, interactions and ability to regulate PI3K activity, providing the cell with a plethora of strategies to fine-tune the levels of autophagy. Being such an important regulator, Beclin 1 is a potential target for therapeutic intervention and interfering with the post-translational regulation of Beclin 1 could be one way of manipulating the levels of autophagy. In this review, we provide an overview of the known post-translational modifications of Beclin 1 that govern its role in autophagy and how these modifications are maintained by input from several upstream signalling pathways. ▓.

Autophagy and the cell biology of age-related disease

Macroautophagy (autophagy) is a conserved lysosomal degradation process essential for cellular homeostasis and adaption to stress. Accumulating evidence indicates that autophagy declines with age and that impaired autophagy predisposes individuals to age-related diseases, whereas interventions that stimulate autophagy often promote longevity. In this Review, we examine how the autophagy pathway restricts cellular damage and degeneration, and the impact of these functions towards tissue health and organismal lifespan.

Beclin 1 Phosphorylation - at the Center of Autophagy Regulation

Autophagy is a tightly regulated catabolic process wherein cells under stress sequester cytosolic constituents like damaged proteins and organelles in double-membrane vesicles called autophagosomes. The autophagosomes degrade their cargo by lysosomal proteolysis generating raw materials for the biosynthesis of vital macromolecules. One of the initial steps in the assembly of autophagosomes from pre-autophagic structures is the recruitment and activation of the class III phosphatidylinositol 3-kinase complex consisting of Beclin 1 (BECN1), VPS34, VPS15, and ATG14 proteins. Several pieces of evidence indicate that the phosphorylation and ubiquitination of BECN1 at an array of residues fine-tune the responses to diverse autophagy modulating stimuli and helps in maintaining the balance between pro-survival autophagy and pro-apoptotic responses. In this mini-review, we will discuss the importance of distinct BECN1 phosphorylation events, the diverse signaling pathways and kinases involved and their role in the regulation of autophagy.

Promoting the clearance of neurotoxic proteins in neurodegenerative disorders of ageing

Neurodegenerative disorders of ageing (NDAs) such as Alzheimer disease, Parkinson disease, frontotemporal dementia, Huntington disease and amyotrophic lateral sclerosis represent a major socio-economic challenge in view of their high prevalence yet poor treatment. They are often called 'proteinopathies' owing to the presence of misfolded and aggregated proteins that lose their physiological roles and acquire neurotoxic properties. One reason underlying the accumulation and spread of oligomeric forms of neurotoxic proteins is insufficient clearance by the autophagic-lysosomal network. Several other clearance pathways are also compromised in NDAs: chaperone-mediated autophagy, the ubiquitin-proteasome system, extracellular clearance by proteases and extrusion into the circulation via the blood-brain barrier and glymphatic system. This article focuses on emerging mechanisms for promoting the clearance of neurotoxic proteins, a strategy that may curtail the onset and slow the progression of NDAs.

High-Throughput Screens To Identify Autophagy Inducers That Function by Disrupting Beclin 1/Bcl-2 Binding

Autophagy, a lysosomal degradation pathway, plays a crucial role in cellular homeostasis, development, immunity, tumor suppression, metabolism, prevention of neurodegeneration, and lifespan extension. Thus, pharmacological stimulation of autophagy may be an effective approach for preventing or treating certain human diseases and/or aging. We sought to establish a method for developing new chemical compounds that specifically induce autophagy. To do this, we developed two assays to identify compounds that target a key regulatory node of autophagy induction-specifically, the binding of Bcl-2 (a negative regulator of autophagy) to Beclin 1 (an allosteric modulator of the Beclin 1/VPS34 lipid kinase complex that functions in autophagy initiation). These assays use either a split-luciferase assay to measure Beclin 1/Bcl-2 binding in cells or an AlphaLISA assay to directly measure direct Beclin 1/Bcl-2 binding in vitro. We screened two different chemical compound libraries, comprising ∼300 K compounds, to identify small molecules that disrupt Beclin 1/Bcl-2 binding and induce autophagy. Three novel compounds were identified that directly inhibit Beclin 1/Bcl-2 interaction with an IC₅₀ in the micromolar range and increase autophagic flux. These compounds do not demonstrate significant cytotoxicity, and they exert selectivity for disruption of Bcl-2 binding to the BH3 domain of Beclin 1 compared with the BH3 domain of the pro-apoptotic Bcl-2 family members, Bax and Bim. Thus, we have identified candidate molecules that serve as lead templates for developing potent and selective Beclin 1/Bcl-2 inhibitors that may be clinically useful as autophagy-inducing agents.