A novel protein complex linking the delta 2 glutamate receptor and autophagy: implications for neurodegeneration in lurcher mice

Increased regional activity of a pro-autophagy pathway in schizophrenia as a contributor to sex differences in the disease pathology

Based on recent genome-wide association studies, it is theorized that altered regulation of autophagy contributes to the pathophysiology of schizophrenia and bipolar disorder. As activity of autophagy-regulatory pathways is controlled by discrete phosphorylation sites on the relevant proteins, phospho-protein profiling is one of the few approaches available for enabling a quantitative assessment of autophagic activity in the brain. Despite this, a comprehensive phospho-protein assessment in the brains of schizophrenia and bipolar disorder subjects is currently lacking. Using this direction, our broad screening identifies an increase in AMP-activated protein kinase (AMPK)-mediated phospho-activation of the pro-autophagy protein beclin-1 solely in the prefrontal cortex of female, but not male, schizophrenia subjects. Using a reverse translational approach, we surprisingly find that this increase in beclin-1 activity facilitates synapse formation and enhances cognition. These findings are interpreted in the context of human studies demonstrating that female schizophrenia subjects have a lower susceptibility to cognitive dysfunction than males.

Impaired neuronal macroautophagy in the prelimbic cortex contributes to comorbid anxiety-like behaviors in rats with chronic neuropathic pain

A large proportion of patients with chronic pain experience co-morbid anxiety. The medial prefrontal cortex (mPFC) is proposed to underlie this comorbidity, but the molecular and neuronal mechanisms are not fully understood. Here, we reported that impaired neuronal macroautophagy in the prelimbic cortical (PrL) subregion of the mPFC paralleled the occurrence of anxiety-like behaviors in rats with chronic spared nerve injury (SNI). Intriguingly, such macroautophagy impairment was mainly observed in a FOS/c-Fos+ neuronal subpopulation in the PrL. Chemogenetic inactivation of this comorbid anxiety-related neuronal ensemble relieved pain-induced anxiety-like behaviors. Rescuing macroautophagy impairment in this neuronal ensemble relieved chronic pain-associated anxiety and mechanical allodynia and restored synaptic homeostasis at the molecular level. By contrast, artificial disruption of macroautophagy induced early-onset co-morbid anxiety in neuropathic rats, but not general anxiety in normal rats. Taken together, our work identifies causal linkage between PrL neuronal macroautophagy dysfunction and comorbid anxiety in neuropathic pain and provides novel insights into the role of PrL by differentiating its contribution in pain-induced comorbid anxiety from its modulation over general anxiety-like behaviors.Abbreviation: AAV: adeno-associated viruses; ACC: anterior cingulate cortex; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG12: autophagy related 12; CAMK2/CaMKII: calcium/calmodulin-dependent protein kinase II; CNO: clozapine-N-oxide; CQ: chloroquine; DIA: data independent acquisition; DIO: double floxed inverse orf; DLG4/PSD-95: discs large MAGUK scaffold protein 4; Dox: doxycycline; GABA: γ-aminobutyric acid; GFP: green fluorescent protein; GO: gene ontology; Gi: inhibitory guanine nucleotide-binding proteins; HsCHRM4/M4D: human cholinergic receptor muscarinic 4; HsSYN: human synapsin; KEGG: Kyoto encyclopedia of genes and genomes; LAMP1: lysosomal-associated membrane protein 1; LC3-II: PE conjugated microtubule-associated protein 1 light chain3; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; mPFC: medial prefrontal cortex; P2A: 2A self-cleaving peptide; PPI: protein-protein interaction networks; PrL: prelimbic cortex; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; rtTA: reverse tetracycline-transactivator; SDS-PAGE: sodium dodecylsulfate-polyacrylamide gel electrophoresis; SHANK3: SH3 and multiple ankyrin repeat domains 3; SLC1A1/EAAC1: solute carrier family 1 (neuronal/epithelial high affinity glutamate transporter, systemXag), member 1; SNAP23: synaptosomal-associated protein 23; SNI:spared nerve injury; SQSTM1/p62: sequestosome 1; SYT3: synaptotagmin 3; TRE: tetracycline-responsive element; TRE3G: third-generation tetracycline-responsive element.

Exosomes derived from human umbilical cord mesenchymal stem cells pretreated by monosialoteterahexosyl ganglioside alleviate intracerebral hemorrhage by down-regulating autophagy

PURPOSE

Intracerebral hemorrhage (ICH) results in substantial morbidity, mortality, and disability. Depleting neural cells in advanced stages of ICH poses a significant challenge to recovery. The objective of our research is to investigate the potential advantages and underlying mechanism of exosomes obtained from human umbilical cord mesenchymal stem cells (hUMSCs) pretreated with monosialoteterahexosyl ganglioside (GM1) in the prevention of secondary brain injury (SBI) resulting from ICH.

PATIENTS AND METHODS

In vitro, hUMSCs were cultured and induced to differentiate into neuron-like cells after they were pretreated with 150 μg/mL GM1. The exosomes extracted from the culture medium following a 6-h pretreatment with 150 μg/mL GM1 were used as the treatment group. Striatal infusion of collagenase and hemoglobin (Hemin) was used to establish in vivo and in vitro models of ICH.

RESULTS

After being exposed to 150 μg/mL GM1 for 6 h, specific cells displayed typical neuron-like cell morphology and expressed neuron-specific enolase (NSE). The rate of differentiation into neuron-like cells was up to (15.9 ± 5.8) %, and the synthesis of N-Acetylgalactosaminyltransferase (GalNAcT), which is upstream of GM1, was detected by Western blot. This study presented an increase in the synthesis of GalNAcT. Compared with the ICH group, apoptosis in the treatment group was remarkably reduced, as detected by TUNEL, and mitochondrial membrane potential was restored by JC-1. Additionally, Western blot revealed the restoration of up-regulated autophagy markers Beclin-1 and LC3 and the down-regulation of autophagy marker p62 after ICH.

CONCLUSION

These findings suggest that GM1 is an effective agent to induce the differentiation of hUMSCs into neuron-like cells. GM1 can potentially increase GalNAcT production through "positive feedback", which generates more GM1 and promotes the differentiation of hUMSCs. After pretreatment with GM1, exosomes derived from hUMSCs (hUMSCs-Exos) demonstrate a neuroprotective effect by inhibiting autophagy in the ICH model. This study reveals the potential mechanism by which GM1 induces differentiation of hUMSCs into neuron-like cells and confirms the therapeutic effect of hUMSCs-Exos pretreated by GM1 (GM1-Exos) on an ICH model, potentially offering a new direction for stem cell therapy in ICH.

Case report: A new de novo 6q21q22.1 interstitial deletion case in a girl with cerebellar vermis hypoplasia and developmental delay and literature review

Interstitial deletions involving 6q chromosomal region are rare. Less than 30 patients have been described to date, and fewer have been characterized by high-resolution techniques, such as chromosomal microarray. Deletions involving 6q21q22.1 region are associated with an extremely wide and heterogeneous clinical spectrum, thus genotype-phenotype correlation based on the size of the rearranged region and on the involved genes is complex, even among individuals with overlapping deletions. Here we describe the phenotypic and molecular characterization of a new 6q interstitial deletion in a girl with developmental delay, intellectual disability, cerebellar vermis hypoplasia, facial peculiar characteristics, ataxia and ocular abnormalities. Microarray analysis of the proposita revealed a 7.9 Mb interstitial de novo deletion at 6q21q22.1 chromosomal region, which spanned from nucleotides 108,337,770 to 116,279,453 (GRCh38/hg38). The present case, alongside with a systematic review of the literature, provides further evidence that could aid to the definition of the Smallest Region of Overlap and of the genomic traits that are associated with particular phenotypes, focusing on neurological findings and especially on cerebellar anomalies.

The Effect of Temperature on the Embryo Development of Cephalopod Sepiella japonica Suggests Crosstalk between Autophagy and Apoptosis

Temperature is a crucial environmental factor that affects embryonic development, particularly for marine organisms with long embryonic development periods. However, the sensitive period of embryonic development and the role of autophagy/apoptosis in temperature regulation in cephalopods remain unclear. In this study, we cultured embryos of Sepiella japonica, a typical species in the local area of the East China Sea, at different incubation temperatures (18 °C, 23 °C, and 28 °C) to investigate various developmental aspects, including morphological and histological characteristics, mortality rates, the duration of embryonic development, and expression patterns of autophagy-related genes (LC3, BECN1, Inx4) and apoptosis marker genes (Cas3, p53) at 25 developmental stages. Our findings indicate that embryos in the high-temperature (28 °C) group had significantly higher mortality and embryonic malformation rates than those in the low-temperature (18 °C) group. Furthermore, high temperature (28 °C) shortened the duration of embryonic development by 7 days compared to the optimal temperature (23 °C), while low temperature (18 °C) caused a delay of 9 days. Therefore, embryos of S. japonica were more intolerant to high temperatures (28 °C), emphasizing the critical importance of maintaining an appropriate incubation temperature (approximately 23 °C). Additionally, our study observed, for the first time, that the Early blastula, Blastopore closure, and Optic vesicle to Caudal end stages were the most sensitive stages. During these periods, abnormalities in the expression of autophagy-related and apoptosis-related genes were associated with higher rates of mortality and malformations, highlighting the strong correlation and potential interaction between autophagy and apoptosis in embryonic development under varying temperature conditions.

The Molecular Mechanism and Therapeutic Application of Autophagy for Urological Disease

Autophagy is a lysosomal degradation process known as autophagic flux, involving the engulfment of damaged proteins and organelles by double-membrane autophagosomes. It comprises microautophagy, chaperone-mediated autophagy (CMA), and macroautophagy. Macroautophagy consists of three stages: induction, autophagosome formation, and autolysosome formation. Atg8-family proteins are valuable for tracking autophagic structures and have been widely utilized for monitoring autophagy. The conversion of LC3 to its lipidated form, LC3-II, served as an indicator of autophagy. Autophagy is implicated in human pathophysiology, such as neurodegeneration, cancer, and immune disorders. Moreover, autophagy impacts urological diseases, such as interstitial cystitis /bladder pain syndrome (IC/BPS), ketamine-induced ulcerative cystitis (KIC), chemotherapy-induced cystitis (CIC), radiation cystitis (RC), erectile dysfunction (ED), bladder outlet obstruction (BOO), prostate cancer, bladder cancer, renal cancer, testicular cancer, and penile cancer. Autophagy plays a dual role in the management of urologic diseases, and the identification of potential biomarkers associated with autophagy is a crucial step towards a deeper understanding of its role in these diseases. Methods for monitoring autophagy include TEM, Western blot, immunofluorescence, flow cytometry, and genetic tools. Autophagosome and autolysosome structures are discerned via TEM. Western blot, immunofluorescence, northern blot, and RT-PCR assess protein/mRNA levels. Luciferase assay tracks flux; GFP-LC3 transgenic mice aid study. Knockdown methods (miRNA and RNAi) offer insights. This article extensively examines autophagy's molecular mechanism, pharmacological regulation, and therapeutic application involvement in urological diseases.

Mycoplasma DnaK increases DNA copy number variants in vivo

The human microbiota affects critical cellular functions, although the responsible mechanism(s) is still poorly understood. In this regard, we previously showed that Mycoplasma fermentans DnaK, an HSP70 chaperone protein, hampers the activity of important cellular proteins responsible for DNA integrity. Here, we describe a novel DnaK knock-in mouse model generated in our laboratory to study the effect of M. fermentans DnaK expression in vivo. By using an array-based comparative genomic hybridization assay, we demonstrate that exposure to DnaK was associated with a higher number of DNA copy number variants (CNVs) indicative of unbalanced chromosomal alterations, together with reduced fertility and a high rate of fetal abnormalities. Consistent with their implication in genetic disorders, one of these CNVs caused a homozygous Grid2 deletion, resulting in an aberrant ataxic phenotype that recapitulates the extensive biallelic deletion in the Grid2 gene classified in humans as autosomal recessive spinocerebellar ataxia 18. Our data highlight a connection between components of the human urogenital tract microbiota, namely Mycoplasmas, and genetic abnormalities in the form of DNA CNVs, with obvious relevant medical, diagnostic, and therapeutic implications.

Beclin 1 regulates astrocyte phagocytosis and phagosomal recruitment of retromer

Phagocytosis plays an important role in maintaining brain homeostasis and when impaired can result in the accumulation of unwanted cellular material. While microglia are traditionally considered the phagocytes of the brain, astrocytes are also capable of phagocytosis and are the most numerous cells in the brain. In Alzheimer's disease (AD), astrocytes can be found surrounding β-amyloid (Aβ) plaques yet they seem unable to eliminate these deposits, suggesting phagocytosis may be impaired in AD. Mechanisms that might diminish astrocyte phagocytosis in AD are currently unclear. Here, we demonstrate that the autophagy protein beclin 1, which is reduced in AD, plays a role in regulating astrocyte phagocytosis. Specifically, we show that reducing beclin 1 in C6 astrocytes impairs the phagocytosis of latex beads, reduces retromer levels, and impairs retromer recruitment to the phagosomal membrane. Furthermore, we show that these beclin 1-mediated changes are accompanied by reduced expression of the phagocytic receptor Scavenger Receptor Class B type I (SR-BI). Collectively, these findings suggest a critical role for the protein beclin 1 in both receptor trafficking and receptor-mediated phagocytosis in astrocytes. Moreover, these findings provide insight into mechanisms by which astrocytes may become impaired in AD.

Macroautophagy in CNS health and disease

Macroautophagy is an evolutionarily conserved process that delivers diverse cellular contents to lysosomes for degradation. As our understanding of this pathway grows, so does our appreciation for its importance in disorders of the CNS. Once implicated primarily in neurodegenerative events owing to acute injury and ageing, macroautophagy is now also linked to disorders of neurodevelopment, indicating that it is essential for both the formation and maintenance of a healthy CNS. In parallel to understanding the significance of macroautophagy across contexts, we have gained a greater mechanistic insight into its physiological regulation and the breadth of cargoes it can degrade. Macroautophagy is a broadly used homeostatic process, giving rise to questions surrounding how defects in this single pathway could cause diseases with distinct clinical and pathological signatures. To address this complexity, we herein review macroautophagy in the mammalian CNS by examining three key features of the process and its relationship to disease: how it functions at a basal level in the discrete cell types of the brain and spinal cord; which cargoes are being degraded in physiological and pathological settings; and how the different stages of the macroautophagy pathway intersect with diseases of neurodevelopment and adult-onset neurodegeneration.

Ubiquitin-like processing of TUG proteins as a mechanism to regulate glucose uptake and energy metabolism in fat and muscle

In response to insulin stimulation, fat and muscle cells mobilize GLUT4 glucose transporters to the cell surface to enhance glucose uptake. Ubiquitin-like processing of TUG (Aspscr1, UBXD9) proteins is a central mechanism to regulate this process. Here, recent advances in this area are reviewed. The data support a model in which intact TUG traps insulin-responsive "GLUT4 storage vesicles" at the Golgi matrix by binding vesicle cargoes with its N-terminus and matrix proteins with its C-terminus. Insulin stimulation liberates these vesicles by triggering endoproteolytic cleavage of TUG, mediated by the Usp25m protease. Cleavage occurs in fat and muscle cells, but not in fibroblasts or other cell types. Proteolytic processing of intact TUG generates TUGUL, a ubiquitin-like protein modifier, as the N-terminal cleavage product. In adipocytes, TUGUL modifies a single protein, the KIF5B kinesin motor, which carries GLUT4 and other vesicle cargoes to the cell surface. In muscle, this or another motor may be modified. After cleavage of intact TUG, the TUG C-terminal product is extracted from the Golgi matrix by the p97 (VCP) ATPase. In both muscle and fat, this cleavage product enters the nucleus, binds PPARγ and PGC-1α, and regulates gene expression to promote fatty acid oxidation and thermogenesis. The stability of the TUG C-terminal product is regulated by an Ate1 arginyltransferase-dependent N-degron pathway, which may create a feedback mechanism to control oxidative metabolism. Although it is now clear that TUG processing coordinates glucose uptake with other aspects of physiology and metabolism, many questions remain about how this pathway is regulated and how it is altered in metabolic disease in humans.

Altered expression of DENND5B in patients with epilepsy and its regulation of seizures in mice

Epilepsy is a high incidence neurological disease, and its repeated attacks cause serious physical and psychological damage to the patient. Differentially expressed in normal and neoplastic cells (DENN) domain containing 5B (DENND5B) is a lipoprotein binding protein that mediates synaptic vesicle transport and regulates neuroplasticity and lipid metabolism. Nevertheless, the effect of DENND5B on seizures remains unclear. We aimed to investigate the association of DENND5B with epilepsy, detect its expression and distribution in the nervous system, and explore its role in epileptogenesis through western blot, immunofluorescence staining, and behavioral studies. In this experiment, two C57BL/6 mice models, which induced seizures by pentylenetetrazole and kainic acid, were established. We observed that the expression of DENND5B was reduced in the brains of patients with temporal lobe epilepsy, and its expression was also similarly decreased in both chronic epileptic mice. The findings strongly suggest that DENND5B may be associated with epileptic seizures. Results of immunofluorescence showed that DENND5B was mainly expressed in the hippocampal region and co-located with neurons but not with astrocytes. Next, we used lentivirus to induce both lentiviral vector-mediated overexpression and knockdown of DENND5B in mice to test the change of susceptibility and severity of seizures in the two chronic seizure models. Knockdown of DENND5B was found to promote epileptic seizures, increase chronic spontaneous recurrent epileptic seizures and epileptic discharge, and reduce the incubation period. However, overexpression of DENND5B showed the opposite effect. These results suggest that DENND5B overexpression decreased the behavioral phenotype of epileptic seizures, but DENND5B downregulation had the opposite effect. In summary, our findings suggest that DENND5B can regulate epileptic seizures and may provide a new target for antiepileptic therapy.

Structural biology of ionotropic glutamate delta receptors and their crosstalk with metabotropic glutamate receptors

Enigmatic orphan glutamate delta receptors (GluD) are one of the four classes of the ionotropic glutamate receptors (iGluRs) that play key roles in synaptic transmission and plasticity. While members of other iGluR families viz AMPA, NMDA, and kainate receptors are gated by glutamate, the GluD receptors neither bind glutamate nor evoke ligand-induced currents upon binding of glycine and D-serine. Thus, the GluD receptors were considered to function as structural proteins that facilitate the formation, maturation, and maintenance of synapses in the hippocampus and cerebellum. Recent work has revealed that GluD receptors have extensive crosstalk with metabotropic glutamate receptors (mGlus) and are also gated by their activation. The latest development of a novel optopharamcological tool and the cryoEM structures of GluD receptors would help define the molecular and chemical basis of the GluD receptor's role in synaptic physiology. This article is part of the special Issue on "Glutamate Receptors - Orphan iGluRs".

Ischemia-induced upregulation of autophagy preludes dysfunctional lysosomal storage and associated synaptic impairments in neurons

Macroautophagy/autophagy is vital for neuronal homeostasis and functions. Accumulating evidence suggest that autophagy is impaired during cerebral ischemia, contributing to neuronal dysfunction and neurodegeneration. However, the outcomes after transient modification in autophagy machinery are not fully understood. This study investigated the effects of ischemic stress on autophagy and synaptic structures using a rat model of oxygen-glucose deprivation (OGD) in hippocampal neurons and a mouse model of middle cerebral artery occlusion (MCAO). Upon acute ischemia, an initial autophagy modification occurred in an upregulation manner. Following, the number of lysosomes increased, as well as lysosomal volume, indicating dysfunctional lysosomal storage. These changes were prevented by inhibiting autophagy via 3-methyladenine (3-MA) treatment or ATG7 (autophagy related 7) knockdown, or were mimicked by rapamycin (RAPA), a known activator of autophagy. This suggests that dysfunctional lysosomal storage is associated with the early burst of autophagy. Dysfunctional lysosomal storage contributed to autophagy dysfunction because the basal level of MTOR-dependent lysosomal biogenesis in the reperfusion was not sufficient to clear undegraded cargoes after transient autophagy upregulation. Further investigation revealed that impairment of synaptic ultra-structures, accompanied by dysfunctional lysosomal storage, may result from a failure in dynamic turnover of synaptic proteins. This indicates a vital role of autophagy-lysosomal machinery in the maintenance of synaptic structures. This study supports previous evidence that dysfunctional lysosomal storage may occur following the upregulation of autophagy in neurons. Appropriate autophagosome-lysosomal functioning is vital for maintenance of neuronal synaptic function and impacts more than the few known synaptic proteins.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AD: Alzheimer disease; ALR: autophagic lysosome reformation; ATG7: autophagy related 7; CTSB: cathepsin B; CTSD: cathepsin D; DAPI: 4',6-diamidino-2-phenylindole; DEGs: differentially expressed genes; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; GO: Gene Ontology; HBSS: Hanks' balanced salt solution; HPCA: hippocalcin; i.c.v: intracerebroventricular; KEGG: kyoto encyclopedia of genes and genomes; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; LSDs: lysosomal storage disorders; MAP2: microtubule-associated protein 2; MCAO: middle cerebral artery occlusion; mCTSB: mature CTSB; mCTSD: mature CTSD; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; OGD/R: oxygen-glucose deprivation/reoxygenation; PBS: phosphate-buffered saline; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; proCTSD: pro-cathepsin D; RAPA: rapamycin; RNA-seq: RNA sequencing; RPS6KB/p70S6K: ribosomal protein S6 kinase; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SIM: Structured Illumination Microscopy; SNAP25: synaptosomal-associated protein 25; SQSTM1/p62: sequestosome 1; SYN1: synapsin I; SYT1: synaptotagmin I; TBST: tris-buffered saline Tween-20; TEM: transmission electron microscopy; TFEB: transcription factor EB; tMCAO: transient middle cerebral artery occlusion; TTC: 2,3,5-triphenyltetrazolium chloride; TUBB3: tubulin, beta 3 class III.

Structural biology and thermodynamics of GluD receptors

Glutamate delta (GluD) receptors are a functionally enigmatic subfamily of ionotropic glutamate receptors. Despite sharing similar sequences and structures with AMPA, NMDA, and kainate receptors, GluD receptors do not bind glutamate nor function as ligand-gated ion channels. Binding d-serine and engaging in transsynaptic protein-protein interactions, GluD receptors are thought to undergo complex conformational rearrangements for non-ionotropic signaling that regulates synaptic plasticity. Recent structural, biochemical, and computational studies have elucidated multiple conformational and thermodynamic factors governing the unique properties of GluD receptors. Here, we review advances in biophysical insights into GluD receptors and discuss the structural thermodynamic relationships that underpin their neurobiological functions.

Targeting AKT/mTOR and Bcl-2 for Autophagic and Apoptosis Cell Death in Lung Cancer: Novel Activity of a Polyphenol Compound

Autophagic cell death (ACD) is an alternative death mechanism in resistant malignant cancer cells. In this study, we demonstrated how polyphenol stilbene compound PE5 exhibits potent ACD-promoting activity in lung cancer cells that may offer an opportunity for novel cancer treatment. Cell death caused by PE5 was found to be concomitant with dramatic autophagy induction, as indicated by acidic vesicle staining, autophagosome, and the LC3 conversion. We further confirmed that the main death induction caused by PE5 was via ACD, since the co-treatment with an autophagy inhibitor could reverse PE5-mediated cell death. Furthermore, the defined mechanism of action and upstream regulatory signals were identified using proteomic analysis. Time-dependent proteomic analysis showed that PE5 affected 2142 and 1996 proteins after 12 and 24 h of treatment, respectively. The crosstalk network comprising 128 proteins that control apoptosis and 25 proteins involved in autophagy was identified. Protein–protein interaction analysis further indicated that the induction of ACD was via AKT/mTOR and Bcl-2 suppression. Western blot analysis confirmed that the active forms of AKT, mTOR, and Bcl-2 were decreased in PE5-treated cells. Taken together, we demonstrated the novel mechanism of PE5 in shifting autophagy toward cell death induction by targeting AKT/mTOR and Bcl-2 suppression.

The TMEM240 Protein, Mutated in SCA21, Is Expressed in Purkinje Cells and Synaptic Terminals

A variety of missense mutations and a stop mutation in the gene coding for transmembrane protein 240 (TMEM240) have been reported to be the causative mutations of spinocerebellar ataxia 21 (SCA21). We aimed to investigate the expression of TMEM240 protein in mouse brain at the tissue, cellular, and subcellular levels. Immunofluorescence labeling showed TMEM240 to be expressed in various areas of the brain, with the highest levels in the hippocampus, isocortex, and cerebellum. In the cerebellum, TMEM240 was detected in the deep nuclei and the cerebellar cortex. The protein was expressed in all three layers of the cortex and various cerebellar neurons. TMEM240 was localized to climbing, mossy, and parallel fiber afferents projecting to Purkinje cells, as shown by co-immunostaining with VGLUT1 and VGLUT2. Co-immunostaining with synaptophysin, post-synaptic fractionation, and confirmatory electron microscopy showed TMEM240 to be localized to the post-synaptic side of synapses near the Purkinje-cell soma. Similar results were obtained in human cerebellar sections. These data suggest that TMEM240 may be involved in the organization of the cerebellar network, particularly in synaptic inputs converging on Purkinje cells. This study is the first to describe TMEM240 expression in the normal mouse brain.

Cystic fibrosis transmembrane conductance regulator-associated ligand protects dopaminergic neurons by differentially regulating metabotropic glutamate receptor 5 in the progression of neurotoxin 6-hydroxydopamine-induced Parkinson's disease model

Due to limitations in early diagnosis and treatments of Parkinson's disease (PD), it is necessary to explore the neuropathological changes that occur early in PD progression and to design neuroprotective therapies to prevent or delay the ongoing degeneration process. Metabotropic glutamate receptor 5 (mGlu₅) has shown both diagnostic and therapeutic potential in preclinical studies on PD. Clinical trials using mGlu₅ negative allosteric modulators to treat PD have, however, raised limitations about the neuroprotective role of mGlu₅. It is likely that mGlu₅ has different regulatory roles in different stages of PD. Here, we investigated a protective role of cystic fibrosis transmembrane conductance regulator-associated ligand (CAL) in the progression of PD by differential regulation of mGlu₅ expression and activity to protect against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity. Following treatment with 6-OHDA, mGlu₅ and CAL expressions were elevated in the early stage and reduced in the late stage, both in vitro and in vivo. Activation of mGlu₅ in the early stage by (RS)-2-chloro-5-hydroxyphenylglycine, or blocking mGlu₅ in the late stage by 2-methyl-6-(phenylethynyl) pyridine, increased cell survival and inhibited apoptosis, but these effects were significantly weakened by knockdown of CAL. CAL alleviated 6-OHDA-induced neurotoxicity by regulating mGlu₅-mediated signaling pathways, thereby maintaining the physiological function of mGlu₅ in different disease stages. In PD rat model, CAL deficiency aggravated 6-OHDA toxicity on dopaminergic neurons and increased motor dysfunction because of lack of regulation of mGlu₅ activity. These data reveal a potential mechanism by which CAL specifically regulates the opposite activity of mGlu₅ in progression of PD to protect against neurotoxicity, suggesting that CAL is a favorable endogenous target for the treatment of PD.

(2R,6R)-Hydroxynorketamine Alleviates Electroconvulsive Shock-Induced Learning Impairment by Inhibiting Autophagy

PURPOSE

Learning impairment after electroconvulsive therapy (ECT) is common. Ketamine, an anesthetic used for ECT, has been demonstrated to attenuate cognitive impairment after ECT. However, the mechanism by which ketamine occurs in this case is still unknown. We aimed to explore the role of ketamine metabolite (2R,6R)-hydroxynorketamine [(2R,6R)-HNK] in the protection against learning impairment and investigate whether autophagy is involved in the protective effect.

MATERIALS AND METHODS

A rat depression model received electroconvulsive shock (ECS; simulated ECT in animal models) daily for 3 days. The Morris water maze was used to assess the spatial learning function of the rats. Western blotting was used to detect the expression of Beclin-1, light chain (LC)3-II/LC3-I, p62, mammalian target of rapamycin (mTOR), and p-mTOR in the hippocampus.

RESULTS

The escape latency for the maze in the ECS group was significantly longer than that in the sham ECS group (P=0.042). Meanwhile, the escape latency in the (2R,6R)-HNK+ECS group was significantly shorter than that in the ECS group (P=0.005). The LC3-II/LC3-I ratio and Beclin-1 expression level significantly increased, and the p62 expression level significantly decreased in the ECS group, compared with those in the sham ECS group (all P<0.001). The (2R,6R)-HNK+ECS group showed lower LC3-II/LC3-I ratio (P<0.001) and Beclin-1 expression level (P<0.001) and higher p62 (P<0.001) and p-mTOR expression levels (P=0.048) than did the ECS group. After small-molecule enhancer of rapamycin 28 (SMER28) administration, the role of (2R,6R)-HNK in protecting against learning impairment and inhibiting autophagy was abrogated, showing no difference in the escape latency; the difference in the LC3-II/LC3-I ratio and p62 expression level between the SMER28+(2R,6R)-HNK+ECS and ECS groups was not as significant as that between the (2R,6R)-HNK+ECS and ECS groups (P<0.05-0.01 vs P<0.001).

CONCLUSION

(2R,6R)-HNK yields cognitive protection by suppressing autophagy through the mTOR signaling pathway in the ECS-treated rat hippocampus.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

The ARFRP1-dependent Golgi scaffolding protein GOPC is required for insulin secretion from pancreatic β-cells

Objective

Hormone secretion from metabolically active tissues, such as pancreatic islets, is governed by specific and highly regulated signaling pathways. Defects in insulin secretion are among the major causes of diabetes. The molecular mechanisms underlying regulated insulin secretion are, however, not yet completely understood. In this work, we studied the role of the GTPase ARFRP1 on insulin secretion from pancreatic β-cells.

Methods

A β-cell-specific Arfrp1 knockout mouse was phenotypically characterized. Pulldown experiments and mass spectrometry analysis were employed to screen for new ARFRP1-interacting proteins. Co-immunoprecipitation assays as well as super-resolution microscopy were applied for validation.

Results

The GTPase ARFRP1 interacts with the Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC). Both proteins are co-localized at the trans-Golgi network and regulate the first and second phase of insulin secretion by controlling the plasma membrane localization of the SNARE protein SNAP25. Downregulation of both GOPC and ARFRP1 in Min6 cells interferes with the plasma membrane localization of SNAP25 and enhances its degradation, thereby impairing glucose-stimulated insulin release from β-cells. In turn, overexpression of SNAP25 as well as GOPC restores insulin secretion in islets from β-cell-specific Arfrp1 knockout mice.

Conclusion

Our results identify a hitherto unrecognized pathway required for insulin secretion at the level of trans-Golgi sorting.

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β-cell specific deletion of the trans-Golgi residing small GTPase ARFRP1 leads to elevated blood glucose levels in mice.

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GOPC is a newly identified ARFRP1 dependent scaffolding protein.

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ARFRP1 and GOPC are required for glucose-stimulated insulin secretion from pancreatic β-cells.

Transcriptional block of AMPK-induced autophagy promotes glutamate excitotoxicity in nutrient-deprived SH-SY5Y neuroblastoma cells

We investigated the role of autophagy, a controlled lysosomal degradation of cellular macromolecules and organelles, in glutamate excitotoxicity during nutrient deprivation in vitro. The incubation in low-glucose serum/amino acid-free cell culture medium synergized with glutamate in increasing AMP/ATP ratio and causing excitotoxic necrosis in SH-SY5Y human neuroblastoma cells. Glutamate suppressed starvation-triggered autophagy, as confirmed by diminished intracellular acidification, lower LC3 punctuation and LC3-I conversion to autophagosome-associated LC3-II, reduced expression of proautophagic beclin-1 and ATG5, increase of the selective autophagic target NBR1, and decreased number of autophagic vesicles. Similar results were observed in PC12 rat pheochromocytoma cells. Both glutamate-mediated excitotoxicity and autophagy inhibition in starved SH-SY5Y cells were reverted by NMDA antagonist memantine and mimicked by NMDA agonists D-aspartate and ibotenate. Glutamate reduced starvation-triggered phosphorylation of the energy sensor AMP-activated protein kinase (AMPK) without affecting the activity of mammalian target of rapamycin complex 1, a major negative regulator of autophagy. This was associated with reduced mRNA levels of autophagy transcriptional activators (FOXO3, ATF4) and molecules involved in autophagy initiation (ULK1, ATG13, FIP200), autophagosome nucleation/elongation (ATG14, beclin-1, ATG5), and autophagic cargo delivery to autophagosomes (SQSTM1). Glutamate-mediated transcriptional repression of autophagy was alleviated by overexpression of constitutively active AMPK. Genetic or pharmacological AMPK activation by AMPK overexpression or metformin, as well as genetic or pharmacological autophagy induction by TFEB overexpression or lithium chloride, reduced the sensitivity of nutrient-deprived SH-SY5Y cells to glutamate excitotoxicity. These data indicate that transcriptional inhibition of AMPK-dependent cytoprotective autophagy is involved in glutamate-mediated excitotoxicity during nutrient deprivation in vitro.

Outside in: Roles of complement in autophagy

The complement system is a well-characterized cascade of extracellular serum proteins that is activated by pathogens and unwanted waste material. Products of activated complement signal to the host cells via cell surface receptors, eliciting responses such as removal of the stimulus by phagocytosis. The complement system therefore functions as a warning system, resulting in removal of unwanted material. This review describes how extracellular activation of the complement system can also trigger autophagic responses within cells, up-regulating protective homeostatic autophagy in response to perceived stress, but also initiating targeted anti-microbial autophagy in order to kill intracellular cytoinvasive pathogens. In particular, we will focus on recent discoveries that indicate that complement may also have roles in detection and autophagy-mediated disposal of unwanted materials within the intracellular environment. We therefore summarize the current evidence for complement involvement in autophagy, both by transducing signals across the cell membrane, as well as roles within the cellular environment. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

δ-Catenin engages the autophagy pathway to sculpt the developing dendritic arbor

The development of the dendritic arbor in pyramidal neurons is critical for neural circuit function. Here, we uncovered a pathway in which δ-catenin, a component of the cadherin-catenin cell adhesion complex, promotes coordination of growth among individual dendrites and engages the autophagy mechanism to sculpt the developing dendritic arbor. Using a rat primary neuron model, time-lapse imaging, immunohistochemistry, and confocal microscopy, we found that apical and basolateral dendrites are coordinately sculpted during development. Loss or knockdown of δ-catenin uncoupled this coordination, leading to retraction of the apical dendrite without altering basolateral dendrite dynamics. Autophagy is a key cellular pathway that allows degradation of cellular components. We observed that the impairment of the dendritic arbor resulting from δ-catenin knockdown could be reversed by knockdown of autophagy-related 7 (ATG7), a component of the autophagy machinery. We propose that δ-catenin regulates the dendritic arbor by coordinating the dynamics of individual dendrites and that the autophagy mechanism may be leveraged by δ-catenin and other effectors to sculpt the developing dendritic arbor. Our findings have implications for the management of neurological disorders, such as autism and intellectual disability, that are characterized by dendritic aberrations.

Smcr8 deficiency disrupts axonal transport-dependent lysosomal function and promotes axonal swellings and gain of toxicity in C9ALS/FTD mouse models

G4C2 repeat expansions in an intron of C9ORF72 cause the most common familial amyotrophic lateral sclerosis and frontotemporal dementia (collectively, C9ALS/FTD). Mechanisms and mediators of C9ALS/FTD pathogenesis remain poorly understood. C9orf72 and Smcr8 form a protein complex. Here, we show that expression of Smcr8, like C9orf72, is reduced in C9ALS/FTD mouse models and patient tissues. Since Smcr8 is highly conserved between human and mouse, we evaluated the effects of Smcr8 downregulation in mice. Smcr8 knockout (KO) mice exhibited motor behavior deficits, which resemble those of C9ALS/FTD mouse models, and displayed axonal swellings in their spinal cords and neuromuscular junctions. These deficits are caused by impaired autophagy-lysosomal functions due to disrupted axonal transport in mutant motor neurons. Consistent with its interaction with C9orf72 and their downregulation in patient tissues, Smcr8 deficiency exacerbated autophagy-lysosomal impairment in C9orf72 KO mice. The disease relevance of Smcr8 downregulation was reflected by exacerbated axonal swellings and gain of toxicity pathology arising from Smcr8 haploinsufficiency in a mouse model of C9ALS/FTD. Thus, our in vivo studies suggested that Smcr8 deficiency impairs axonal transport dependent autophagy-lysosomal function and exacerbates axonal degeneration and gain of toxicity in C9ALS/FTD mouse models.

Optical induction of autophagy via Transcription factor EB (TFEB) reduces pathological tau in neurons

Pathological accumulation of microtubule associated protein tau in neurons is a major neuropathological hallmark of Alzheimer's disease (AD) and related tauopathies. Several attempts have been made to promote clearance of pathological tau (p-Tau) from neurons. Transcription factor EB (TFEB) has shown to clear p-Tau from neurons via autophagy. However, sustained TFEB activation and autophagy can create burden on cellular bioenergetics and can be deleterious. Here, we modified previously described two-plasmid systems of Light Activated Protein (LAP) from bacterial transcription factor-EL222 and Light Responsive Element (LRE) to encode TFEB. Upon blue-light (465 nm) illumination, the conformation changes in LAP induced LRE-driven expression of TFEB, its nuclear entry, TFEB-mediated expression of autophagy-lysosomal genes and clearance of p-Tau from neuronal cells and AD patient-derived human iPSC-neurons. Turning the blue-light off reversed the expression of TFEB-target genes and attenuated p-Tau clearance. Together, these results suggest that optically regulated TFEB expression unlocks the potential of opto-therapeutics to treat AD and other dementias.

Embryonic Cerebellar Graft Morphology Differs in Two Mouse Models of Cerebellar Degeneration

Cerebellar diseases causing substantial cell loss often lead to severe functional deficits and restoration of cerebellar function is difficult. Neurotransplantation therapy could become a hopeful method, but there are still many limitations and unknown aspects. Studies in a variety of cerebellar mutant mice reflecting heterogeneity of human cerebellar degenerations show promising results as well as new problems and questions to be answered. The aim of this work was to compare the development of embryonic cerebellar grafts in adult B6CBA Lurcher and B6.BR pcd mutant mice and strain-matched healthy wild type mice. Performance in the rotarod test, graft survival, structure, and volume was examined 2 months after the transplantation or sham-operation. The grafts survived in most of the mice of all types. In both B6CBA and B6.BR wild type mice and in pcd mice, colonization of the host's cerebellum was a common finding, while in Lurcher mice, the grafts showed a low tendency to infiltrate the host's cerebellar tissue. There were no significant differences in graft volume between mutant and wild type mice. Nevertheless, B6CBA mice had smaller grafts than their B6.BR counterparts. The transplantation did not improve the performance in the rotarod test. The study showed marked differences in graft integration into the host's cerebellum in two types of cerebellar mutants, suggesting disease-specific factors influencing graft fate.

Consensus Paper. Cerebellar Reserve: From Cerebellar Physiology to Cerebellar Disorders

Cerebellar reserve refers to the capacity of the cerebellum to compensate for tissue damage or loss of function resulting from many different etiologies. When the inciting event produces acute focal damage (e.g., stroke, trauma), impaired cerebellar function may be compensated for by other cerebellar areas or by extracerebellar structures (i.e., structural cerebellar reserve). In contrast, when pathological changes compromise cerebellar neuronal integrity gradually leading to cell death (e.g., metabolic and immune-mediated cerebellar ataxias, neurodegenerative ataxias), it is possible that the affected area itself can compensate for the slowly evolving cerebellar lesion (i.e., functional cerebellar reserve). Here, we examine cerebellar reserve from the perspective of the three cornerstones of clinical ataxiology: control of ocular movements, coordination of voluntary axial and appendicular movements, and cognitive functions. Current evidence indicates that cerebellar reserve is potentiated by environmental enrichment through the mechanisms of autophagy and synaptogenesis, suggesting that cerebellar reserve is not rigid or fixed, but exhibits plasticity potentiated by experience. These conclusions have therapeutic implications. During the period when cerebellar reserve is preserved, treatments should be directed at stopping disease progression and/or limiting the pathological process. Simultaneously, cerebellar reserve may be potentiated using multiple approaches. Potentiation of cerebellar reserve may lead to compensation and restoration of function in the setting of cerebellar diseases, and also in disorders primarily of the cerebral hemispheres by enhancing cerebellar mechanisms of action. It therefore appears that cerebellar reserve, and the underlying plasticity of cerebellar microcircuitry that enables it, may be of critical neurobiological importance to a wide range of neurological/neuropsychiatric conditions.

Beclin 1 Complex and Neurodegenerative Disorders

Beclin1 is the mammalian orthologue of yeast Atg6/vacuolar protein sorting-30 (VPS30). Beclin1 interacts with various biological macromolecules like ATG14, BIF-1, NRBF2, RUBICON, UVRAG, AMBRA1, HMGB1, PINK1, and PARKIN. Such interactions promote Beclin1-PI3KC3 complex formation. Autophagy is blocked in apoptosis owing to the breakdown of Beclin1 by caspase whereas autophagy induction inhibits effector caspase degradation, therefore, blocks apoptosis. Thus, the Beclin1 is an essential biomolecular species for cross-regulation between autophagy and apoptosis. Various studies carried out in neurodegenerative animal models associated with aggregated proteins have confirmed that multifunctional Beclin1 protein is necessary for neuronal integrity. The role of Beclin1 protein has been investigated and was reported in various human neurodegeneration disorders. This chapter aims to provide an insight into the role of Beclin1 in the development of neurodegenerative disorders.

PDZ Scaffold Protein CAL Couples with Metabotropic Glutamate Receptor 5 to Protect Against Cell Apoptosis and Is a Potential Target in the Treatment of Parkinson's Disease

Targeting mGluR5 has been an attractive strategy to modulate glutamate excitotoxicity for neuroprotection. Although human clinical trials using mGluR5 negative allosteric modulators (NAMs) have included some disappointments, recent investigations have added several more attractive small molecules to this field, providing a promise that the identification of more additional strategies to modulate mGluR5 activity might be potentially beneficial for the advancement of PD treatment. Here, we determined the role of the interacting partner CAL (cystic fibrosis transmembrane conductance regulator-associated ligand) in mGluR5-mediated protection in vitro and in vivo. In astroglial C6 cells, CAL deficiency blocked (S)-3, 5-dihydroxyphenylglycine (DHPG)-elicited p-AKT and p-ERK1/2, subsequently prevented group I mGluRs-mediated anti-apoptotic protection, which was blocked by receptor antagonist 1-aminoindan-1, 5-dicarboxylic acid (AIDA), and PI3K or MEK inhibitor LY294002 or U0126. In rotenone-treated MN9D cells, both CAL and mGluR5 expressions were decreased in a time- and dose-dependent manner, and the correlation between these 2 proteins was confirmed by lentivirus-delivered CAL overexpression and knockdown. Moreover, CAL coupled with mGluR5 upregulated mGluR5 protein expression by inhibition of ubiquitin-proteasome-dependent degradation to suppress mGluR5-mediated p-JNK and to protect against cell apoptosis. Additionally, CAL also inhibited rotenone-induced glutamate release to modulate mGluR5 activity. Furthermore, in the rotenone-induced rat model of PD, AAV-delivered CAL overexpression attenuated behavioral deficits and dopaminergic neuronal death, while CAL deficiency aggravated rotenone toxicity. On the other hand, the protective effect of the mGluR5 antagonist MPEP was weakened by knocking down CAL. In vivo experiments also confirmed that CAL inhibited ubiquitination-proteasome-dependent degradation to modulate mGluR5 expression and JNK phosphorylation. Our findings show that CAL protects against cell apoptosis via modulating mGluR5 activity, and may be a new molecular target for an effective therapeutic strategy for PD.

Modifications of autophagy influenced the Alzheimer-like changes in SH-SY5Y cells promoted by ultrafine black carbon

Ambient ultrafine black carbon (uBC) can potentially cross blood-brain barrier, however, very little is currently known about the effects they may have on central nervous system. This study aimed to explore the roles of autophagy in Alzheimer-like pathogenic changes promoted by uBC in SH-SY5Y cells. We firstly found uBC could cause cytotoxicity and oxidative stress in SH-SY5Y cells. Additionally we found uBC initiated progressive development of Alzheimer's disease (AD) associated features, mainly including neuro-inflammation and phosphorylation of tau protein (p-Tau) accumulation. Meanwhile, autophagy process was activated by uBC probably through phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. RNA interference and autophagosome-lysosome fusion inhibitor were applied to block autophagy process at different stages. Autophagy dysfunction at the initial membrane expansion stage could aggravate p-Tau accumulation and other Alzheimer-like changes in SH-SY5Y cells promoted by uBC. However, autophagy inhibition at the final stage could alleviate p-Tau accumulation caused by uBC. This suggested that inhibition of the infusion of autophagosome and lysosome could possibly activate ubiquitination degradation pathway to regulate p-Tau equilibrium in SH-SY5Y cells. Our findings further raise the concerns about the effects of uBC on the risk of AD and indicate potential roles of autophagy in early Alzheimer-like pathogenic changes caused by ambient uBC.

Functions of Rhotekin, an Effector of Rho GTPase, and Its Binding Partners in Mammals

Rhotekin is an effector protein for small GTPase Rho. This protein consists of a Rho binding domain (RBD), a pleckstrin homology (PH) domain, two proline-rich regions and a C-terminal PDZ (PSD-95, Discs-large, and ZO-1)-binding motif. We, and other groups, have identified various binding partners for Rhotekin and carried out biochemical and cell biological characterization. However, the physiological functions of Rhotekin, per se, are as of yet largely unknown. In this review, we summarize known features of Rhotekin and its binding partners in neuronal tissues and cancer cells.

Cell Specific Changes of Autophagy in a Mouse Model of Contusive Spinal Cord Injury

Autophagy is an essential process of cellular waist clearance that becomes altered following spinal cord injury (SCI). Details on these changes, including timing after injury, underlying mechanisms, and affected cells, remain controversial. Here we present a characterization of autophagy in the mice spinal cord before and after a contusive SCI. In the undamaged spinal cord, analysis of LC3 and Beclin 1 autophagic markers reveals important differences in basal autophagy between neurons, oligodendrocytes, and astrocytes and even within cell populations. Following moderate contusion, western blot analyses of LC3 indicates that autophagy increases to a maximum at 7 days post injury (dpi), whereas unaltered Beclin 1 expression and increase of p62 suggests a possible blockage of autophagosome clearance. Immunofluorescence analyses of LC3 and Beclin 1 provide additional details that reveal a complex, cell-specific scenario. Autophagy is first activated (1 dpi) in the severed axons, followed by a later (7 dpi) accumulation of phagophores and/or autophagosomes in the neuronal soma without signs of increased initiation. Oligodendrocytes and reactive astrocytes also accumulate phagophores and autophagosomes at 7 dpi, but whereas the accumulation in astrocytes is associated with an increased autophagy initiation, it seems to result from a blockage of the autophagic flux in oligodendrocytes. Comparison with previous studies highlights the complex and heterogeneous autophagic responses induced by the SCI, leading in many cases to contradictory results and interpretations. Future studies should consider this complexity in the design of therapeutic interventions based on the modulation of autophagy to treat SCI.

Sphingosine kinase 1-associated autophagy differs between neurons and astrocytes

Autophagy is a degradative pathway for removing aggregated proteins, damaged organelles, and parasites. Evidence indicates that autophagic pathways differ between cell types. In neurons, autophagy plays a homeostatic role, compared to a survival mechanism employed by starving non-neuronal cells. We investigated if sphingosine kinase 1 (SK1)-associated autophagy differs between two symbiotic brain cell types—neurons and astrocytes. SK1 synthesizes sphingosine-1-phosphate, which regulates autophagy in non-neuronal cells and in neurons. We found that benzoxazine autophagy inducers upregulate SK1 and neuroprotective autophagy in neurons, but not in astrocytes. Starvation enhances SK1-associated autophagy in astrocytes, but not in neurons. In astrocytes, SK1 is cytoprotective and promotes the degradation of an autophagy substrate, mutant huntingtin, the protein that causes Huntington’s disease. Overexpressed SK1 is unexpectedly toxic to neurons, and its toxicity localizes to the neuronal soma, demonstrating an intricate relationship between the localization of SK1’s activity and neurotoxicity. Our results underscore the importance of cell type-specific autophagic differences in any efforts to target autophagy therapeutically.

Autophagy precedes apoptosis among at risk cerebellar Purkinje cells in the shaker mutant rat: an ultrastructural study

Cerebellar Purkinje cell (PC) death has been shown to occur in essential tremor, ataxia, and many other neurodegenerative diseases in humans. Shaker mutant rats have an X-linked recessive mutation that causes hereditary degeneration of "at risk" cerebellar PCs. This defect can occur in the restricted anterior (ADC) and posterior (PDC) vermal degeneration compartments postnatally within 7 to 14 weeks of age as a natural phenotype in the shaker mutant rat. "Secure" PCs persist in a flocculonodular survival compartment (FNSC). Because we have previously shown that "at risk" PCs die due to apoptosis in the shaker mutant rat, we hypothesized that the PC death observed in the hereditary shaker mutant rat may be due to the activation of more than one type of death pathway. This ultrastructural investigation suggests that "at risk" PCs die due to apoptosis as a result of autophagic activation. Moreover, our data suggest that both apoptosis and autophagy must be simultaneously inhibited to rescue "at risk" PCs from death.

The HERC2 ubiquitin ligase is essential for embryonic development and regulates motor coordination

A mutation in the HERC2 gene has been linked to a severe neurodevelopmental disorder with similarities to the Angelman syndrome. This gene codifies a protein with ubiquitin ligase activity that regulates the activity of tumor protein p53 and is involved in important cellular processes such as DNA repair, cell cycle, cancer, and iron metabolism. Despite the critical role of HERC2 in these physiological and pathological processes, little is known about its relevance in vivo. Here, we described a mouse with targeted inactivation of the Herc2 gene. Homozygous mice were not viable. Distinct from other ubiquitin ligases that interact with p53, such as MDM2 or MDM4, p53 depletion did not rescue the lethality of homozygous mice. The HERC2 protein levels were reduced by approximately one-half in heterozygous mice. Consequently, HERC2 activities, including ubiquitin ligase and stimulation of p53 activity, were lower in heterozygous mice. A decrease in HERC2 activities was also observed in human skin fibroblasts from individuals with an Angelman-like syndrome that express an unstable mutant protein of HERC2. Behavioural analysis of heterozygous mice identified an impaired motor synchronization with normal neuromuscular function. This effect was not observed in p53 knockout mice, indicating that a mechanism independent of p53 activity is involved. Morphological analysis showed the presence of HERC2 in Purkinje cells and a specific loss of these neurons in the cerebella of heterozygous mice. In these animals, an increase of autophagosomes and lysosomes was observed. Our findings establish a crucial role of HERC2 in embryonic development and motor coordination.

Neurotransmission systems in Parkinson’s disease

Parkinson’s disease (PD) is histologically characterized by the accumulation of α-synuclein particles, known as Lewy bodies. The second most common neurodegenerative disorder, PD is widely known because of the typical motor manifestations of active tremor, rigidity, and postural instability, while several prodromal non-motor symptoms including REM sleep behavior disorders, depression, autonomic disturbances, and cognitive decline are being more extensively recognized. Motor symptoms most commonly arise from synucleinopathy of nigrostriatal pathway. Glutamatergic, γ-aminobutyric acid (GABA)ergic, cholinergic, serotoninergic, and endocannabinoid neurotransmission systems are not spared from the global cerebral neurodegenerative assault. Wide intrabasal and extrabasal of the basal ganglia provide enough justification to evaluate network circuits disturbance of these neurotransmission systems in PD. In this comprehensive review, English literature in PubMed, Science direct, EMBASE, and Web of Science databases were perused. Characteristics of dopaminergic and non-dopaminergic systems, disturbance of these neurotransmitter systems in the pathophysiology of PD, and their treatment applications are discussed.

Modulation of Autophagy by BDNF Underlies Synaptic Plasticity

Autophagy is crucial for neuronal integrity. Loss of key autophagic components leads to progressive neurodegeneration and structural defects in pre- and postsynaptic morphologies. However, the molecular mechanisms regulating autophagy in the brain remain elusive. Similarly, while it is widely accepted that protein turnover is required for synaptic plasticity, the contribution of autophagy to the degradation of synaptic proteins is unknown. Here, we report that BDNF signaling via the tropomyosin receptor kinase B (TrkB) and the phosphatidylinositol-3' kinase (PI3K)/Akt pathway suppresses autophagy in vivo. In addition, we demonstrate that suppression of autophagy is required for BDNF-induced synaptic plasticity and for memory enhancement under conditions of nutritional stress. Finally, we identify three key remodelers of postsynaptic densities as cargo of autophagy. Our results establish autophagy as a pivotal component of BDNF signaling, which is essential for BDNF-induced synaptic plasticity. This molecular mechanism underlies behavioral adaptations that increase fitness in times of scarcity.

Beclin-1-mediated Autophagy Protects Against Cadmium-activated Apoptosis via the Fas/FasL Pathway in Primary Rat Proximal Tubular Cell Culture

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. Here we demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. The antiapoptotic effect of autophagy was blocked by 3-MA, an autophagy inhibitor. The interactions between Beclin-1 and Fas, FasL, FADD, caspase-8 and BID/tBID were relatively weak, with the exception of cleaved caspase-8, indicated that minimal interactions between these proteins and Beclin-1 are involved in maintaining the balance of autophagy and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1. These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway.

Conformational flexibility of BECN1: Essential to its key role in autophagy and beyond

BECN1 (Beclin 1), a highly conserved eukaryotic protein, is a key regulator of autophagy, a cellular homeostasis pathway, and also participates in vacuolar protein sorting, endocytic trafficking, and apoptosis. BECN1 is important for embryonic development, the innate immune response, tumor suppression, and protection against neurodegenerative disorders, diabetes, and heart disease. BECN1 mediates autophagy as a core component of the class III phosphatidylinositol 3-kinase complexes. However, the exact mechanism by which it regulates the activity of these complexes, or mediates its other diverse functions is unclear. BECN1 interacts with several diverse protein partners, perhaps serving as a scaffold or interaction hub for autophagy. Based on extensive structural, biophysical and bioinformatics analyses, BECN1 consists of an intrinsically disordered region (IDR), which includes a BH3 homology domain (BH3D); a flexible helical domain (FHD); a coiled-coil domain (CCD); and a β-α-repeated autophagy-specific domain (BARAD). Each of these BECN1 domains mediates multiple diverse interactions that involve concomitant conformational changes. Thus, BECN1 conformational flexibility likely plays a key role in facilitating diverse protein interactions. Further, BECN1 conformation and interactions are also modulated by numerous post-translational modifications. A better structure-based understanding of the interplay between different BECN1 conformational and binding states, and the impact of post-translational modifications will be essential to elucidating the mechanism of its multiple biological roles.

Lower Beclin 1 downregulates HER2 expression to enhance tamoxifen sensitivity and predicts a favorable outcome for ER positive breast cancer

Tamoxifen(TAM) is one of the most effective endocrine treatment for estrogen receptor(ER)-positive breast cancer, however drug resistance greatly limits benefit of it. Our purpose is to uncover the role of Beclin 1 in tamoxifen resistance and prognosis of ER positive breast cancer. We established a tamoxifen resistant ER-positive breast cancer cell subline MCF-7R presenting with higher Beclin 1 and human epidermal growth factor receptor 2(HER2) levels than MCF-7. Silencing Beclin 1 decreased levels of HER2 and significantly promoted TAM sensitivity of MCF-7 and MCF-7R in vitro. Overexpression of HER2 could reverse TAM sensitivity, which was formerly increased in Beclin 1 downregulated cell. Beclin 1 level was not only positively correlated with level of HER2 but also negatively correlated with overall survival of ER-positive breast cancer patients. Using bioinformatic methods, Beclin 1 mRNA was found to be negatively correlated with overall survival in breast cancer patients receiving TAM treatment. This study indicated for the first time that lower HER2 expression by Beclin 1 downregulation contributes to alteration of tamoxifen sensitivity and low Beclin 1 predicts favorable outcome in ER-positive breast cancer.

Propofol Mitigates Learning and Memory Impairment After Electroconvulsive Shock in Depressed Rats by Inhibiting Autophagy in the Hippocampus

Background

The present study explored the effects of propofol on hippocampal autophagy and synaptophysin in depression-model rats undergoing electroconvulsive shock (ECS).

Material/Methods

The rat depression model was established by exposing Sprague-Dawley rats to stress for 28 consecutive days. Forty rats were assigned randomly into the depression group (group D; no treatment), the ECS group (group E), the propofol group (group P), and the propofol + ECS group (group PE). Open field tests and sucrose preference tests were applied to evaluate the depression behavior; and Morris water maze tests were used to assess the learning and memory function of the rats. Western blotting was used to detect the expression of Beclin-1 and LC3-II/I; and ELISA was applied to assess the expression of synaptophysin.

Results

Rats in group E and group PE scored higher in the open field and sucrose preference tests compared with those in group D. Furthermore, rats in group E also had a longer escape latency, a shorter space exploration time, and increased expression of Beclin-1, LC3-II/I, and synaptophysin. Compared with group E, rats in group PE possessed a shorter escape latency, a longer space exploration time, reduced expression of Beclin-1, LC3-II/I, and synaptophysin.

Conclusions

Propofol could inhibit excessive ECS-induced autophagy and synaptophysin overexpression in the hippocampus, thus protecting the learning and memory functions in depressed rats after ECS. The inhibitory effects of propofol on the overexpression of synaptophysin may result from its inhibitory effects on the excessive induction of autophagy.

Smaller Absolute Quantities but Greater Relative Densities of Microvessels Are Associated with Cerebellar Degeneration in Lurcher Mice

Degenerative affections of nerve tissues are often accompanied by changes of vascularization. In this regard, not much is known about hereditary cerebellar degeneration. In this study, we compared the vascularity of the individual cerebellar components and the mesencephalon of 3-month-old wild type mice (n = 5) and Lurcher mutant mice, which represent a model of hereditary olivocerebellar degeneration (n = 5). Paraformaldehyde-fixed brains were processed into 18-μm thick serial sections with random orientation. Microvessels were visualized using polyclonal rabbit anti-laminin antibodies. Then, the stacks comprised of three 5-μm thick optical sections were recorded using systematic uniform random sampling. Stereological assessment was conducted based on photo-documentation. We found that each of the cerebellar components has its own features of vascularity. The greatest number and length of vessels were found in the granular layer; the number of vessels was lower in the molecular layer, and the lowest number of vessels was observed in the cerebellar nuclei corresponding with their low volume. Nevertheless, the nuclei had the greatest density of blood vessels. The reduction of cerebellum volume in the Lurcher mice was accompanied by a reduction in vascularization in the individual cerebellar components, mainly in the cortex. Moreover, despite the lower density of microvessels in the Lurcher mice compared with the wild type mice, the relative density of microvessels in the cerebellar cortex and nuclei was greater in Lurcher mice. The complete primary morphometric data, in the form of continuous variables, is included as a supplement. Mapping of the cerebellar and midbrain microvessels has explanatory potential for studies using mouse models of neurodegeneration.

HERC 1 Ubiquitin Ligase Mutation Affects Neocortical, CA3 Hippocampal and Spinal Cord Projection Neurons: An Ultrastructural Study

The spontaneous mutation tambaleante is caused by the Gly483Glu substitution in the highly conserved N terminal RCC1-like domain of the HERC1 protein, which leads to the increase of mutated protein levels responsible for cerebellar Purkinje cell death by autophagy. Until now, Purkinje cells have been the only central nervous neurons reported as being targeted by the mutation, and their degeneration elicits an ataxic syndrome in adult mutant mice. However, the ultrastructural analysis performed here demonstrates that signs of autophagy, such as autophagosomes, lysosomes, and altered mitochondria, are present in neocortical pyramidal, CA3 hippocampal pyramidal, and spinal cord motor neurons. The main difference is that the reduction in the number of neurons affected in the tambaleante mutation in the neocortex, the hippocampus, and the spinal cord is not so evident as the dramatic loss of cerebellar Purkinje cells. Interestingly, signs of autophagy are absent in both interneurons and neuroglia cells. Affected neurons have in common that they are projection neurons which receive strong and varied synaptic inputs, and possess the highest degree of neuronal activity. Therefore, because the integrity of the ubiquitin-proteasome system is essential for protein degradation and hence, for normal protein turnover, it could be hypothesized that the deleterious effects of the misrouting of these pathways would depend directly on the neuronal activity.

Valosin-containing protein is a key mediator between autophagic cell death and apoptosis in adult hippocampal neural stem cells following insulin withdrawal

BACKGROUND

Programmed cell death (PCD) plays essential roles in the regulation of survival and function of neural stem cells (NSCs). Abnormal regulation of this process is associated with developmental and degenerative neuronal disorders. However, the mechanisms underlying the PCD of NSCs remain largely unknown. Understanding the mechanisms of PCD in NSCs is crucial for exploring therapeutic strategies for the treatment of neurodegenerative diseases.

RESULT

We have previously reported that adult rat hippocampal neural stem (HCN) cells undergo autophagic cell death (ACD) following insulin withdrawal without apoptotic signs despite their normal apoptotic capabilities. It is unknown how interconnection between ACD and apoptosis is mediated in HCN cells. Valosin-containing protein (VCP) is known to be essential for autophagosome maturation in mammalian cells. VCP is abundantly expressed in HCN cells compared to hippocampal tissue and neurons. Pharmacological and genetic inhibition of VCP at basal state in the presence of insulin modestly impaired autophagic flux, consistent with its known role in autophagosome maturation. Of note, VCP inaction in insulin-deprived HCN cells significantly decreased ACD and down-regulated autophagy initiation signals with robust induction of apoptosis. Overall autophagy level was also substantially reduced, suggesting the novel roles of VCP at initial step of autophagy.

CONCLUSION

Taken together, these data demonstrate that VCP may play an essential role in the initiation of autophagy and mediation of crosstalk between ACD and apoptosis in HCN cells when autophagy level is high upon insulin withdrawal. This is the first report on the role of VCP in regulation of NSC cell death. Elucidating the mechanism by which VCP regulates the crosstalk of ACD and apoptosis will contribute to understanding the molecular mechanism of PCD in NSCs.

Cell death and neurodegeneration in the postnatal development of cerebellar vermis in normal and Reeler mice

Programmed cell death (PCD) was demonstrated in neurons and glia in normal brain development, plasticity, and aging, but also in neurodegeneration. (Macro)autophagy, characterized by cytoplasmic vacuolization and activation of lysosomal hydrolases, and apoptosis, typically entailing cell shrinkage, chromatin and nuclear condensation, are the two more common forms of PCD. Their underlying intracellular pathways are partly shared and neurons can die following both modalities, according to the type of death-triggering stimulus. Reelin is an extracellular protein necessary for proper neuronal migration and brain lamination. In the mutant Reeler mouse, its absence causes neuronal mispositioning, with a notable degree of cerebellar hypoplasia that was tentatively related to an increase in PCD. We have carried out an ultrastructural analysis on the occurrence and type of postnatal PCD affecting the cerebellar neurons in normal and Reeler mice. In the forming cerebellar cortex, PCD took the form of apoptosis or autophagy and mainly affected the cerebellar granule cells (CGCs). Densities of apoptotic CGCs were comparable in both mouse strains at P0-P10, while, in mutants, they increased to become significantly higher at P15. In WT mice the density of autophagic neurons did not display statistically significant differences in the time interval examined in this study, whereas it was reduced in Reeler in the P0-P10 interval, but increased at P15. Besides CGCs, the Purkinje neurons also displayed autophagic features in both WT and Reeler mice. Therefore, cerebellar neurons undergo different types of PCD and a Reelin deficiency affects the type and degree of neuronal death during postnatal development of the cerebellum.

Deficit of RACK1 contributes to the spatial memory impairment via upregulating BECLIN1 to induce autophagy

AIMS

Deficiency of activated C kinase1 (RACK1) in the brain of aging animal and Alzheimer's disease was characterized by cognitive dementia and spatial memory impairment. However, the correlation between the RACK1 and spatial memory impairment and the mechanism involved in it remains unknown.

MAIN METHODS

Spatial memory impairment was performed in mice by lateral ventricle injection of Aβ25-35 (n=16, 10μl) and intraperitoneal injection of scopolamine (n=16, 10ml/kg). After the Morris water maze (MWM) which was performed to determine the ability of learning and memory in mice, expression of RACK1 was tested and the damage of hippocampus was confirmed by histopathology test. ShRACK1 was then used to decrease the level of RACK1 in hippocampus to test the ability of learning and memory and histopathology changes in hippocampus. To look into the mechanism of RACK1 on spatial memory impairment, we further measured the expression of autophagy proteins BECLIN1 and LC3-II/I in hippocampus of all mice.

KEY FINDINGS

Both the Aβ25-35, scopolamine impaired the spatial memory in mice (for escape latency, P=0.0004, P<0.0001) and severely damaged hippocampal DG neurons (P=0.012, P=0.014). The expression of RACK1 was significantly decreased which was concomitant with elevated BECLIN1 and LC3-II/I (P<0.001). Suppression of RACK1 by ShRACK1 plasmid (shGnb2l1) significantly impaired the spatial memory in mice, damaged hippocampal DG neurons (P=0.013), and increased the proteins of BECLIN1 and LC3-II/I (P<0.005).

SIGNIFICANCE

It demonstrated that the deficit of RACK1 in hippocampus impairs the ability of learning and memory in mice via up regulating autophagy.

SiRNA-mediated serotonin transporter knockdown in the dorsal raphe nucleus rescues single prolonged stress-induced hippocampal autophagy in rats

The neurobiological mechanisms underlying the development of post-traumatic stress disorder (PTSD) remain elusive. One of the hypotheses is the dysfunction of serotonin (5-HT) neurotransmission, which is critically regulated by serotonin transporter (SERT). Therefore, we hypothesized that attenuation of SERT gene expression in the hippocampus could prevent hippocampal autophagy and the development of PTSD-like behavior. To this end, we infused SLC6A4 siRNAs into the dorsal raphe nucleus (DRN) to knockdown SERT gene expression after a single prolonged stress (SPS) treatment in rats. Then, we evaluated the effects of SERT gene knockdown on anxiety-related behaviors and extinction of contextual fear memory. We also examined the histological changes and the expression of Beclin-1, LC3-I, and LC3-II in the hippocampus. We found that SPS treatment did not alter anxiety-related behaviors but prolonged the extinction of contextual fear memory, and such a behavioral phenomenon was correlated with increased hippocampal autophagy, decreased 5-HT level, and increased expression of Beclin-1 and LC3-II/LC3-I ratio in the hippocampus. Furthermore, intra-DRN infusion of SLC6A4 siRNAs promoted the extinction of contextual fear memory, prevented hippocampal autophagy, increased 5-HT level, and decreased expression of Beclin-1 and LC3-II/LC3-I ratio. These results indicated that SERT may play a critical role in the pathogenesis of hippocampal autophagy, and is likely involved in the development of PTSD.