14-3-3 Proteins are Regulators of Autophagy

Dopaminergic REST/NRSF is protective against manganese-induced neurotoxicity in mice

Chronic exposure to elevated levels of manganese (Mn) may cause a neurological disorder referred to as manganism. The transcription factor REST is dysregulated in several neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. REST upregulated tyrosine hydroxylase and induced protection against Mn toxicity in neuronal cultures. In the present study, we investigated if dopaminergic REST plays a critical role in protecting against Mn-induced toxicity in vivo using dopaminergic REST conditional knockout (REST-cKO) mice and REST loxP mice as wild-type (WT) controls. Restoration of REST in the substantia nigra (SN) with neuronal REST AAV vector infusion was performed to further support the role of REST in Mn toxicity. Mice were exposed to Mn (330 ug, intranasal, daily for 3 weeks), followed by behavioral tests and molecular biology experiments. Results showed that Mn decreased REST mRNA/protein levels in the SN-containing midbrain, as well as locomotor activity and motor coordination in WT mice, which were further decreased in REST-cKO. Mn-induced mitochondrial insults, such as impairment of fission/fusion and mitophagy, apoptosis, and oxidative stress, in the midbrain of WT mice were more pronounced in REST-cKO. However, REST restoration in the SN of REST cKO mice attenuated Mn-induced neurotoxicity. REST's molecular target for its protection is unclear, but REST attenuated Mn-induced mitochondrial dysregulation, indicating that it is a primary intracellular target for both Mn and REST. These novel findings suggest that dopaminergic REST in the nigrostriatal pathway is critical in protecting against Mn toxicity, underscoring REST as a potential therapeutic target for treating manganism.

Role of 14-3-3 protein family in the pathobiology of EBV in immortalized B cells and Alzheimer's disease

Background and Aims

Several studies have revealed that Epstein-Barr virus (EBV) infection raised the likelihood of developing Alzheimer's disease (AD) via infecting B lymphocytes. The purpose of the current investigation was to assess the possible association between EBV infection and AD.

Methods

The microarray datasets GSE49628, GSE126379, GSE122063, and GSE132903 were utilized to extract DEGs by using the GEO2R tool of the GEO platform. The STRING tool was used to determine the interaction between the DEGs, and Cytoscape was used to visualize the results. The DEGs that were found underwent function analysis, including pathway and GO, using the DAVID 2021 and ClueGo/CluePedia. By using MNC, MCC, Degree, and Radiality of cytoHubba, we identified seven common key genes. Gene co-expression analysis was performed through the GeneMANIA web tool. Furthermore, expression analysis of key genes was performed through GTEx software, which have been identified in various human brain regions. The miRNA-gene interaction was performed through the miRNet v 2.0 tool. DsigDB on the Enrichr platform was utilized to extract therapeutic drugs connected to key genes.

Results

In GEO2R analysis of datasets with |log2FC|≥ 0.5 and p-value <0.05, 8386, 10,434, 7408, and 759 genes were identified. A total of 141 common DEGs were identified by combining the extracted genes of different datasets. A total of 141 nodes and 207 edges were found during the PPI analysis. The DEG GO analysis with substantial alterations disclosed that they are associated to molecular functions and biological processes, such as positive regulation of neuron death, autophagy regulation of mitochondrion, response of cell to insulin stimulus, calcium signaling regulation, organelle transport along microtubules, protein kinase activity, and phosphoserine binding. Kyoto Encyclopedia of Genes and Genomes analysis discovered the correlation between the DEGs in pathways of neurodegeneration: multiple disease, cell cycle, and cGMP-PKG signaling pathway. Finally, YWHAH, YWHAG, YWHAB, YWHAZ, MAP2K1, PPP2CA, and TUBB genes were identified that are strongly linked to EBV and AD. Three miRNAs, i.e., hsa-mir-15a-5p, hsa-let-7a-5p, and hsa-mir-7-5p, were identified to regulate most of hub genes that are associated with EBV and AD. Further top 10 significant therapeutic drugs were predicted.

Conclusion

We have discovered new biomarkers and therapeutic targets for AD, as well as the possible biological mechanisms whereby infection with EBV may be involved in AD susceptibility for the first time.

A-Syn(ful) MAM: A Fresh Perspective on a Converging Domain in Parkinson's Disease

Parkinson's disease (PD) is a disease of an unknown origin. Despite that, decades of research have provided considerable evidence that alpha-synuclein (αSyn) is central to the pathogenesis of disease. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are functional domains formed at contact sites between the ER and mitochondria, with a well-established function of MAMs being the control of lipid homeostasis within the cell. Additionally, there are numerous proteins localized or enriched at MAMs that have regulatory roles in several different molecular signaling pathways required for cellular homeostasis, such as autophagy and neuroinflammation. Alterations in several of these signaling pathways that are functionally associated with MAMs are found in PD. Taken together with studies that find αSyn localized at MAMs, this has implicated MAM (dys)function as a converging domain relevant to PD. This review will highlight the many functions of MAMs and provide an overview of the literature that finds αSyn, in addition to several other PD-related proteins, localized there. This review will also detail the direct interaction of αSyn and αSyn-interacting partners with specific MAM-resident proteins. In addition, recent studies exploring new methods to investigate MAMs will be discussed, along with some of the controversies regarding αSyn, including its several conformations and subcellular localizations. The goal of this review is to highlight and provide insight on a domain that is incompletely understood and, from a PD perspective, highlight those complex interactions that may hold the key to understanding the pathomechanisms underlying PD, which may lead to the targeted development of new therapeutic strategies.

Usnic Acid Targets 14-3-3 Proteins and Suppresses Cancer Progression by Blocking Substrate Interaction

The anticancer therapeutic effects of usnic acid (UA), a lichen secondary metabolite, have been demonstrated in vitro and in vivo. However, the mechanism underlying the anticancer effect of UA remains to be clarified. In this study, the target protein of UA was identified using a UA-linker-Affi-Gel molecule, which showed that UA binds to the 14-3-3 protein. UA binds to 14-3-3, causing the degradation of proteasomal and autophagosomal proteins. The interaction of UA with 14-3-3 isoforms modulated cell invasion, cell cycle progression, aerobic glycolysis, mitochondrial biogenesis, and the Akt/mTOR, JNK, STAT3, NF-κB, and AP-1 signaling pathways in colorectal cancer. A peptide inhibitor of 14-3-3 blocked or regressed the activity of UA and inhibited its effects. The results suggest that UA binds to 14-3-3 isoforms and suppresses cancer progression by affecting 14-3-3 targets and phosphorylated proteins.

14-3-3ζ inhibits maladaptive repair in renal tubules by regulating YAP and reduces renal interstitial fibrosis

Acute kidney injury (AKI) refers to a group of common clinical syndromes characterized by acute renal dysfunction, which may lead to chronic kidney disease (CKD), and this process is called the AKI-CKD transition. The transcriptional coactivator YAP can promote the AKI-CKD transition by regulating the expression of profibrotic factors, and 14-3-3 protein zeta (14-3-3ζ), an important regulatory protein of YAP, may prevent the AKI-CKD transition. We established an AKI-CKD model in mice by unilateral renal ischemia-reperfusion injury and overexpressed 14-3-3ζ in mice using a fluid dynamics-based gene transfection technique. We also overexpressed and knocked down 14-3-3ζ in vitro. In AKI-CKD model mice, 14-3-3ζ expression was significantly increased at the AKI stage. During the development of chronic disease, the expression of 14-3-3ζ tended to decrease, whereas active YAP was consistently overexpressed. In vitro, we found that 14-3-3ζ can combine with YAP, promote the phosphorylation of YAP, inhibit YAP nuclear translocation, and reduce the expression of fibrosis-related proteins. In an in vivo intervention experiment, we found that the overexpression of 14-3-3ζ slowed the process of renal fibrosis in a mouse model of AKI-CKD. These findings suggest that 14-3-3ζ can affect the expression of fibrosis-related proteins by regulating YAP, inhibit the maladaptive repair of renal tubular epithelial cells, and prevent the AKI-CKD transition.

Physiological Consequences of Targeting 14-3-3 and Its Interacting Partners in Neurodegenerative Diseases

The mammalian 14-3-3 family comprises seven intrinsically unstructured, evolutionarily conserved proteins that bind >200 protein targets, thereby modulating cell-signaling pathways. The presence of 14-3-3 proteins in cerebrospinal fluid provides a sensitive and specific biomarker of neuronal damage associated with Alzheimer’s disease (AD), Creutzfeldt−Jakob disease (CJD), spongiform encephalitis, brain cancers, and stroke. We observed significant enrichment of 14-3-3 paralogs G, S, and Z in human brain aggregates diagnostic of AD. We used intra-aggregate crosslinking to identify 14-3-3 interaction partners, all of which were significantly enriched in AD brain aggregates relative to controls. We screened FDA-approved drugs in silico for structures that could target the 14-3-3G/hexokinase interface, an interaction specific to aggregates and AD. C. elegans possesses only two 14-3-3 orthologs, which bind diverse proteins including DAF-16 (a FOXO transcription factor) and SIR-2.1 (a sensor of nutrients and stress), influencing lifespan. Top drug candidates were tested in C. elegans models of neurodegeneration-associated aggregation and in a human neuroblastoma cell-culture model of AD-like amyloidosis. Several drugs opposed aggregation in all models assessed and rescued behavioral deficits in C. elegans AD-like neuropathy models, suggesting that 14-3-3 proteins are instrumental in aggregate accrual and supporting the advancement of drugs targeting 14-3-3 protein complexes with their partners.

14-3-3 proteins contribute to autophagy by modulating SINAT-mediated degradation of ATG13

In multicellular eukaryotes, autophagy is a conserved process that delivers cellular components to the vacuole or lysosome for recycling during development and stress responses. Induction of autophagy activates AUTOPHAGY-RELATED PROTEIN 1 (ATG1) and ATG13 to form a protein kinase complex that initiates autophagosome formation. However, the detailed molecular mechanism underlying the regulation of this protein complex in plants remains unclear. Here, we determined that in Arabidopsis thaliana, the regulatory proteins 14-3-3λ and 14-3-3κ redundantly modulate autophagy dynamics by facilitating SEVEN IN ABSENTIA OF ARABIDOPSIS THALIANA (SINAT)-mediated proteolysis of ATG13a and ATG13b. 14-3-3λ and 14-3-3κ directly interacted with SINATs and ATG13a/b in vitro and in vivo. Compared to wild-type (WT), the 14-3-3λ 14-3-3κ double mutant showed increased tolerance to nutrient starvation, delayed leaf senescence, and enhanced starvation-induced autophagic vesicles. Moreover, 14-3-3s were required for SINAT1-mediated ubiquitination and degradation of ATG13a. Consistent with their roles in ATG degradation, the 14-3-3λ 14-3-3κ double mutant accumulated higher levels of ATG1a/b/c and ATG13a/b than the WT upon nutrient deprivation. Furthermore, the specific association of 14-3-3s with phosphorylated ATG13a was crucial for ATG13a stability and formation of the ATG1-ATG13 complex. Thus, our findings demonstrate that 14-3-3λ and 14-3-3κ function as molecular adaptors to regulate autophagy by modulating the homeostasis of phosphorylated ATG13.

High-Resolution Crystal Structure of Muscle Phosphoglycerate Mutase Provides Insight into Its Nuclear Import and Role

Phosphoglycerate mutase (PGAM) is a glycolytic enzyme converting 3-phosphoglycerate to 2-phosphoglycerate, which in mammalian cells is expressed in two isoforms: brain (PGAM1) and muscle (PGAM2). Recently, it was shown that besides its enzymatic function, PGAM2 can be imported to the cell nucleus where it co-localizes with the nucleoli. It was suggested that it functions there to stabilize the nucleolar structure, maintain mRNA expression, and assist in the assembly of new pre-ribosomal subunits. However, the precise mechanism by which the protein translocates to the nucleus is unknown. In this study, we present the first crystal structure of PGAM2, identify the residues involved in the nuclear localization of the protein and propose that PGAM contains a “quaternary nuclear localization sequence (NLS)”, i.e., one that consists of residues from different protein chains. Additionally, we identify potential interaction partners for PGAM2 in the nucleoli and demonstrate that 14-3-3ζ/δ is indeed an interaction partner of PGAM2 in the nucleus. We also present evidence that the insulin/IGF1–PI3K–Akt–mTOR signaling pathway is responsible for the nuclear localization of PGAM2.

hucMSC-sEVs-Derived 14-3-3ζ Serves as a Bridge between YAP and Autophagy in Diabetic Kidney Disease

As nanoscale membranous vesicles, human umbilical cord mesenchymal stem cell-derived small extracellular vesicles (hucMSC-sEVs) have attracted extensive attention in the field of tissue regeneration. Under the premise that the mechanisms of hucMSC-sEVs on the treatment of diabetic kidney disease (DKD) have not been revealed clearly, we constructed DKD rat model with success. After tail vein injection, hucMSC-sEVs effectively reduced blood glucose, maintained body weight and improved renal function in DKD rats. Notably, we found that hucMSC-sEVs suppressed YAP expression in renal cortical regions. Further in vitro experiments, we confirmed that the expression of YAP in the nucleus of renal podocytes was increased, and the level of autophagy was inhibited in the high-glucose environment, which could be reversed by intervention with hucMSC-sEVs. We screened out the key protein 14-3-3ζ, which could not only promote YAP cytoplasmic retention instead of entering the nucleus, but also enhance the level of autophagy in the cytoplasm. Ultimately, excessive YAP protein was removed by autophagy, a classic way of protein degradation. In conclusion, our study provides new strategies for the prevention of DKD and proposes the possibility of hucMSC-sEVs becoming a new treatment for DKD in the future.

Curcumin ameliorates H2O2‑induced inflammatory response in chondrocytes by inducing autophagy activation

Relapsing polychondritis (RP) is a clinical disease characterized by inflammation of cartilage tissue and chondrocytes. The principal curcuminoid curcumin is the most active component in turmeric and has been reported to have a chondroprotective effect, including anti-inflammatory activity, which is vitally important for mitigating RP symptoms and prognosis. However, the mechanisms underlying these actions have remained to be fully elucidated. In the present study, the chondroprotective mechanisms of curcumin on hydrogen peroxide (H₂O₂)-treated primary chondrocytes were examined in vitro. The viability of chondrocytes treated with H₂O₂ was significantly reduced in a dose- and time-dependent manner. Cotreatment of curcumin with H₂O₂ significantly decreased growth inhibition. It was observed that curcumin inhibited the expression levels of the inflammatory mediators interleukin (IL)-1β, IL-6 and inducible nitric oxide synthase and induced autophagy activation. Curcumin increased the protein levels of the autophagy marker beclin-1 and light chain 3-II and decreased the expression levels of P62 in H₂O₂-treated chondrocytes. The curcumin-induced anti-inflammatory effects were markedly abrogated by the autophagy inhibitor 3-methyladenine. In conclusion, the present study suggested that curcumin regulates inflammatory factors by activating autophagy in chondrocytes. The protective role of curcumin in chondrocytes was demonstrated, suggesting that it should be explored for the prophylactic treatment of RP in the clinic in the future.

14-3-3 proteins at the crossroads of neurodevelopment and schizophrenia

The 14-3-3 family comprises multifunctional proteins that play a role in neurogenesis, neuronal migration, neuronal differentiation, synaptogenesis and dopamine synthesis. 14-3-3 members function as adaptor proteins and impact a wide variety of cellular and physiological processes involved in the pathophysiology of neurological disorders. Schizophrenia is a psychiatric disorder and knowledge about its pathophysiology is still limited. 14-3-3 have been proven to be linked with the dopaminergic, glutamatergic and neurodevelopmental hypotheses of schizophrenia. Further, research using genetic models has demonstrated the role played by 14-3-3 proteins in neurodevelopment and neuronal circuits, however a more integrative and comprehensive approach is needed for a better understanding of their role in schizophrenia. For instance, we still lack an integrated assessment of the processes affected by 14-3-3 proteins in the dopaminergic and glutamatergic systems. In this context, it is also paramount to understand their involvement in the biology of brain cells other than neurons. Here, we present previous and recent research that has led to our current understanding of the roles 14-3-3 proteins play in brain development and schizophrenia, perform an assessment of their functional protein association network and discuss the use of protein-protein interaction modulators to target 14-3-3 as a potential therapeutic strategy.

Molecular Mechanisms of Mesenchymal Stem Cell-Based Therapy in Acute Kidney Injury

Acute kidney injury (AKI) causes a lot of harm to human health but is treated by only supportive therapy in most cases. Recent evidence shows that mesenchymal stem cells (MSCs) benefit kidney regeneration through releasing paracrine factors and extracellular vesicles (EVs) to the recipient kidney cells and are considered to be promising cellular therapy for AKI. To develop more efficient, precise therapies for AKI, we review the therapeutic mechanism of MSCs and MSC-derived EVs in AKI and look for a better understanding of molecular signaling and cellular communication between donor MSCs and recipient kidney cells. We also review recent clinical trials of MSC-EVs in AKI. This review summarizes the molecular mechanisms of MSCs' therapeutic effects on kidney regeneration, expecting to comprehensively facilitate future clinical application for treating AKI.

Targeting PRAS40: a novel therapeutic strategy for human diseases

Proline-rich Akt substrate of 40 kD (PRAS40) is not only the substrate of protein kinase B (PKB/Akt), but also the binding protein of 14-3-3 protein. PRAS40 is expressed in a variety of tissues in vivo and has multiple phosphorylation sites, which its activity is closely related to phosphorylation. Studies have shown that PRAS40 is involved in regulating cell growth, cell apoptosis, oxidative stress, autophagy and angiogenesis, as well as various of signalling pathways such as mammalian target of mammalian target rapamycin (mTOR), protein kinase B (PKB/Akt), nuclear factor kappa-B(NF-κB), proto-oncogene serine/threonine-protein kinase PIM-1(PIM1) and pyruvate kinase M2 (PKM2). The interactive roles between PRAS40 and these signal proteins were analysed by bioinformatics in this paper. Moreover, it is of great necessity for analyse the important roles of PRAS40 in some human diseases including cardiovascular disease, ischaemia-reperfusion injury, neurodegenerative disease, cancer, diabetes and other metabolic diseases. Finally, the effects of miRNA on the regulation of PRAS40 function and the occurrence and development of PRAS40-related diseases are also discussed. Overall, PRAS40 is expected to be a drug target and provide a new treatment strategy for human diseases.

The role of 14-3-3 proteins in cell signalling pathways and virus infection

14-3-3 proteins are highly conserved in species ranging from yeast to mammals and regulate numerous signalling pathways via direct interactions with proteins carrying phosphorylated 14-3-3-binding motifs. Recent studies have shown that 14-3-3 proteins can also play a role in viral infections. This review summarizes the biological functions of 14-3-3 proteins in protein trafficking, cell-cycle control, apoptosis, autophagy and other cell signal transduction pathways, as well as the associated mechanisms. Recent findings regarding the role of 14-3-3 proteins in viral infection and innate immunity are also reviewed.

Endonuclease G promotes autophagy by suppressing mTOR signaling and activating the DNA damage response

Endonuclease G (ENDOG), a mitochondrial nuclease, is known to participate in many cellular processes, including apoptosis and paternal mitochondrial elimination, while its role in autophagy remains unclear. Here, we report that ENDOG released from mitochondria promotes autophagy during starvation, which we find to be evolutionally conserved across species by performing experiments in human cell lines, mice, Drosophila and C. elegans. Under starvation, Glycogen synthase kinase 3 beta-mediated phosphorylation of ENDOG at Thr-128 and Ser-288 enhances its interaction with 14-3-3γ, which leads to the release of Tuberin (TSC2) and Phosphatidylinositol 3-kinase catalytic subunit type 3 (Vps34) from 14-3-3γ, followed by mTOR pathway suppression and autophagy initiation. Alternatively, ENDOG activates DNA damage response and triggers autophagy through its endonuclease activity. Our results demonstrate that ENDOG is a crucial regulator of autophagy, manifested by phosphorylation-mediated interaction with 14-3-3γ, and its endonuclease activity-mediated DNA damage response.

An endogenous PI3K interactome promoting astrocyte-mediated neuroprotection identifies a novel association with RNA-binding protein ZC3H14

Astrocytes can support neuronal survival through a range of secreted signals that protect against neurotoxicity, oxidative stress, and apoptotic cascades. Thus, analyzing the effects of the astrocyte secretome may provide valuable insight into these neuroprotective mechanisms. Previously, we characterized a potent neuroprotective activity mediated by retinal astrocyte conditioned media (ACM) on retinal and cortical neurons in metabolic stress models. However, the molecular mechanism underlying this complex activity in neuronal cells has remained unclear. Here, a chemical genetics screen of kinase inhibitors revealed phosphoinositide 3-kinase (PI3K) as a central player transducing ACM-mediated neuroprotection. To identify additional proteins contributing to the protective cascade, endogenous PI3K was immunoprecipitated from neuronal cells exposed to ACM or control media, followed by MS/MS proteomic analyses. These data pointed toward a relatively small number of proteins that coimmunoprecipitated with PI3K, and surprisingly only five were regulated by the ACM signal. These hits included expected PI3K interactors, such as the platelet-derived growth factor receptor A (PDGFRA), as well as novel RNA-binding protein interactors ZC3H14 (zinc finger CCCH-type containing 14) and THOC1 (THO complex protein 1). In particular, ZC3H14 has recently emerged as an important RNA-binding protein with multiple roles in posttranscriptional regulation. In validation studies, we show that PI3K recruitment of ZC3H14 is necessary for PDGF-induced neuroprotection and that this interaction is present in primary retinal ganglion cells. Thus, we identified a novel non-cell autonomous neuroprotective signaling cascade mediated through PI3K that requires recruitment of ZC3H14 and may present a promising strategy to promote astrocyte-secreted prosurvival signals.

Myocardial proteomic profile in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare, fatal, and incurable disorder. Although advances in the understanding of the PAH pathobiology have been seen in recent years, molecular processes underlying heart remodelling over the course of PAH are still insufficiently understood. Therefore, the aim of this study was to investigate myocardial proteomic profile of rats at different stages of monocrotaline-induced PAH. Samples of left and right ventricle (LV and RV) free wall collected from 32 Wistar rats were subjected to proteomic analysis using an isobaric tag for relative quantitation method. Hemodynamic parameters indicated development of mild elevation of pulmonary artery pressure in the early PAH group (27.00 ± 4.93 mmHg) and severe elevation in the end-stage PAH group (50.50 ± 11.56 mmHg). In early PAH LV myocardium proteins that may be linked to an increase in inflammatory response, apoptosis, glycolytic process and decrease in myocardial structural proteins were differentially expressed compared to controls. During end-stage PAH an increase in proteins associated with apoptosis, fibrosis and cardiomyocyte Ca2+ currents as well as decrease in myocardial structural proteins were observed in LV. In RV during early PAH, especially proteins associated with myocardial structural components and fatty acid beta-oxidation pathway were upregulated. During end-stage PAH significant changes in RV proteins abundance related to the increased myocardial structural components, intensified fibrosis and glycolytic processes as well as decreased proteins related to cardiomyocyte Ca2+ currents were observed. At both PAH stages changes in RV proteins linked to apoptosis inhibition were observed. In conclusion, we identified changes of the levels of several proteins and thus of the metabolic pathways linked to the early and late remodelling of the left and right ventricle over the course of monocrotaline-induced PAH to delineate potential therapeutic targets for the treatment of this severe disease.

Systemic inhibition of miR-451 increases fibrotic signaling and diminishes autophagic response to exacerbate renal damage in Tallyho/Jng mice

miRNAs provide fine tuning of gene expression via inhibition of translation. miR-451 has a modulatory role in cell cycling via downregulation of mechanistic target of rapamycin. We aimed to test whether chronic systemic inhibition of miR-451 would enhance renal fibrosis (associated with deranged autophagy). Adult TallyHo/Jng mice (obese insulin resistant) were randomized to two treatment groups to receive either miR-451 inhibition [via a locked nucleic acid construct] or a similar scrambled locked nucleic acid control for 8 wk. All mice were fed a high-fat diet (60% kcal from fat) ad libitum and humanely euthanized after 12 wk. Kidneys and blood were collected for analysis. Renal expression of miR-451 was sixfold lower in inhibitor-treated mice compared with control mice. miR-451 inhibition increased kidney weight and collagen and glycogen deposition. Blood chemistry revealed significantly higher Na⁺ and anion gap (relative metabolic acidosis) in inhibitor-treated mice. Western blot analysis and immunohistochemistry of the kidney revealed that the inhibitor increased markers of renal injury and fibrosis, e.g., kidney injury molecule 1, neutrophil gelatinase-associated lipocalin, transforming growth factor-β, 14-3-3 protein-ζ, mechanistic target of rapamycin, AMP-activated protein kinase-α, calcium-binding protein 39, matrix metallopeptidase-9, and the autophagy receptor sequestosome 1. In contrast, the inhibitor reduced the epithelial cell integrity marker collagen type IV and the autophagy markers microtubule-associated protein 1A/1B light chain 3B and beclin-1. Taken together, these results support a protective role for miR-451 in reducing renal fibrosis by enhancing autophagy in obese mice.

Variable protein expression in marine-derived filamentous fungus Penicillium chrysogenum in response to varying copper concentrations and salinity

Copper is one of the essential trace dietary minerals for all living organisms, but is potentially toxic at higher concentrations, mainly due to the redox reactions in its transition state. Tolerance of microbes towards copper is primarily attributed to chelation and biosorption. In this study, marine-derived filamentous fungi were evaluated for their ability to remove Cu(ii) from a culture medium. Further, the cellular response of a select isolate to salinity stress (0, 35 and 100 PSU) and Cu(ii) stress (0, 100, and 500 ppm) was studied using the peptide mass fingerprinting technique, which revealed expression of 919 proteins, of which 55 proteins were commonly expressed across all conditions. Housekeeping proteins such as citrate synthase, pyruvate carboxylase, ribosomal proteins, ATP synthases, and more were expressed across all conditions. Reactive oxygen species scavenging proteins such as glutaredoxin, mitochondrial peroxiredoxins and thioredoxins were expressed under Cu(ii) and salinity stresses individually as well as in combination. Up-regulation of glutaredoxin under Cu(ii) stress with fold change values of 18.3 and 13.9 under 100 ppm and 500 ppm of Cu(ii) indicated active scavenging of free radicals to combat oxidative damage. The common mechanisms reported were enzymatic scavenging of free radicals, activation of DNA damage and repair proteins and probable intracellular metal chelation. This indicated multiple stress mechanisms employed by the isolate to combat the singular and synergistic effects of Cu(ii) and salinity stress.

Salvia miltiorrhiza-Derived Sal-miR-58 Induces Autophagy and Attenuates Inflammation in Vascular Smooth Muscle Cells

Autophagy is associated with the cytoprotection of physiological processes against inflammation and oxidative stress. Salvia miltiorrhiza possesses cardiovascular protective actions and has powerful anti-oxidative and anti-inflammatory effects; however, whether and how Salvia miltiorrhiza-derived microRNAs (miRNAs) protect vascular smooth muscle cells (VSMCs) by inducing autophagy across species are unknown. We first screened and identified Sal-miR-58 from Salvia miltiorrhiza as a natural autophagy inducer. Synthetic Sal-miR-58 suppresses chronic angiotensin II (Ang II) infusion-induced abdominal aortic aneurysm (AAA) formation in mice, as well as induces autophagy in VSMCs and attenuates the inflammatory response elicited by Ang II in vivo and in vitro. Mechanistically, Sal-miR-58 downregulates Krüppel-like factor 3 (KLF3) expression through direct binding to the 3' UTR of KLF3, which in turn relieves KLF3 repression of E3 ubiquitin ligase neural precursor cell-expressed developmentally downregulated 4-like (NEDD4L) expression, whereas NEDD4L upregulation increases the ubiquitination and degradation of the platelet isoform of phosphofructokinase (PFKP), subsequently leading to a decrease in the activation of Akt/mammalian target of rapamycin (mTOR) signaling and facilitating VSMC autophagy induced by Sal-miR-58 in the context of chronic Ang II stimulation and aneurysm formation. Our results provide the first evidence that plant-derived Sal-miR-58 induces autophagy and attenuates inflammation in VSMCs through cross-species modulation of the KLF3/NEDD4L/PFKP regulatory pathway.

Interplay Between Lipid Metabolism and Autophagy

Autophagy is a self-eating process of using lysosomes to degrade macromolecular substances (e.g., proteins and organelles) that are damaged, degenerated, or aging. Lipid metabolism is the synthesis and degradation of lipids (e.g., triglycerides, steroids, and phospholipids) to generate energy or produce the structural components of cell membranes. There is a complex interplay between lipid metabolism (e.g., digestion, absorption, catabolism, biosynthesis, and peroxidation) and autophagy machinery, leading to the modulation of cell homeostasis, including cell survival and death. In particular, lipid metabolism is involved in the formation of autophagic membrane structures (e.g., phagophores and autophagosomes) during stress. Moreover, autophagy, especially selective autophagy (e.g., lipophagy, ferritinophagy, clockophagy, and mitophagy), promotes lipid catabolism or lipid peroxidation-induced ferroptosis through the degradation of various substances within the cell. A better understanding of the mechanisms of autophagy and possible links to lipid metabolism will undoubtedly promote potential treatments for a variety of diseases.

Regenerative abilities of mesenchymal stem cells via acting as an ideal vehicle for subcellular component delivery in acute kidney injury

Cell‐to‐cell communication and information exchange is one of the most important events in multiple physiological processes, including multicellular organism development, cellular function regulation, external stress response, homeostasis maintenance and tissue regeneration. New findings support the concept that subcellular component delivery may account for the beneficial effects of mesenchymal stem cell (MSC)‐based therapy‐mediated protection against acute kidney injury (AKI). Through the secretion of extracellular vesicles (EVs), formation of tunnelling nanotubes (TNTs) and development of cellular fusions, a broad range of subcellular components, including proteins, nucleic acids (mRNA and miRNA) or even organelles can be transferred from MSCs into injured renal cells, significantly promoting cell survival, favouring tissue repair and accelerating renal recovery. In this review, we outline an extensive and detailed description of the regenerative consequences of subcellular component delivery from MSCs into injured renal cells during AKI, by which the potential mechanism underlying MSC‐based therapies against AKI can be elucidated.

Loss of Mitochondrial DNA by Gemcitabine Triggers Mitophagy and Cell Death

Gemcitabine (2,2-difluorodeoxycytidine nucleic acid), an anticancer drug exhibiting a potent ability to kill cancer cells, is a frontline chemotherapy drug. Although some chemotherapeutic medicines are known to induce nuclear DNA damage, no investigation into mitochondrial DNA (mtDNA) damage currently exists. When we treated insulinoma pancreatic β-cells (line INS-1) with high mitochondrial activity with gemcitabine for 24 h, the mtDNA contents were decreased. Gemcitabine induced a decrease in the number of mitochondria and the average potential of mitochondrial membrane in the cell but increased the superoxide anion radical levels. We observed that treatment with gemcitabine to induce cell death accompanied by autophagy-related protein markers, Atg5 and Atg7; these were significantly prevented by the autophagy inhibitors. The localization of Atg5 co-occurred with the location of mitochondria with membranes having high potential and mitophagy in cells treated with gemcitabine. The occurrence of mitophagy was inhibited by the inhibitors of the phosphatidylinositol 3-kinase/Akt pathway. Our results led us to the conclusion that gemcitabine induced cell death through mitophagy with the loss of mtDNA. These findings may provide a rationale for the combination of mtDNA damage with mitophagy in future clinical applications for cancer cells.

Regulation of 14-3-3β/α gene expression in response to salinity, thermal, and bacterial stresses in Siberian sturgeon (Acipenser baeri)

The 14-3-3 proteins are a family of widely expressed acidic proteins, which are involved in the regulation of many biological processes of animals. However, no research regarding 14-3-3 has been described in sturgeon to date, one of the most primitive Actinopterygii species. Here, we identified the first 14-3-3 gene from Siberian sturgeon (Acipenser baeri), named Ab14-3-3β/α (GenBank Accession No. KY094076.1). The cDNA of Ab14-3-3β/α is 1212 bp in length, containing a 5'-untranslated region (UTR) of 82 bp, a 3'UTR of 392 bp, and an open reading frame (ORF) of 738 bp, encoding a polypeptide of 245 amino acids which contains a 14-3-3 homologs domain (PF00244). Phylogenetic analysis showed that the 14-3-3 gene product from Acipenser baeri is a counterpart of vertebrate 14-3-3β/α. The deduced Ab14-3-3β/α protein shares high identities of 46.5-95.5% with the homologs of other species. Ab14-3-3β/α mRNA was constitutively expressed in all examined tissues, with high expression levels in the blood and gill. Furthermore, the expression level of Ab14-3-3β/α mRNA increased significantly in the gill at 1 h under acute salinity shock by transfer of Siberian sturgeons from fresh water (FW) to 15 ppt. In fish subjected to a high temperature (31 °C), Ab14-3-3β/α showed a significant upregulation in the liver at 3 h compared with the control group (24 °C). A 4.85-fold increase of Ab14-3-3β/α expression in the spleen of Siberian sturgeon was observed at 24 h following Aeromonas hydrophila challenge. Collectively, these results indicated that Ab14-3-3β/α might play a certain role in sturgeon in response to some environmental stresses and bacterial challenge.

TmAtg6 Plays an Important Role in Anti-Microbial Defense Against Listeria monocytogenes in the Mealworm, Tenebrio molitor

Autophagy-related gene-6 (Beclin-1 in mammals) plays a pivotal role in autophagy and is involved in autophagosome formation and autolysosome maturation. In this study, we identified and characterized the autophagy-related gene-6 from Tenebrio molitor (TmAtg6) and analyzed its functional role in the survival of the insect against infection. The expression of TmAtg6 was studied using qRT-PCR for the assessment of the transcript levels at various developmental stages in the different tissues. The results showed that TmAtg6 was highly expressed at the 6-day-old pupal stage. Tissue-specific expression studies revealed that TmAtg6 was highly expressed in the hemocytes of late larvae. The induction patterns of TmAtg6 in different tissues of T. molitor larvae were analyzed by injecting Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, or Candida albicans. The intracellular Gram-positive bacteria, L. monocytogenes, solely induced the expression of TmAtg6 in hemocytes at 9 h-post-injection, whilst in the fat body and gut, bimodal expression times were observed. RNAi-mediated knockdown of the TmAtg6 transcripts, followed by a challenge with microbes, showed a significant reduction in larval survival rate against L. monocytogenes. Taken together, our results suggest that TmAtg6 plays an essential role in anti-microbial defense against intracellular bacteria.

Neural stem cell small extracellular vesicle-based delivery of 14-3-3t reduces apoptosis and neuroinflammation following traumatic spinal cord injury by enhancing autophagy by targeting Beclin-1

Neural stem cell-derived small extracellular vesicles (NSC-sEVs) play an important role in the repair of tissue damage. Our previous in vitro and in vivo studies found that preconditioning with NSC-sEVs promoted the recovery of functional behaviors following spinal cord injury by activating autophagy. However, the underlying mechanisms for such observations remain unclear. In this study, we further explored the mechanisms by which NSC-sEVs repair spinal cord injury via autophagy. We found that NSC-sEVs contain 14-3-3t protein, of which the overexpression or knockdown enhanced and decreased autophagy, respectively. In addition, 14-3-3t overexpression enhanced the anti-apoptotic and anti-inflammatory effects of NSC-sEVs, further promoting functional behavior recovery following spinal cord injury. The overexpression of 14-3-3t was used to further validate the in vivo results through a series of in vitro experiments. Conversely, knockdown of 14-3-3t attenuated the anti-apoptotic and anti-inflammatory effects of NSC-sEVs. Further studies also confirmed that NSC-sEVs increased Beclin-1 expression, with which 14-3-3t interacted and promoted its localization to autophagosome precursors. In this study, we found that NSC-sEVs deliver 14-3-3t, which interacts with Beclin-1 to activate autophagy. Our results indicate that 14-3-3t acts via a newly-discovered mechanism for the activation of autophagy by NSC-sEVs.

Downregulation of 14-3-3 Proteins in a Kainic Acid-Induced Neurotoxicity Model

The 14-3-3 proteins are among the most abundant proteins expressed in the brain, comprising about 1% of the total amount of soluble brain proteins. Through phosphoserine- and phosphothreonine-binding motifs, 14-3-3 proteins regulate many signaling proteins and cellular processes including cell death. In the present study, we utilized a well-known kainic acid (KA)-induced excitotoxicity rat model and examined the expression of 14-3-3 and its isoforms in the frontal cortex of KA-treated and control animals. Among the different 14-3-3 isoforms, abundant levels of eta and tau were detected in the frontal cortex, followed by sigma, epsilon, and gamma, while the expression levels of alpha/beta and zeta/delta isoforms were low. Compared to the control animals, KA treatment induced a significant downregulation of the overall 14-3-3 protein level as well as the levels of the abundant isoforms eta, tau, epsilon, and gamma. We also investigated two 14-3-3-interacting proteins that are involved in the cell death process: Bcl-2-associated X (BAX) and extracellular signal-regulated kinase (ERK). Both BAX and phosphorylated ERK showed increased levels following KA treatment. Together, these findings demonstrate an abundance of several 14-3-3 isoforms in the frontal cortex and that KA treatment can cause a downregulation of 14-3-3 expression and an upregulation of 14-3-3-interacting proteins BAX and phospho-ERK. Thus, downregulation of 14-3-3 proteins could be one of the early molecular events associated with excitotoxicity. This could lead to subsequent upregulation of 14-3-3-binding proteins such as BAX and phospho-ERK that contribute to further downstream apoptosis processes, eventually leading to cell death. Maintaining sufficient levels of 14-3-3 expression and function may become a target of therapeutic intervention for excitotoxicity-induced neurodegeneration.

14-3-3/Tau Interaction and Tau Amyloidogenesis

The major function of microtubule-associated protein tau is to promote microtubule assembly in the central nervous system. However, aggregation of abnormally phosphorylated tau is a hallmark of tauopathies. Although the molecular mechanisms of conformational transitions and assembling of tau molecules into amyloid fibril remain largely unknown, several factors have been shown to promote tau aggregation, including mutations, polyanions, phosphorylation, and interactions with other proteins. 14-3-3 proteins are a family of highly conserved, multifunctional proteins that are mainly expressed in the central nervous system. Being a scaffolding protein, 14-3-3 proteins interact with tau and regulate tau phosphorylation by bridging tau with various protein kinases. 14-3-3 proteins also directly regulate tau aggregation via specific and non-specific interactions with tau. In this review, we summarize recent advances in characterization of tau conformation and tau/14-3-3 interaction. We discuss the connection between 14-3-3 binding and tau aggregation with a special emphasis on the regulatory role of 14-3-3 on tau conformation.

Extracellular vesicles degradation pathway based autophagy lysosome pathway

As an ancient intracellular degradation pathway, the autophagy lysosome pathway exists in various cells continuously and stably and maintains cellular homeostasis by degrading damaged organelles and misfolded proteins that are prejudicial to cells. Extracellular vesicles (EVs) including microparticles and exosomes, are derived from varieties of mammalian tissue cells such as platelets, endothelial cells, cardiomyocytes. Through large quantity of active substances carried by EVs, EVs exert momentous biological functions. Recent researches have revealed the molecular mechanism of the interaction between extracellular vesicles and autophagy. In this review, we first elaborate that extracellular vesicles are identified and internalized by target cells by means of receptor-ligand. Since extracellular vesicles contain multiple functional molecules, we subsequently describe the process of intracellular autophagy pathway induced by extracellular vesicles, which activates autophagy-related pathways or delivers autophagy-associated molecules. Finally, we introduced the effects of extracellular vesicle-induced autophagy on extracellular vesicles and target cells respectively. In conclusion, this article integrates relevant theoretical knowledge of autophagy caused by extracellular vesicles and provides a new direction for the study of extracellular vesicles in the future.

14-3-3 protein and ubiquitin C acting as SjIAP interaction partners facilitate tegumental integrity in Schistosoma japonicum

Schistosomiasis, caused by trematodes of the genus Schistosoma, remains an important public health issue. Adult schistosomes can survive in the definitive host for several decades, although they are subject to the host immune response. Consequently, understanding the mechanism underlying worm survival in the definitive hosts could aid in developing novel strategies against schistosomiasis. We previously found that an inhibitor of apoptosis in Schistosoma japonicum (SjIAP) could negatively regulate apoptosis by inhibiting caspase activity, which plays a critical role in maintaining tegument integrity. The current study aimed to further analyze the mechanism related to SjIAP governing worm tegument integrity; therefore, we used a yeast two-hybrid screen and identified a series of putative interacting partners of SjIAP, including 14-3-3 (Sj14-3-3) and ubiquitin C (SjUBC). Quantitative real time PCR (qRT-PCR) analysis indicated that transcript profiles of Sj14-3-3 and SjUBC increased together with worm development in definitive hosts, which corresponds to those of SjIAP in S. japonicum. Immunohistochemical analysis showed Sj14-3-3 and SjUBC were located in the tegument of adult parasites while they were also ubiquitously distributed in the bodies of worms. Silencing of Sj14-3-3/SjUBC expression led to increased caspase activity and induced worm death. Inhibition of Sj14-3-3 or SjUBC resulted in significant morphological alterations in the schistosome tegument. Overall, our findings indicated that Sj14-3-3 and SjUBC interacting with SjIAP may belong to another strategy of S. japonicum to maintain the tegument integrity.

Myosin IIA Regulated Tight Junction in Oxygen Glucose-Deprived Brain Endothelial Cells Via Activation of TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 Signal Transduction Pathway

Non-muscle myosin heavy chain IIA (NMMHC IIA), a member of Myosin II family, plays a critical role in various cellular physiological processes. Our previous research had suggested that NMMHC IIA could participate in regulating tight junction morphological changes induced by ischemia stroke. Thus, in the current study, we attempted to uncover the regulation pattern of NMMHC IIA on tight junction dysfunction in oxygen glucose-deprived (OGD) mouse brain bEND.3 endothelial cells. The regulation of NMMHC IIA on tight junction in OGD-stimulated bEND.3 cells was evaluated by western blotting assay. Morphologic change of occludin, claudin-5, and ZO-1 tight junction proteins was compared with pretreatment with NMMHC II inhibitor blebbistatin via immunohistochemical staining. Detection of activation of NMMHC IIA on OGD-mediated tight junction transduction pathway was investigated via Koch's postulate using corresponding protein inhibitor. Our results showed that NMMHC IIA was activated in OGD-stimulated bEND.3 endothelial cells. The inhibition of NMMHC IIA could attenuate the morphologic change of occludin, claudin-5, and ZO-1 tight junction proteins. NMMHC IIA participated in regulating downstream transduction pathway TLR4, phosphatidylinositol 3-kinase (PI3K), Akt, JNK1/2, 14-3-3ε, nuclear factor kappa B (NF-кB) and matrix metalloprotein 9 (MMP9). Blocking of these pathways using indicated inhibitors demonstrated that NMMHC IIA destroyed the connection of tight junction via the activation of TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 pathway. Our study described the key role of NMMHC IIA in OGD-stimulated mouse brain bEND.3 endothelial cells, while also exhibited the molecule effect on tight junction dysfunction via TLR4/PI3K/Akt/JNK1/2/14-3-3ε/NF-κB/MMP9 signal transduction pathway.

NorUDCA promotes degradation of α1-antitrypsin mutant Z protein by inducing autophagy through AMPK/ULK1 pathway

Alpha-1 Antitrypsin (α1AT) Deficiency is a genetic disease in which accumulation of α1AT mutant Z (α1ATZ) protein in the ER of hepatocytes causes chronic liver injury, liver fibrosis, and hepatocellular carcinoma. No effective medical therapy is currently available for the disease. We previously found that norUDCA improves the α1AT deficiency associated liver disease by promoting autophagic degradation of α1ATZ protein in liver in a mouse model of the disease. The current study unravels the novel underlying cellular mechanism by which norUDCA modulates autophagy. HTOZ cells, modified from HeLa Tet-Off cells by transfection with the resulting pTRE1-ATZ plasmid and expressing mutant Z proteins, were studied in these experiments. The role of norUDCA in inducing autophagy, autophagy-mediated degradation of α1ATZ and the role of AMPK in norUDCA-induced autophagy were examined in the current report. NorUDCA promoted disposal of α1ATZ via autophagy-mediated degradation of α1ATZ in HTOZ cells. Activation of AMPK was required for norUDCA-induced autophagy and α1ATZ degradation. Moreover, mTOR/ULK1 was involved in norUDCA-induced AMPK activation and autophagy in HTOZ cells. Our results provide novel mechanistic insights into the therapeutic action of norUDCA in promoting the clearance of α1ATZ in vitro and suggest a novel therapeutic approach for the treatment of α1ATZ deficiency disease and its associated liver diseases.

Molecular Cloning and Effects of Tm14-3-3ζ-Silencing on Larval Survivability Against E. coli and C. albicans in Tenebrio molitor

The 14-3-3 family of proteins performs key regulatory functions in phosphorylation-dependent signaling pathways including cell survival and proliferation, apoptosis, regulation of chromatin structure and autophagy. In this study, the zeta isoform of 14-3-3 proteins (designated as Tm14-3-3ζ) was identified from the expressed sequence tags (ESTs) and RNA sequencing (RNA-Seq) database of the coleopteran pest, Tenebrio molitor. Tm14-3-3ζ messenger RNA (mRNA) is expressed at higher levels in the immune organs of the larval and adult stages of the insect and exhibit almost five-fold induction within 3 h post-infection of the larvae with Escherichia coli and Candida albicans. To investigate the biological function of Tm14-3-3ζ, a peptide-based Tm14-3-3ζ polyclonal antibody was generated in rabbit and the specificity was confirmed using Western blot analysis. Immunostaining and confocal microscopic analyses indicate that Tm14-3-3ζ is mainly expressed in the membranes of midgut epithelial cells, the nuclei of fat body and the cytosol of hemocytes. Gene silencing of Tm14-3-3ζ increases mortality of the larvae at 7 days post-infection with E. coli and C. albicans. Our findings demonstrate that 14-3-3ζ in T. molitor is essential in the host defense mechanisms against bacteria and fungi.

The family of 14-3-3 proteins and specifically 14-3-3σ are up-regulated during the development of renal pathologies

Chronic kidney disease, the end result of most renal and some systemic diseases, is a common condition where renal function is compromised due to fibrosis. During renal fibrosis, calreticulin, a multifunctional chaperone of the endoplasmic reticulum (ER) is up‐regulated in tubular epithelial cells (TECs) both in vitro and in vivo. Proteomic analysis of cultured TECs overexpressing calreticulin led to the identification of the family of 14‐3‐3 proteins as key proteins overexpressed as well. Furthermore, an increased expression in the majority of 14‐3‐3 family members was observed in 3 different animal models of renal pathologies: the unilateral ureteric obstruction, the nephrotoxic serum administration and the ischaemia‐reperfusion. In all these models, the 14‐3‐3σ isoform (also known as stratifin) was predominantly overexpressed. As in all these models ischaemia is a common denominator, we showed that the ischaemia‐induced transcription factor HIF1α is specifically associated with the promoter region of the 14‐3‐3σ gene. Finally, we evaluated the expression of the family of 14‐3‐3 proteins and specifically 14‐3‐3σ in biopsies from IgA nephropathy and membranous nephropathy patients. These results propose an involvement of 14‐3‐3σ in renal pathology and provide evidence for the first time that hypoxia may be responsible for its altered expression.

Fhit, a tumor suppressor protein, induces autophagy via 14-3-3τ in non-small cell lung cancer cells

Inactivation of the fragile histidine triad (Fhit) gene has been reported in the majority of human cancers, particularly in lung cancer. The role of Fhit as a tumor suppressor gene has been well documented, and restoration of Fhit expression suppresses tumorigenicity in tumor cell lines and in mouse models by inducing apoptosis and inhibiting proliferation of tumor cells. Autophagy is a catabolic pathway, whereby cytoplasmic proteins and organelles are sequestered in vacuoles and delivered to lysosomes for degradation and recycling. Although autophagy is necessary for cell survival under stress conditions, recent studies have shown that autophagy can also promote cell death. Due to the fact that both autophagy induction and Fhit expression are commonly associated with nutrient starvation, we hypothesized that Fhit expression may be related to autophagy induction. In the present study, we assessed whether Fhit overexpression by gene transfer induces autophagy in Fhit-deficient non-small cell lung cancer (NSCLC) cells. The results of our study indicate that Fhit protein induces autophagy in NSCLC cells, and that this autophagy prevents apoptotic cell death in vivo and in vitro in a 14-3-3τ protein-dependent manner. To the best of our knowledge, this is the first report to describe Fhit-induced autophagy. Suppressing autophagy might be a promising therapeutic option to enhance the efficacy of Fhit gene therapy in NSCLC.

HucMSC exosomes-delivered 14-3-3ζ enhanced autophagy via modulation of ATG16L in preventing cisplatin-induced acute kidney injury

The clinical application of cisplatin is restricted by its side effects of nephrotoxicity. Human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-ex) have an important effect in tissue injury repair. Our previous work discovered that pretreatment with human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-ex) alleviated cisplatin-induced acute kidney injury (AKI) by activating autophagy both in vitro and in vivo. In this study, we further explored the mechanisms of hucMSC-ex in autophagy for preventing cisplatin-induced nephrotoxicity. We discovered that 14-3-3ζ was contained in hucMSC-ex, and knockdown and overexpression 14-3-3ζ reduced and enhanced the autophagic activity respectively. Furthermore, Knockdown of 14-3-3ζ alleviated the preventive effect of hucMSC-ex. In contrast, overexpression of 14-3-3ζ enhanced the effect. Further results confirmed that hucMSC-ex increased ATG16L expression and that 14-3-3ζ interacted with ATG16L, promoting the localization of ATG16L at autophagosome precursors. In this study, we revealed that hucMSC-ex-delivered 14-3-3ζ interacted with ATG16L to activate autophagy. Our findings suggest that 14-3-3ζ is a novel mechanism for MSC-exosomes-activated autophagy and provides a new strategy for the prevention of cisplatin-induced nephrotoxicity.

Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation

ATG9 is a membrane protein that is essential for autophagy and is considered to be directly involved in the early steps of autophagosome formation. Yeast Atg9 is mainly localized to small vesicles (Atg9 vesicles), whereas mammalian ATG9A is reportedly localized to the trans-Golgi network, the endosomal compartment, and other unidentified membrane structures. To dissect the ATG9A-containing membranes, we examined the subcellular localization of ATG9A and performed immunoisolation of those membranes. ATG9A-green fluorescent protein in human culture cells was observed as numerous puncta that move rapidly throughout the cytoplasm. We isolated these cytoplasmic membranes and found that they were small vesicles that resemble the yeast Atg9 vesicle. One of the proteins obtained via proteomic analyses of the mammalian ATG9A vesicle was Rab1, a small GTPase that is essential in endoplasmic reticulum-to-Golgi vesicle trafficking. Knockdown studies of Rab1B showed a suppression of autophagy. In these Rab1B-depleted cells, ATG9A accumulated in intermediate membrane structures at autophagosome formation sites. These results indicate that Rab1B is involved in regulating the proper development of autophagosomes.-Kakuta, S., Yamaguchi, J., Suzuki, C., Sasaki, M., Kazuno, S., Uchiyama, Y. Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation.

MicroRNA-30a-5p promotes replication of porcine circovirus type 2 through enhancing autophagy by targeting 14-3-3

Accumulating evidence demonstrates that autophagy and microRNAs (miRNAs) play key roles in regulating virus-host interactions and can restrict or facilitate viral replication. In the present study we examined whether a functional relationship exists between autophagy, miRNA and porcine circovirus type 2 (PCV2) infection, using several approaches. We demonstrated that there was a positive correlation between PCV2 infection and autophagy in 3D4/21 cells and autophagy induced by PCV2 infection triggered PCV2 replication. Four miRNA were selected by real-time PCR and further studied, but only miR-30a-5p mimic had a significant effect on PCV2 replication. Overexpression of miR-30a-5p significantly enhanced PCV2 infection and autophagy in a dose-dependent manner. Blockage of miR-30a-5p significantly decreased PCV2 replication. We provided further evidence that miR-30a-5p regulate the link between PCV2 infection and host immune system. Furthermore, miR-30a-5p targeted and regulated 14-3-3 gene, which is a regulator of autophagy. Flow cytometry data demonstrated that miR-30a-5p promotes cell cycle arrest at the G2 phase to regulate PCV2 replication and autophagy by interacting directly with 14-3-3, but not with the PCV2 genome. These data not only provide new insights into virus-host interactions during PCV2 infection but also suggest a potential new antiviral therapeutic strategy against PCV2 infection.

EXTENDED CYTOPROTECTIVE EFFECT OF AUTOPHAGY IN THE LATE STAGES OF SEPSIS AND FLUCTUATIONS IN SIGNAL TRANSDUCTION PATHWAYS IN A RAT EXPERIMENTAL MODEL OF KIDNEY INJURY

The impact of a potential autophagy (LC3a/b) deregulation in hyper and in hypo stages during sepsis-induced kidney injury and the temporal profile of phosphorylated extracellular signal-related kinase, P38 (pP38), Akt (pAKT), and 13-3-3β protein were investigated in the current study, using a rat cecal ligation and puncture (CLP) model, by means of flow cytometry and immunohistochemistry. Cell viability was assessed by protein C zymogen concentrate (PC), 7-aminoactinomycin D (7-AAD) staining and inflammation by S100 protein immunostaining. The impact of reduced kidney inflammation in autophagy was assessed by PC administration, an anti-inflammatory and cytoprotective substance. Sepsis induction increased LC3a/b expression, which presented two peaks at 6 and 36 h after CLP, both in the percentage of positive cells (P = 0.024, P = 0.025, respectively) and in fluorescence intensity. At 6 h when inflammation was already apparent, LC3a/b increase was escorted by phosphorylated extracellular signal-related kinase stimulation and high cell viability (65%), designating autophagy as a cytoprotective mechanism against microbial infection. The phosphorylation of P38 was delayed to 12 h after CLP, when autophagy was reduced. pAkt and 14-3-3β expression was stimulated between 6 and 36 h after CLP, although a slight inhibition of pAkt within each cell was detected (lower MnIX value). During the second peak, inflammation was intensified, necrosis was significantly increased with LC3a/b+/7-AAD + cells to present a 1.5-fold increase. Protein C zymogen concentrate administration declined autophagy at 6 and 36 h after CLP and reduced necrosis, whereas double positive LC3a/b and 7-AAD cells were increased by 1.68 and 2.78-fold, respectively. These data open new prospectives in sepsis treatment, since they further support that autophagy represents a cytoprotective mechanism triggered by stress conditions, rather than an alternative cell death pathway.

Stabilization and Degradation Mechanisms of Cytoplasmic Ataxin-1

Aggregation-prone proteins in neurodegenerative disease disrupt cellular protein stabilization and degradation pathways. The neurodegenerative disease spinocerebellar ataxia type 1 (SCA1) is caused by a coding polyglutamine expansion in the Ataxin-1 gene (ATXN1), which gives rise to the aggregation-prone mutant form of ATXN1 protein. Cerebellar Purkinje neurons, preferentially vulnerable in SCA1, produce ATXN1 protein in both cytoplasmic and nuclear compartments. Cytoplasmic stabilization of ATXN1 by phosphorylation and 14-3-3-mediated mechanisms ultimately drive translocation of the protein to the nucleus where aggregation may occur. However, experimental inhibition of phosphorylation and 14-3-3 binding results in rapid degradation of ATXN1, thus preventing nuclear translocation and cellular toxicity. The exact mechanism of cytoplasmic ATXN1 degradation is currently unknown; further investigation of degradation may provide future therapeutic targets. This review examines the present understanding of cytoplasmic ATXN1 stabilization and potential degradation mechanisms during normal and pathogenic states.

Anchoring of both PKA-RIIα and 14-3-3θ regulates retinoic acid induced 16 mediated phosphorylation of heat shock protein 70

Our previous study reported that retinoic acid induced 16 (RAI16) could enhance tumorigenesis in hepatocellular carcinoma (HCC). However, the cellular functions of RAI16 are still unclear. In this study, by immunoprecipitation and tandem (MS/MS) mass spectrometry analysis, we identified that RAI16 interacted with the type II regulatory subunit of PKA (PKA-RIIα), acting as a novel protein kinase A anchoring protein (AKAP). In addition, RAI16 also interacted with heat shock protein 70 (HSP70) and 14-3-3θ. Further studies indicated that RAI16 mediated PKA phosphorylation of HSP70 at serine 486, resulting in anti-apoptosis events. RAI16 was also phosphorylated by the anchored PKA at serine 325, which promoted the recruitment of 14-3-3θ, which, in turn, inhibited RAI16 mediated PKA phosphorylation of HSP70. These findings offer mechanism insight into RAI16 mediated anti-apoptosis signaling in HCC.

14-3-3 Proteins regulate Akt Thr308 phosphorylation in intestinal epithelial cells

Akt activation has been associated with proliferation, differentiation, survival and death of epithelial cells. Phosphorylation of Thr308 of Akt by phosphoinositide-dependent kinase 1 (PDK1) is critical for optimal stimulation of its kinase activity. However, the mechanism(s) regulating this process remain elusive. Here, we report that 14-3-3 proteins control Akt Thr308 phosphorylation during intestinal inflammation. Mechanistically, we found that IFNγ and TNFα treatment induce degradation of the PDK1 inhibitor, 14-3-3η, in intestinal epithelial cells. This mechanism requires association of 14-3-3ζ with raptor in a process that triggers autophagy and leads to 14-3-3η degradation. Notably, inhibition of 14-3-3 function by the chemical inhibitor BV02 induces uncontrolled Akt activation, nuclear Akt accumulation and ultimately intestinal epithelial cell death. Our results suggest that 14-3-3 proteins control Akt activation and regulate its biological functions, thereby providing a new mechanistic link between cell survival and apoptosis of intestinal epithelial cells during inflammation.

The role of the 14-3-3 protein family in health, disease, and drug development

14-3-3 proteins regulate intracellular signaling pathways, such as signal transduction, protein trafficking, cell cycle, and apoptosis. In addition to the ubiquitous roles of 14-3-3 isoforms, unique tissue-specific functions are also described for each isoform. Owing to their role in regulating cell cycle, protein trafficking, and steroidogenesis, 14-3-3 proteins are prevalent in human diseases, such as cancer, neurodegeneration, and reproductive disorders, and, therefore, serve as valuable drug targets. In this review, we summarize the role of 14-3-3 proteins in normal and disease states, with a focus on 14-3-3γ and ɛ. We also discuss drug compounds targeting 14-3-3 proteins and their potential therapeutic uses.

Phosphoproteomic Analysis Using the WW and FHA Domains as Biological Filters

Protein phosphorylation plays a key role in regulating nearly all intracellular biological events. However, poorly developed phospho-specific antibodies and low phosphoprotein abundance make it difficult to study phosphoproteins. Cellular protein phosphorylation data have been obtained using phosphoproteomic approaches, but the detection of low-abundance or fast-cycling phosphorylation sites remains a challenge. Enrichment of phosphoproteins together with phosphopeptides may greatly enhance the spectrum of low-abundance but biologically important phosphoproteins. Previously, we used 14-3-3ζ to selectively enrich for HeLa cell lysate phosphoproteins. However, because 14-3-3 does not isolate phosphoproteins lacking the 14-3-3-binding motif, we looked for other domains that could complementarily enrich for phosphoproteins. We here assessed and characterized the phosphoprotein binding domains Pin1-WW, CHEK2-FHA, and DLG1-GK. Using a strategy based on affinity chromatography, phosphoproteins were collected from the lysates of HeLa cells treated with phosphatase inhibitor or cAMP activator. We identified different subsets of phosphoproteins associated with WW or FHA after calyculin A, okadaic acid, or forskolin treatment. Our Kinase-Oriented Substrate Screening (KiOSS) method, which used phosphoprotein-binding domains, showed that WW and FHA are applicable and useful for the identification of novel phospho-substrates for kinases and can therefore be used as biological filters for comprehensive phosphoproteome analysis.