UBQLN2 and HSP70 participate in Parkin-mediated mitophagy by facilitating outer mitochondrial membrane rupture.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two aging-related neurodegenerative diseases that share common key features, including aggregation of pathogenic proteins, dysfunction of mitochondria, and impairment of autophagy. Mutations in ubiquilin 2 (UBQLN2), a shuttle protein in the ubiquitin-proteasome system (UPS), can cause ALS/FTD, but the mechanism underlying UBQLN2-mediated pathogenesis is still uncertain. Recent studies indicate that mitophagy, a selective form of autophagy which is crucial for mitochondrial quality control, is tightly associated with neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and ALS. In this study, we show that after Parkin-dependent ubiquitination of damaged mitochondria, UBQLN2 is recruited to poly-ubiquitinated mitochondria through the UBA domain. UBQLN2 cooperates with the chaperone HSP70 to promote UPS-driven degradation of outer mitochondrial membrane (OMM) proteins. The resulting rupture of the OMM triggers the autophagosomal recognition of the inner mitochondrial membrane receptor PHB2. UBQLN2 is required for Parkin-mediated mitophagy and neuronal survival upon mitochondrial damage, and the ALS/FTD pathogenic mutations in UBQLN2 impair mitophagy in primary cultured neurons. Taken together, our findings link dysfunctional mitophagy to UBQLN2-mediated neurodegeneration.

Combined inhibition of pyruvate dehydrogenase kinase 1 and hexokinase 2 induces apoptsis in non-small cell lung cancer cell models.

Many cancer cells exhibit enhanced glycolysis, which is seen as one of the hallmark metabolic alterations, known as Warburg effect. Substantial evidence shows that upregulated glycolytic enzymes are often linked to malignant growth. Using glycolytic inhibitors for anticancer treatment has become appealing in recent years for therapeutic intervention in cancers with highly glycolytic characteristic, including non-small cell lung cancer (NSCLC). In this work, we studied the anticancer effects and the underlying mechanisms of combination of benzerazide hydrocholoride (Benz), a hexokinase 2 (HK2) inhibitor and 64, a pyruvate dehydrogenase kinase 1 (PDK1) inhibitor, in several NSCLC cell lines. We found that combination of Benz and 64 exhibited strong synergistic anticancer effects in NCI-H1975, HCC827, NCI-H1299 and SK-LU-1 cell lines. With this combination treatment, we observed changes of certain mechanistic determinants associated with metabolic stress caused by glycolysis restriction, such as mitochondrial membrane potential depolarization, overproduction of reactive oxygen species [1], activation of AMPK and down-regulation of mTOR, which contributed to enhanced apoptosis. Moreover, Benz and 64 together significantly suppressed the tumor growth in HCC827 cell mouse xenograft model. Taken together, our study may suggest that combined inhibition of HK2 and PDK1 using Benz and 64 could be a viable anticancer strategy for NSCLC.

The interaction between E3 ubiquitin ligase Parkin and mitophagy receptor PHB2 links inner mitochondrial membrane ubiquitination to efficient mitophagy.

The autophagic clearance of mitochondria has been defined as mitophagy, which is triggered by mitochondrial damage and serves as a major pathway for mitochondrial homeostasis and cellular quality control. PINK1 and Parkin-mediated mitophagy is the most extensively studied form of mitophagy, which has been linked to the pathogenesis of neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The current paradigm of this particular mitophagy pathway is that the ubiquitination of the outer mitochondrial membrane is the key step to enable the recognition of damaged mitochondria by the core autophagic component autophagosome. However, whether the inner mitochondrial membrane (IMM) is ubiquitinated by Parkin and its contribution to sufficient mitophagy remain unclear. Here, using molecular, cellular, and biochemical approaches, we report that prohibitin 2 (PHB2), an essential IMM receptor for mitophagy, is ubiquitinated by Parkin and thereby gains higher affinity to the autophagosome during mitophagy. Our findings suggest that Parkin directly binds to PHB2 through its RING1 domain and promotes K11- and K33-linked ubiquitination on K142/K200 sites of PHB2, thereby enhancing the interaction between PHB2 and MAP1LC3B/LC3B. Interestingly and importantly, our study allows us to propose a novel model in which IMM protein PHB2 serves as both a receptor and a ubiquitin-mediated base for autophagosome recruitment to ensure efficient mitophagy.

Epigallocatechin gallate circumvents drug-induced resistance in non-small-cell lung cancer by modulating glucose metabolism and AMPK/AKT/MAPK axis.

Upon prolonged use of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in non-small-cell lung cancer (NSCLC), acquired drug resistance inevitably occurs. This study investigates the combined use of EGFR-TKIs (gefitinib or osimertinib) with epigallocatechin gallate (EGCG) to overcome acquired drug resistance in NSCLC models. The in vitro antiproliferative effects of EGFR-TKIs and EGCG combination in EGFR-mutant parental and resistant cell lines were evaluated. The in vivo efficacy of the combination was assessed in xenograft mouse models derived from EGFR-TKI-resistant NSCLC cells. We found that the combined use of EGFR-TKIs and EGCG significantly reversed the Warburg effect by suppressing glycolysis while boosting mitochondrial respiration, which was accompanied by increased cellular ROS and decreased lactate secretion. The combination effectively activated the AMPK pathway while inhibited both ERK/MAPK and AKT/mTOR pathways, leading to cell cycle arrest and apoptosis, particularly in drug-resistant NSCLC cells. The in vivo results obtained from mouse tumor xenograft model confirmed that EGCG effectively overcame osimertinib resistance. This study revealed that EGCG suppressed cancer bypass survival signaling and altered cancer metabolic profiles, which is a promising anticancer adjuvant of EGFR-TKIs to overcome acquired drug resistance in NSCLC.

Trichosanthin Promotes Anti-Tumor Immunity through Mediating Chemokines and Granzyme B Secretion in Hepatocellular Carcinoma.

Trichosanthin (TCS) is a type I ribosome-inactivating protein extracted from the tuberous root of the plant Trichosanthes. TCS shows promising potential in clinical drug abortion, anti-tumor and immunological regulation. However, the molecular mechanisms of its anti-tumor and immune regulation properties are still not well discovered. In the present study, we investigated the anti-tumor activity of TCS in hepatocellular carcinoma (HCC), both in vitro and in vivo. Both HCC cell lines and xenograft tumor tissues showed considerable growth inhibition after they were treated with TCS. TCS provoked caspase-mediated apoptosis in HCC cells and xenograft tumor tissues. The recruitment of CD8+ T cells to HCC tissues and the expression of chemokines, CCL2 and CCL22, were promoted upon TCS treatment. In addition, TCS induced an upregulation of Granzyme B (GrzB), TNF-α and IFN-γ in HCC tissues, which are the major cytotoxic mediators produced by T cells. Furthermore, TCS also resulted in an increase of mannose-6-phosphate receptor (M6PR), the major receptor of GrzB, in HCC tissues. In summary, these results suggest that TCS perhaps increases T-cell immunity via promoting the secretion of chemokines and accelerating the entry of GrzB to HCC cells, which highlights the potential role of TCS in anti-tumor immunotherapy.

A Model of Hereditary Sensory and Autonomic Neuropathy Type 1 Reveals a Role of Glycosphingolipids in Neuronal Polarity.

Hereditary sensory and autonomic neuropathy Type 1 (HSAN1) is a rare autosomal dominantly inherited neuropathy, clinically characterized by a loss of distal peripheral sensory and motoneuronal function. Mutations in subunits of serine palmitoyltransferase (SPT) have been linked to the majority of HSAN1 cases. SPTs catalyze the condensation of l-serine with palmitoyl-CoA, the first committed and rate-limiting step in de novo sphingolipid biosynthesis. Despite extensive investigation, the molecular pathogenesis of HSAN1 remains controversial. Here, we established a Caenorhabditis elegans (C. elegans) model of HSAN1 by generating a sptl-1(c363g) mutation, encoding SPTL-1(C121W) and equivalent to human SPTLC1C133W, at the C. elegans genomic locus through CRISPR. The sptl-1(c363g) homozygous mutants exhibited the same larval lethality and epithelial polarity defect as observed in sptl-1(RNAi) animals, suggesting a loss-of-function effect of the SPTL-1(C121W) mutation. sptl-1(c363g)/+ heterozygous mutants displayed sensory dysfunction with concomitant neuronal morphology and axon-dendrite polarity defects, demonstrating that the C. elegans model recapitulates characteristics of the human disease. sptl-1(c363g)-derived neuronal defects were copied in animals with defective sphingolipid biosynthetic enzymes downstream of SPTL-1, including ceramide glucosyltransferases, suggesting that SPTLC1C133W contributes to the HSAN1 pathogenesis by limiting the production of complex sphingolipids, including glucosylceramide. Overexpression of SPTL-1(C121W) led to similar epithelial and neuronal defects and to reduced levels of complex sphingolipids, specifically glucosylceramide, consistent with a dominant-negative effect of SPTL-1(C121W) that is mediated by loss of this downstream product. Genetic interactions between SPTL-1(C121W) and components of directional trafficking in neurons suggest that the neuronal polarity phenotype could be caused by glycosphingolipid-dependent defects in polarized vesicular trafficking.SIGNIFICANCE STATEMENT The symptoms of inherited metabolic diseases are often attributed to the accumulation of toxic intermediates or byproducts, no matter whether the disease-causing enzyme participates in a biosynthetic or a degradation pathway. By showing that the phenotypes observed in a C. elegans model of HSAN1 disease could be caused by loss of a downstream product (glucosylceramide) rather than the accumulation of a toxic byproduct, our work provides new insights into the origins of the symptoms of inherited metabolic diseases while expanding the repertoire of sphingolipid functions, specifically, of glucosylceramides. These findings not only have their most immediate relevance for neuroprotective treatments for HSAN1, they may also have implications for a much broader range of neurologic conditions.

Synthesis and biological effect of lysosome-targeting fluorescent anion transporters with enhanced anionophoric activity.

Two lysosome-targeting fluorescent anion transporters derived from coumarins, trifluoromethylated arylsquaramides and morpholines were synthesized, and their specificity and efficiency to target and alkalize lysosomes were investigated. They are able to target lysosomes specifically. Compared with the previous analogue without trifluoromethyl substituents, these two conjugates, in particular the one having a 3,5-bis(trifluoromethyl) substituent, exhibit significantly higher ability to facilitate the transport of chloride anions, alkalize lysosomes and reduce the activity of lysosomal Cathepsin B enzyme. The present finding suggests that improving the anionophoric activity of lysosome-targeting fluorescent anion transporters is favorable to the efficiency to alkalize lysosomes and deactivate lysosomal Cathepsin B enzyme.

Identification of a Wells-Dawson polyoxometalate-based AP-2γ inhibitor with pro-apoptotic activity.

AP-2 gamma (AP-2γ) is a transcription factor that plays pivotal roles in breast cancer biology. To search for small molecule inhibitors of AP-2γ, we performed a high-throughput fluorescence anisotropy screen and identified a polyoxometalate compound with Wells-Dawson structure K6[P2Mo18O62] (Dawson-POM) that blocks the DNA-binding activity of AP-2γ. We showed that this blocking activity is due to the direct binding of Dawson-POM to AP-2γ. We also provided evidence to show that Dawson-POM decreases AP-2γ-dependent transcription similar to silencing the gene. Finally, we demonstrated that Dawson-POM contains anti-proliferative and pro-apoptotic effects in breast cancer cells. In summary, we identified the first small molecule inhibitor of AP-2γ and showed Dawson-POM-mediated inhibition of AP-2γ as a potential avenue for cancer therapy.

Liquid Chromatography-Tandem Mass Spectrometry Method Revealed that Lung Cancer Cells Exhibited Distinct Metabolite Profiles upon the Treatment with Different Pyruvate Dehydrogenase Kinase Inhibitors.

Pyruvate dehydrogenase kinases (PDKs) dominate the critical switch between mitochondria-based respiration and cytoplasm-based glycolysis by controlling pyruvate dehydrogenase (PDH) activity. Up-regulated PDKs play a great role in the Warburg effect in cancer cells and accordingly present a therapeutic target. Dichloroacetate (DCA) and AZD7545 are the two most-well-known PDK inhibitors exhibiting distinct pharmacological profiles. DCA showed anticancer effects in various preclinical models and clinical studies, while the primary preclinical indication of AZD7545 was on the improvement of glucose control in type II diabetes. Little, if any, study has been undertaken the elucidation of the effects of PDK inhibition on the metabolites in the tricarboxylic acid (TCA) cycle. Herein, the metabolite alterations of lung cancer cells (A549) upon the treatment with PDK inhibitors were studied using a reliable liquid-chromatography-based tandem mass spectrometry method. The developed method was validated for quantification of all common glycolysis and TCA cycle catabolites with good sensitivity and reproducibility, including glucose, pyruvate, lactate, acetyl coenzyme A, citrate, α-ketoglutarate, fumarate, succinate, malate, and oxaloacetate. Our results suggested that A549 cells exhibited distinct metabolite profiles following the treatment with DCA or AZD7545, which may reflect the different pharmacological indications of these two drugs.

Dichloroacetophenones targeting at pyruvate dehydrogenase kinase 1 with improved selectivity and antiproliferative activity: Synthesis and structure-activity relationships.

Dichloroacetophenone is a pyruvate dehydrogenase kinase 1 (PDK1) inhibitor with suboptimal kinase selectivity. Herein, we report the synthesis and biological evaluation of a series of novel dichloroacetophenones. Structure-activity relationship analyses (SARs) enabled us to identify three potent compounds, namely 54, 55, and 64, which inhibited PDK1 function, activated pyruvate dehydrogenase complex, and reduced the proliferation of NCI-H1975 cells. Mitochondrial bioenergetics assay suggested that 54, 55, and 64 enhanced the oxidative phosphorylation in cancer cells, which might contribute to the observed anti-proliferation effects. Collectively, these results suggested that 54, 55, and 64 could be promising compounds for the development of potent PDK1 inhibitors.

Dual-target inhibitors of cholinesterase and GSK-3ß to modulate Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease that affects over 55 million patients worldwide. Most of the approved small-molecule drugs for AD have been designed to tackle a single pathological hallmark, such as cholinergic dysfunction or amyloid toxicity, and thus may not fully address the multifactorial nature of the disease. Inhibition of both cholinesterase and glycogen synthase kinase-3ß (GSK-3ß) has emerged as a promising strategy to modulate AD. However, the dual inhibition of these two targets posts challenges in molecular design: issues related to target engagements and biopharmaceutical properties in particular must be overcome. In this review, we discuss the physiopathological roles and structures of cholinesterase and GSK-3ß as well as recently reported dual-target inhibitors. We critically evaluate the current status of the discovery of dual-target inhibitors of cholinesterase and GSK-3ß, and highlight further perspectives.

Exploring casual effects and shared molecular mechanism between psoriasis and liver cancer through Mendelian randomization and comprehensive bioinformatic analyses.

Psoriasis (Ps), a chronic inflammatory disease affecting approximately 2 % of the global population, has been associated with an increased risk of liver cancer in observational studies. However, their causal relationships as well as underlying shared molecular mechanisms between Ps and liver cancer remain unclear. Using bidirectional Mendelian randomization analysis, we revealed that a genetic predisposition to liver cancer increased the risk of Ps in European and East Asian populations but not the other way around. Moreover, we analyzed three transcriptomic datasets of patients with Ps and liver cancer from open-source databases. Differentially expressed genes (DEGs) and disease-specific gene co-expression module analyses revealed that cell-cycle dysregulation was the shared mechanism of Ps and liver cancer. Moreover, we identified a rank-conservative gene signature shared between these two diseases, which demonstrated significance in diagnostic and prognostic predictions. These findings provided valuable insights into the interconnections between Ps and liver cancer, which may be helpful to guide therapeutic management.

ALS-linked C9orf72 dipeptide repeats inhibit starvation-induced autophagy through modulating BCL2-BECN1 interaction.

Growing evidences indicate that dysfunction of autophagy contributes to the disease pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two neurodegenerative disorders. The GGGGCC·GGCCCC repeat RNA expansion in chromosome 9 open reading frame 72 (C9orf72) is the most genetic cause of both ALS and FTD. According to the previous studies, GGGGCC·GGCCCC repeat undergoes the unconventional repeat-associated non-ATG translation, which produces dipeptide repeat (DPR) proteins. Although there is a growing understanding that C9orf72 DPRs have a strong ability to harm neurons and induce C9orf72-linked ALS/FTD, whether these DPRs can affect autophagy remains unclear. In the present study, we find that poly-GR and poly-PR, two arginine-containing DPRs which display the most cytotoxic properties according to the previous studies, strongly inhibit starvation-induced autophagy. Moreover, our data indicate that arginine-rich DPRs enhance the interaction between BCL2 and BECN1/Beclin 1 by inhibiting BCL2 phosphorylation, therefore they can impair autophagic clearance of neurodegenerative disease-associated protein aggregates under starvation condition in cells. Importantly, our study not only highlights the role of C9orf72 DPR in autophagy dysfunction, but also provides novel insight that pharmacological intervention of autophagy using SW063058, a small molecule compound that can disrupt the interaction between BECN1 and BCL2, may reduce C9orf72 DPR-induced neurotoxicity.

Evaluations of the neuroprotective effects of a dual-target isoquinoline inhibitor in the triple transgenic mouse model of Alzheimer's disease.

Alzheimer's disease (AD) patients exhibit neuropathological features, such as amyloid-beta (Aß) plaques and neurogenic fibrillary tangles. These features are thought to play important pathogenic roles, including neuronal dysfunction and apoptosis in the disease progression. Herein, we systematically evaluated a previously reported dual-target isoquinoline inhibitor (9S) for cholinesterase and Aß aggregation in in vitro and in vivo models of AD. 9S exhibited neuroprotective effects in Aß-induced and PHF6-induced PC12 cell models as well as in an okadaic acid-induced SH-SY5Y cell model, which were due to attenuated neuronal apoptosis through modulations of GSK-3ß phosphorylation and reactive oxygen species. One-month administration of 9S to triple transgenic AD (3 × Tg-AD) female mice (aged 6 months) led to significant improvement in cognitive deficits. Whereas similar treatment regimens for older 3 × Tg-AD female mice (aged 10 months) showed negligible neuroprotective effects. These findings suggest the importance of therapeutic intervention at the early stage of the disease.

Cytosolic malic enzyme and glucose-6-phosphate dehydrogenase modulate redox balance in NSCLC with acquired drug resistance.

Lung cancer cells often show elevated levels of reactive oxygen species (ROS) and nicotinamide adenine dinucleotide phosphate (NADPH). However, the connections between deregulated redox homeostasis in different subtypes of lung cancer and acquired drug resistance in lung cancer have not yet been fully established. Herein, we analyzed different subtypes of lung cancer data reported in the Cancer Cell Line Encyclopedia (CCLE) database, the Cancer Genome Atlas program (TCGA), and the sequencing data obtained from a gefitinib-resistant non-small-cell lung cancer (NSCLC) cell line (H1975GR). Using flux balance analysis (FBA) model integrated with multiomics data and gene expression profiles, we identified cytosolic malic enzyme 1 (ME1) and glucose-6-phosphate dehydrogenase as the major contributors to the significantly upregulated NADPH flux in NSCLC tissues as compared with normal lung tissues, and gefitinib-resistant NSCLC cell line as compared with the parental cell line. Silencing the gene expression of either of these two enzymes in two osimertinib-resistant NSCLC cell lines (H1975OR and HCC827OR) exhibited strong antiproliferative effects. Our findings not only underscored the pivotal roles of cytosolic ME1 and glucose-6-phosphate dehydrogenase in regulating redox states in NSCLC cells but also provided novel insights into their potential roles in drug-resistant NSCLC cells with disturbed redox states.

Dichloroacetophenone biphenylsulfone ethers as anticancer pyruvate dehydrogenase kinase inhibitors in non-small cell lung cancer models.

Pyruvate dehydrogenase kinase 1 (PDK1) is an important metabolic enzyme which is often overexpressed in many types of cancers, including non-small-cell lung cancers (NSCLC). Targeting PDK1 appears to be an attractive anticancer strategy. Based on a previously reported moderate potent anticancer PDK1 inhibitor, 64, we developed three dichloroacetophenone biphenylsulfone ethers, 30, 31 and 32, which showed strong PDK1 inhibitions of 74%, 83% and 72% at 10 µM, respectively. Then we investigated the anticancer effects of 31 in two NSCLC cell lines, namely, NCI-H1299 and NCI-H1975. It was found that 31 exhibited sub-micromolar cancer cell IC50s, suppressed colony formation, induced mitochondrial membrane potential depolarization, triggered apoptosis, altered cellular glucose metabolism, with concomitant reductions in extracellular lactate levels and enhanced the generation of reactive oxygen species in NSCLC cells. Moreover, 31 significantly suppressed the tumor growth in an NCI-H1975 mouse xenograft model, outperforming the anticancer effects of 64. Taken together our results suggested that inhibition of PDK1 via dichloroacetophenone biphenylsulfone ethers may provide a novel direction leading to an alternative treatment option in NSCLC therapy.

Repurposing the Hedgehog pathway inhibitor, BMS-833923, as a phosphatidylglycerol-selective membrane-disruptive colistin adjuvant against ESKAPE pathogens.

The rapid emergence and spread of multi-drug- or pan-drug-resistant bacterial pathogens, such as ESKAPE, pose a serious threat to global health. However, the development of novel antibiotics is hindered by difficulties in identifying new antibiotic targets and the rapid development of drug resistance. Drug repurposing is an effective alternative strategy for combating antibiotic resistance that both saves resources and extends the life of existing antibiotics in combination treatment regimens. Screening of a chemical compound library identified BMS-833923 (BMS), a smoothened antagonist that kills Gram-positive bacteria directly, and potentiates colistin to destroy various Gram-negative bacteria. BMS did not induce detectable antibiotic resistance in vitro, and showed effective activity against drug-resistant bacteria in vivo. Mechanistic studies revealed that BMS caused membrane disruption by targeting the membrane phospholipids phosphatidylglycerol and cardiolipin, promoting membrane dysfunction, metabolic disturbance, leakage of cellular components, and, ultimately, cell death. This study describes a potential strategy to enhance the efficacy of colistin and combat multi-drug-resistant ESKAPE pathogens.

Combined inhibition of pyruvate dehydrogenase kinase 1 and lactate dehydrogenase a induces metabolic and signaling reprogramming and enhances lung adenocarcinoma cell killing.

Lung adenocarcinoma (LUAD) is one of the most prevalent and aggressive types of lung cancer. Metabolic reprogramming plays a critical role in the development and progression of LUAD. Pyruvate dehydrogenase kinase 1 (PDK1) and lactate dehydrogenase A (LDHA) are two key enzymes involved in glucose metabolism, whilst their aberrant expressions are often associated with tumorigenesis. Herein, we investigated the anticancer effects of combined inhibition of PDK1 and LDHA in LUAD in vitro and in vivo and its underlying mechanisms of action. The combination of a PDK1 inhibitor, 64, and a LDHA inhibitor, NHI-Glc-2, led to a synergistic growth inhibition in 3 different LUAD cell lines and more than additively suppressed tumor growth in the LUAD xenograft H1975 model. This combination also inhibited cellular migration and colony formation, while it induced a metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) resulting in mitochondrial depolarization and apoptosis in LUAD cells. These effects were related to modulation of multiple cell signaling pathways, including AMPK, RAS/ERK, and AKT/mTOR. Our findings demonstrate that simultaneous inhibition of multiple glycolytic enzymes (PDK1 and LDHA) is a promising novel therapeutic approach for LUAD.

Chlorpromazine affects autophagy in association with altered Rag GTPase-mTORC1-TFEB signaling.

Autophagy is a critical protein and organelle quality control system, which regulates cellular homeostasis and survival. Growing pieces of evidence suggest that autophagic dysfunction is strongly associated with many human diseases, including neurological diseases and cancer. Among various autophagic regulators, microphthalmia (MiT)/TFE transcription factors, including transcription factor EB (TFEB), have been shown to act as the master regulators of autophagosome and lysosome biogenesis in both physiological and pathological conditions. According to the previous studies, chlorpromazine (CPZ), an FDA-approved antipsychotic drug, affects autophagy in diverse cell lines, but the underlying mechanism remains elusive. In our present study, we find that CPZ treatment induces TFEB nuclear translocation through Rag GTPases, the upstream regulators of mechanistic target of rapamycin complex 1 (mTORC1) signaling. Meanwhile, CPZ treatment also blocks autophagosome-lysosome fusion. Notably, we find a significant accumulation of immature autophagosome vesicles in CPZ-treated cells, which may impede cellular homeostasis due to the dysfunction of the autophagy-lysosome pathway. Interestingly and importantly, our data suggest that the expression of the active form of Rag GTPase heterodimers helps in reducing the accumulation of autophagosomes in CPZ-treated cells, further suggesting a major contribution of the Rag GTPase-mTORC1-TFEB signaling axis in CPZ-induced autophagic impairment.

Pathological mechanisms and therapeutic strategies for Alzheimer's disease.

Alzheimer's disease is a rather complex neurodegenerative disease, which is attributed to a combination of multiple factors. Among the many pathological pathways, synaptic dysfunctions, such as synapses loss and deficits in synaptic plasticity, were thought to be strongly associated with cognitive decline. The deficiencies in various sorts of neurotransmissions are responsible for the multifarious neurodegenerative symptoms in Alzheimer's disease, for example, the cholinergic and glutamatergic deficits for cognitive decline, the excitatory and inhibitory neurotransmission dyshomeostasis for synaptic plasticity deficits and epileptiform symptoms, and the monoamine neurotransmission for neuropsychiatric symptoms. Amyloid cascade hypothesis is the most popular pathological theory to explain Alzheimer's disease pathogenesis and attracts considerable attention. Multiple lines of genetic and pathological evidence support the predominant role of amyloid beta in Alzheimer's disease pathology. Neurofibrillary tangles assembled by microtubule-associated protein tau are other important histopathological characteristics in Alzheimer's disease brains. Cascade of tau toxicity was proved to lead to neuron damage, neuroinflammation and oxidative stress in brain. Ageing is the main risk factor of neurodegenerative diseases, and is associated with inflammation, oxidative stress, reduced metabolism, endocrine insufficiencies and organ failures. These aging related risk factors were also proved to be some of the risk factors contributing to Alzheimer's disease. In Alzheimer's disease drug development, many good therapeutic strategies have been investigated in clinical evaluations. However, complex mechanism of Alzheimer's disease and the interplay among different pathological factors call for the come out of all-powerful therapies with multiple curing functions. This review seeks to summarize some of the representative treatments targeting different pathological pathways currently under clinical evaluations. Multi-target therapies as an emerging strategy for Alzheimer's disease treatment will be highlighted.