Transcriptional regulation of Annexin A2 promotes starvation-induced autophagy

The mammalian actin elongation factor ENAH/MENA contributes to autophagosome formation via its actin regulatory function

Macroautophagy/autophagy is a catabolic process crucial for degrading cytosolic components and damaged organelles to maintain cellular homeostasis, enabling cells to survive in extreme extracellular environments. ENAH/MENA, a member of the Ena/VASP protein family, functions as a highly efficient actin elongation factor. In this study, our objective was to explore the role of ENAH in the autophagy process. Initially, we demonstrated that depleting ENAH in cancer cells inhibits autophagosome formation. Subsequently, we observed ENAH's colocalization with MAP1LC3/LC3 during tumor cell starvation, dependent on actin cytoskeleton polymerization and the interaction between ENAH and BECN1 (beclin 1). Additionally, mammalian ATG9A formed a ring-like structure around ENAH-LC3 puncta during starvation, relying on actin cytoskeleton polymerization. Furthermore, ENAH's EVH1 and EVH2 domains were found to be indispensable for its colocalization with LC3 and BECN1, while the PRD domain played a crucial role in the formation of the ATG9A ring. Finally, our study revealed ENAH-led actin comet tails in autophagosome trafficking. In conclusion, our findings provide initial insights into the regulatory role of the mammalian actin elongation factor ENAH in autophagy.Abbreviations: 3-MA 3-methyladenine; ABPs actin-binding proteins; ATG autophagy related; ATG9A autophagy related 9A; Baf A1 bafilomycin A1; CM complete medium; CytERM endoplasmic reticulum signal-anchor membrane protein; Cyto D cytochalasin D; EBSS Earl's balanced salt solution; ENAH/MENA ENAH actin regulator; EVH1 Ena/VASP homology 1 domain; EVH2 Ena/VASP homology 2 domain; GAPDH glyceraldehyde-3-phosphate dehydrogenase; Lat B latrunculin B; LC3-I unlipidated form of LC3; LC3-II phosphatidylethanolamine-conjugated form of LC3; MAP1LC3/LC3 microtubule associated protein 1 light chain 3; mEGFP monomeric enhanced green fluorescent protein; mTagBFP2 monomeric Tag blue fluorescent protein 2; OSER organized smooth endoplasmic reticulum; PRD proline-rich domain; PtdIns3K class III phosphatidylinositol 3-kinase; WM wortmannin.

Stabilization of MOF (KAT8) by USP10 promotes esophageal squamous cell carcinoma proliferation and metastasis through epigenetic activation of ANXA2/Wnt signaling

Dysregulation of MOF (also known as MYST1, KAT8), a highly conserved H4K16 acetyltransferase, plays important roles in human cancers. However, its expression and function in esophageal squamous cell carcinoma (ESCC) remain unknown. Here, we report that MOF is highly expressed in ESCC tumors and predicts a worse prognosis. Depletion of MOF in ESCC significantly impedes tumor growth and metastasis both in vitro and in vivo, whereas ectopic expression of MOF but not catalytically inactive mutant (MOF-E350Q) promotes ESCC progression, suggesting that MOF acetyltransferase activity is crucial for its oncogenic activity. Further analysis reveals that USP10, a deubiquitinase highly expressed in ESCC, binds to and deubiquitinates MOF at lysine 410, which protects it from proteosome-dependent protein degradation. MOF stabilization by USP10 promotes H4K16ac enrichment in the ANXA2 promoter to stimulate ANXA2 transcription in a JUN-dependent manner, which subsequently activates Wnt/β-Catenin signaling to facilitate ESCC progression. Our findings highlight a novel USP10/MOF/ANXA2 axis as a promising therapeutic target for ESCC.

ANXA2 (annexin A2) is crucial to ATG7-mediated autophagy, leading to tumor aggressiveness in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is associated with a poor prognosis and metastatic growth. TNBC cells frequently undergo macroautophagy/autophagy, contributing to tumor progression and chemotherapeutic resistance. ANXA2 (annexin A2), a potential therapeutic target for TNBC, has been reported to stimulate autophagy. In this study, we investigated the role of ANXA2 in autophagic processes in TNBC cells. TNBC patients exhibited high levels of ANXA2, which correlated with poor outcomes. ANXA2 increased LC3B-II levels following bafilomycin A1 treatment and enhanced autophagic flux in TNBC cells. Notably, ANXA2 upregulated the phosphorylation of HSF1 (heat shock transcription factor 1), resulting in the transcriptional activation of ATG7 (autophagy related 7). The mechanistic target of rapamycin kinase complex 2 (MTORC2) played an important role in ANXA2-mediated ATG7 transcription by HSF1. MTORC2 did not affect the mRNA level of ANXA2, but it was involved in the protein stability of ANXA2. HSPA (heat shock protein family A (Hsp70)) was a potential interacting protein with ANXA2, which may protect ANXA2 from lysosomal proteolysis. ANXA2 knockdown significantly increased sensitivity to doxorubicin, the first-line chemotherapeutic regimen for TNBC treatment, suggesting that the inhibition of autophagy by ANXA2 knockdown may overcome doxorubicin resistance. In a TNBC xenograft mouse model, we demonstrated that ANXA2 knockdown combined with doxorubicin administration significantly inhibited tumor growth compared to doxorubicin treatment alone, offering a promising avenue to enhance the effectiveness of chemotherapy. In summary, our study elucidated the molecular mechanism by which ANXA2 modulates autophagy, suggesting a potential therapeutic approach for TNBC treatment.Abbreviation: ATG: autophagy related; ChIP: chromatin-immunoprecipitation; HBSS: Hanks' balanced salt solution; HSF1: heat shock transcription factor 1; MTOR: mechanistic target of rapamycin kinase; TNBC: triple-negative breast cancer; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3.

NPFs-mediated actin cytoskeleton: a new viewpoint on autophagy regulation

Macroautophagy/autophagy is a lysosome-dependent catabolic process induced by various cellular stress conditions, maintaining the homeostasis of cells, tissues and organs. Autophagy is a series of membrane-related events involving multiple autophagy-related (ATG) proteins. Most studies to date have focused on various signaling pathways affecting ATG proteins to control autophagy. However, mounting evidence reveals that the actin cytoskeleton acts on autophagy-associated membranes to regulate different events of autophagy. The actin cytoskeleton assists in vesicle formation and provides the mechanical forces for cellular activities that involve membrane deformation. Although the interaction between the actin cytoskeleton and membrane makes the role of actin in autophagy recognized, how the actin cytoskeleton is recruited and assembles on membranes during autophagy needs to be detailed. Nucleation-promoting factors (NPFs) activate the Arp2/3 complex to produce actin cytoskeleton. In this review, we summarize the important roles of the actin cytoskeleton in autophagy regulation and focus on the effect of NPFs on actin cytoskeleton assembly during autophagy, providing new insights into the occurrence and regulatory mechanisms of autophagy. Video Abstract.

Brain clearance of protein aggregates: a close-up on astrocytes

Protein misfolding and accumulation defines a prevailing feature of many neurodegenerative disorders, finally resulting in the formation of toxic intra- and extracellular aggregates. Intracellular aggregates can enter the extracellular space and be subsequently transferred among different cell types, thus spreading between connected brain districts.Although microglia perform a predominant role in the removal of extracellular aggregated proteins, mounting evidence suggests that astrocytes actively contribute to the clearing process. However, the molecular mechanisms used by astrocytes to remove misfolded proteins are still largely unknown.Here we first provide a brief overview of the progressive transition from soluble monomers to insoluble fibrils that characterizes amyloid proteins, referring to α-Synuclein and Tau as archetypical examples. We then highlight the mechanisms at the basis of astrocyte-mediated clearance with a focus on their potential ability to recognize, collect, internalize and digest extracellular protein aggregates. Finally, we explore the potential of targeting astrocyte-mediated clearance as a future therapeutic approach for the treatment of neurodegenerative disorders characterized by protein misfolding and accumulation.

Annexin A5 derived from matrix vesicles protects against osteoporotic bone loss via mineralization

Matrix vesicles (MVs) have shown strong effects in diseases such as vascular ectopic calcification and pathological calcified osteoarthritis and in wound repair of the skeletal system due to their membranous vesicle characteristics and abundant calcium and phosphorus content. However, the role of MVs in the progression of osteoporosis is poorly understood. Here, we report that annexin A5, an important component of the matrix vesicle membrane, plays a vital role in bone matrix homeostasis in the deterioration of osteoporosis. We first identified annexin A5 from adherent MVs but not dissociative MVs of osteoblasts and found that it could be sharply decreased in the bone matrix during the occurrence of osteoporosis based on ovariectomized mice. We then confirmed its potential in mediating the mineralization of the precursor osteoblast lineage via its initial binding with collagen type I to achieve MV adhesion and the subsequent activation of cellular autophagy. Finally, we proved its protective role in resisting bone loss by applying it to osteoporotic mice. Taken together, these data revealed the importance of annexin A5, originating from adherent MVs of osteoblasts, in bone matrix remodeling of osteoporosis and provided a new strategy for the treatment and intervention of bone loss.

Annexin A2 modulates phospholipid membrane composition upstream of Arp2 to control angiogenic sprout initiation

The intersection of protein and lipid biology is of growing importance for understanding how cells address structural challenges during adhesion and migration. While protein complexes engaged with the cytoskeleton play a vital role, support from the phospholipid membrane is crucial for directing localization and assembly of key protein complexes. During angiogenesis, dramatic cellular remodeling is necessary for endothelial cells to shift from a stable monolayer to invasive structures. However, the molecular dynamics between lipids and proteins during endothelial invasion are not defined. Here, we utilized cell culture, immunofluorescence, and lipidomic analyses to identify a novel role for the membrane binding protein Annexin A2 (ANXA2) in modulating the composition of specific membrane lipids necessary for cortical F-actin organization and adherens junction stabilization. In the absence of ANXA2, there is disorganized cortical F-actin, reduced junctional Arp2, excess sprout initiation, and ultimately failed sprout maturation. Furthermore, we observed reduced filipin III labeling of membrane cholesterol in cells with reduced ANXA2, suggesting there is an alteration in phospholipid membrane dynamics. Lipidomic analyses revealed that 42 lipid species were altered with loss of ANXA2, including an accumulation of phosphatidylcholine (16:0_16:0). We found that supplementation of phosphatidylcholine (16:0_16:0) in wild-type endothelial cells mimicked the ANXA2 knock-down phenotype, indicating that ANXA2 regulated the phospholipid membrane upstream of Arp2 recruitment and organization of cortical F-actin. Altogether, these data indicate a novel role for ANXA2 in coordinating events at endothelial junctions needed to initiate sprouting and show that proper lipid modulation is a critical component of these events.

Combination of Small Extracellular Vesicle-Derived Annexin A2 Protein and mRNA as a Potential Predictive Biomarker for Chemotherapy Responsiveness in Aggressive Triple-Negative Breast Cancer

Small extracellular vesicles (sEVs), mainly exosomes, are nanovesicles that shed from the membrane as intraluminal vesicles of the multivesicular bodies, serve as vehicles that carry cargo influential in modulating the tumor microenvironment for the multi-step process of cancer metastasis. Annexin A2 (AnxA2), a calcium(Ca²⁺)-dependent phospholipid-binding protein, is among sEV cargoes. sEV-derived AnxA2 (sEV-AnxA2) protein is involved in the process of metastasis in triple-negative breast cancer (TNBC). The objective of the current study is to determine whether sEV-AnxA2 protein and/or mRNA could be a useful biomarkers to predict the responsiveness of chemotherapy in TNBC. Removal of Immunoglobulin G (IgG) from the serum as well as using the System Bioscience's ExoQuick Ultra kit resulted in efficient sEV isolation and detection of sEV-AnxA2 protein and mRNA compared to the ultracentrifugation method. The standardized method was applied to the twenty TNBC patient sera for sEV isolation. High levels of sEV-AnxA2 protein and/or mRNA were associated with stage 3 and above in TNBC. Four patients who responded to neoadjuvant chemotherapy had high expression of AnxA2 protein and/or mRNA in sEVs, while other four who did not respond to chemotherapy had low levels of AnxA2 protein and mRNA in sEVs. Our data suggest that the sEV-AnxA2 protein and mRNA could be a combined predictive biomarker for responsiveness to chemotherapy in aggressive TNBC.

A genome-wide CRISPR screen identifies WDFY3 as a regulator of macrophage efferocytosis

Phagocytic clearance of dying cells, termed efferocytosis, is essential for maintaining tissue homeostasis, yet our understanding of efferocytosis regulation remains incomplete. Here we perform a FACS-based, genome-wide CRISPR knockout screen in primary mouse macrophages to search for novel regulators of efferocytosis. The results show that Wdfy3 knockout in macrophages specifically impairs uptake, but not binding, of apoptotic cells due to defective actin disassembly. Additionally, WDFY3 interacts with GABARAP, thus facilitating LC3 lipidation and subsequent lysosomal acidification to permit the degradation of apoptotic cell components. Mechanistically, while the C-terminus of WDFY3 is sufficient to rescue the impaired degradation induced by Wdfy3 knockout, full-length WDFY3 is required to reconstitute the uptake of apoptotic cells. Finally, WDFY3 is also required for efficient efferocytosis in vivo in mice and in vitro in primary human macrophages. This work thus expands our knowledge of the mechanisms of macrophage efferocytosis, as well as supports genome-wide CRISPR screen as a platform for interrogating complex functional phenotypes in primary macrophages.

Annexin A2 plays a key role in protecting against cisplatin-induced AKI through β-catenin/TFEB pathway

Acute kidney injury (AKI) is in high prevalence in the world. However, the therapeutic strategies for AKI are still in mystery. Studies have shown to improve autophagy and lysosomal function could inhibit AKI. But their modulators need to be explored in detail. Annexin A2 (ANXA2) is a phospholipid-binding protein involving in organelle membrane integrity function, suggesting its important role in autophagy and lysosome homeostasis. It implicates ANXA2 potentially protects against AKI. However, this has not been elucidated. Herein, we found that ANXA2 is increased in renal tubules in cisplatin-induced AKI mice. Ectopic expression of ANXA2 improved lysosomal functions and enhanced autophagic flux, further protecting against renal tubular cell apoptosis and kidney injury. Conversely, knockdown of ANXA2 inhibited lysosomal function and autophagy, which aggravated the progression of AKI. Transcriptome sequencing revealed β-catenin signaling is highly responsible for this process. In vitro, we found ANXA2 induced β-catenin activation, further triggering T-cell factor-4 (TCF4)-induced transcription factor EB (TFEB). Furthermore, TFEB promoted lysosome biogenesis to enhance autophagic flux, resulting in the alleviation of AKI. Our new findings underline ANXA2 is a new therapeutic potential for AKI through modulating autophagy and lysosomal function. The underlying mechanism is associated with its inductive effects on β-catenin/TFEB pathway.

Actin dynamics in protein homeostasis

Cell homeostasis is maintained in all organisms by the constant adjustment of cell constituents and organisation to account for environmental context. Fine-tuning of the optimal balance of proteins for the conditions, or protein homeostasis, is critical to maintaining cell homeostasis. Actin, a major constituent of the cytoskeleton, forms many different structures which are acutely sensitive to the cell environment. Furthermore, actin structures interact with and are critically important for the function and regulation of multiple factors involved with mRNA and protein production and degradation, and protein regulation. Altogether, actin is a key, if often overlooked, regulator of protein homeostasis across eukaryotes. In this review, we highlight these roles and how they are altered following cell stress, from mRNA transcription to protein degradation.

Pathobiological functions and clinical implications of annexin dysregulation in human cancers

Annexins are an extensive superfamily of structurally related calcium- and phospholipid-binding proteins, largely conserved and widely distributed among species. Twelve human annexins have been identified, referred to as Annexin A1-13 (A12 remains as of yet unassigned), whose genes are spread throughout the genome on eight different chromosomes. According to their distinct tissue distribution and subcellular localization, annexins have been functionally implicated in a variety of biological processes relevant to both physiological and pathological conditions. Dysregulation of annexin expression patterns and functions has been revealed as a common feature in multiple cancers, thereby emerging as potential biomarkers and molecular targets for clinical application. Nevertheless, translation of this knowledge to the clinic requires in-depth functional and mechanistic characterization of dysregulated annexins for each individual cancer type, since each protein exhibits varying expression levels and phenotypic specificity depending on the tumor types. This review specifically and thoroughly examines the current knowledge on annexin dysfunctions in carcinogenesis. Hence, available data on expression levels, mechanism of action and pathophysiological effects of Annexin A1-13 among different cancers will be dissected, also further discussing future perspectives for potential applications as biomarkers for early diagnosis, prognosis and molecular-targeted therapies. Special attention is devoted to head and neck cancers (HNC), a complex and heterogeneous group of aggressive malignancies, often lately diagnosed, with high mortality, and scarce therapeutic options.

Blocking Lipid Uptake Pathways Does not Prevent Toxicity in Adipose Triglyceride Lipase (ATGL) Deficiency

Lipid accumulation in nonadipose tissues can cause lipotoxicity, leading to cell death and severe organ dysfunction. Adipose triglyceride lipase (ATGL) deficiency causes human neutral lipid storage disease and leads to cardiomyopathy; ATGL deficiency has no current treatment. One possible approach to alleviate this disorder has been to alter the diet and reduce the supply of dietary lipids and, hence, myocardial lipid uptake. However, in this study, when we supplied cardiac Atgl KO mice a low- or high-fat diet, we found that heart lipid accumulation, heart dysfunction, and death were not altered. We next deleted lipid uptake pathways in the ATGL-deficient mice through the generation of double KO mice also deficient in either cardiac lipoprotein lipase or cluster of differentiation 36, which is involved in an lipoprotein lipase-independent pathway for FA uptake in the heart. We show that neither deletion ameliorated ATGL-deficient heart dysfunction. Similarly, we determined that non-lipid-containing media did not prevent lipid accumulation by cultured myocytes; rather, the cells switched to increased de novo FA synthesis. Thus, we conclude that pathological storage of lipids in ATGL deficiency cannot be corrected by reducing heart lipid uptake.

Single-cell transcriptomic analysis reveals circadian rhythm disruption associated with poor prognosis and drug-resistance in lung adenocarcinoma

Circadian rhythm disruption (CRD) represents a major contributor to tumor proliferation. Nonetheless, the role of CRD in the clinical prediction of cancer outcomes has not been well studied. In this study, we developed a computational algorithm, which was implemented in an open-source R package CRDscore, to define the intratumoral status of circadian disruption in three representative single-cell RNA-seq data sets of lung adenocarcinoma. We found that the malignant cells with high CRDscore were characterized by activation of glycolysis and epithelial-mesenchymal transition pathways. Furthermore, cell communication analysis indicated that CRD played a pivotal role in T cell exhaustion, which may be responsible for the poor prognosis of the malignancy. We then validated the findings with public bulk transcriptome datasets involving 22 cancer types. Cox regression analysis revealed that the CRDscore was a valuable prognostic biomarker. A model containing 23 circadian-related genes performed well in predicting immunotherapeutic outcomes in 14 independent cohorts. Importantly, decreased CRDscore was detect by RNA sequencing on H1299 cells with melatonin treatment. Meanwhile, the cells downregulated the expression level of SNAIL and TWIST, which contributed to an invasive phenotype. In conclusion, this study provides a novel computational framework for characterizing CRD status using single-cell transcriptomic data and further confirmed the molecular mechanisms underlying metabolic reprogramming and T cell exhaustion under CRD. The better understanding of the mechanisms may provide new possibilities for incorporating "anticancer approaches based on circadian clocks" into the treatment protocols of precision medicine.

SPATA33 affects the formation of cell adhesion complex by interacting with CTNNA3 in TM4 cells

Communication between Sertoli cell is essential during spermatogenesis and testicular development in mice, and the dynamic balance of this communication is regulated by some adhesion proteins. In this study, we found that SPATA33 and CTNNA3 were involved in this process. Quantitative real-time PCR and western blotting showed similar trend of expression of two proteins in the testis of mice of different ages. Subsequently, CRISPR-Cas9 technique was used to prepare Spata33 knockout cell lines with TM4 cells, cell wound scratch assay showed that Spata33 gene knockout affected cell migration, and flow cytometry assay showed that Spata33 knockout resulted in a decreased percentage of G1 phase cells in TM4 cell line. In addition, phalloidin staining assay showed that Spata33 gene knockout disrupted the formation of F-actin. Moreover, the protein immunoprecipitation experiment showed the interaction between SPATA33 and CTNNA3, which affected the interaction between CTNNA3 and CTNNB1. SPATA33 inhibits the formation of CDH1-CTNNB1-CTNNA3 complex through its interaction with CTNNA3, thus weakening adhesion between Sertoli cell and promoting cell migration.

Transcriptional regulatory networks of the proteasome in mammalian systems

The tight regulation of proteostasis is essential for physiological cellular function. Mammalian cells possess a network of mechanisms that ensure proteome integrity under normal or stress conditions. The proteasome, being the major cellular proteolytic machinery, is central to proteostasis maintenance in response to distinct intracellular and extracellular conditions. The proteasomes are multisubunit protease complexes that selectively catalyze the degradation of short-lived regulatory proteins and damaged peptides. Different forms of the proteasome complexes comprising of different subunits and attached regulators directly affect the substrate selectivity and degradation. Thus, the proteasome participates in the turnover of a multitude of factors that control key processes that affect the cellular state, such as adaptation to environmental cues, growth, development, metabolism, signaling, senescence, pluripotency, differentiation, and immunity. Aberrations on its function are related to normal processes like aging and pathological conditions such as neurodegeneration and cancer. The past few years of research have highlighted that proteasome abundance, activity, assembly, and localization are subject to a dynamic transcriptional control that secures the continuous adaptation of the proteasome to internal or external stimuli. This review focuses on the factors and signaling pathways that are involved in the regulation of the mammalian proteasome at the transcriptional level. A comprehensive understanding of proteasome regulation has critical implications on disease prevention and treatment.

Presenilin 1 Regulates Membrane Homeostatic Pathways that are Dysregulated in Alzheimer's Disease

Mutations in the PSEN1 gene, encoding presenilin 1 (PS1), are the most common cause of familial Alzheimer's disease (fAD). Since the first mutations in the PSEN1 gene were discovered more than 25 years ago, many postulated functions of PS1 have been investigated. The majority of earlier studies focused on its role as the catalytic component of the γ-secretase complex, which in concert with β site amyloid precursor protein cleaving enzyme 1 (BACE1), mediates the formation of Aβ from amyloid-β protein precursor (AβPP). Though mutant PS1 was originally considered to cause AD by promoting Aβ pathology through its protease function, it is now becoming clear that PS1 is a multifunctional protein involved in regulating membrane dynamics and protein trafficking. Therefore, through loss of these abilities, mutant PS1 has the potential to impair numerous cellular functions such as calcium flux, organization of proteins in different compartments, and protein turnover via vacuolar metabolism. Impaired calcium signaling, vacuolar dysfunction, mitochondrial dysfunction, and increased ER stress, among other related membrane-dependent disturbances, have been considered critical to the development and progression of AD. Given that PS1 plays a key regulatory role in all these processes, this review will describe the role of PS1 in different cellular compartments and provide an integrated view of how PS1 dysregulation (due to mutations or other causes) could result in impairment of various cellular processes and result in a "multi-hit", integrated pathological outcome that could contribute to the etiology of AD.

Revealing NOTCH-dependencies in synaptic targets associated with Alzheimer's disease

Recent studies have identified NOTCH signaling as a contributor of neurodegeneration including Alzheimer's disease' (AD) pathophysiology. As part of the efforts to understand molecular mechanisms and players involved in neurodegenerative dementia, we employed transgenic mouse models with Notch1 and Rbpjk loss of function (LOF) mutation in pyramidal neurons of the CA fields. Using RNA-seq, we have investigated the differential expression of NOTCH-dependent genes either upon environmental enrichment (EE) or upon kainic acid (KA) injury. We found a substantial genetic diversity in absence of both NOTCH1 receptor or RBPJK transcriptional activator. Among differentially expressed genes, we observed a significant upregulation of Gabra2a in both knockout models, suggesting a role for NOTCH signaling in the modulation of E/I balance. Upon excitotoxic stimulation, loss of RBPJK results in decreased expression of synaptic proteins with neuroprotective effects. We confirmed Nptx2, Npy, Pdch8, TncC as direct NOTCH1/RBPJK targets and Bdnf and Scg2 as indirect targets. Finally, we translate these findings into human entorhinal cortex containing the hippocampal region from AD patients performing targeted transcripts analysis. We observe an increased trend for RBPJK and the ligand DNER starting in the mild-moderate stage of the disease with no change of NOTCH1 expression. Alongside, expression of the Notch targets Hes5 and Hey1 tend to rise in the intermediate stage of the disease and drop in severe AD. Similarly the newly discovered NOTCH targets, NPTX2, NPY, BDNF show an up-warding tendency during the mild-moderate stage, and decline in the severe phase of the disease. This study identifies NOTCH as a central signaling cascade capable of modulating synaptic transmission in response to excitatory insult through the activation of neuroprotective genes that have been associated to AD.

MIR99AHG is a noncoding tumor suppressor gene in lung adenocarcinoma

Little is known about noncoding tumor suppressor genes. An effective way to identify these genes is by analyzing somatic copy number variation (CNV)-related noncoding genes. By integrated bioinformatics analyses of differentially expressed long noncoding RNAs (lncRNAs) and arm-level CNVs in lung adenocarcinoma (LUAD), we identified a potential antitumor gene, MIR99AHG, encoding lncRNA MIR99AHG as well as a miR-99a/let-7c/miR-125b2 cluster on chromosome 21q. All four of these transcripts were downregulated in LUAD tissues partly due to the copy number deletion of the MIR99AHG gene. Both MIR99AHG and miR-99a expression was positively correlated with the survival of LUAD patients. MIR99AHG suppressed proliferation and metastasis and promoted autophagy both in vitro and in vivo. Mechanistically, the interaction between MIR99AHG and ANXA2 could accelerate the ANXA2-induced ATG16L⁺ vesicle biogenesis, thus promoting phagophore assembly. Additionally, miR-99a targeted a well-known autophagy suppressor, mammalian target of rapamycin (mTOR), thereby synergistically promoting autophagy and postponing LUAD progression with MIR99AHG. In summary, MIR99AHG emerges as a noncoding tumor suppressor gene in LUAD, providing a new strategy for antitumor therapy.

Advances in cancer treatment: a new therapeutic target, Annexin A2

Annexin A2 (ANXA2) is a calcium regulated phospholipid-binding protein. It is expressed in some tumor cells, endothelial cells, macrophages, and mononuclear cells, affecting cell survival and mediating interactions between intercellular and extracellular microenvironment. Aberrant expression of ANXA2 can be used as a potential predictive factor, diagnostic biomarker and therapeutic target in cancer therapy. Investigators used various technologies to target ANXA2 in a preclinical model of human cancers and demonstrated encouraging results. In this review article, we discuss the diagnosis and prognosis latent capacity of ANXA2 in progressive cancers, focus on the exploration of restorative interventions targeting ANXA2 in cancer treatment. Further, we comment on a promising candidate therapy that is conceivable for clinical translation.

Aberrant proteins expressed in skin fibroblasts of Parkinson's disease patients carrying heterozygous variants of glucocerebrosidase and parkin genes

Parkinson's disease (PD) is a neurodegenerative disorder that affects movement, and its development is associated with environmental and genetic factors. Genetic variants in GBA and PARK2 are important risk factors implicated in the development of PD; however, their precise roles have yet to be elucidated. The present study aimed to identify and analyse proteins from the skin fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants, and from healthy controls. Liquid chromatography coupled with tandem mass spectrometry and label-free quantitative proteomics were performed to identify and compare differential protein expression levels. Moreover, protein-protein interaction networks were assessed using Search Tool for Retrieval of Interacting Genes analysis. Using these proteomic approaches, 122 and 119 differentially expressed proteins from skin fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants, respectively, were identified and compared. According to the results of protein-protein interaction and Gene Ontology analyses, 14 proteins involved in the negative regulation of macromolecules and mRNA metabolic processes, and protein targeting to the membrane exhibited the largest degree of differential expression in the fibroblasts of patients with PD with a GBA variant, whereas 20 proteins involved in the regulation of biological quality, NAD metabolic process and cytoskeletal organization exhibited the largest degree of differential expression in the fibroblasts of patients with PD with a PARK2 variant. Among these, the expression levels of annexin A2 and tubulin β chain, were most strongly upregulated in the fibroblasts of patients with GBA-PD and PARK2-PD, respectively. Other predominantly expressed proteins were confirmed by western blotting, and the results were consistent with those of the quantitative proteomic analysis. Collectively, the results of the present study demonstrated that the proteomic patterns of fibroblasts of patients with PD carrying heterozygous GBA and PARK2 variants are different and unique. Aberrant expression of the proteins affected by these variants may reflect physiological changes that also occur in neurons, resulting in PD development and progression.

Parkinson's Disease-Associated LRRK2 Interferes with Astrocyte-Mediated Alpha-Synuclein Clearance

Parkinson's disease (PD) is a neurodegenerative, progressive disease without a cure. To prevent PD onset or at least limit neurodegeneration, a better understanding of the underlying cellular and molecular disease mechanisms is crucial. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent one of the most common causes of familial PD. In addition, LRRK2 variants are risk factors for sporadic PD, making LRRK2 an attractive therapeutic target. Mutations in LRRK2 have been linked to impaired alpha-synuclein (α-syn) degradation in neurons. However, in which way pathogenic LRRK2 affects α-syn clearance by astrocytes, the major glial cell type of the brain, remains unclear. The impact of astrocytes on PD progression has received more attention and recent data indicate that astrocytes play a key role in α-syn-mediated pathology. In the present study, we aimed to compare the capacity of wild-type astrocytes and astrocytes carrying the PD-linked G2019S mutation in Lrrk2 to ingest and degrade fibrillary α-syn. For this purpose, we used two different astrocyte culture systems that were exposed to sonicated α-syn for 24 h and analyzed directly after the α-syn pulse or 6 days later. To elucidate the impact of LRRK2 on α-syn clearance, we performed various analyses, including complementary imaging, transmission electron microscopy, and proteomic approaches. Our results show that astrocytes carrying the G2019S mutation in Lrrk2 exhibit a decreased capacity to internalize and degrade fibrillar α-syn via the endo-lysosomal pathway. In addition, we demonstrate that the reduction of α-syn internalization in the Lrrk2 G2019S astrocytes is linked to annexin A2 (AnxA2) loss of function. Together, our findings reveal that astrocytic LRRK2 contributes to the clearance of extracellular α-syn aggregates through an AnxA2-dependent mechanism.

Autophagy Paradox of Cancer: Role, Regulation, and Duality

Autophagy, a catabolic process, degrades damaged and defective cellular materials through lysosomes, thus working as a recycling mechanism of the cell. It is an evolutionarily conserved and highly regulated process that plays an important role in maintaining cellular homeostasis. Autophagy is constitutively active at the basal level; however, it gets enhanced to meet cellular needs in various stress conditions. The process involves various autophagy-related genes that ultimately lead to the degradation of targeted cytosolic substrates. Many factors modulate both upstream and downstream autophagy pathways like nutritional status, energy level, growth factors, hypoxic conditions, and localization of p53. Any problem in executing autophagy can lead to various pathological conditions including neurodegeneration, aging, and cancer. In cancer, autophagy plays a contradictory role; it inhibits the formation of tumors, whereas, during advanced stages, autophagy promotes tumor progression. Besides, autophagy protects the tumor from various therapies by providing recycled nutrition and energy to the tumor cells. Autophagy is stimulated by tumor suppressor proteins, whereas it gets inhibited by oncogenes. Due to its dynamic and dual role in the pathogenesis of cancer, autophagy provides promising opportunities in developing novel and effective cancer therapies along with managing chemoresistant cancers. In this article, we summarize different strategies that can modulate autophagy in cancer to overcome the major obstacle, i.e., resistance developed in cancer to anticancer therapies.

TRIM21-regulated Annexin A2 plasma membrane trafficking facilitates osteosarcoma cell differentiation through the TFEB-mediated autophagy

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, which is characterized by dysfunctional autophagy and poor differentiation. Our recent studies have suggested that the tripartite motif containing-21 (TRIM21) plays a crucial role in regulating OS cell senescence and proliferation via interactions with several proteins. Yet, its implication in autophagy and differentiation in OS is largely unknown. In the present study, we first showed that TRIM21 could promote OS cell autophagy, as determined by the accumulation of LC3-II, and the degradation of cargo receptor p62. Further, we were able to identify that Annexin A2 (ANXA2), as a novel interacting partner of TRIM21, was critical for TIRM21-induced OS cell autophagy. Although TRIM21 had a negligible effect on the mRNA and protein expressions of ANXA2, we did find that TRIM21 facilitated the translocation of ANXA2 toward plasma membrane (PM) in OS cells through a manner relying on TRIM21-mediated cell autophagy. This functional link has been confirmed by observing a nice co-expression of TRIM21 and ANXA2 (at the PM) in the OS tissues. Mechanistically, we demonstrated that TRIM21, via facilitating the ANXA2 trafficking at the PM, enabled to release the transcription factor EB (TFEB, a master regulator of autophagy) from the ANXA2-TFEB complex, which in turn entered into the nucleus for the regulation of OS cell autophagy. In accord with previous findings that autophagy plays a critical role in the control of differentiation, we also demonstrated that autophagy inhibited OS cell differentiation, and that the TRIM21/ANXA2/TFEB axis is implicated in OS cell differentiation through the coordination with autophagy. Taken together, our results suggest that the TRIM21/ANXA2/TFEB axis is involved in OS cell autophagy and subsequent differentiation, indicating that targeting this signaling axis might lead to a new clue for OS treatment.

Annexin A2 regulates unfolded protein response via IRE1-XBP1 axis in macrophages during P. aeruginosa infection

Pseudomonas aeruginosa is a severe Gram-negative opportunistic bacterium that causes a spectrum of organ system diseases, particularly in immunocompromised patients. This bacterium has been shown to induce unfolded protein response (UPR) during mammalian infection. Annexin A2 (AnxA2) is a multicompartmental protein relating to a number of cellular processes; however, it remains unknown whether AnxA2 coordinates a UPR pathway under bacterial infection conditions. Here, we report that the endoplasmic reticulum stress inositol-requiring enzyme 1 (IRE1)-X-box binding protein 1 (XBP1) pathway was up-regulated by AnxA2 through p38 MAPK signaling following P. aeruginosa infection in macrophages, whereas ATF4 and ATF6 not. In addition, XBP1 was found as a positive regulator of innate immunity to tame P. aeruginosa challenges by enhancing autophagy and bacterial clearance. XBP1 also facilitated NF-κB activation to elicit the release of proinflammatory cytokines predominantly in macrophages. Together, our findings identify AnxA2 as a regulator for XBP1-mediated UPR pathway.

Ginsenoside Rh2 represses autophagy to promote cervical cancer cell apoptosis during starvation

Background

Cancer cells through autophagy-mediated recycling to meet the metabolic demands of growth and proliferation. The steroidal saponin 20(S)-ginsenoside Rh2 effectively inhibits the growth and survival of a variety of tumor cell lines and animal models, but the effects of Rh2 on autophagy remain elusive.

Methods

Cell viability was measured by CCK-8 (cell counting kit-8) assays. Apoptosis, ROS generation and mitochondrial membrane potential were analyzed by flow cytometry. Western blot analyses were used to determine changes in protein levels. Morphology of apoptotic cells and autophagosome accumulation were analyzed by DAPI staining and transmission electron microscopy. Autophagy induction was monitored by acidic vesicular organelle staining, EGFP-LC3 and mRFP-GFP-LC3 transfection. Atg7 siRNA and autophagy regulator was used to assess the effect of autophagy on apoptosis induced by G-Rh2.

Results

In this study, we found that low concentration G-Rh2 attenuated cancer cell growth and induced apoptosis upon serum-free starvation. Caspase 3 inhibitors failed to block apoptosis in G-Rh2-treated cells, indicating a caspase-independent mechanism. G-Rh2-treated cells in serum-deprived conditions showed impaired mitochondrial function, increased release and nuclear translocation of apoptosis-inducing factor, but little changes in the mitochondrial and cytoplasmic distributions of cytochrome C. Annexin A2 overexpression in 293T cells inhibited G-Rh2-induced apoptosis under serum-starved conditions. Meanwhile, G-Rh2 reduced lysosomal activity and inhibited the fusion of autophagosome and lysosome, leading to a block of autophagic flux. Knockdown Atg7 significantly inhibited autophagy and triggered AIF-induced apoptosis in serm free condition. The autophagy inducer significantly decreased the apoptosis levels of G-Rh2-treated cells in serum-free conditions.

Conclusions

Under nutrient deficient conditions, G-Rh2 represses autophagy in cervical cancer cells and enhanced apoptosis through an apoptosis-inducing factor mediated pathway.

The roles and functions of Paneth cells in Crohn's disease: A critical review

Paneth cells (PCs) are located at the base of small intestinal crypts and secrete the α‐defensins, human α‐defensin 5 (HD‐5) and human α‐defensin 6 (HD‐6) in response to bacterial, cholinergic and other stimuli. The α‐defensins are broad‐spectrum microbicides that play critical roles in controlling gut microbiota and maintaining intestinal homeostasis. Inflammatory bowel disease, including ulcerative colitis and Crohn's disease (CD), is a complicated autoimmune disorder. The pathogenesis of CD involves genetic factors, environmental factors and microflora. Surprisingly, with regard to genetic factors, many susceptible genes and pathogenic pathways of CD, including nucleotide‐binding oligomerization domain 2 (NOD2), autophagy‐related 16‐like 1 (ATG16L1), immunity‐related guanosine triphosphatase family M (IRGM), wingless‐related integration site (Wnt), leucine‐rich repeat kinase 2 (LRRK2), histone deacetylases (HDACs), caspase‐8 (Casp8) and X‐box‐binding protein‐1 (XBP1), are relevant to PCs. As the underlying mechanisms are being unravelled, PCs are identified as the central element of CD pathogenesis, integrating factors among microbiota, intestinal epithelial barrier dysfunction and the immune system. In the present review, we demonstrate how these genes and pathways regulate CD pathogenesis via their action on PCs and what treatment modalities can be applied to deal with these PC‐mediated pathogenic processes.

Autophagy and Redox Homeostasis in Parkinson's: A Crucial Balancing Act

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated primarily from endogenous biochemical reactions in mitochondria, endoplasmic reticulum (ER), and peroxisomes. Typically, ROS/RNS correlate with oxidative damage and cell death; however, free radicals are also crucial for normal cellular functions, including supporting neuronal homeostasis. ROS/RNS levels influence and are influenced by antioxidant systems, including the catabolic autophagy pathways. Autophagy is an intracellular lysosomal degradation process by which invasive, damaged, or redundant cytoplasmic components, including microorganisms and defunct organelles, are removed to maintain cellular homeostasis. This process is particularly important in neurons that are required to cope with prolonged and sustained operational stress. Consequently, autophagy is a primary line of protection against neurodegenerative diseases. Parkinson's is caused by the loss of midbrain dopaminergic neurons (mDANs), resulting in progressive disruption of the nigrostriatal pathway, leading to motor, behavioural, and cognitive impairments. Mitochondrial dysfunction, with associated increases in oxidative stress, and declining proteostasis control, are key contributors during mDAN demise in Parkinson's. In this review, we analyse the crosstalk between autophagy and redoxtasis, including the molecular mechanisms involved and the detrimental effect of an imbalance in the pathogenesis of Parkinson's.

ANXA6 suppresses the tumorigenesis of cervical cancer through autophagy induction

Background

Autophagy is an intracellular degradation pathway conserved in eukaryotes. ANXA6 (annexin A6) belongs to a family of calcium‐dependent membrane and phospholipid‐binding proteins. Here, we identify ANXA6 as a newly synthesized protein in starvation‐induced autophagy and validate it as a novel autophagy modulator that regulates autophagosome formation.

Results

ANXA6 knockdown attenuates starvation‐induced autophagy, while restoration of its expression enhances autophagy. GO (gene ontology) analysis of ANXA6 targets showed that ANXA6 interacts with many RAB GTPases and targets endocytosis and phagocytosis pathways, indicating that ANXA6 exerts its function through protein trafficking. ATG9A (autophagy‐related 9A) is the sole multispanning transmembrane protein and its trafficking through recycling endosomes is an essential step for autophagosome formation. Our results showed that ANXA6 enables appropriate ATG9A⁺ vesicle trafficking from endosomes to autophagosomes through RAB proteins or F‐actin. In addition, restoration of ANXA6 expression suppresses mTOR (mammalian target of rapamycin) activity through the inhibition of the PI3K (phosphoinositide 3‐kinase)‐AKT and ERK (extracellular signal‐regulated kinase) signaling pathways, which is a negative regulator of autophagy. Functionally, ANXA6 expression is correlated with LC3 (microtubule‐associated protein 1 light chain 3) expression in cervical cancer, and ANXA6 inhibits tumorigenesis through autophagy induction.

Conclusions

Our results reveal an important mechanism for ANXA6 in tumor suppression and autophagy regulation.

Identification of Annexin A2 as a key mTOR target to induce roller coaster pattern of autophagy fluctuation in stress

Autophagy can either be cytoprotective or promote cell death in a context-dependent manner in response to stress. How autophagy leads to autophagy dependent cell death requires further clarification. In this study, we document a nonlinear roller coaster form of autophagy oscillation when cells are subjected to different stress conditions. Serum starvation induces an initial primary autophagic peak at 6 h, that helps to replenish cells with de novo fluxed nutrients, but protracted stress lead to a secondary autophagic peak around 48 h. Time kinetic studies indicate that the primary autophagic peak is reversible, whereas the secondary autophagic peak is irreversible and leads to cell death. Key players involved in different stages of autophagy including initiation, elongation and degradation during this oscillatory sequence were identified. A similar molecular pattern was intensified under apoptosis-deficient conditions. mTOR was the central molecule regulating this autophagic activity, and upon knockdown a steady increase of autophagy without any non-linear fluctuation was evident. An unbiased proteome screening approach was employed to identify the autophagy molecules potentially regulating these autophagic peaks. Our proteomics analysis has identified Annexin A2 as a stress-induced protein to implicate in autophagy fluctuation and its deficiency reduced autophagy. Moreover, we report that mTOR in its phosphorylated condition interacts with Annexin A2 to induce autophagy fluctuation by altering its cellular localization. The work highlights the molecular mechanism of a mTOR-dependent roller coaster fluctuation of autophagy and autophagy dependent cell death during prolong stress.

Roles of Annexin A protein family in autophagy regulation and therapy

Annexin A is a kind of calcium-dependent phospholipid-binding proteins, which contributes to the formation of the cell membranes and cytoskeleton and played a part as a membrane skeleton to stabilize lipid bilayer. Autophagy is one of the most important programmed cell death mechanisms. And recently some reports suggest that annexin A family protein is associated with autophagy for annexin A can regulate the formation of vesicular lipid membranes and promote cell exocytosis. In this review, we summarized the roles of annexin A protein family in autophagy regulation and targeted medical treatment for better diagnoses and therapies.

Annexin A2 in Inflammation and Host Defense

Annexin A2 (AnxA2) is a multifunctional calcium²⁺ (Ca²⁺) and phospholipid-binding protein that is expressed in a wide spectrum of cells, including those participating in the inflammatory response. In acute inflammation, the interaction of AnxA2 with actin and adherens junction VE-cadherins underlies its role in regulating vascular integrity. In addition, its contribution to endosomal membrane repair impacts several aspects of inflammatory regulation, including lysosome repair, which regulates inflammasome activation, and autophagosome biogenesis, which is essential for macroautophagy. On the other hand, AnxA2 may be co-opted to promote adhesion, entry, and propagation of bacteria or viruses into host cells. In the later stages of acute inflammation, AnxA2 contributes to the initiation of angiogenesis, which promotes tissue repair, but, when dysregulated, may also accompany chronic inflammation. AnxA2 is overexpressed in malignancies, such as breast cancer and glioblastoma, and likely contributes to cancer progression in the context of an inflammatory microenvironment. We conclude that annexin AnxA2 normally fulfills a spectrum of anti-inflammatory functions in the setting of both acute and chronic inflammation but may contribute to disease states in settings of disordered homeostasis.

NMMHC IIA triggers neuronal autophagic cell death by promoting F-actin-dependent ATG9A trafficking in cerebral ischemia/reperfusion

Previous findings have shown that non-muscle myosin heavy-chain IIA (NMMHC IIA) is involved in autophagy induction triggered by starvation in D. melanogaster; however, its functional contribution to neuronal autophagy remains unclear. The aim of this study is to explore the function of NMMHC IIA in cerebral ischemia-induced neuronal autophagy and the underlying mechanism related to autophagy-related gene 9A (ATG9A) trafficking. Functional assays and molecular mechanism studies were used to investigate the role of NMMHC IIA in cerebral ischemia-induced neuronal autophagy in vivo and in vitro. A middle cerebral artery occlusion (MCAO) model in mice was used to evaluate the therapeutic effect of blebbistatin, a myosin II ATPase inhibitor. Herein, either depletion or knockdown of NMMHC IIA led to increased cell viability in both primary cultured cortical neurons and pheochromocytoma (PC12) cells exposed to oxygen–glucose deprivation/reoxygenation (OGD/R). In addition, NMMHC IIA and autophagic marker LC3B were upregulated by OGD/R, and inhibition of NMMHC IIA significantly reduced OGD-induced neuronal autophagy. Furthermore, NMMHC IIA-induced autophagy is through its interactions with F-actin and ATG9A in response to OGD/R. The NMMHC IIA–actin interaction contributes to ATG9A trafficking and autophagosome formation. Inhibition of the NMMHC IIA–actin interaction using blebbistatin and the F-actin polymerization inhibitor cytochalasin D significantly suppressed ATG9A trafficking and autophagy induction. Furthermore, blebbistatin significantly improved neurological deficits and infarct volume after ischemic attack in mice, accompanied by ATG9A trafficking and autophagy inhibition. These findings demonstrate neuroprotective effects of NMMHC IIA inhibition on regulating ATG9A trafficking-dependent autophagy activation in the context of cerebral ischemia/reperfusion.

Roles of N-terminal Annexin A2 phosphorylation sites and miR-206 in colonic adenocarcinoma

AIMS

Annexin A2 (ANXA2) is closely associated with tumor malignancy and its N-terminus includes a vital domain for its function. The aims are to explore the correlation between the sites (Tyr23, Ser1, Ser11 and Ser25) in the domain and its roles.

MAIN METHODS

We re-expressed ANXA2 with mutated sites in ANXA2-deleted human colonic adenocarcinoma cell line caco2 (ANXA2-/-caco2). A series of analyses were used to determine the correlation of each site with ANXA2 activation, cell malignancy enhancement and motility-associated microstructural development. Bioinformatics and luciferase reporter assays were employed to validate ANXA2-targeted miRNAs.

KEY FINDINGS

The in vitro results showed that all single and multiple mutations of the ANXA2 N-terminal sites inhibited ANXA2 phosphorylation at different levels and subsequently inhibited the proliferation, motility, and polymerization of F-actin and β-tubulin in caco2 cells. Motility-associated microstructures were significantly remodeled when these sites were mutated. The forced expression of miR-206 significantly suppressed the proliferation, motility and epithelial-mesenchymal transition (EMT) of caco2 cells. The in vivo results showed that all the ANXA2 N-terminal site mutations and forced expression of miR-206 significantly inhibited tumor growth. Overall, this study demonstrated that the sites of the ANXA2 N-terminus, especially Tyr23, play crucial roles in maintaining the high malignancy of colonic adenocarcinoma. Furthermore, miR-206 targets ANXA2 and plays a role as a cancer suppressor in colonic adenocarcinoma.

SIGNIFICANCE

Our study provided evidence that further elucidates the molecular mechanism of ANXA2 and its roles in colonic adenocarcinoma and suggested potential targets of ANXA2 for colonic adenocarcinoma therapy by using miR-206 as a novel strategy.

Quantitative Mitochondrial Proteomics Reveals ANXA7 as a Crucial Factor in Mitophagy

Mitochondria are involved in many crucial cellular processes. Maintaining healthy mitochondria is essential for cellular homeostasis. Parkin-dependent mitophagy plays an important role in selectively eliminating damaged mitochondria in mammalian cells. However, mechanisms of Parkin-dependent mitophagy remain elusive. In this research, we performed data-independent acquisition-based quantitative mitochondrial proteomics to study the proteomic alterations of carbonyl cyanide m-chlorophenylhydrazone (CCCP)-induced Parkin-mediated mitophagy. We identified 222 differentially expressed proteins, with 76 upregulations and 146 downregulations, which were potentially involved in mitophagy. We then demonstrated that annexin A7 (ANXA7), a calcium-dependent phospholipid-binding protein, can translocate to impaired mitochondria upon CCCP treatment, where it played a pivotal part in the process of Parkin-dependent mitophagy via interacting with BASP1. As a mitochondrial uncoupling agent, CCCP indirectly regulated ANXA7 and BASP1 to induce Parkin-dependent mitophagy.

Compounds targeting YadC of uropathogenic Escherichia coli and its host receptor annexin A2 decrease bacterial colonization in bladder

Background

Uropathogenic Escherichia coli (UPEC) is the leading cause of urinary tract infections (UTIs), and fimbrial tip adhesins, play important roles in UPEC colonization. Few fimbrial tip adhesins and their receptors on host cells, which have the potential to be the therapeutic targets, have been identified.

Methods

the UPEC wild-type strain CFT073, ΔyadC and the complemented strain were used to perform assays in vitro and in vivo. The effects of D-xylose targeting YadC on UPEC colonization were evaluated. A YadC receptor was identified by far-western blotting, LC-MS/MS and co-immunoprecipitation. The effects of compounds targeting the receptor on UPEC colonization were tested.

Findings

YadC was investigated for its mediation of UPEC adhesion and invasion to bladder epithelial cells in vitro; and its promotion of UPEC colonization in bladder in vivo. D-xylose, targeting YadC, showed prophylactic and therapeutic effects on UPEC colonization. Annexin A2 (ANXA2) was identified as a YadC receptor, involved in UPEC infection. ANXA2 inhibitors attenuated UPEC infections. The yadC gene was widely present in UPEC clinical isolates and phylogenetic analysis of yadC was performed.

Interpretation

YadC and its receptor ANXA2 play important roles in UPEC colonization in bladder, leading to novel treatment strategies targeting YadC or ANXA2 for acute UTIs.

Fund

This study was supported by grants from the National Natural Science Foundation of China (NSFC) Programs (31670071 and 31970133), the National Key Technologies R&D Program, Intergovernmental international innovation cooperation (2018YFE0102000), Tianjin Science and Technology Commissioner Project (18JCZDJC36000), the Science & Technology Development Fund of Tianjin Education Commission for Higher Education (2017ZD12). The Science Foundation of Tianjin Medical University (2016KY2M08).

Involvement of Actin in Autophagy and Autophagy-Dependent Multidrug Resistance in Cancer

Currently, autophagy in the context of cancer progression arouses a lot of controversy. It is connected with the possibility of switching the nature of this process from cytotoxic to cytoprotective and vice versa depending on the treatment. At the same time, autophagy of cytoprotective character may be one of the factors determining multidrug resistance, as intensification of the process is observed in patients with poorer prognosis. The exact mechanism of this relationship is not yet fully understood; however, it is suggested that one of the elements of the puzzle may be a cytoskeleton. In the latest literature reports, more and more attention is paid to the involvement of actin in the autophagy. The role of this protein is linked to the formation of autophagosomes, which are necessary element of the process. However, based on the proven effectiveness of manipulation of the actin pool, it seems to be an attractive alternative in breaking autophagy-dependent multidrug resistance in cancer.

Annexin A2 upregulation protects human retinal endothelial cells from oxygen-glucose deprivation injury by activating autophagy

Retinal neovascularization is a common pathological change in multiple diseases of the eyes and the upregulation of annexin A2 (A2) under a hypoxic and ischemic microenvironment has been demonstrated to be a key factor in the pathological process. However, the underlying mechanism by which A2 regulates retinal neovascularization remains unclear. In the present study, oxygen-glucose deprivation (OGD) was used to mimic the hypoxic and ischemic microenvironment, to observe the role of A2 in retinal neovascularization regulation by focusing on autophagy. The results showed that OGD treatment significantly increased the mRNA and protein levels of A2 in human retinal endothelial cells (HRECs), which was dependent on activation of hypoxia inducible factor (HIF)-1α signaling. The OGD-induced activation of autophagy was attenuated when A2 was silenced, but increased when A2 was overexpressed, suggesting that A2 upregulation contributed to OGD-induced cell autophagy activation. Furthermore, knockdown of A2 decreased cell viability and promoted cell apoptosis under OGD conditions. Overexpression of A2 increased cell viability and reduced cell apoptosis under OGD conditions, and inhibiting autophagy using an inhibitor, reversed these changes, suggesting that upregulation of A2 by OGD serves a cytoprotective role by inducing cell autophagy in HRECs. Taken together, the results of the present study suggested that promoting retinal endothelial cell survival by autophagy activation via the HIF-1α signaling pathway in a hypoxic and ischemic microenvironment may underlie the mechanism by which A2 regulates retinal neovascularization. The present study is the first study to demonstrate the novel role of A2 during retinal neovascularization under pathological conditions, to the best of our knowledge. Therefore, A2 may serve as a potential therapeutic target for treating neovascularization-associated conditions of the eye.

A repertoire of 124 potential autoantigens for autoimmune kidney diseases identified by dermatan sulfate affinity enrichment of kidney tissue proteins

Autoantigens are the molecular targets in autoimmune diseases. They are a cohort of seemingly unrelated self-molecules present in different parts of the body, yet they can trigger a similar chain of autoimmune responses such as autoantibody production. We previously reported that dermatan sulfate (DS) can bind self-molecules of dying cells to stimulate autoreactive CD5+ B cells to produce autoantibodies. The formation of autoantigen-DS complexes converts the normally non-antigenic self-molecules to none-self antigens, and thus DS-affinity represents a common underlying biochemical property for autoantigens. This study sought to apply this property to identify potential autoantigens in the kidney. Total proteins were extracted from mouse kidney tissues and loaded onto DS-Sepharose resins. Proteins without affinity were washed off the resins, whereas those with increasing DS-affinity were eluted with step gradients of increasing salt strength. Fractions with strong and moderate DS-affinity were sequenced by mass spectrometry and yielded 25 and 99 proteins, respectively. An extensive literature search was conducted to validate whether these had been previously reported as autoantigens. Of the 124 proteins, 79 were reported autoantigens, and 19 out of 25 of the strong-DS-binding ones were well-known autoantigens. Moreover, these proteins largely fell into the two most common autoantibody categories in autoimmune kidney diseases, including 40 ANA (anti-nuclear autoantibodies) and 25 GBM (glomerular basement membrane) autoantigens. In summary, this study compiles a large repertoire of potential autoantigens for autoimmune kidney diseases. This autoantigen-ome sheds light on the molecular etiology of autoimmunity and further supports our hypothesis DS-autoantigen complexes as a unifying principle of autoantigenicity.

Annexin A2 (ANX A2): An emerging biomarker and potential therapeutic target for aggressive cancers

ANX A2 is an important member of annexin family of proteins expressed on surface of endothelial cells (ECs), macrophages, mononuclear cells and various types of cancer cells. It exhibits high affinity binding for calcium (Ca⁺⁺ ) and phospholipids. ANX A2 plays an important role in many biological processes such as endocytosis, exocytosis, autophagy, cell-cell communications and biochemical activation of plasminogen. On the cell surface ANX A2 organizes the assembly of plasminogen (PLG) and tissue plasminogen activator (tPA) for efficient conversion of PLG to plasmin, a serine protease. Proteolytic activity of plasmin is required for activation of inactive pro-metalloproteases (pro-MMPs) and latent growth factors for their biological actions. These activation steps are critical for degradation of extracellular matrix (ECM) and basement proteins (BM) for cancer cell invasion and metastasis. Increased expression of ANX A2 protein/gene has been correlated with invasion and metastasis in a variety of human cancers. Moreover, clinical studies have positively correlated ANX A2 protein expression with aggressive cancers and with resistance to anticancer drugs, shorter disease-free survival (DFS), and worse overall survival (OS). The mechanism(s) by which ANX A2 regulates cancer invasion and metastasis are beginning to emerge. Investigators used various technologies to target ANX A2 in preclinical model of human cancers and demonstrated exciting results. In this review article, we analyzed existing literature concurrent with our own findings and provided a critical overview of ANX A2-dependent mechanism(s) of cancer invasion and metastasis.

[Selective autophagy mechanism against Group A Streptococcus infection]

Autophagy acts as an intracellular host defense system against invading pathogenic microorganisms such as Group A Streptococcus (GAS). Autophagy is a membrane-mediated degradation system that is regulated by intracellular membrane trafficking regulators, including small GTPase Rab proteins. Here, we revealed Rab GTPase network that regulate autophagosome formation against GAS. A unique set of Rab GTPases coordinates autophagy to enable to form huge autophagosomes surrounding GAS by linking recycling endosomes and trans Golgi-network. We also found that NLRP4, one of intracellular pathogen recognition receptor, directs Rho signaling to facilitate autophagosome formation. In this article, we would like to show our findings on how host autophagy regulators coordinate autophagy during GAS infection.

Contact inhibition controls cell survival and proliferation via YAP/TAZ-autophagy axis

Contact inhibition enables noncancerous cells to cease proliferation and growth when they contact each other. This characteristic is lost when cells undergo malignant transformation, leading to uncontrolled proliferation and solid tumor formation. Here we report that autophagy is compromised in contact-inhibited cells in 2D or 3D-soft extracellular matrix cultures. In such cells, YAP/TAZ fail to co-transcriptionally regulate the expression of myosin-II genes, resulting in the loss of F-actin stress fibers, which impairs autophagosome formation. The decreased proliferation resulting from contact inhibition is partly autophagy-dependent, as is their increased sensitivity to hypoxia and glucose starvation. These findings define how mechanically repressed YAP/TAZ activity impacts autophagy to contribute to core phenotypes resulting from high cell confluence that are lost in various cancers.

At high cell density or when plated on soft matrix, YAP/TAZ are redistributed from the nucleus to the cytosol, becoming transcriptionally inactive. Here the authors show that at high cell density, autophagosome formation is impaired due to reduced YAP/TAZ-dependent transcription of actomyosin genes

The Cytoskeleton-Autophagy Connection

Actin cytoskeleton dynamics play vital roles in most forms of intracellular trafficking by promoting the biogenesis and transport of vesicular cargoes. Mounting evidence indicates that actin dynamics and membrane-cytoskeleton scaffolds also have essential roles in macroautophagy, the process by which cellular waste is isolated inside specialized vesicles called autophagosomes for recycling and degradation. Branched actin polymerization is necessary for the biogenesis of autophagosomes from the endoplasmic reticulum (ER) membrane. Actomyosin-based transport is then used to feed the growing phagophore with pre-selected cargoes and debris derived from different membranous organelles inside the cell. Finally, mature autophagosomes detach from the ER membrane by an as yet unknown mechanism, undergo intracellular transport and then fuse with lysosomes, endosomes and multivesicular bodies through mechanisms that involve actin- and microtubule-mediated motility, cytoskeleton-membrane scaffolds and signaling proteins. In this review, we highlight the considerable progress made recently towards understanding the diverse roles of the cytoskeleton in autophagy.

Identification of ANXA2 (annexin A2) as a specific bleomycin target to induce pulmonary fibrosis by impeding TFEB-mediated autophagic flux

Bleomycin is a clinically potent anticancer drug used for the treatment of germ-cell tumors, lymphomas and squamous-cell carcinomas. Unfortunately, the therapeutic efficacy of bleomycin is severely hampered by the development of pulmonary fibrosis. However, the mechanisms underlying bleomycin-induced pulmonary fibrosis, particularly the molecular target of bleomycin, remains unknown. Here, using a chemical proteomics approach, we identify ANXA2 (annexin A2) as a direct binding target of bleomycin. The interaction of bleomycin with ANXA2 was corroborated both in vitro and in vivo. Genetic depletion of anxa2 in mice mitigates bleomycin-induced pulmonary fibrosis. We further demonstrate that Glu139 (E139) of ANXA2 is required for bleomycin binding in lung epithelial cells. A CRISPR-Cas9-engineered ANXA2^E139A mutation in lung epithelial cells ablates bleomycin binding and activates TFEB (transcription factor EB), a master regulator of macroautophagy/autophagy, resulting in substantial acceleration of autophagic flux. Pharmacological activation of TFEB elevates bleomycin-initiated autophagic flux, inhibits apoptosis and proliferation of epithelial cells, and ameliorates pulmonary fibrosis in bleomycin-treated mice. Notably, we observe lowered TFEB and LC3B levels in human pulmonary fibrosis tissues compared to normal controls, suggesting a critical role of TFEB-mediated autophagy in pulmonary fibrosis. Collectively, our data demonstrate that ANXA2 is a specific bleomycin target, and bleomycin binding with ANXA2 impedes TFEB-induced autophagic flux, leading to induction of pulmonary fibrosis. Our findings provide insight into the mechanisms of bleomycin-induced fibrosis and may facilitate development of optimized bleomycin therapeutics devoid of lung toxicity.

Autophagy and Hallmarks of Cancer

Autophagy is a catabolic program that is responsible for the degradation of dysfunctional or unnecessary proteins and organelles to maintain cellular homeostasis. Mechanistically, it involves the formation of double-membrane autophagosomes that sequester cytoplasmic material and deliver it to lysosomes for degradation. Eventually, the material is recycled back to the cytoplasm. Abnormalities of autophagy often lead to human diseases, such as neurodegeneration and cancer. In the case of cancer, increasing evidence has revealed the paradoxical roles of autophagy in both tumor inhibition and tumor promotion. Here, we summarize the context-dependent role of autophagy and its complicated molecular mechanisms in the hallmarks of cancer. Moreover, we discuss how therapeutics targeting autophagy can counter malignant transformation and tumor progression. Overall, the findings of studies discussed here shed new light on exploiting the complicated mechanisms of the autophagic machinery and relevant small-molecule modulators as potential antitumor agents to improve therapeutic outcomes.

SIRT6 Is a Target of Regulation by UBE3A That Contributes to Liver Tumorigenesis in an ANXA2-Dependent Manner

UBE3A is an E3 ubiquitin ligase well known for its role in the proteasomal degradation of p53 in human papillomavirus (HPV)-associated cancers. Here we report that UBE3A ubiquitylates and triggers degradation of the tumor-suppressive sirtuin SIRT6 in hepatocellular carcinoma. UBE3A ubiquitylated the highly conserved Lys160 residue on SIRT6. FOXO1-mediated transcriptional repression of UBE3A was sufficient to stabilize SIRT6 and to epigenetically repress ANXA2, a key mediator of UBE3A oncogenic function. Thus, UBE3A-mediated SIRT6 degradation promoted the proliferative capacity, migration potential, and invasiveness of cells. In mouse models of hepatocellular carcinoma, SIRT6 downregulation and consequent induction of ANXA2 were critical for UBE3A-mediated tumorigenesis. Furthermore, in clinical specimens, increased UBE3A levels correlated with reduced SIRT6 levels and elevated ANXA2 levels in increasing tumor grades. Overall, our findings show how the tumor suppressor SIRT6 is regulated in hepatocellular carcinoma and establish the mechanism underlying UBE3A-mediated tumorigenesis in this disease.Significance: These findings provide mechanistic insights into regulation of the tumor suppressive sirtuin SIRT6 and its implications for the development of hepatocellular carcinoma. Cancer Res; 78(3); 645-58. ©2017 AACR.

The intracellular microbial sensor NLRP4 directs Rho-actin signaling to facilitate Group A Streptococcus-containing autophagosome-like vacuole formation

Xenophagy, also known as antibacterial autophagy, functions as a crucial defense system that can utilize intracellular pattern recognition sensors, such as NLRP4, to recognize and selectively eliminate bacterial pathogens. However, little is known about how NLRP4 regulates xenophagy. Here, we report that NLRP4 binds ARHGDIA (Rho GDP dissociation inhibitor α) to regulate Rho GTPase signaling and facilitate actin-mediated xenophagy. Specifically, NLRP4 is recruited to Group A Streptococcus (GAS) and colocalizes with GAS-containing autophagosome-like vacuoles (GcAVs), where it regulates ARHGDIA-Rho GTPase recruitment to promote autophagosome formation. The interaction between NLRP4, ARHGDIA, and Rho GTPases is regulated by ARHGDIA Tyr156 phosphorylation, which acts as a gate to induce Rho-mediated xenophagy. Moreover, ARHGDIA and Rho GTPase are involved in actin-mediated ATG9A recruitment to phagophores, facilitating elongation to form autophagosomes. Collectively, these findings demonstrate that NLRP4 functions as a Rho receptor complex to direct actin dynamics regulating xenophagy.

The identification of molecular target of (20S) ginsenoside Rh2 for its anti-cancer activity

The 20S ginsenoside Rh2 (G-Rh2) effectively inhibits cancer cell growth and survival in both animal models and cell lines. However, its molecular targets and mechanism of action remain largely unknown. By screening for molecules that interact with (20S)G-Rh2 in a phage display assay, we have identified Annexin A2 as a potential target that mediates its anti-cancer activity. Isothermal titration calorimetry and a cellular thermal shift assay demonstrated that (20S)G-Rh2 directly bound to either recombinant or intracellular Annexin A2. This binding inhibited the interaction between Annexin A2 and the NF-кB p50 subunit, which attenuated the nuclear translocations of NF-кB p50 subunit and reduced the transactivation activity of NF-кB. Correspond to this result, (20S)G-Rh2 treatment significantly down-regulated the expression of IAPs (inhibitors of apoptosis), the well-established NF-кB targets that promote cell survival. Moreover, (20S)G-Rh2 synergized with Annexin A2 inactivation to promote apoptosis. Taken together, this study for the first time suggests a cellular target and a molecular pathway by which (20S)G-Rh2 inhibits cancer cell growth. As over-expression of Annexin A2 was evident in human hepatoma, (20S)G-Rh2 might be a promising natural compound for targeted liver cancer therapy.

Transcriptional regulation of mammalian autophagy at a glance

Macroautophagy, hereafter referred to as autophagy, is a catabolic process that results in the lysosomal degradation of cytoplasmic contents ranging from abnormal proteins to damaged cell organelles. It is activated  under diverse conditions, including nutrient deprivation and hypoxia. During autophagy, members of the core autophagy-related (ATG) family of proteins mediate membrane rearrangements, which lead to the engulfment and degradation of cytoplasmic cargo. Recently, the nuclear regulation of autophagy, especially by transcription factors and histone modifiers, has gained increased attention. These factors are not only involved in rapid responses to autophagic stimuli, but also regulate the long-term outcome of autophagy. Now there are more than 20 transcription factors that have been shown to be linked to the autophagic process. However, their interplay and timing appear enigmatic as several have been individually shown to act as major regulators of autophagy. This Cell Science at a Glance article and the accompanying poster highlights the main cellular regulators of transcription involved in mammalian autophagy and their target genes.

Annexin A2-S100A10 heterotetramer is upregulated by PML/RARα fusion protein and promotes plasminogen-dependent fibrinolysis and matrix invasion in acute promyelocytic leukemia

Aberrant expression of annexin A2-S100A10 heterotetramer (AIIt) associated with PML/RARα fusion protein causes lethal hyperfibrinolysis in acute promyelocytic leukemia (APL), but the mechanism is unclear. To facilitate the investigation of regulatory association between ANXA2 and promyelocytic leukemia/retinoic acid receptor a (PML/RARα) fusion protein, this work was performed to determine the transcription start site of ANXA2 promoter with rapid amplification of 5'-cDNA ends analysis. Zinc-induced U937/PR9 cells expressed PML/RARα fusion protein, and resultant increases in ANXA2 transcripts and translational expressions of both ANXA2 and S100A10, while S100A10 transcripts remained constitutive. The transactivation of ANXA2 promoter by PML/RARα fusion protein was 3.29 ± 0.13 fold higher than that by control pSG5 vector or wild-type RARα. The overexpression of ANXA2 in U937 transfected with full-length ANXA2 cDNA was associated with increased S100A10 subunit, although S100A10 transcripts remained constitutive. The tPA-dependent initial rate of plasmin generation (IRPG) in zinc-treated U937/PR9 increased by 2.13-fold, and cell invasiveness increased by 27.6%. Antibodies against ANXA2, S100A10, or combination of both all remarkably inhibited the IRPG and invasiveness in U937/PR9 and NB4. Treatment of zinc-induced U937/PR9 or circulating APL blasts with all-trans retinoic acid (ATRA) significantly reduced cell surface ANXA2 and S100A10 and associated reductions in IRPG and invasiveness. Thus, PML/RARα fusion protein transactivated the ANXA2 promoter to upregulate ANXA2 and accumulate S100A10. Increased AIIt promoted IRPG and invasiveness, both of which were partly abolished by antibodies against ANXA2 and S100A10 or by ATRA.