Regulation of autophagy by the Rab GTPase network

MicroRNAs as the critical regulators of autophagy-mediated cisplatin response in tumor cells

Chemotherapy is one of the most common therapeutic methods in advanced and metastatic tumors. Cisplatin (CDDP) is considered as one of the main first-line chemotherapy drugs in solid tumors. However, there is a high rate of CDDP resistance in cancer patients. Multi-drug resistance (MDR) as one of the main therapeutic challenges in cancer patients is associated with various cellular processes such as drug efflux, DNA repair, and autophagy. Autophagy is a cellular mechanism that protects the tumor cells toward the chemotherapeutic drugs. Therefore, autophagy regulatory factors can increase or decrease the chemotherapy response in tumor cells. MicroRNAs (miRNAs) have a pivotal role in regulation of autophagy in normal and tumor cells. Therefore, in the present review, we discussed the role of miRNAs in CDDP response through the regulation of autophagy. It has been reported that miRNAs mainly increased the CDDP sensitivity in tumor cells by inhibition of autophagy. PI3K/AKT signaling pathway and autophagy-related genes (ATGs) were the main targets of miRNAs in the regulation of autophagy-mediated CDDP response in tumor cells. This review can be an effective step to introduce the miRNAs as efficient therapeutic options to increase autophagy-mediated CDDP sensitivity in tumor cells.

Secretory autophagy promotes RAB37-mediated insulin secretion under glucose stimulation both in vitro and in vivo

High blood glucose is one of the risk factors for metabolic disease and INS (insulin) is the key regulatory hormone for glucose homeostasis. Hypoinsulinemia accompanied with hyperglycemia was diagnosed in mice with pancreatic β-cells exhibiting autophagy deficiency; however, the underlying mechanism remains elusive. The role of secretory autophagy in the regulation of metabolic syndrome is gaining more attention. Our data demonstrated that increased macroautophagic/autophagic activity leads to induction of insulin secretion in β-cells both in vivo and in vitro under high-glucose conditions. Moreover, proteomic analysis of purified autophagosomes from β-cells identified a group of vesicular transport proteins participating in insulin secretion, implying that secretory autophagy regulates insulin exocytosis. RAB37, a small GTPase, regulates vesicle biogenesis, trafficking, and cargo release. We demonstrated that the active form of RAB37 increased MAP1LC3/LC3 lipidation (LC3-II) and is essential for the promotion of insulin secretion by autophagy, but these phenomena were not observed in rab37 knockout (rab37^-/-) cells and mice. Unbalanced insulin and glucose concentration in the blood was improved by manipulating autophagic activity using a novel autophagy inducer niclosamide (an antihelminthic drug) in a high-fat diet (HFD)-obesity mouse model. In summary, we reveal that secretory autophagy promotes RAB37-mediated insulin secretion to maintain the homeostasis of insulin and glucose both in vitro and in vivo.

GTP energy dependence of endocytosis and autophagy in the aging brain and Alzheimer's disease

Increased interest in the aging and Alzheimer's disease (AD)-related impairments in autophagy in the brain raise important questions about regulation and treatment. Since many steps in endocytosis and autophagy depend on GTPases, new measures of cellular GTP levels are needed to evaluate energy regulation in aging and AD. The recent development of ratiometric GTP sensors (GEVALS) and findings that GTP levels are not homogenous inside cells raise new issues of regulation of GTPases by the local availability of GTP. In this review, we highlight the metabolism of GTP in relation to the Rab GTPases involved in formation of early endosomes, late endosomes, and lysosomal transport to execute the autophagic degradation of damaged cargo. Specific GTPases control macroautophagy (mitophagy), microautophagy, and chaperone-mediated autophagy (CMA). By inference, local GTP levels would control autophagy, if not in excess. Additional levels of control are imposed by the redox state of the cell, including thioredoxin involvement. Throughout this review, we emphasize the age-related changes that could contribute to deficits in GTP and AD. We conclude with prospects for boosting GTP levels and reversing age-related oxidative redox shift to restore autophagy. Therefore, GTP levels could regulate the numerous GTPases involved in endocytosis, autophagy, and vesicular trafficking. In aging, metabolic adaptation to a sedentary lifestyle could impair mitochondrial function generating less GTP and redox energy for healthy management of amyloid and tau proteostasis, synaptic function, and inflammation.

Steatosis in metabolic diseases: A focus on lipolysis and lipophagy

Fatty acids (FAs), as part of lipids, are involved in cell membrane composition, cellular energy storage, and cell signaling. FAs can also be toxic when their concentrations inside and/or outside the cell exceed physiological levels, which is called "lipotoxicity", and steatosis is a form of lipotoxity. To facilitate the storage of large quantities of FAs in cells, they undergo a process called lipolysis or lipophagy. This review focuses on the effects of lipolytic enzymes including cytoplasmic "neutral" lipolysis, lysosomal "acid" lipolysis, and lipophagy. Moreover, the impact of related lipolytic enzymes on lipid metabolism homeostasis and energy conservation, as well as their role in lipid-related metabolic diseases. In addition, we describe how they affect lipid metabolism homeostasis and energy conservation in lipid-related metabolic diseases with a focus on hepatic steatosis and cancer and the pathogenesis and therapeutic targets of AMPK/SIRTs/FOXOs, PI3K/Akt, PPARs/PGC-1α, MAPK/ERK1/2, TLR4/NF-κB, AMPK/mTOR/TFEB, Wnt/β-catenin through immune inflammation, oxidative stress and autophagy-related pathways. As well as the current application of lipolytic enzyme inhibitors (especially Monoacylglycerol lipase (MGL) inhibitors) to provide new strategies for future exploration of metabolic programming in metabolic diseases.

Autophagic mechanisms in longevity intervention: role of natural active compounds

The term 'autophagy' literally translates to 'self-eating' and alterations to autophagy have been identified as one of the several molecular changes that occur with aging in a variety of species. Autophagy and aging, have a complicated and multifaceted relationship that has recently come to light thanks to breakthroughs in our understanding of the various substrates of autophagy on tissue homoeostasis. Several studies have been conducted to reveal the relationship between autophagy and age-related diseases. The present review looks at a few new aspects of autophagy and speculates on how they might be connected to both aging and the onset and progression of disease. Additionally, we go over the most recent preclinical data supporting the use of autophagy modulators as age-related illnesses including cancer, cardiovascular and neurodegenerative diseases, and metabolic dysfunction. It is crucial to discover important targets in the autophagy pathway in order to create innovative therapies that effectively target autophagy. Natural products have pharmacological properties that can be therapeutically advantageous for the treatment of several diseases and they also serve as valuable sources of inspiration for the development of possible new small-molecule drugs. Indeed, recent scientific studies have shown that several natural products including alkaloids, terpenoids, steroids, and phenolics, have the ability to alter a number of important autophagic signalling pathways and exert therapeutic effects, thus, a wide range of potential targets in various stages of autophagy have been discovered. In this review, we summarised the naturally occurring active compounds that may control the autophagic signalling pathways.

Time-of-day defines NAD+ efficacy to treat diet-induced metabolic disease by synchronizing the hepatic clock in mice

The circadian clock is an endogenous time-tracking system that anticipates daily environmental changes. Misalignment of the clock can cause obesity, which is accompanied by reduced levels of the clock-controlled, rhythmic metabolite NAD⁺. Increasing NAD⁺ is becoming a therapy for metabolic dysfunction; however, the impact of daily NAD⁺ fluctuations remains unknown. Here, we demonstrate that time-of-day determines the efficacy of NAD⁺ treatment for diet-induced metabolic disease in mice. Increasing NAD⁺ prior to the active phase in obese male mice ameliorated metabolic markers including body weight, glucose and insulin tolerance, hepatic inflammation and nutrient sensing pathways. However, raising NAD⁺ immediately before the rest phase selectively compromised these responses. Remarkably, timed NAD⁺ adjusted circadian oscillations of the liver clock until completely inverting its oscillatory phase when increased just before the rest period, resulting in misaligned molecular and behavioral rhythms in male and female mice. Our findings unveil the time-of-day dependence of NAD⁺-based therapies and support a chronobiology-based approach.

Autophagy and neurodegeneration: Unraveling the role of C9ORF72 in the regulation of autophagy and its relationship to ALS-FTD pathology

The proper functioning of the cell clearance machinery is critical for neuronal health within the central nervous system (CNS). In normal physiological conditions, the cell clearance machinery is actively involved in the elimination of misfolded and toxic proteins throughout the lifetime of an organism. The highly conserved and regulated pathway of autophagy is one of the important processes involved in preventing and neutralizing pathogenic buildup of toxic proteins that could eventually lead to the development of neurodegenerative diseases (NDs) such as Alzheimer’s disease or Amyotrophic lateral sclerosis (ALS). The most common genetic cause of ALS and frontotemporal dementia (FTD) is a hexanucleotide expansion consisting of GGGGCC (G4C2) repeats in the chromosome 9 open reading frame 72 gene (C9ORF72). These abnormally expanded repeats have been implicated in leading to three main modes of disease pathology: loss of function of the C9ORF72 protein, the generation of RNA foci, and the production of dipeptide repeat proteins (DPRs). In this review, we discuss the normal physiological role of C9ORF72 in the autophagy-lysosome pathway (ALP), and present recent research deciphering how dysfunction of the ALP synergizes with C9ORF72 haploinsufficiency, which together with the gain of toxic mechanisms involving hexanucleotide repeat expansions and DPRs, drive the disease process. This review delves further into the interactions of C9ORF72 with RAB proteins involved in endosomal/lysosomal trafficking, and their role in regulating various steps in autophagy and lysosomal pathways. Lastly, the review aims to provide a framework for further investigations of neuronal autophagy in C9ORF72-linked ALS-FTD as well as other neurodegenerative diseases.

Identifying autophagy-related genes as potential targets for immunotherapy in tuberculosis

PURPOSE

Identifying of host-directed targets and molecular markers of immune response for tuberculosis (TB) immunotherapy is urgent and meaningful. Previous studies have demonstrated an important role of autophagy in the course and pathophysiology of TB and is associated with the efficacy of TB treatment. However, its role in TB immunotherapy is still incomplete.

METHODS

The effect of autophagy on intracellular bacteria load was examined in sulforaphane (SFN)-treated THP-1 cells. The immune infiltration was assessed based on public databases. Functional enrichment analysis revealed the pathways involved. LASSO Cox regression analysis was employed to identify hub genes. Moreover, machine learning analysis was used to obtain important targets of TB immunotherapy. Finally, the relationship between hub genes and immune infiltration was assessed, as well as the relevance of chemokines.

RESULTS

We found that SFN reduced intracellular bacteria load by enhancing autophagy in THP-1 cells. Thirty-two autophagy-related genes (ARGs) were identified, three types of immune cells (macrophages, neutrophils, and DC cells) were significantly enriched in TB patients, and 6 hub genes (RAB5A, SQSTM1, MYC, MAPK8, MAPK3, and FOXO1) were closely related to TB immune infiltration. The 32 ARGs were mainly involved in autophagy, apoptosis, and tuberculosis pathways. FOXO1, SQSTM1, and RAB5A were identified as important target genes according to the ranking of variable importance, with FOXO1 being a potential autophagy-related target of TB immunotherapy.

CONCLUSION

This study highlights the association between autophagy-related genes and immune infiltration in TB. Three key genes, especially FOXO1, regulated by SFN, will provide new insights into diagnostic and immunotherapy strategies for clinical tuberculosis.

Rab32 promotes glioblastoma migration and invasion via regulation of ERK/Drp1-mediated mitochondrial fission

The highly widespread and infiltrative nature of glioblastoma multiforme (GBM) makes complete surgical resection hard, causing high recurrence rate and poor patients' prognosis. However, the mechanism underlying GBM migration and invasion is still unclear. In this study, we investigated the role of a Ras-related protein Rab32 on GBM and uncovered its underlying molecular and subcellular mechanisms that contributed to GBM aggressiveness. The correlation of Rab32 expression with patient prognosis and tumor grade was investigated by public dataset analysis and clinical specimen validation. The effect of Rab32 on migration and invasion of GBM had been evaluated using wound healing assay, cell invasion assay, as well as protein analysis upon Rab32 manipulations. Mitochondrial dynamics of cells upon Rab32 alterations were detected by immunofluorescence staining and western blotting. Both the subcutaneous and intracranial xenograft tumor model were utilized to evaluate the effect of Rab32 on GBM in vivo. The expression level of Rab32 is significantly elevated in the GBM, especially in the most malignant mesenchymal subtype, and is positively correlated with tumor pathological grade and poor prognosis. Knockdown of Rab32 attenuated the capability of GBM's migration and invasion. It also suppressed the expression levels of invasion-related proteins (MMP2 and MMP9) as well as mesenchymal transition markers (N-cadherin, vimentin). Interestingly, Rab32 transported Drp1 to mitochondrial from the cytoplasm and modulated mitochondrial fission in an ERK_1/2 signaling-dependent manner. Furthermore, silencing of Rab32 in vivo suppressed tumor malignancy via ERK/Drp1 axis. Rab32 regulates ERK_1/2/Drp1-dependent mitochondrial fission and causes mesenchymal transition, promoting migration and invasion of GBM. It serves as a novel therapeutic target for GBM, especially for the most malignant mesenchymal subtype. Schematic of Rab32 promotes GBM aggressiveness via regulation of ERK/Drp1-mediated mitochondrial fission. Rab32 transports Drp1 from the cytoplasm to the mitochondria and recruits ERK_1/2 to activate the ser616 site of Drp1, which in turn mediates mitochondrial fission and promotes mesenchymal transition, migration and invasion of GBM.

Determination of the Salmonella intracellular lifestyle by the diversified interaction of Type III secretion system effectors and host GTPases

Intracellular bacteria have developed sophisticated strategies to subvert the host endomembrane system to establish a stable replication niche. Small GTPases are critical players in regulating each step of membrane trafficking events, such as vesicle biogenesis, cargo transport, tethering, and fusion events. Salmonella is a widely studied facultative intracellular bacteria. Salmonella delivers several virulence proteins, termed effectors, to regulate GTPase dynamics and subvert host trafficking for their benefit. In this review, we summarize an updated and systematic understanding of the interactions between bacterial effectors and host GTPases in determining the intracellular lifestyle of Salmonella. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

Impaired hepatic autophagy exacerbates hepatotoxin induced liver injury

Hepatotoxins activate the hepatic survival pathway, but it is unclear whether impaired survival pathways contribute to liver injury caused by hepatotoxins. We investigated the role of hepatic autophagy, a cellular survival pathway, in cholestatic liver injury driven by a hepatotoxin. Here we demonstrate that hepatotoxin contained DDC diet impaired autophagic flux, resulting in the accumulation of p62-Ub-intrahyaline bodies (IHBs) but not the Mallory Denk-Bodies (MDBs). An impaired autophagic flux was associated with a deregulated hepatic protein-chaperonin system and significant decline in Rab family proteins. Additionally, p62-Ub-IHB accumulation activated the NRF2 pathway rather than the proteostasis-related ER stress signaling pathway and suppressed the FXR nuclear receptor. Moreover, we demonstrate that heterozygous deletion of Atg7, a key autophagy gene, aggravated the IHB accumulation and cholestatic liver injury. Conclusion: Impaired autophagy exacerbates hepatotoxin-induced cholestatic liver injury. The promotion of autophagy may represent a new therapeutic approach for hepatotoxin-induced liver damage.

Effect of 11-Deoxycorticosterone in the Transcriptomic Response to Stress in Rainbow Trout Skeletal Muscle

In aquaculture, many stressors can negatively affect growth in teleosts. It is believed that cortisol performs glucocorticoid and mineralocorticoid functions because teleosts do not synthesize aldosterone. However, recent data suggest that 11-deoxycorticosterone (DOC) released during stress events may be relevant to modulate the compensatory response. To understand how DOC modifies the skeletal muscle molecular response, we carried out a transcriptomic analysis. Rainbow trout (Oncorhynchus mykiss) were intraperitoneally treated with physiological doses of DOC in individuals pretreated with mifepristone (glucocorticoid receptor antagonist) or eplerenone (mineralocorticoid receptor antagonist). RNA was extracted from the skeletal muscles, and cDNA libraries were constructed from vehicle, DOC, mifepristone, mifepristone plus DOC, eplerenone, and eplerenone plus DOC groups. The RNA-seq analysis revealed 131 differentially expressed transcripts (DETs) induced by DOC with respect to the vehicle group, mainly associated with muscle contraction, sarcomere organization, and cell adhesion. In addition, a DOC versus mifepristone plus DOC analysis revealed 122 DETs related to muscle contraction, sarcomere organization, and skeletal muscle cell differentiation. In a DOC versus eplerenone plus DOC analysis, 133 DETs were associated with autophagosome assembly, circadian regulation of gene expression, and regulation of transcription from RNA pol II promoter. These analyses indicate that DOC has a relevant function in the stress response of skeletal muscles, whose action is differentially modulated by GR and MR and is complementary to cortisol.

Mitochondrial cargo export in exosomes: Possible pathways and implication in disease biology

Exosome biogenesis occurs parallel to multiple endocytic traffic routes. These coexisting routes drive cargo loading in exosomes via overlapping of exosome biogenesis with endosomal pathways. One such pathway is autophagy which captures damaged intracellular organelles or their components in an autophagosome vesicle and route them for lysosomal degradation. However, in case of a noncanonical fusion event between autophagosome and maturing multivesicular body (MVB)-a site for exosome biogenesis, the autophagic cargo is putatively loaded in exosomes and subsequent released out of the cell via formation of an "amphisome" like structure. Similarly, during "mitophagy" or mitochondrial (mt) autophagy, amphisome formation routes mitophagy cargo to exosomes. These mt-cargo enriched exosomes or mt-enREXO are often positive for LC3 protein-an autophagic flux marker, and potent regulators of paracrine signaling with both homeostatic and pathological roles. Here, I review this emerging concept and discuss how intracellular autophagic routes helps in generation of mt-enREXO and utility of these vesicles in paracrine cellular signaling and diagnostic areas.

The role of autophagy in viral infections

Autophagy is an evolutionarily conserved catabolic cellular process that exerts antiviral functions during a viral invasion. However, co-evolution and co-adaptation between viruses and autophagy have armed viruses with multiple strategies to subvert the autophagic machinery and counteract cellular antiviral responses. Specifically, the host cell quickly initiates the autophagy to degrade virus particles or virus components upon a viral infection, while cooperating with anti-viral interferon response to inhibit the virus replication. Degraded virus-derived antigens can be presented to T lymphocytes to orchestrate the adaptive immune response. Nevertheless, some viruses have evolved the ability to inhibit autophagy in order to evade degradation and immune responses. Others induce autophagy, but then hijack autophagosomes as a replication site, or hijack the secretion autophagy pathway to promote maturation and egress of virus particles, thereby increasing replication and transmission efficiency. Interestingly, different viruses have unique strategies to counteract different types of selective autophagy, such as exploiting autophagy to regulate organelle degradation, metabolic processes, and immune responses. In short, this review focuses on the interaction between autophagy and viruses, explaining how autophagy serves multiple roles in viral infection, with either proviral or antiviral functions.

Ciliogenesis membrane dynamics and organization

Ciliogenesis is a complex multistep process used to describe assembly of cilia and flagella. These organelles play essential roles in motility and signaling on the surface of cells. Cilia are built at the distal ends of centrioles through the formation of an axoneme that is surrounded by the ciliary membrane. As is the case in the biogenesis of other cellular organelles, regulators of membrane trafficking play essential roles in ciliogenesis, albeit with a unique feature that membranes are organized around microtubule-based structures. Membrane association with the distal end of the centriole is a critical initiating step for ciliogenesis. Studies of this process in different cell types suggests that a singular mechanism may not be utilized to initiate cilium assembly. In this review, we focus on recent insights into cilium biogenesis and the roles membrane trafficking regulators play in described ciliogenesis mechanisms with relevance to human disease.

Autophagy induced by Rab1a-ULK1 interaction promotes porcine reproductive and respiratory syndrome virus replication

Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus from the Nidovirales order, continues to be a threat to the swine industry worldwide causing reproductive failure and respiratory disease in pigs. Previous studies have demonstrated that autophagy plays a positive role in PRRSV replication. However, its mechanism is less clearly understood. Herein, we report first that the protein level of Rab1a, a member of the Ras superfamily of GTPases, is upregulated during PRRSV infection. Subsequently, we demonstrate that Rab1a enhances PRRSV replication through an autophagy pathway as evidenced by knocking down the autophagy-related 7 (ATG7) gene, the key adaptor of autophagy. Importantly, we reveal that Rab1a interacts with ULK1 and promotes ULK1 phosphorylation dependent on its GTP-binding activity. These data indicate that PRRSV utilizes the Rab1a-ULK1 complex to initiate autophagy, which, in turn, benefits viral replication. These findings further highlight the interplay between PRRSV replication and the autophagy pathway, deepening our understanding of PRRSV infection.

Clustering analysis revealed the autophagy classification and potential autophagy regulators' sensitivity of pancreatic cancer based on multi-omics data

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy and is unresponsive to conventional therapeutic modalities due to its high heterogeneity, expounding the necessity, and priority of searching for effective biomarkers and drugs. Autophagy, as an evolutionarily conserved biological process, is upregulated in PDAC and its regulation is linked to a poor prognosis. Increased autophagy sequestered MHC-I on PDAC cells and weaken the antigen presentation and antitumor immune response, indicating the potential therapeutic strategies of autophagy inhibitors.

METHODS

By performing 10 state-of-the-art multi-omics clustering algorithms, we constructed a robust PDAC classification model to reveal the autophagy-related genes among different subgroups.

OUTCOMES

After building a more comprehensive regulating network for potential autophagy regulators exploration, we concluded the top 20 autophagy-related hub genes (GAPDH, MAPK3, RHEB, SQSTM1, EIF2S1, RAB5A, CTSD, MAP1LC3B, RAB7A, RAB11A, FADD, CFKN2A, HSP90AB1, VEGFA, RELA, DDIT3, HSPA5, BCL2L1, BAG3, and ERBB2), six miRNAs, five transcription factors, and five immune infiltrated cells as biomarkers. The drug sensitivity database was screened based on the biomarkers to predict possible drug-targeting signal pathways, hoping to yield novel insights, and promote the progress of the anticancer therapeutic strategy.

CONCLUSION

We succefully constructed an autophagy-related mRNA/miRNA/TF/Immune cells network based on a 10 state-of art algorithm multi-omics analysis, and screened the drug sensitivity dataset for detecting potential signal pathway which might be possible autophagy modulators' targets.

Secretory autophagy promotes Rab37-mediated exocytosis of tissue inhibitor of metalloproteinase 1

BACKGROUND

Rab37-mediated exocytosis of tissue inhibitor of metalloproteinase 1 (TIMP1), an inflammatory cytokine, under serum-depleted conditions which leads to suppression of lung cancer cell metastasis has been reported. Starvation is also a stimulus of autophagic activity. Herein, we reveal that starvation activates Rab37 and induces autophagy.

METHODS

We used an overexpression/knockdown system to determine the relationship between autophagy and Rab37 in vitro and in vivo. The autophagy activity was detected by immunoblotting, transmission electron microscope, autophagosome purification, and immunofluorescence under the confocal microscope. Lung-to-lung metastasis mouse model was used to clarify the role of autophagy and Rab37 in lung cancer. Clinical lung cancer patient specimens and an online big database were analyzed.

RESULTS

Initially, we demonstrated that active-form Rab37 increased LC3-II protein level (the marker of autophagosome) and TIMP1 secretion. Accordingly, silencing of Rab37 gene expression alleviated Rab37 and LC3-II levels as well as TIMP1 secretion, and induction of autophagy could not increase TIMP1 exocytosis under such conditions. Moreover, silencing the Atg5 or Atg7 gene of lung cancer cells harboring active-mutant Rab37 (Q89L) led to decreased autophagy activity and TIMP1 secretion. In the lung-to-lung metastasis mouse model, increased TIMP1 expression accompanied by amiodarone-induced autophagy led to decreased tumor nodules and cancer cell metastasis. These phenomena were reversed by silencing the Atg5 or Atg7 gene. Notably, increasing autophagy activity alone showed no effect on TIMP1 secretion under either Rab37 or Sec22b silencing conditions. We further detected colocalization of LC3 with either Rab37 or TIMP1, identified Rab37 and Sec22b proteins in the purified autophagosomes of the lung cancer cells harboring the active-form Rab37 gene, and confirmed that these proteins are involved in the secretion of TIMP1. We reveal that autophagic activity was significantly lower in the tumors compared to the non-tumor parts and was associated with the overall lung cancer patient survival rate.

CONCLUSIONS

We are the first to report that autophagy plays a promoting role in TIMP1 secretion and metastasis in a Rab37-dependent manner in lung cancer cells and the lung-to-lung mouse model.

Small GTPase Rab40C is upregulated by 20-hydroxyecdysone and insulin pathways to regulate ovarian development and fecundity

The insulin and 20-hydroxyecdysone (20E) pathways coordinately regulate insect vitellogenesis and ovarian development. However, the detailed molecular mechanisms such as the genes mediating the cooperation of the interaction of these 2 pathways in regulating insect reproductive development are not well understood. In the present study, a small GTPase, Rab40C, was identified from the notorious agricultural pest Bactrocera dorsalis. In addition to the well-known RAB domain, it also has a unique SOCS-box domain, which is different from other Rab-GTPases. Moreover, we found that Rab40C was enriched in the ovaries of sexually mature females. RNA interference (RNAi)-mediated knockdown of BdRab40C resulted in a decrease in vitellogenin synthesis, underdeveloped ovaries, and low fertility. Furthermore, depletion of insulin receptor InR or the heterodimer receptor of 20E (EcR or USP) by RNAi significantly decreased the transcription of BdRab40C and resulted in lower fecundity. Further studies revealed that the transcription of BdRab40C could be upregulated by the injection of insulin or 20E. These results indicate that Rab40C participates in the insulin and 20E pathways to coordinately regulate reproduction in B. dorsalis. Our results not only provide new insights into the insulin- and 20E-stimulated regulatory pathways controlling female reproduction in insects but also contribute to the development of potential eco-friendly strategies for pest control.

Intercellular transfer of activated STING triggered by RAB22A-mediated non-canonical autophagy promotes antitumor immunity

STING, an endoplasmic reticulum (ER) transmembrane protein, mediates innate immune activation upon cGAMP stimulation and is degraded through autophagy. Here, we report that activated STING could be transferred between cells to promote antitumor immunity, a process triggered by RAB22A-mediated non-canonical autophagy. Mechanistically, RAB22A engages PI4K2A to generate PI4P that recruits the Atg12-Atg5-Atg16L1 complex, inducing the formation of ER-derived RAB22A-mediated non-canonical autophagosome, in which STING activated by agonists or chemoradiotherapy is packaged. This RAB22A-induced autophagosome fuses with RAB22A-positive early endosome, generating a new organelle that we name Rafeesome (RAB22A-mediated non-canonical autophagosome fused with early endosome). Meanwhile, RAB22A inactivates RAB7 to suppress the fusion of Rafeesome with lysosome, thereby enabling the secretion of the inner vesicle of the autophagosome bearing activated STING as a new type of extracellular vesicle that we define as R-EV (RAB22A-induced extracellular vesicle). Activated STING-containing R-EVs induce IFNβ release from recipient cells to the tumor microenvironment, promoting antitumor immunity. Consistently, RAB22A enhances the antitumor effect of the STING agonist diABZI in mice, and a high RAB22A level predicts good survival in nasopharyngeal cancer patients treated with chemoradiotherapy. Our findings reveal that Rafeesome regulates the intercellular transfer of activated STING to trigger and spread antitumor immunity, and that the inner vesicle of non-canonical autophagosome originated from ER is secreted as R-EV, providing a new perspective for understanding the intercellular communication of organelle membrane proteins.

Melatonin Attenuates Ischemic-like Cell Injury by Promoting Autophagosome Maturation via the Sirt1/FoxO1/Rab7 Axis in Hippocampal HT22 Cells and in Organotypic Cultures

Dysfunctional autophagy is linked to neuronal damage in ischemia/reperfusion injury. The Ras-related protein 7 (Rab7), a member of the Rab family of small GTPases, appears crucial for the progression of the autophagic flux, and its activity is strictly interconnected with the histone deacetylase Silent information regulator 1 (Sirt1) and transcription factor Forkhead box class O1 (FoxO1). The present study assessed the neuroprotective role of melatonin in the modulation of the Sirt1/FoxO1/Rab7 axis in HT22 cells and organotypic hippocampal cultures exposed to oxygen-glucose deprivation followed by reoxygenation (OGD/R). The results showed that melatonin re-established physiological levels of autophagy and reduced propidium iodide-positive cells, speeding up autophagosome (AP) maturation and increasing lysosomal activity. Our study revealed that melatonin modulates autophagic pathways, increasing the expression of both Rab7 and FoxO1 and restoring the Sirt1 expression affected by OGD/R. In addition, the Sirt1 inhibitor EX-527 significantly reduced Rab7, Sirt1, and FoxO1 expression, as well as autolysosomes formation, and blocked the neuroprotective effect of melatonin. Overall, our findings provide, for the first time, new insights into the neuroprotective role of melatonin against ischemic injury through the activation of the Sirt1/FoxO1/Rab7 axis.

Altered extracellular mRNA communication in postpartum depression is associated with decreased autophagy

We investigated whether extracellular RNA communication, which is a recently discovered mode of intercellular communication that is involved in a variety of important biological processes including pregnancy, is associated with postpartum depression (PPD). Extracellular RNA communication is increased during pregnancy and is involved in embryo implantation, uterine spiral artery remodeling, parturition, preterm birth, immunity, and the inflammatory response. Since immune anomalies are associated with PPD, we characterized the mRNA content of extracellular vesicles (EV) in a cohort of prospectively collected blood plasma samples at six time-points throughout pregnancy and the postpartum (2nd trimester, 3rd trimester, 2 weeks postpartum, 6 weeks postpartum, 3 months postpartum, and 6 months postpartum) in an academic medical setting from women who went on to develop PPD (N = 7, defined as euthymic in pregnancy with postpartum-onset depressive symptoms assessed by Edinburgh Postnatal Depression Scale ≥13 at any postpartum time point) and matched unaffected controls (N = 7, defined as euthymic throughout pregnancy and postpartum). Blood samples were available for all participants at the T2 and W6 timepoints, with fewer samples available at other time points. This analysis revealed that EV mRNA levels during pregnancy and the postpartum period were extensively altered in women who went on to develop PPD. Gene set enrichment analysis revealed that mRNAs associated with autophagy were decreased in PPD cases. In contrast, EV mRNAs from ribosomes and mitochondria, two organelles that are selectively targeted by autophagy, were elevated in PPD cases. Cellular deconvolution analysis discovered that EV mRNAs associated with PPD originated from monocytes and macrophages. Quantitative PCR analysis for four relevant genes in another cohort replicated these findings and confirmed that extracellular RNA levels are altered in PPD. We demonstrate that EV mRNA communication is robustly altered during pregnancy and the postpartum period in women who go on to develop PPD. Our work also establishes a direct link between reduced autophagy and PPD in patient samples. These data warrant investigating the feasibility of developing EV mRNA based biomarkers and therapeutic agents for PPD.

Deciphering the interplay between autophagy and polarity in epithelial tubulogenesis

The Metazoan complexity arises from a primary building block, the epithelium, which comprises a layer of polarized cells that divide the organism into compartments. Most of these body compartments are organs formed by epithelial tubes that enclose an internal hollow space or lumen. Over the last decades, multiple studies have unmasked the paramount events required to form this lumen de novo. In epithelial cells, these events mainly involve recognizing external clues, establishing and maintaining apicobasal polarity, endo-lysosomal trafficking, and expanding the created lumen. Although canonical autophagy has been classically considered a catabolic process needed for cell survival, multiple studies have also emphasized its crucial role in epithelial polarity, morphogenesis and cellular homeostasis. Furthermore, non-canonical autophagy pathways have been recently discovered as atypical secretory routes. Both canonical and non-canonical pathways play essential roles in epithelial polarity and lumen formation. This review addresses how the molecular machinery for epithelial polarity and autophagy interplay in different processes and how autophagy functions influence lumenogenesis, emphasizing its role in the lumen formation key events.

Age-related Huntington's disease progression modeled in directly reprogrammed patient-derived striatal neurons highlights impaired autophagy

Huntington's disease (HD) is an inherited neurodegenerative disorder with adult-onset clinical symptoms, but the mechanism by which aging drives the onset of neurodegeneration in patients with HD remains unclear. In this study we examined striatal medium spiny neurons (MSNs) directly reprogrammed from fibroblasts of patients with HD to model the age-dependent onset of pathology. We found that pronounced neuronal death occurred selectively in reprogrammed MSNs from symptomatic patients with HD (HD-MSNs) compared to MSNs derived from younger, pre-symptomatic patients (pre-HD-MSNs) and control MSNs from age-matched healthy individuals. We observed age-associated alterations in chromatin accessibility between HD-MSNs and pre-HD-MSNs and identified miR-29b-3p, whose age-associated upregulation promotes HD-MSN degeneration by impairing autophagic function through human-specific targeting of the STAT3 3' untranslated region. Reducing miR-29b-3p or chemically promoting autophagy increased the resilience of HD-MSNs against neurodegeneration. Our results demonstrate miRNA upregulation with aging in HD as a detrimental process driving MSN degeneration and potential approaches for enhancing autophagy and resilience of HD-MSNs.

Co-alterations of circadian clock gene transcripts in human placenta in preeclampsia

Pre-eclampsia (PE) is a hypertensive condition that occurs during pregnancy and complicates up to 4% of pregnancies. PE exhibits several circadian-related characteristics, and the placenta possesses a functioning molecular clock. We examined the associations of 17 core circadian gene transcripts in placenta with PE vs. non-PE (a mixture of pregnant women with term, preterm, small-for-gestational-age, or chorioamnionitis) using two independent gene expression datasets: GSE75010-157 (80 PE vs. 77 non-PE) and GSE75010-173 (77 PE and 96 non-PE). We found a robust difference in circadian gene expression between PE and non-PE across the two datasets, where CRY1 mRNA increases and NR1D2 and PER3 transcripts decrease in PE placenta. Gene set variation analysis revealed an interplay between co-alterations of circadian clock genes and PE with altered hypoxia, cell migration/invasion, autophagy, and membrane trafficking pathways. Using human placental trophoblast HTR-8 cells, we show that CRY1/2 and NR1D1/2 regulate trophoblast migration. A subgroup study including only term samples demonstrated that CLOCK, NR1D2, and PER3 transcripts were simultaneously decreased in PE placenta, a finding supported by CLOCK protein downregulation in an independent cohort of human term PE placenta samples. These findings provide novel insights into the roles of the molecular clock in the pathogenesis of PE.

Transcriptomic and epigenomic landscapes of Alzheimer's disease evidence mitochondrial-related pathways

Alzheimers disease (AD) is the main cause of dementia and it is defined by cognitive decline coupled to extracellular deposit of amyloid-beta protein and intracellular hyperphosphorylation of tau protein. Historically, efforts to target such hallmarks have failed in numerous clinical trials. In addition to these hallmark-targeted approaches, several clinical trials focus on other AD pathological processes, such as inflammation, mitochondrial dysfunction, and oxidative stress. Mitochondria and mitochondrial-related mechanisms have become an attractive target for disease-modifying strategies, as mitochondrial dysfunction prior to clinical onset has been widely described in AD patients and AD animal models. Mitochondrial function relies on both the nuclear and mitochondrial genome. Findings from omics technologies have shed light on AD pathophysiology at different levels (e.g., epigenome, transcriptome and proteome). Most of these studies have focused on the nuclear-encoded components. The first part of this review provides an updated overview of the mechanisms that regulate mitochondrial gene expression and function. The second part of this review focuses on evidence of mitochondrial dysfunction in AD. We have focused on published findings and datasets that study AD. We analyzed published data and provide examples for mitochondrial-related pathways. These pathways are strikingly dysregulated in AD neurons and glia in sex-, cell- and disease stage-specific manners. Analysis of mitochondrial omics data highlights the involvement of mitochondria in AD, providing a rationale for further disease modeling and drug targeting.

Gasdermin B over-expression modulates HER2-targeted therapy resistance by inducing protective autophagy through Rab7 activation

Background

Gasdermin B (GSDMB) over-expression promotes poor prognosis and aggressive behavior in HER2 breast cancer by increasing resistance to therapy. Decoding the molecular mechanism of GSDMB-mediated drug resistance is crucial to identify novel effective targeted treatments for HER2/GSDMB aggressive tumors.

Methods

Different in vitro approaches (immunoblot, qRT-PCR, flow cytometry, proteomic analysis, immunoprecipitation, and confocal/electron microscopy) were performed in HER2 breast and gastroesophageal carcinoma cell models. Results were then validated using in vivo preclinical animal models and analyzing human breast and gastric cancer samples.

Results

GSDMB up-regulation renders HER2 cancer cells more resistant to anti-HER2 agents by promoting protective autophagy. Accordingly, the combination of lapatinib with the autophagy inhibitor chloroquine increases the therapeutic response of GSDMB-positive cancers in vitro and in zebrafish and mice tumor xenograft in vivo models. Mechanistically, GSDMB N-terminal domain interacts with the key components of the autophagy machinery LC3B and Rab7, facilitating the Rab7 activation during pro-survival autophagy in response to anti-HER2 therapies. Finally, we validated these results in clinical samples where GSDMB/Rab7/LC3B co-expression associates significantly with relapse in HER2 breast and gastric cancers.

Conclusion

Our findings uncover for the first time a functional link between GSDMB over-expression and protective autophagy in response to HER2-targeted therapies. GSDMB behaves like an autophagy adaptor and plays a pivotal role in modulating autophagosome maturation through Rab7 activation. Finally, our results provide a new and accessible therapeutic approach for HER2/GSDMB + cancers with adverse clinical outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02497-w.

Rab11a promotes the malignant progression of ovarian cancer by inducing autophagy

BACKGROUND

Rab11a is a novel identified tumorigenic factor involved in different cancers.

OBJECTIVE

This study aimed to assess the biological function of Rab11a in ovarian cancer (OC).

METHODS

GEPIA database and real-time PCR were used to determine Rab11a expression in OC tissues and normal ovarian tissues. CCK-8, cell cycle, wound healing, transwell, and enzyme linked immunosorbent assay were used to detect the effects of Rab11a knockdown or overexpression on the proliferation, migration, and invasion of OC cells. Western blot analysis of autophagy-related markers and immunofluorescence staining of LC3 were performed to determine autophagy induction in Rab11a-silenced or overexpressed OC cells. Moreover, autophagy inhibitor 3-MA was employed to clarify the effects of Rab11a-regulated autophagy on the malignant phenotypes of OC cells.

RESULTS

The mRNA level of Rab11a was increased in tumor tissues from OC patients as compared to the normal ovarian tissues. Knockdown of Rab11a in OVCAR-3 cells inhibited the growth of OC cells and led to cell cycle arrest, accompanied by reduced expression of PCNA and Cyclin D1. Rab11a deficiency suppressed migration and invasion of OC cells, accompanied by decreased secretion of MMP-2 and MMP-9. Silence of Rab11a impeded autophagy induction, as evidenced by decreased LC3 puncta formation, reduced abundance of LC3II and Beclin1, and increased p62 protein expression. In contrast, the ectopic expression of Rab11a in A2780 cells exerted opposite effects. Interestingly, autophagy inhibitor 3-MA abolished the effects of Rab11a overexpression on autophagy, proliferation, migration, and invasion.

CONCLUSIONS

Rab11a promotes the malignant phenotypes of OC cells by inducing autophagy.

Host Cell Signatures of the Envelopment Site within Beta-Herpes Virions

Beta-herpesvirus infection completely reorganizes the membrane system of the cell. This system is maintained by the spatiotemporal arrangement of more than 3000 cellular proteins that continuously adapt the configuration of membrane organelles according to cellular needs. Beta-herpesvirus infection establishes a new configuration known as the assembly compartment (AC). The AC membranes are loaded with virus-encoded proteins during the long replication cycle and used for the final envelopment of the newly formed capsids to form infectious virions. The identity of the envelopment membranes is still largely unknown. Electron microscopy and immunofluorescence studies suggest that the envelopment occurs as a membrane wrapping around the capsids, similar to the growth of phagophores, in the area of the AC with the membrane identities of early/recycling endosomes and the trans-Golgi network. During wrapping, host cell proteins that define the identity and shape of these membranes are captured along with the capsids and incorporated into the virions as host cell signatures. In this report, we reviewed the existing information on host cell signatures in human cytomegalovirus (HCMV) virions. We analyzed the published proteomes of the HCMV virion preparations that identified a large number of host cell proteins. Virion purification methods are not yet advanced enough to separate all of the components of the rich extracellular material, including the large amounts of non-vesicular extracellular particles (NVEPs). Therefore, we used the proteomic data from large and small extracellular vesicles (lEVs and sEVs) and NVEPs to filter out the host cell proteins identified in the viral proteomes. Using these filters, we were able to narrow down the analysis of the host cell signatures within the virions and determine that envelopment likely occurs at the membranes derived from the tubular recycling endosomes. Many of these signatures were also found at the autophagosomes, suggesting that the CMV-infected cell forms membrane organelles with phagophore growth properties using early endosomal host cell machinery that coordinates endosomal recycling.

Autophagy in renal fibrosis: Protection or promotion?

Autophagy is a process that degrades endogenous cellular protein aggregates and damaged organelles via the lysosomal pathway to maintain cellular homeostasis and energy production. Baseline autophagy in the kidney, which serves as a quality control system, is essential for cellular metabolism and organelle homeostasis. Renal fibrosis is the ultimate pathological manifestation of progressive chronic kidney disease. In several experimental models of renal fibrosis, different time points, stimulus intensities, factors, and molecular mechanisms mediating the upregulation or downregulation of autophagy may have different effects on renal fibrosis. Autophagy occurring in a single lesion may also exert several distinct biological effects on renal fibrosis. Thus, whether autophagy prevents or facilitates renal fibrosis remains a complex and challenging question. This review explores the different effects of the dual regulatory function of autophagy on renal fibrosis in different renal fibrosis models, providing ideas for future work in related basic and clinical research.

JIB-04, a histone demethylase Jumonji C domain inhibitor, regulates phenotypic switching of vascular smooth muscle cells

Background

Vascular smooth muscle cell (VSMC) phenotype switching is critical for neointima formation, which is the major cause of restenosis after stenting or coronary artery bypass grafting. However, the epigenetic mechanisms regulating phenotype switching of VSMCs, especially histone methylation, are not well understood. As a main component of histone lysine demethylases, Jumonji demethylases might be involved in VSMC phenotype switching and neointima formation.

Methods and results

A mouse carotid injury model and VSMC proliferation model were constructed to investigate the relationship between histone methylation of H3K36 (downstream target molecule of Jumonji demethylase) and neointima formation. We found that the methylation levels of H3K36 negatively correlated with VSMC proliferation and neointima formation. Next, we revealed that JIB-04 (a pan-inhibitor of the Jumonji demethylase superfamily) could increase the methylation levels of H3K36. Furthermore, we found that JIB-04 obviously inhibited HASMC proliferation, and a cell cycle assay showed that JIB-04 caused G2/M phase arrest in HASMCs by inhibiting the phosphorylation of RB and CDC2 and promoting the phosphorylation of CHK1. Moreover, JIB-04 inhibited the expression of MMP2 to suppress the migration of HASMCs and repressed the expression of contraction-related genes. RNA sequencing analysis showed that the biological processes associated with the cell cycle and autophagy were enriched by using Gene Ontology analysis after HASMCs were treated with JIB-04. Furthermore, we demonstrated that JIB-04 impairs autophagic flux by downregulating STX17 and RAB7 expression to inhibit the fusion of autophagosomes and lysosomes.

Conclusion

JIB-04 suppresses the proliferation, migration, and contractile phenotype of HASMCs by inhibiting autophagic flux, which indicates that JIB-04 is a promising reagent for the treatment of neointima formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01321-8.

The Role of Rab Proteins in Parkinson's Disease Synaptopathy

In patients affected by Parkinson's disease (PD), the most common neurodegenerative movement disorder, the brain is characterized by the loss of dopaminergic neurons in the nigrostriatal system, leading to dyshomeostasis of the basal ganglia network activity that is linked to motility dysfunction. PD mostly arises as an age-associated sporadic disease, but several genetic forms also exist. Compelling evidence supports that synaptic damage and dysfunction characterize the very early phases of either sporadic or genetic forms of PD and that this early PD synaptopathy drives retrograde terminal-to-cell body degeneration, culminating in neuronal loss. The Ras-associated binding protein (Rab) family of small GTPases, which is involved in the maintenance of neuronal vesicular trafficking, synaptic architecture and function in the central nervous system, has recently emerged among the major players in PD synaptopathy. In this manuscript, we provide an overview of the main findings supporting the involvement of Rabs in either sporadic or genetic PD pathophysiology, and we highlight how Rab alterations participate in the onset of early synaptic damage and dysfunction.

Recent advances in conventional and unconventional vesicular secretion pathways in the tumor microenvironment

All cells in the changing tumor microenvironment (TME) need a class of checkpoints to regulate the balance among exocytosis, endocytosis, recycling and degradation. The vesicular trafficking and secretion pathways regulated by the small Rab GTPases and their effectors convey cell growth and migration signals and function as meditators of intercellular communication and molecular transfer. Recent advances suggest that Rab proteins govern conventional and unconventional vesicular secretion pathways by trafficking widely diverse cargoes and substrates in remodeling TME. The mechanisms underlying the regulation of conventional and unconventional vesicular secretion pathways, their action modes and impacts on the cancer and stromal cells have been the focus of much attention for the past two decades. In this review, we discuss the current understanding of vesicular secretion pathways in TME. We begin with an overview of the structure, regulation, substrate recognition and subcellular localization of vesicular secretion pathways. We then systematically discuss how the three fundamental vesicular secretion processes respond to extracellular cues in TME. These processes are the conventional protein secretion via the endoplasmic reticulum-Golgi apparatus route and two types of unconventional protein secretion via extracellular vesicles and secretory autophagy. The latest advances and future directions in vesicular secretion-involved interplays between tumor cells, stromal cell and host immunity are also described.

The Rab GTPase in the heart: Pivotal roles in development and disease

Rab proteins are a family of small GTPases that function as molecular switches of intracellular vesicle formation and membrane trafficking. As a key factor, Rab GTPase participates in autophagy and protein transport and acts as the central hub of membrane trafficking in eukaryotes. The role of Rab GTPase in neurodegenerative disorders, such as Alzheimer's and Parkinson's, has been extensively investigated; however, its implication in cardiovascular embryogenesis and diseases remains largely unknown. In this review, we summarize previous findings and reveal their importance in the onset and progression of cardiac diseases, as well as their emergence as potential therapeutic targets for cardiovascular disease.

Fine-tuning cell organelle dynamics during mitosis by small GTPases

During mitosis, the allocation of genetic material concurs with organelle transformation and distribution. The coordination of genetic material inheritance with organelle dynamics directs accurate mitotic progression, cell fate determination, and organismal homeostasis. Small GTPases belonging to the Ras superfamily regulate various cell organelles during division. Being the key regulators of membrane dynamics, the dysregulation of small GTPases is widely associated with cell organelle disruption in neoplastic and non-neoplastic diseases, such as cancer and Alzheimer's disease. Recent discoveries shed light on the molecular properties of small GTPases as sophisticated modulators of a remarkably complex and perfect adaptors for rapid structure reformation. This review collects current knowledge on small GTPases in the regulation of cell organelles during mitosis and highlights the mediator role of small GTPase in transducing cell cycle signaling to organelle dynamics during mitosis.

The Rab11-regulated endocytic pathway and BDNF/TrkB signaling: Roles in plasticity changes and neurodegenerative diseases

Neurons are highly polarized cells that rely on the intracellular transport of organelles. This process is regulated by molecular motors such as dynein and kinesins and the Rab family of monomeric GTPases that together help move cargo along microtubules in dendrites, somas, and axons. Rab5-Rab11 GTPases regulate receptor trafficking along early-recycling endosomes, which is a process that determines the intracellular signaling output of different signaling pathways, including those triggered by BDNF binding to its tyrosine kinase receptor TrkB. BDNF is a well-recognized neurotrophic factor that regulates experience-dependent plasticity in different circuits in the brain. The internalization of the BDNF/TrkB complex results in signaling endosomes that allow local signaling in dendrites and presynaptic terminals, nuclear signaling in somas and dynein-mediated long-distance signaling from axons to cell bodies. In this review, we briefly discuss the organization of the endocytic pathway and how Rab11-recycling endosomes interact with other endomembrane systems. We further expand upon the roles of the Rab11-recycling pathway in neuronal plasticity. Then, we discuss the BDNF/TrkB signaling pathways and their functional relationships with the postendocytic trafficking of BDNF, including axonal transport, emphasizing the role of BDNF signaling endosomes, particularly Rab5-Rab11 endosomes, in neuronal plasticity. Finally, we discuss the evidence indicating that the dysfunction of the early-recycling pathway impairs BDNF signaling, contributing to several neurodegenerative diseases.

Xiaoyaosan Exerts Antidepressant-Like Effect by Regulating Autophagy Involves the Expression of GLUT4 in the Mice Hypothalamic Neurons

Many studies have proven that autophagy plays a pivotal role in the development of depression and it also affects the expression of GLUT4 in the hypothalamus. Xiaoyaosan has been shown to exert antidepressant effects in a variety of ways, but its underlying mechanism by which Xiaoyaosan regulates autophagy as well as GLUT4 in the hypothalamus remains unclear. Thus, in this study, we established a mouse model of depression induced by chronic unpredictable mild stress (CUMS), and set up autophagy blockade as a control to explore whether Xiaoyaosan exerts antidepressant effect by affecting autophagy. We examined the effects of Xiaoyaosan on behaviors exhibited during the open field test, tail suspension test and sucrose preference test, and the changes in autophagy in hypothalamic neurons as well as changes in GLUT4 and the related indicators of glucose metabolism in CUMS-induced depressive mouse model. We found that CUMS- and 3-MA-induced mice exhibited depressive-like behavioral changes, with decreased LC3 expression and increased p62 expression, suggesting decreased levels of autophagy in the mouse hypothalamus. The expression of GLUT4 was also decreased, and it was closely related to the level of autophagy through Rab8 and Rab10. Nevertheless, after the intervention of Xiaoyaosan, the above changes were effectively reversed. These results show that Xiaoyaosan can regulate the autophagy in hypothalamic neurons and the expression of GLUT4 in depressed mice.

Autophagy Dysfunction in ALS: from Transport to Protein Degradation

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting upper and lower motor neurons (MNs). Since the identification of the first ALS mutation in 1993, more than 40 genes have been associated with the disorder. The most frequent genetic causes of ALS are represented by mutated genes whose products challenge proteostasis, becoming unable to properly fold and consequently aggregating into inclusions that impose proteotoxic stress on affected cells. In this context, increasing evidence supports the central role played by autophagy dysfunctions in the pathogenesis of ALS. Indeed, in early stages of disease, high levels of proteins involved in autophagy are present in ALS MNs; but at the same time, with neurodegeneration progression, autophagy-mediated degradation decreases, often as a result of the accumulation of toxic protein aggregates in affected cells. Autophagy is a complex multistep pathway that has a central role in maintaining cellular homeostasis. Several proteins are involved in its tight regulation, and importantly a relevant fraction of ALS-related genes encodes products that directly take part in autophagy, further underlining the relevance of this key protein degradation system in disease onset and progression. In this review, we report the most relevant findings concerning ALS genes whose products are involved in the several steps of the autophagic pathway, from phagophore formation to autophagosome maturation and transport and finally to substrate degradation.

Novel Effects of Statins on Cancer via Autophagy

Cancer is one of the main causes of death globally. Most of the molecular mechanisms underlying cancer are marked by complex aberrations that activate the critical cell-signaling pathways that play a pivotal role in cell metabolism, tumor development, cytoskeletal reorganization, and metastasis. The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of the rapamycin (PI3K/AKT/mTOR) pathway is one of the main signaling pathways involved in carcinogenesis and metastasis. Autophagy, a cellular pathway that delivers cytoplasmic components to lysosomes for degradation, plays a dual role in cancer, as either a tumor promoter or a tumor suppressor, depending on the stage of the carcinogenesis. Statins are the group of drugs of choice to lower the level of low-density lipoprotein (LDL) cholesterol in the blood. Experimental and clinical data suggest the potential of statins in the treatment of cancer. In vitro and in vivo studies have demonstrated the molecular mechanisms through which statins inhibit the proliferation and metastasis of cancer cells in different types of cancer. The anticancer properties of statins have been shown to result in the suppression of tumor growth, the induction of apoptosis, and autophagy. This literature review shows the dual role of the autophagic process in cancer and the latest scientific evidence related to the inducing effect exerted by statins on autophagy, which could explain their anticancer potential.

Exploration of the Shared Gene and Molecular Mechanisms Between Endometriosis and Recurrent Pregnancy Loss

Endometriosis (EMs) is a common benign gynecological disease in women of childbearing age, which usually causes pelvic pain, secondary dysmenorrhea, and infertility. EMs has been linked to recurrent pregnancy loss (RPL) in epidemiological data. The relationship of both, however, remains unknown. The purpose of this study is to explore the underlying pathological mechanisms between EMs and RPL. We searched Gene Expression Omnibus (GEO) database to obtain omics data of EMs and RPL. Co-expression modules for EMs and RPL were investigated by using weighted gene co-expression network analysis (WGCNA). The intersections of gene modules with the strong correlation to EMs or RPL obtained by WGCNA analysis were considered as shared genes. MicroRNAs (miRNAs) and their corresponding target genes linked to EMs and RPL were found though the Human MicroRNA Disease Database (HMDD) and the miRTarbase database. Finally, we constructed miRNAs-mRNAs regulatory networks associated with the two disorders by using the intersection of previously obtained target genes and shared genes. We discovered as significant modules for EMs and RPL, respectively, by WGCNA. The energy metabolism might be the common pathogenic mechanism of EMs and RPL, according to the findings of a Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. We discovered several target genes that might be linked to these two disorders, as well as the potential mechanisms. RAB8B, GNAQ, H2AFZ, SUGT1, and LEO1 could be therapeutic candidates for RPL and EMs. The PI3K-Akt signaling pathway and platelet activation were potentially involved in the mechanisms of EM-induced RPL. Our findings for the first time revealed the underlying pathological mechanisms of EM-induced RPL and identified several useful biomarkers and potential therapeutic targets.

FKBP8 is a novel molecule that participates in the regulation of the autophagic pathway

Autophagy is a homeostatic process by which misfolded proteins, organelles and cytoplasmic material are engulfed in autophagosomal vesicles and degraded through a lisosomal pathway. FKBP8 is a member of the FK506-binding proteins family (FKBP) usually found in mitochondria and the endoplasmic reticulum. This protein plays a critical role in cell functions such as protein trafficking and folding. In the present report we demonstrate that the depletion of FKBP8 abrogated autophagy activation induced by starvation, whereas the overexpression of this protein triggered the autophagy cascade. We found that FKBP8 co-localizes with ATG14L and BECN1, both members of the VPS34 lipid kinase complex, which regulates the initial steps in the autophagosome formation process. We have also demonstrated that FKBP8 is necessary for VPS34 activity. Our findings indicate that the regulatory function of FKBP8 in the autophagy process depends of its transmembrane domain. Surprisingly, this protein was not found in autophagosomal vesicles, which reinforces the notion that the FKBP8 only participates in the initial steps of the autophagosome formation process. Taken together, our data provide evidence that FKBP8 modulates the early steps of the autophagosome formation event by interacting with the VPS34 lipid kinase complex. SUMMARY: In this article, the protein FKBP38 is reported to be a novel modulator of the initial steps of the autophagic pathway, specifically in starvation-induced autophagy. FKBP38 interacts with the VPS34 lipid kinase complex, with the transmembrane domain of FKBP38 being critical for its biological function.

Rab33b-exocyst interaction mediates localized secretion for focal adhesion turnover and cell migration

Rab proteins are well known regulators of intracellular trafficking; however, more and more studies point to their function also in other cellular processes, including cell migration. In this work, we have performed an siRNA screen to identify Rab proteins that influence cell migration. The screen revealed Rab33b as the strongest candidate that affected cell motility. Rab33b has been previously reported to localize at the Golgi apparatus to regulate Golgi-to-ER retrograde trafficking and Golgi homeostasis. We revealed that Rab33b also mediates post-Golgi transport to the plasma membrane. We further identified Exoc6, a subunit of the exocyst complex, as an interactor of Rab33b. Moreover, our data indicate that Rab33b regulates focal adhesion dynamics by modulating the delivery of cargo such as integrins to focal adhesions. Altogether, our results demonstrate a role for Rab33b in cell migration by regulating the delivery of integrins to focal adhesions through the interaction with Exoc6.

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RNAi screen reveals a role for Rab33b in cell migration

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Rab33b influences focal adhesion dynamics

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Rab33b interacts with the exocyst subunit Exoc6

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Rab33b together with Exoc6 mediates the delivery of β1 integrin to adhesion points

Knockout of GGPPS1 restrains rab37-mediated autophagy in response to ventilator-induced lung injury

Mechanical ventilation may cause ventilator-induced lung injury (VILI) in patients requiring ventilator support. Inhibition of autophagy is an important approach to ameliorate VILI as it always enhances lung injury after exposure to various stress agents. This study aimed to further reveal the potential mechanisms underlying the effects of geranylgeranyl diphosphate synthase large subunit 1 (GGPPS1) knockout and autophagy in VILI using C57BL/6 mice with lung-specific GGPPS1 knockout that were subjected to mechanical ventilation. The results demonstrate that GGPPS1 knockout mice exhibit significantly attenuated VILI based on the histologic score, the lung wet-to-dry ratio, total protein levels, neutrophils in bronchoalveolar lavage fluid, and reduced levels of inflammatory cytokines. Importantly, the expression levels of autophagy markers were obviously decreased in GGPPS1 knockout mice compared with wild-type mice. The inhibitory effects of GGPPS1 knockout on autophagy were further confirmed by measuring the ultrastructural change of lung tissues under transmission electron microscopy. In addition, knockdown of GGPPS1 in RAW264.7 cells reduced cyclic stretch-induced inflammation and autophagy. The benefits of GGPPS1 knockout for VILI can be partially eliminated through treatment with rapamycin. Further analysis revealed that Rab37 was significantly downregulated in GGPPS1 knockout mice after mechanical ventilation, while it was highly expressed in the control group. Simultaneously, Rab37 overexpression significantly enhances autophagy in cells that are treated with cyclin stretch, including GGPPS1 knockout cells. Collectively, our results indicate that GGPPS1 knockout results in reduced expression of Rab37 proteins, further restraining autophagy and VILI.

Molecular and cytological profiling of biological aging of mouse cochlear inner and outer hair cells

Age-related hearing loss (ARHL) negatively impacts quality of life in the elderly population. The prevalent cause of ARHL is loss of mechanosensitive cochlear hair cells (HCs). The molecular and cellular mechanisms of HC degeneration remain poorly understood. Using RNA-seq transcriptomic analyses of inner and outer HCs isolated from young and aged mice, we show that HC aging is associated with changes in key molecular processes, including transcription, DNA damage, autophagy, and oxidative stress, as well as genes related to HC specialization. At the cellular level, HC aging is characterized by loss of stereocilia, shrinkage of HC soma, and reduction in outer HC mechanical properties, suggesting that functional decline in mechanotransduction and cochlear amplification precedes HC loss and contributes to ARHL. Our study reveals molecular and cytological profiles of aging HCs and identifies genes such as Sod1, Sirt6, Jund, and Cbx3 as biomarkers and potential therapeutic targets for ameliorating ARHL.

Using RNA-seq, advanced imaging, and electrophysiology, Liu et al. reveal molecular and cytological profiles of aging cochlear hair cells. Their study also suggests that a functional decline in mechanotransduction and cochlear amplification precedes hair cell loss and contributes to age-related hearing loss.

Functional Diversity of Macropinocytosis

Eukaryotic cells are capable of internalizing different types of cargo by plasma membrane ruffling and forming vesicles in a process known as endocytosis. The most extensively characterized endocytic pathways are clathrin-coated pits, lipid raft/caveolae-mediated endocytosis, phagocytosis, and macropinocytosis. Macropinocytosis is unique among all the endocytic processes due to its nonselective internalization of extracellular fluid, solutes, and membrane in large endocytic vesicles known as macropinosomes with unique susceptibility toward Na+/H+ exchanger inhibitors. Range of cell types capable of macropinocytosis and known to play important role in different physiological processes, which include antigen presentation, nutrient sensing, migration, and signaling. Understanding the physiological function of macropinocytosis will be helpful in filling the gaps in our knowledge and which can be exploited to develop novel therapeutic targets. In this chapter, we discuss the different molecular mechanisms that initiate the process of macropinocytosis with special emphasis on proteins involved and their diversified role in different cell types.

Autophagy Modulators in Coronavirus Diseases: A Double Strike in Viral Burden and Inflammation

Coronaviruses are the etiologic agents of several diseases. Coronaviruses of critical medical importance are characterized by highly inflammatory pathophysiology, involving severe pulmonary impairment and infection of multiple cell types within the body. Here, we discuss the interplay between coronaviruses and autophagy regarding virus life cycle, cell resistance, and inflammation, highlighting distinct mechanisms by which autophagy restrains inflammatory responses, especially those involved in coronavirus pathogenesis. We also address different autophagy modulators available and the rationale for drug repurposing as an attractive adjunctive therapy. We focused on pharmaceuticals being tested in clinical trials with distinct mechanisms but with autophagy as a common target. These autophagy modulators act in cell resistance to virus infection and immunomodulation, providing a double-strike to prevent or treat severe disease development and death from coronaviruses diseases.

RAB26 contributes to the progression of non-small cell lung cancer after being transcriptionally activated by SMAD3

Non-small cell lung cancer (NSCLC) accounts for 85% of all cases of lung cancer, which constitutes the leading cause of cancer mortality. RAB26, a member of Rab GTPase superfamily, has been suggested to play a role in the tumorigenesis of NSCLC. The present work aimed to explore whether and how RAB26 contributed to the progression of NSCLC. NSCLC cell line A549 was transfection with short hairpin RNA (shRNA) or overexpression (Ov) vector to knockdown RAB26 or overexpress SMAD3, respectively. Then the malignant processes of A549 cells including proliferation, migration, invasion and apoptosis were evaluated by CCK-8, colony formation, wound-healing, transwell and TUNEL assays, respectively. Expression of proteins involved in these processes was measured by western blot. A549 xenograft mice model was established to confirm the effect of RAB26 silence on NSCLC progression in vivo. The relationship between RAB26 and SMAD3 was analyzed by bioinformatics and then verified by dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays. We found that silence of RAB26 inhibited the proliferation, migration and invasion but promoted apoptosis of A549 cells. In vivo studies revealed that the tumor growth of A549 xenograft was markedly suppressed upon RAB26 silence. Moreover, it was confirmed that SMAD3 bound to the promoter of RAB26 and enhance its expression. Finally, we observed that overexpression of SMAD3 significantly blocked the inhibitory effect of RAB26 silence on NSCLC progression. Collectively, RAB26 may contribute to the progression of NSCLC after being transcriptionally activated by SMAD3.

Incomplete autophagy: Trouble is a friend

Incomplete autophagy is an impaired self-eating process of intracellular macromolecules and organelles in which accumulated autophagosomes do not fuse with lysosomes for degradation, resulting in the blockage of autophagic flux. In this review, we summarized the literature over the past decade describing incomplete autophagy, and found that different from the double-edged sword effect of general autophagy on promoting cell survival or death, incomplete autophagy plays a crucial role in disrupting cellular homeostasis, and promotes only cell death. What matters is that incomplete autophagy is closely relevant to the pathogenesis and progression of various human diseases, which, meanwhile, intimately linking to the pharmacologic and toxicologic effects of several compounds. Here, we comprehensively reviewed the latest progress of incomplete autophagy on molecular mechanisms and signaling pathways. Moreover, implications of incomplete autophagy for pharmacotherapy are also discussed, which has great relevance for our understanding of the distinctive role of incomplete autophagy in cellular physiology and disease. Consequently, targeting incomplete autophagy may contribute to the development of novel generation therapeutic agents for diverse human diseases.