Autophagy proteins regulate ERK phosphorylation

Polymyxin B induces pigmentation by upregulating ATG2A-ERK/CREB-MITF-PMEL17 signaling axis

Polymyxin B serves as the last line of defense in treating multidrug-resistant Gram-negative bacterial infections. However, its distinctive side effect of hyperpigmentation significantly impacts patients' psychological well-being and treatment adherence. Currently, the underlying mechanism of polymyxin B-induced pigmentation remains to be incompletely investigated. This study aims to explore the correlation between polymyxin B-induced pigmentation and autophagy in zebrafish and melanoma cells. Comparative analysis between polymyxin B and its analog polymyxin E reveals opposite effects of the two polymyxins on PMEL17 expression and autophagic flux. Polymyxin B increases PMEL17 expression, correlating with elevated LC3B-II/I level and inhibition of autolysosomal degradation activity, while polymyxin E exerts the contrary effects. RNA-seq analysis of autophagy genes identifies a significant upregulation of ATG2A expression induced by polymyxin B. Moreover, polymyxin B, dependent on ATG2A, promotes MITF overexpression through the LC3B-II/pERK/pCREB pathway, subsequently enhancing PMEL17 expression. This study elucidates the mechanism linking polymyxin B-induced pigmentation and autophagy, demonstrating that polymyxin B causes the accumulation of PMEL17 within autophagosomes and inhibits its autophagic degradation, suggesting that autophagosomes may transform into melanosomes. These findings further contribute to the theoretical basis for autophagy regulating melanin synthesis, highlighting the multifaceted functions of autophagic proteins beyond degradation within autolysosomes.

MGAT3 and MGAT5 overexpression alters the protein cargo of extracellular vesicles released by metastatic melanoma cells

Extracellular vesicles (EVs) are potential non-invasive diagnostic, prognostic and therapeutic tools. Additionally, they are important contributors to tumorigenesis. Glycosylation has been found to modulate the composition of the EV proteome. Increased amounts of β1,6-branched N-glycans, synthesized by N-acetylglucosaminyltransferase V (GnT-V), are most commonly observed in melanoma and are associated with decreased cell adhesion and increased metastasis. The opposite effect is caused by the addition of bisecting GlcNAc by N-acetylglucosaminyltransferase III (GnT-III). To date, the impact of these enzymes on EV cargo in melanoma remains unexplored. Flow cytometry was used to study the surface glycosylation of genetic variants of WM266-4 melanoma cells with induced overexpression of GnT-III or GnT-V encoding genes (MGAT3 or MGAT5) and EVs released by these cells. LC-MS/MS proteomics was applied to analyze the effect of altered glycosylation on the proteome of released EVs, followed by detailed bioinformatic analysis. Flow cytometry analysis revealed dynamic changes in the surface glycosylation of EVs derived from melanoma cells overexpressing MGAT3 or MGAT5. Induced overexpression of MGAT3 or MGAT5 also caused significant changes in the proteome of EVs. The proteomic analysis identified a total of 1770 microvesicular and 704 exosomal proteins that play different roles in melanoma progression, including those with established diagnostic/prognostic potential and those closely associated with melanoma onset. Proteomic profiling of EVs derived from cells overexpressing MGAT3 and MGAT5 revealed functional changes in EV protein content driven by glycosylation modifications. The study presented a potential multifaced application of melanoma-derived EVs for diagnostic and prognostic purposes.

Discovery of Novel Aromatic Urea-Imidazole Salt Derivatives for Cancer Therapy via Targeting ERK1/2

Extracellular signal-regulated kinases (ERKs) are pivotal signaling molecules in the RAS-RAF-MEK-ERK signaling pathway and have emerged as potential antitumor targets, providing a promising strategy for tumor therapy. Therefore, the development of antitumor drugs targeting ERK protein has received extensive attention. Here, we developed a compound library based on a series of novel aromatic urea-imidazole salt derivatives and conducted phenotypic screening against various cancer cell lines. Notably, 21y exhibited high efficacy against MCF-7 cells (IC50 = 0.67 μM). Furthermore, label-free drug affinity responsive target stability (DARTS) and LC-MS/MS proteomics techniques revealed that 21y directly targets ERK1/2. Mechanistically, 21y induced cell apoptosis and autophagy-related cell death. In vivo studies confirmed that 21y strongly inhibited tumor growth and lung metastasis in breast cancer. Taken together, 21y targets ERK1/2 as a promising therapeutic agent for breast cancer therapy.

Tumor dormancy and relapse: understanding the molecular mechanisms of cancer recurrence

Cancer recurrence, driven by the phenomenon of tumor dormancy, presents a formidable challenge in oncology. Dormant cancer cells have the ability to evade detection and treatment, leading to relapse. This review emphasizes the urgent need to comprehend tumor dormancy and its implications for cancer recurrence. Despite notable advancements, significant gaps remain in our understanding of the mechanisms underlying dormancy and the lack of reliable biomarkers for predicting relapse. This review provides a comprehensive analysis of the cellular, angiogenic, and immunological aspects of dormancy. It highlights the current therapeutic strategies targeting dormant cells, particularly combination therapies and immunotherapies, which hold promise in preventing relapse. By elucidating these mechanisms and proposing innovative research methodologies, this review aims to deepen our understanding of tumor dormancy, ultimately facilitating the development of more effective strategies for preventing cancer recurrence and improving patient outcomes.

Aging, cancer, and autophagy: connections and therapeutic perspectives

Aging and cancer are intricately linked through shared molecular processes that influence both the onset of malignancy and the progression of age-related decline. As organisms age, cellular stress, genomic instability, and an accumulation of senescent cells create a pro-inflammatory environment conducive to cancer development. Autophagy, a cellular process responsible for degrading and recycling damaged components, plays a pivotal role in this relationship. While autophagy acts as a tumor-suppressive mechanism by preventing the accumulation of damaged organelles and proteins, cancer cells often exploit it to survive under conditions of metabolic stress and treatment resistance. The interplay between aging, cancer, and autophagy reveals key insights into tumorigenesis, cellular senescence, and proteostasis dysfunction. This review explores the molecular connections between these processes, emphasizing the potential for autophagy-targeted therapies as strategies that could be further explored in both aging and cancer treatment. Understanding the dual roles of autophagy in suppressing and promoting cancer offers promising avenues for therapeutic interventions aimed at improving outcomes for elderly cancer patients while addressing age-related deterioration.

Niraparib perturbs autophagosome-lysosome fusion in pancreatic ductal adenocarcinoma and exhibits anticancer potential against gemcitabine-resistant PDAC

While poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) have achieved specific clinical benefits in a subset of pancreatic ductal adenocarcinoma (PDAC) patients, the potential role of the PARPi niraparib in PDAC necessitates further exploration. In this study, we demonstrated that Niraparib exhibited a pronounced inhibitory effect on autophagy in PDAC both in vitro and in vivo. Mechanistically, this inhibition was primarily attributed to niraparib's ability to disrupt the fusion process between autophagosomes and lysosomes, while potentially exerting a relatively minor impact on the initial stage of autophagy. The blockade effect observed may be mediated via modulation of the ERK signaling pathway, and this effect can be mitigated by the application of an ERK inhibitor (FR180204). Notably, the combined treatment regimen of niraparib and gemcitabine failed to elicit the anticipated synergistic effects in wild-type PANC-1 cells, instead exhibiting pronounced antagonistic interactions. However, in gemcitabine-resistant PANC-1 cells, the combination of niraparib and gemcitabine exhibited modest additive effects. Furthermore, niraparib demonstrated a heightened cytotoxic potency against gemcitabine-resistant PANC-1 cells compared to wild-type PANC-1 cells, both in vitro and in vivo. Our research established that niraparib inhibits late-stage autophagy in PDAC, potentially representing a valuable salvage therapy for gemcitabine-resistant PDAC. Further clinical studies are justified.

Unveiling the physiological impact of ESCRT-dependent autophagosome closure by targeting the VPS37A ubiquitin E2 variant-like domain

Macroautophagy (autophagy) involves the formation of phagophores that mature into autophagosomes. The impact of inhibiting autophagosome closure remains unclear. Here, we report the generation and analysis of mice with impaired autophagosome closure by targeting the ubiquitin E2 variant-like (UEVL) β strands of the endosomal sorting complex required for transport (ESCRT) I subunit VPS37A. The VPS37A UEVL mutation (Δ43-139) impairs bulk autophagic flux without disrupting ESCRT-I complex assembly and endosomal function. Homozygous mutant mice exhibit signs of autophagy impairment, including p62/SQSTM1 and ubiquitinated protein accumulation, neuronal dysfunction, growth retardation, antioxidant gene upregulation, and tissue abnormalities. However, about half of the mutant neonates survive to adulthood without severe liver injury. LC3 proximity proteomics reveals that the VPS37A UEVL mutation leads to active TANK-binding kinase 1 (TBK1) accumulation on phagophores, resulting in increased p62 phosphorylation and inclusion formation. These findings reveal a previously unappreciated role of LC3-conjugated phagophores in facilitating protein aggregation and sequestration, potentially alleviating proteotoxicity.

VPS4A is the selective receptor for lipophagy in mice and humans

Lipophagy is a ubiquitous mechanism for degradation of lipid droplets (LDs) in lysosomes. Autophagy receptors selectively target organelles for lysosomal degradation. The selective receptor for lipophagy remains elusive. Using mouse liver phosphoproteomics and human liver transcriptomics, we identify vacuolar-protein-sorting-associated protein 4A (VPS4A), a member of a large family AAA+ ATPases, as a selective receptor for lipophagy. We show that phosphorylation of VPS4A on Ser95,97 and its localization to LDs in response to fasting drives lipophagy. Imaging/three-dimensional (3D) reconstruction and biochemical analyses reveal the concomitant degradation of VPS4A and LDs in lysosomes in an autophagy-gene-7-sensitive manner. Either silencing VPS4A or targeting VPS4AS95,S97 phosphorylation or VPS4A binding to LDs or LC3 blocks lipophagy without affecting other forms of selective autophagy. Finally, VPS4A levels and markers of lipophagy are markedly reduced in human steatotic livers-revealing a fundamental role of VPS4A as the lipophagy receptor in mice and humans.

Rational design of a poly-L-glutamic acid-based combination conjugate for hormone-responsive breast cancer treatment

Breast cancer represents the most prevalent tumor type worldwide, with hormone-responsive breast cancer the most common subtype. Despite the effectiveness of endocrine therapy, advanced disease forms represent an unmet clinical need. While drug combination therapies remain promising, differences in pharmacokinetic profiles result in suboptimal ratios of free drugs reaching tumors. We identified a synergistic combination of bisdemethoxycurcumin and exemestane through drug screening and rationally designed star-shaped poly-L-glutamic acid-based combination conjugates carrying these drugs conjugated through pH-responsive linkers for hormone-responsive breast cancer treatment. We synthesized/characterized single and combination conjugates with synergistic drug ratios/loadings. Physicochemical characterization/drug release kinetics studies suggested that lower drug loading prompted a less compact conjugate conformation that supported optimal release. Screening in monolayer and spheroid breast cancer cell cultures revealed that combination conjugates possessed enhanced cytotoxicity/synergism compared to physical mixtures of single-drug conjugates/free drugs; moreover, a combination conjugate with the lowest drug loading outperformed remaining conjugates. This candidate inhibited proliferation-associated signaling, reduced inflammatory chemokine/exosome levels, and promoted autophagy in spheroids; furthermore, it outperformed a physical mixture of single-drug conjugates/free drugs regarding cytotoxicity in patient-derived breast cancer organoids. Our findings highlight the importance of rational design and advanced in vitro models for the selection of polypeptide-based combination conjugates.

Gadd45A-mediated autophagy regulation and its impact on Alzheimer's disease pathogenesis: Deciphering the molecular Nexus

BACKGROUND

The growth arrest and DNA damage-inducible 45 (Gadd45) gene has been implicated in various central nervous system (CNS) functions, both normal and pathological, including aging, memory, and neurodegenerative diseases. In this study, we examined whether Gadd45A deletion triggers pathways associated with neurodegenerative diseases including Alzheimer's disease (AD).

METHODS

Utilizing transcriptome data from AD-associated hippocampus samples, we identified Gadd45A as a pivotal regulator of autophagy. Comprehensive analyses, including Gene Ontology enrichment and protein-protein interaction network assessments, highlighted Cdkn1A as a significant downstream target of Gadd45A. Experimental validation confirmed Gadd45A's role in modulating Cdkn1A expression and autophagy levels in hippocampal cells. We also examined the effects of autophagy on hippocampal functions and proinflammatory cytokine secretion. Additionally, a murine model was employed to validate the importance of Gadd45A in neuroinflammation and AD pathology.

RESULTS

Our study identified 20 autophagy regulatory factors associated with AD, with Gadd45A emerging as a critical regulator. Experimental findings demonstrated that Gadd45A influences hippocampal cell fate by reducing Cdkn1A expression and suppressing autophagic activity. Comparisons between wild-type (WT) and Gadd45A knockout (Gadd45A-/-) mice revealed that Gadd45A-/- mice exhibited significant cognitive impairments, including deficits in working and spatial memory, increased Tau hyperphosphorylation, and elevated levels of kinases involved in Tau phosphorylation in the hippocampus. Additionally, Gadd45A-/- mice showed significant increases in pro-inflammatory cytokines and decreases autophagy markers in the brain. Neurotrophin levels and dendritic spine length were also reduced in Gadd45A-/- mice, likely contributing to the observed cognitive deficits.

CONCLUSIONS

These findings support the direct involvement of the Gadd45A gene in AD pathogenesis, and enhancing the expression of Gadd45A may represent a promising therapeutic strategy for the treatment of AD.

Targeting DNM1L/DRP1-FIS1 axis inhibits high-grade glioma progression by impeding mitochondrial respiratory cristae remodeling

BACKGROUND

The dynamics of mitochondrial respiratory cristae (MRC) and its impact on oxidative phosphorylation (OXPHOS) play a crucial role in driving the progression of high-grade glioma (HGG). However, the underlying mechanism remains unclear.

METHODS

In the present study, we employed machine learning-based transmission electron microscopy analysis of 7141 mitochondria from 54 resected glioma patients. Additionally, we conducted bioinformatics analysis and multiplex immunohistochemical (mIHC) staining of clinical glioma microarrays to identify key molecules involved in glioma. Subsequently, we modulated the expression levels of mitochondrial dynamic-1-like protein (DNM1L/DRP1), and its two receptors, mitochondrial fission protein 1 (FIS1) and mitochondrial fission factor (MFF), via lentiviral transfection to further investigate the central role of these molecules in the dynamics of glioblastoma (GBM) cells and glioma stem cells (GSCs). We then evaluated the potential impact of DNM1L/DRP1, FIS1, and MFF on the proliferation and progression of GBM cells and GSCs using a combination of CCK-8 assay, Transwell assay, Wound Healing assay, tumor spheroid formation assay and cell derived xenograft assay employing NOD/ShiLtJGpt-Prkdcem26Cd52Il2rgem26Cd22/Gpt (NCG) mouse model. Subsequently, we validated the ability of the DNM1L/DRP1-FIS1 axis to remodel MRC structure through mitophagy by utilizing Seahorse XF analysis technology, mitochondrial function detection, MRC abundance detection and monitoring dynamic changes in mitophagy.

RESULTS

Our findings revealed that compared to low-grade glioma (LGG), HGG exhibited more integrated MRC structures. Further research revealed that DNM1L/DRP1, FIS1, and MFF played pivotal roles in governing mitochondrial fission and remodeling MRC in HGG. The subsequent validation demonstrated that DNM1L/DRP1 exerts a positive regulatory effect on FIS1, whereas the interaction between MFF and FIS1 demonstrates a competitive inhibition relationship. The down-regulation of the DNM1L/DRP1-FIS1 axis significantly impaired mitophagy, thereby hindering the remodeling of MRC and inhibiting OXPHOS function in glioma, ultimately leading to the inhibition of its aggressive progression. In contrast, MFF exerts a contrasting effect on MRC integrity, OXPHOS activity, and glioma progression.

CONCLUSIONS

This study highlights that the DNM1L/DRP1-FIS1 axis stabilizes MRC structures through mitophagy in HGG cells while driving their OXPHOS activity ultimately leading to robust disease progression. The inhibition of the DNM1L/DRP1-FIS1 axis hinders MRC remodeling and suppresses GBM progression. We propose that down-regulation of the DNM1L/DRP1-FIS1 axis could be a potential therapeutic strategy for treating HGG.

Beyond self‑eating: Emerging autophagy‑independent functions for the autophagy molecules in cancer (Review)

Autophagy is a conserved catabolic process that controls organelle quality, removes misfolded or abnormally aggregated proteins and is part of the defense mechanisms against intracellular pathogens. Autophagy contributes to the suppression of tumor initiation by promoting genome stability, cellular integrity, redox balance and proteostasis. On the other hand, once a tumor is established, autophagy can support cancer cell survival and promote epithelial‑to‑mesenchymal transition. A growing number of molecules involved in autophagy have been identified. In addition to their key canonical activity, several of these molecules, such as ATG5, ATG12 and Beclin‑1, also exert autophagy‑independent functions in a variety of biological processes. The present review aimed to summarize autophagy‑independent functions of molecules of the autophagy machinery and how the activity of these molecules can influence signaling pathways that are deregulated in cancer progression.

Autophagy activates EGR1 via MAPK/ERK to induce FGF2 in renal tubular cells for fibroblast activation and fibrosis during maladaptive kidney repair

Macroautophagy/autophagy contributes to maladaptive kidney repair by inducing pro-fibrotic factors such as FGF2 (fibroblast growth factor 2), but the underlying mechanism remains elusive. Here, we show that EGR1 (early growth response 1) was induced in injured proximal tubules after ischemic acute kidney injury (AKI) and this induction was suppressed by autophagy deficiency in inducible, renal tubule-specific atg7 (autophagy related 7) knockout (iRT-atg7 KO) mice. In cultured proximal tubular cells, TGFB1 (transforming growth factor beta 1) induced EGR1 and this induction was also autophagy dependent. Egr1 knockdown in tubular cells reduced FGF2 expression during TGFB1 treatment, leading to less FGF2 secretion and decreased paracrine effects on fibroblasts. ChIP assay detected an increased binding of EGR1 to the Fgf2 gene promoter in TGFB1-treated tubular cells. Both Fgf2 and Egr1 transcription was inhibited by FGF2 neutralizing antibody, suggesting a positive feedback for EGR1-mediated FGF2 autoregulation. This feedback was confirmed using fgf2-deficient tubular cells and fgf2-deficient mice. Upstream of EGR1, autophagy deficiency in mice suppressed MAPK/ERK (mitogen-activated protein kinase) activation in post-ischemic renal tubules. This inhibition correlated with SQSTM1/p62 (sequestosome 1) aggregation and its sequestration of MAPK/ERK. SQSTM1/p62 interacted with MAPK/ERK and blocked its activation during TGFB1 treatment in autophagy-deficient tubular cells. Inhibition of MAPK/ERK suppressed EGR1 and FGF2 expression in maladaptive tubules, leading to the amelioration of renal fibrosis and improvement of renal function. These results suggest that autophagy activates MAPK/ERK in renal tubular cells, which induces EGR1 to transactivate FGF2. FGF2 is then secreted into the interstitium to stimulate fibroblasts for fibrogenesis.Abbreviation: 3-MA: 3-methyladenine; ACTA2/α-SMA: actin alpha 2, smooth muscle, aorta; ACTB/β-actin: actin, beta; AKI: acute kidney injury; aa: amino acid; ATG/Atg: autophagy related; BUN: blood urea nitrogen; ChIP: chromatin immunoprecipitation; CKD: chronic kidney disease; CM: conditioned medium; COL1A1: collagen, type I, alpha 1; COL4A1: collagen, type IV, alpha 1; CQ: chloroquine; DBA: dolichos biflorus agglutinin; EGR1: early growth response 1; ELK1: ELK1, member of ETS oncogene family; FGF2: fibroblast growth factor 2; FN1: fibronectin 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HAVCR1/KIM-1: hepatitis A virus cellular receptor 1; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2K/MEK: mitogen-activated protein kinase kinase; MAPK: mitogen-activated protein kinase; NFKB: nuclear factor kappa B; PB1: Phox and Bem1; PFT: pifithrin α; PPIB/cyclophilin B: peptidylprolyl isomerase B; RT-qPCR: real time-quantitative PCR; SQSTM1/p62: sequestosome 1; TGFB1/TGF-β1: transforming growth factor beta 1; VIM: vimentin.

Removal of hypersignaling endosomes by simaphagy

Activated transmembrane receptors continue to signal following endocytosis and are only silenced upon ESCRT-mediated internalization of the receptors into intralumenal vesicles (ILVs) of the endosomes. Accordingly, endosomes with dysfunctional receptor internalization into ILVs can cause sustained receptor signaling which has been implicated in cancer progression. Here, we describe a surveillance mechanism that allows cells to detect and clear physically intact endosomes with aberrant receptor accumulation and elevated signaling. Proximity biotinylation and proteomics analyses of ESCRT-0 defective endosomes revealed a strong enrichment of the ubiquitin-binding macroautophagy/autophagy receptors SQSTM1 and NBR1, a phenotype that was confirmed in cell culture and fly tissue. Live cell microscopy demonstrated that loss of the ESCRT-0 subunit HGS/HRS or the ESCRT-I subunit VPS37 led to high levels of ubiquitinated and phosphorylated receptors on endosomes. This was accompanied by dynamic recruitment of NBR1 and SQSTM1 as well as proteins involved in autophagy initiation and autophagosome biogenesis. Light microscopy and electron tomography revealed that endosomes with intact limiting membrane, but aberrant receptor downregulation were engulfed by phagophores. Inhibition of autophagy caused increased intra- and intercellular signaling and directed cell migration. We conclude that dysfunctional endosomes are surveyed and cleared by an autophagic process, simaphagy, which serves as a failsafe mechanism in signal termination.Abbreviations: AKT: AKT serine/threonine kinase; APEX2: apurinic/apyrimidinic endodoexyribonuclease 2; ctrl: control; EEA1: early endosome antigen 1; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; ESCRT: endosomal sorting complex required for transport; GFP: green fluorescent protein; HGS/HRS: hepatocyte growth factor-regulated tyrosine kinase substrate; IF: immunofluorescence; ILV: intralumenal vesicle; KO: knockout; LIR: LC3-interacting region; LLOMe: L-leucyl-L-leucine methyl ester (hydrochloride); MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; NBR1: NBR1 autophagy cargo receptor; PAG10: Protein A-conjugated 10-nm gold; RB1CC1/FIP200: RB1 inducible coiled-coil 1; siRNA: small interfering RNA; SQSTM1: sequestosome 1; TUB: Tubulin; UBA: ubiquitin-associated; ULK1: unc-51 like autophagy activating kinase 1; VCL: Vinculin; VPS37: VPS37 subunit of ESCRT-I; WB: western blot; WT: wild-type.

Loss of mitogen-activated protein kinase phosphate-5 aggravates islet dysfunction in mice with type 1 and type 2 diabetes

Impaired functionality and loss of islet β-cells are the primary abnormalities underlying the pathogenesis of both type 1 and 2 diabetes (T1DM and T2DM). However, specific therapeutic and preventive mechanisms underlying these conditions remain unclear. Mitogen-activated protein kinase phosphatase-5 (MKP-5) has been implicated in carcinogenesis, lipid metabolism regulation, and immune cell activation. In a previous study, we demonstrated the involvement of exogenous MKP-5 in the regulation of obesity-induced T2DM. However, the role of endogenous MKP-5 in the T1DM and T2DM processes is unclear. Thus, mice with MKP-5 knockout (KO) were generated and used to establish mouse models of both T1DM and T2DM. Our results showed that MKP-5 KO exacerbated diabetes-related symptoms in mice with both T1DM and T2DM. Given that most phenotypic studies on islet dysfunction have focused on mice with T2DM rather than T1DM, we specifically aimed to investigate the role of endoplasmic reticulum stress (ERS) and autophagy in T2DM KO islets. To accomplish this, we performed RNA sequence analysis to gain comprehensive insight into the molecular mechanisms associated with ERS and autophagy in T2DM KO islets. The results showed that the islets from mice with MKP-5 KO triggered 5' adenosine monophosphate-activated protein kinase (AMPK)-mediated autophagy inhibition and glucose-regulated protein 78 (GRP-78)-dominated ERS. Hence, we concluded that the autophagy impairment, resulting in islet dysfunction in mice with MKP-5 KO, is mediated through GRP-78 involvement. These findings provide valuable insights into the molecular pathogenesis of diabetes and highlight the significant role of MKP-5. Moreover, this knowledge holds promise for novel therapeutic strategies targeting MKP-5 for diabetes management.

Autophagy supports PDGFRA-dependent brain tumor development by enhancing oncogenic signaling

Autophagy is a conserved cellular degradation process. While autophagy-related proteins were shown to influence the signaling and trafficking of some receptor tyrosine kinases, the relevance of this during cancer development is unclear. Here, we identify a role for autophagy in regulating platelet-derived growth factor receptor alpha (PDGFRA) signaling and levels. We find that PDGFRA can be targeted for autophagic degradation through the activity of the autophagy cargo receptor p62. As a result, short-term autophagy inhibition leads to elevated levels of PDGFRA but an unexpected defect in PDGFA-mediated signaling due to perturbed receptor trafficking. Defective PDGFRA signaling led to its reduced levels during prolonged autophagy inhibition, suggesting a mechanism of adaptation. Importantly, PDGFA-driven gliomagenesis in mice was disrupted when autophagy was inhibited in a manner dependent on Pten status, thus highlighting a genotype-specific role for autophagy during tumorigenesis. In summary, our data provide a mechanism by which cells require autophagy to drive tumor formation.

The aging mouse CNS is protected by an autophagy-dependent microglia population promoted by IL-34

Microglia harness an unutilized health-promoting potential in age-related neurodegenerative and neuroinflammatory diseases, conditions like progressive multiple sclerosis (MS). Our research unveils an microglia population emerging in the cortical brain regions of aging mice, marked by ERK1/2, Akt, and AMPK phosphorylation patterns and a transcriptome indicative of activated autophagy - a process critical for cellular adaptability. By deleting the core autophagy gene Ulk1 in microglia, we reduce this population in the central nervous system of aged mice. Notably, this population is found dependent on IL-34, rather than CSF1, although both are ligands for CSF1R. When aging mice are exposed to autoimmune neuroinflammation, the loss of autophagy-dependent microglia leads to neural and glial cell death and increased mortality. Conversely, microglial expansion mediated by IL-34 exhibits a protective effect. These findings shed light on an autophagy-dependent neuroprotective microglia population as a potential target for treating age-related neuroinflammatory conditions, including progressive MS.

Targeting the RAS/RAF/MAPK pathway for cancer therapy: from mechanism to clinical studies

Metastatic dissemination of solid tumors, a leading cause of cancer-related mortality, underscores the urgent need for enhanced insights into the molecular and cellular mechanisms underlying metastasis, chemoresistance, and the mechanistic backgrounds of individuals whose cancers are prone to migration. The most prevalent signaling cascade governed by multi-kinase inhibitors is the mitogen-activated protein kinase (MAPK) pathway, encompassing the RAS-RAF-MAPK kinase (MEK)-extracellular signal-related kinase (ERK) pathway. RAF kinase is a primary mediator of the MAPK pathway, responsible for the sequential activation of downstream targets, such as MEK and the transcription factor ERK, which control numerous cellular and physiological processes, including organism development, cell cycle control, cell proliferation and differentiation, cell survival, and death. Defects in this signaling cascade are associated with diseases such as cancer. RAF inhibitors (RAFi) combined with MEK blockers represent an FDA-approved therapeutic strategy for numerous RAF-mutant cancers, including melanoma, non-small cell lung carcinoma, and thyroid cancer. However, the development of therapy resistance by cancer cells remains an important barrier. Autophagy, an intracellular lysosome-dependent catabolic recycling process, plays a critical role in the development of RAFi resistance in cancer. Thus, targeting RAF and autophagy could be novel treatment strategies for RAF-mutant cancers. In this review, we delve deeper into the mechanistic insights surrounding RAF kinase signaling in tumorigenesis and RAFi-resistance. Furthermore, we explore and discuss the ongoing development of next-generation RAF inhibitors with enhanced therapeutic profiles. Additionally, this review sheds light on the functional interplay between RAF-targeted therapies and autophagy in cancer.

Transcriptomics Analysis Revealed Key Genes Associated with Macrophage Autophagolysosome in Male ApoE-/- Mice Aortic Atherosclerosis

Purpose

Atherosclerosis (AS) is the most common cause of cardiovascular and cerebrovascular diseases. However, the mechanisms underlying atherosclerotic plaque progression remain unclear. This study aimed to investigate the genes associated with the development of atherosclerosis in the aorta of ApoE-/- male mice, which could serve as novel biomarkers and therapeutic targets in interventions to halt plaque progression.

Methods

Eight-week-old ApoE-/- mice were fed a normal purified laboratory diet or a Western Diet (WD) for 6 or 22 weeks. High-throughput sequencing technology was used to analyze the transcriptomes of the aortas of four groups of mice that were exposed to different dietary conditions. We retrieved and downloaded the human Arteriosclerosis Disease Chip dataset GSE100927 from the Gene Expression Omnibus (GEO) database and selected 29 cases of carotid atherosclerotic lesions and 12 cases of normal carotid tissues as the experimental and control groups, respectively, to further verify our dataset. In addition, we used quantitative reverse transcription polymerase chain reaction (QT-PCR) to verify the expression levels of the core genes in an atherosclerosis mouse model.

Results

There were 265 differentially expressed genes (DEGs) between the ApoE-/- Male mice AS22W group and Sham22W group. In addition to the well-known activation of inflammation and immune response, t the autophagy-lysosome system is also an important factor that affects the development of atherosclerosis. We identified five core genes (Atp6ap2, Atp6v0b, Atp6v0d2, Atp6v1a, and Atp6v1d) in the protein-protein interaction (PPI) network that were closely related to autophagosomes. Hub genes were highly expressed in the carotid atherosclerosis group in the GSE100927 dataset (P < 0.001). QT-PCR showed that the RNA level of Atp6v0d2 increased significantly during the development of atherosclerotic plaque in ApoE-/- male mice.

Conclusion

Five core genes which affect the development of aortic atherosclerosis through the autophagy-lysosome system, especially Atp6v0d2, were screened and identified using bioinformatic techniques.

Unraveling the interplay between RAS/RAF/MEK/ERK signaling pathway and autophagy in cancer: From molecular mechanisms to targeted therapy

RAS/RAF/MEK/ERK signaling pathway is one of the most important pathways of Mitogen-activated protein kinases (MAPK), which widely participate in regulating cell proliferation, differentiation, apoptosis and signaling transduction. Autophagy is an essential mechanism that maintains cellular homeostasis by degrading aged and damaged organelles. Recently, some studies revealed RAS/RAF/MEK/ERK signaling pathway is closely related to autophagy regulation and has a dual effect in tumor cells. However, the specific mechanism by which RAS/RAF/MEK/ERK signaling pathway participates in autophagy regulation is not fully understood. This article provides a comprehensive review of the research progress with regard to the RAS/RAF/MEK/ERK signaling pathway and autophagy, as well as their interplay in cancer therapy. The impact of small molecule inhibitors that target the RAS/RAF/MEK/ERK signaling pathway on autophagy is discussed in this study. The advantages and limitations of the clinical combination of these small molecule inhibitors with autophagy inhibitors are also explored. The findings from this study may provide additional perspectives for future cancer treatment strategies.

Post-translational modifications of the apelin receptor regulate its functional expression

Post-translational modifications (PTMs) are protein modifications that occur after protein biosynthesis, playing a crucial role in regulating protein function. They are involved in the functional expression of G-protein-coupled receptors (GPCRs), as well as intracellular and secretory protein signaling. Here, we aimed to investigate the PTMs of the apelin receptor (APLNR), a GPCR and their potential influence on the receptor's function. In an in vitro experiment using HEK cells, we only observed glycosylation as a PTM of the APLNR and ineffective receptor signaling by the agonist, (Pyr1)-apelin-13. In contrast, when analyzing mouse spinal cord, we detected glycosylation and other PTMs, excluding isopeptidation. This suggests that additional PTMs are involved in the functional expression of the APLNR in vitro. In summary, these findings suggest that the APLNR in vivo requires multiple PTMs for functional expression. To comprehensively understand the pharmacological effects of the APLNR, it is essential to establish an in vitro system that adequately replicates the receptor's PTM profile. Nonetheless, it is crucial to overcome the challenge of heat-sensitive proteolysis in APLNR studies. By elucidating the regulation of PTMs, further research has the potential to advance the analysis and pharmacological studies of both the apelin/APLNR system and GPCR signal modulation.

Duality of Valproic Acid Effects on Inflammation, Oxidative Stress and Autophagy in Human Eosinophilic Cells

Eosinophils function in rapid innate immune responses and allergic reactions. Recent research has raised the possibility that the histone deacetylase inhibitor valproic acid (VPA) may be a promising therapeutic agent for treatment of allergic responses and certain cancers. However, its effects on eosinophils remain unclear. Utilizing the EoL-1 human eosinophil cell line as a model, we investigated the effects of VPA on oxidative stress- and autophagy-mediated immune responses. We found that VPA induced reactive oxidative species (ROS) generation and eosinophil activation without affecting cell viability. Moreover, VPA treatment suppressed the negative regulator of antioxidant transcription factor Nrf2, which is known to activate antioxidant defense. Interestingly, VPA was able to increase autophagic markers, as well as NLRP3 and NLRC4 mRNA activation, in Eol-1 cells in a dose-dependent manner. Collectively, our results indicate that VPA could increase the severity of allergic responses, and if so, it clearly would not be a suitable drug for the treatment of allergic reactions. However, VPA does have the potential to induce autophagy and to regulate the inflammatory responses via inflammasome-driven caspase-1 deactivation in a dose-dependent manner.

Artemisia sieberi Besser essential oil inhibits the growth and migration of breast cancer cells via induction of S-phase arrest, caspase-independent cell death and downregulation of ERK

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia sieberi Besser is a medicinal herb that has been traditionally used across the Middle East for the treatment of cancer. Further pharmacological studies on its extracts revealed that they possess cytotoxic activity against certain cancer cells, however, there were no studies conducted on the anticancer potential of Artemisia sieberi essential oil (ASEO).

AIM OF THE STUDY

To evaluate the anticancer potential of ASEO, elucidate the oil's mode of action for the first time and investigate its chemical composition.

MATERIALS AND METHODS

Artemisia sieberi was collected from Hail, Saudi Arabia, and its essential oil was obtained via hydrodistillation. The oil's activity against HCT116, HepG2, A549 and MCF-7 cells was assessed using SRB assay, while its anti-metastatic potential was assessed via a migration assay. Cell-cycle analysis and apoptosis assay were conducted via flow cytometry, while protein expression levels were investigated using Western blotting. The oil's chemical constituents were identified using GCMS.

RESULTS

ASEO exerted its highest cytotoxic activity against MCF-7 with an IC₅₀ value of 38.7 μg/ml. Further studies showed that the oil inhibited MCF-7 cells' migration, induced S-phase arrest and apoptosis. Western blot analysis showed no change in the expression level of caspase-3 after treatment, indicating the induction of caspase-independent apoptosis-like cell death in MCF-7. Treatment of MCF-7 with the oil resulted in downregulation of the protein expression levels of total ERK and its downstream target, LC3, indicating that any potential activation of the ERK signalling pathway during the cancer cells' growth would be inhibited. Finally, GCMS analysis identified the oil's major components as cis-crysanthenyl acetate (48.56%), davanone (10.28%), 1,8-cineole (6.81%) and caryophyllene diepoxide (5.34%), whereby it is suggested that these compounds might be responsible for the oil's bioactivity.

CONCLUSION

ASEO possessed in vitro anticancer activity and modulated the ERK signalling pathway. This is the first study to explore the anticancer potential of ASEO in detail and reflects the significance of investigating essential oils from medicinal plants that have been traditionally used against cancer. This work might pave the way for further in vivo studies that could result in developing the oil into a natural effective anticancer treatment.

Autophagy and autophagy-related pathways in cancer

Maintenance of protein homeostasis and organelle integrity and function is critical for cellular homeostasis and cell viability. Autophagy is the principal mechanism that mediates the delivery of various cellular cargoes to lysosomes for degradation and recycling. A myriad of studies demonstrate important protective roles for autophagy against disease. However, in cancer, seemingly opposing roles of autophagy are observed in the prevention of early tumour development versus the maintenance and metabolic adaptation of established and metastasizing tumours. Recent studies have addressed not only the tumour cell intrinsic functions of autophagy, but also the roles of autophagy in the tumour microenvironment and associated immune cells. In addition, various autophagy-related pathways have been described, which are distinct from classical autophagy, that utilize parts of the autophagic machinery and can potentially contribute to malignant disease. Growing evidence on how autophagy and related processes affect cancer development and progression has helped guide efforts to design anticancer treatments based on inhibition or promotion of autophagy. In this Review, we discuss and dissect these different functions of autophagy and autophagy-related processes during tumour development, maintenance and progression. We outline recent findings regarding the role of these processes in both the tumour cells and the tumour microenvironment and describe advances in therapy aimed at autophagy processes in cancer.

Emerging roles of the cellular prion protein (PrPC) and 37/67 kDa laminin receptor (RPSA) interaction in cancer biology

The cellular prion protein (PrPC) is well-known for its involvement, under its pathogenic protease-resistant form (PrPSc), in a group of neurodegenerative diseases, known as prion diseases. PrPC is expressed in nervous system, as well as in other peripheral organs, and has been found overexpressed in several types of solid tumors. Notwithstanding, studies in recent years have disclosed an emerging role for PrPC in various cancer associated processes. PrPC has high binding affinity for 37/67 kDa laminin receptor (RPSA), a molecule that acts as a key player in tumorigenesis, affecting cell growth, adhesion, migration, invasion and cell death processes. Recently, we have characterized at cellular level, small molecules able to antagonize the direct PrPC binding to RPSA and their intracellular trafficking. These findings are very crucial considering that the main function of RPSA is to modulate key events in the metastasis cascade. Elucidation of the role played by PrPC/RPSA interaction in regulating tumor development, progression and response to treatment, represents a very promising challenge to gain pathogenetic information and discover novel specific biomarkers and/or therapeutic targets to be exploited in clinical settings. This review attempts to convey a detailed description of the complexity surrounding these multifaceted proteins from the perspective of cancer hallmarks, but with a specific focus on the role of their interaction in the control of proliferation, migration and invasion, genome instability and mutation, as well as resistance to cell death controlled by autophagic pathway.

Progranulin Protects against Hyperglycemia-Induced Neuronal Dysfunction through GSK3β Signaling

Type II diabetes affects over 530 million individuals worldwide and contributes to a host of neurological pathologies. Uncontrolled high blood glucose (hyperglycemia) is a major factor in diabetic pathology, and glucose regulation is a common goal for maintenance in patients. We have found that the neuronal growth factor progranulin protects against hyperglycemic stress in neurons, and although its mechanism of action is uncertain, our findings identified Glycogen Synthase Kinase 3β (GSK3β) as being potentially involved in its effects. In this study, we treated mouse primary cortical neurons exposed to high-glucose conditions with progranulin and a selective pharmacological inhibitor of GSK3β before assessing neuronal health and function. Whole-cell and mitochondrial viability were both improved by progranulin under high-glucose stress in a GSK3β-dependent manner. This extended to autophagy flux, indicated by the expressions of autophagosome marker Light Chain 3B (LC3B) and lysosome marker Lysosome-Associated Membrane Protein 2A (LAMP2A), which were affected by progranulin and showed heterogeneous changes from GSK3β inhibition. Lastly, GSK3β inhibition attenuated downstream calcium signaling and neuronal firing effects due to acute progranulin treatment. These data indicate that GSK3β plays an important role in progranulin's neuroprotective effects under hyperglycemic stress and serves as a jumping-off point to explore progranulin's protective capabilities in other neurodegenerative models.

mTORC2-NDRG1-CDC42 axis couples fasting to mitochondrial fission

Fasting triggers diverse physiological adaptations including increases in circulating fatty acids and mitochondrial respiration to facilitate organismal survival. The mechanisms driving mitochondrial adaptations and respiratory sufficiency during fasting remain incompletely understood. Here we show that fasting or lipid availability stimulates mTORC2 activity. Activation of mTORC2 and phosphorylation of its downstream target NDRG1 at serine 336 sustains mitochondrial fission and respiratory sufficiency. Time-lapse imaging shows that NDRG1, but not the phosphorylation-deficient NDRG1Ser336Ala mutant, engages with mitochondria to facilitate fission in control cells, as well as in those lacking DRP1. Using proteomics, a small interfering RNA screen, and epistasis experiments, we show that mTORC2-phosphorylated NDRG1 cooperates with small GTPase CDC42 and effectors and regulators of CDC42 to orchestrate fission. Accordingly, RictorKO, NDRG1Ser336Ala mutants and Cdc42-deficient cells each display mitochondrial phenotypes reminiscent of fission failure. During nutrient surplus, mTOR complexes perform anabolic functions; however, paradoxical reactivation of mTORC2 during fasting unexpectedly drives mitochondrial fission and respiration.

The emerging theme of 3'UTR mRNA isoform regulation in reprogramming of cell metabolism

The 3' untranslated region (3'UTR) of mRNA plays a key role in the post-transcriptional regulation of gene expression. Most eukaryotic protein-coding genes express 3'UTR isoforms owing to alternative cleavage and polyadenylation (APA). The 3'UTR isoform expression profile of a cell changes in cell proliferation, differentiation, and stress conditions. Here, we review the emerging theme of regulation of 3'UTR isoforms in cell metabolic reprogramming, focusing on cell growth and autophagy responses through the mTOR pathway. We discuss regulatory events that converge on the Cleavage Factor I complex, a master regulator of APA in 3'UTRs, and recent understandings of isoform-specific m6A modification and endomembrane association in determining differential metabolic fates of 3'UTR isoforms.

Atg1, a key regulator of autophagy, functions to promote MAPK activation and cell death upon calcium overload in fission yeast

Autophagy promotes or inhibits cell death depending on the environment and cell type. Our previous findings suggested that Atg1 is genetically involved in the regulation of Pmk1 MAPK in fission yeast. Here, we showed that Δatg1 displays lower levels of Pmk1 MAPK phosphorylation than did the wild-type (WT) cells upon treatment with a 1,3-β-D-glucan synthase inhibitor micafungin or CaCl₂, both of which activate Pmk1. Moreover, the overproduction of Atg1, but not that of the kinase inactivating Atg1^D193A activates Pmk1 without any extracellular stimuli, suggesting that Atg1 may promote Pmk1 MAPK signaling activation. Notably, the overproduction of Atg1 induces a toxic effect on the growth of WT cells and the deletion of Pmk1 failed to suppress the cell death induced by Atg1, indicating that the Atg1-mediated cell death requires additional mechanism(s) other than Pmk1 activation. Moreover, atg1 gene deletion induces tolerance to micafungin and CaCl₂, whereas pmk1 deletion induces severe sensitivities to these compounds. The Δatg1Δpmk1 double mutants display intermediate sensitivities to these compounds, showing that atg1 deletion partly suppressed growth inhibition induced by Δpmk1. Thus, Atg1 may act to promote cell death upon micafungin and CaCl₂ stimuli regardless of Pmk1 MAPK activity. Since micafungin and CaCl₂ are intracellular calcium inducers, our data reveal a novel role of the autophagy regulator Atg1 to induce cell death upon calcium overload independent of its role in Pmk1 MAPK activation.

Targeting Unc51-like Autophagy Activating Kinase 1 (ULK1) Overcomes Adaptive Drug Resistance in Acute Myelogenous Leukemia

Despite effective new therapies, adaptive resistance remains the main obstacle in acute myelogenous leukemia (AML) therapy. Autophagy induction is a key mechanism for adaptive resistance. Leukemic blasts at diagnosis express higher levels of the apical autophagy kinase ULK1 compared with normal hematopoietic cells. Exposure to chemotherapy and targeted agents upregulate ULK1, hence we hypothesize that developing ULK1 inhibitors may present the unique opportunity for clinical translation of autophagy inhibition. Accordingly, we demonstrate that ULK1 inhibition, by genetic and pharmacologic means, suppresses treatment-induced autophagy, overcomes adaptive drug-resistance, and synergizes with chemotherapy and emerging antileukemia agents like venetoclax (ABT-199). The study next aims at exploring the underlying mechanisms. Mechanistically, ULK1 inhibition downregulates MCL1 antiapoptotic gene, impairs mitochondrial function and downregulates components of the CD44-xCT system, resulting in impaired reactive oxygen species (ROS) mitigation, DNA damage, and apoptosis. For further validation, several mouse models of AML were generated. In these mouse models, ULK1 deficiency impaired leukemic cell homing and engraftment, delayed disease progression, and improved survival. Therefore, in the study, we validated our hypothesis and identified ULK1 as an important mediator of adaptive resistance to therapy and an ideal candidate for combination therapy in AML. Therefore, we propose ULK1 inhibition as a therapeutically relevant treatment option to overcome adaptive drug-resistance in AML.

IMPLICATIONS

ULK1 drives a cell-intrinsic adaptive resistance in AML and targeting ULK1-mediated autophagy can synergize with existing and emerging AML therapies to overcome drug-resistance and induce apoptosis.

Apoptotic Cell Death in Bicuspid-Aortic-Valve-Associated Aortopathy

The bicuspid aortic valve (BAV) is the most common cardiovascular congenital abnormality and is frequently associated with proximal aortopathy. We analyzed the tissues of patients with bicuspid and tricuspid aortic valve (TAV) regarding the protein expression of the receptor for advanced glycation products (RAGE) and its ligands, the advanced glycation end products (AGE), as well as the S100 calcium-binding protein A6 (S100A6). Since S100A6 overexpression attenuates cardiomyocyte apoptosis, we investigated the diverse pathways of apoptosis and autophagic cell death in the human ascending aortic specimen of 57 and 49 patients with BAV and TAV morphology, respectively, to identify differences and explanations for the higher risk of patients with BAV for severe cardiovascular diseases. We found significantly increased levels of RAGE, AGE and S100A6 in the aortic tissue of bicuspid patients which may promote apoptosis via the upregulation of caspase-3 activity. Although increased caspase-3 activity was not detected in BAV patients, increased protein expression of the 48 kDa fragment of vimentin was detected. mTOR as a downstream protein of Akt was significantly higher in patients with BAV, whereas Bcl-2 was increased in patients with TAV, assuming a better protection against apoptosis. The autophagy-related proteins p62 and ERK1/2 were increased in patients with BAV, assuming that cells in bicuspid tissue are more likely to undergo apoptotic cell death leading to changes in the wall and finally to aortopathies. We provide first-hand evidence of increased apoptotic cell death in the aortic tissue of BAV patients which may thus provide an explanation for the increased risk of structural aortic wall deficiency possibly underlying aortic aneurysm formation or acute dissection.

Knockdown of PKMYT1 is associated with autophagy inhibition and apoptosis induction and suppresses tumor progression in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a cancerous tumor that ranks as the third leading cause of cancer death across the globe. Protein kinase membrane-associated tyrosine/threonine kinase 1 (PKMYT1) is overexpressed in many cancer types, including HCC, but the potential mechanism and biological function of PKMYT1 are not fully understood.

MATERIALS AND METHODS

The expression level of PKMYT1 was detected in human HCC tissues and adjacent tissues. We then established HCC cell lines with PKMYT1 knockdown and observed proliferation, migration, autophagy, apoptosis in cell lines and tumor growth in a nude mouse model. To investigate the underlying mechanism by which PKMYT1 regulates autophagy and apoptosis, RNA sequencing was performed in HCC-LM3 cells with and without PKMYT1 knockdown.

RESULTS

Here, we observed that human HCC tissues had higher expression of PKMYT1 than adjacent tissues. Overexpression of PKMYT1 was closely associated with poor prognosis in HCC patients. PKMYT1 knockdown inhibited the proliferative potential and migration of HCC cell lines. We also found that downregulation of PKMYT1 inhibited autophagy and induced apoptosis. RNA sequencing analysis showed that the MAPK and PI3K-AKT pathways, which have been reported to affect autophagy and apoptosis, may be regulated after PKMYT1 knockdown by KEGG pathway enrichment analysis. Furthermore, we identified that knockdown of PKMYT1 attenuated the phosphorylation levels of p38 MAPK, ERK and PI3K/Akt/mTOR, which might mediate autophagy inhibition and apoptosis induction via these signaling pathways to inhibit the development of HCC.

CONCLUSION

Our study suggests that PKMYT1 functions as an oncogene and may be a new target for HCC treatment.

Upregulation of ATF4-LAMP3 Axis by ORF45 Facilitates Lytic Replication of Kaposi's Sarcoma-Associated Herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is a γ-oncogenic herpesvirus, and both lytic and latent infections play important roles in its pathogenesis and tumorigenic properties. Multiple cellular pathways and diverse mediators are hijacked by viral proteins and are used to support KSHV lytic replication. In previous studies, we revealed that KSHV ORF45 promoted KSHV transcription and translation by inducing sustained p90 ribosomal S6 kinase (RSK) activation and the phosphorylation of its substrates c-Fos and eIF4B. However, the cellular mediators required for lytic replication remain largely unknown. Here, we reveal that ORF45 activates eIF2α phosphorylation and ATF4 translation and then upregulates the expression of lysosome-associated membrane protein 3 (LAMP3) in an ATF4-dependent manner during KSHV lytic replication. Consequently, LAMP3 promotes Akt and ERK activation and then facilitates lytic gene expression and virion production. Furthermore, ATF4 enhances lytic replication through LAMP3, and LAMP3 acts in an ATF4-independent manner. Our findings suggest that the ATF4-LAMP3 axis is upregulated by ORF45 through ER stress activation during the KSHV lytic life cycle and, in turn, facilitates optimal lytic replication. IMPORTANCE The lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) reprograms cellular transcription and translation to generate viral proteins and virion particles. Here, we show that the mediator of ER stress ATF4 and the expression of the downstream gene LAMP3 are upregulated by ORF45 during lytic replication. Consequently, increased LAMP3 expression activates Akt and ERK and promotes lytic replication. Although several UPR transcription factors are able to promote KSHV lytic replication, the proviral effect of ATF4 on lytic replication is attenuated by LAMP3 silencing, whereas the effect of LAMP3 does not directly require ATF4 expression, indicating that LAMP3 primarily exerts effects on KSHV lytic replication downstream of ATF4 and ER stress. Taken together, our findings suggest that the ORF45-upregulated ATF4-LAMP3 axis plays an essential role in KSHV lytic replication.

Protection of adipose-derived mesenchymal stromal cells during acute lung injury requires autophagy maintained by mTOR

Previous studies suggest that mesenchymal stem cells may represent a promising cellular therapy for acute lung injury (ALI); however, the underlying relevant molecular mechanisms remain unclear. Adipose-derived mesenchymal stem cells (ADSCs) were isolated and characterized by alizarin red staining, oil red staining, and flow cytometry. Lung injury and inflammatory cell infiltration were determined using the Evans blue method, wet/dry weight ratio, and H&E staining. An ELISA was used to detect the concentrations of IFN-γ, IL-2, and TNF-α. Autophagy was detected with an mRFP-GFP-LC3 dual-fluorescence autophagy indicator system, Western blotting, and electron microscopy. We first demonstrated that ADSCs did alleviate the inflammatory responses and tissue damage in lipopolysaccharide (LPS)-induced ALI. Next, we further demonstrated in vivo that autophagy plays a key role in the maintenance of ADSC therapeutic efficacy. In vitro experiments demonstrated that ADSCs co-cultured with alveolar epithelial cells depend on autophagy for significant anti-inflammatory functions. Moreover, the mammalian target of rapamycin (mTOR) is a key regulator of autophagy. Taken together, our findings demonstrate that the effect of ADSC on ALI, especially on alveolar epithelial cells, is dependent on mTOR-mediated autophagy maintenance. The significance of our study for ALI therapy is discussed with respect to a more complete understanding of the therapeutic strategy paradigm.

Acute systemic knockdown of Atg7 is lethal and causes pancreatic destruction in shRNA transgenic mice

The notion that macroautophagy/autophagy is a potentially attractive therapeutic target for a variety of diseases, including cancer, largely stems from pre-clinical mouse studies. Most of these examine the effects of irreversible and organ confined autophagy deletion using site specific Cre-loxP recombination of the essential autophagy regulating genes Atg7 or Atg5. Model systems with the ability to impair autophagy systemically and reversibly at all disease stages would allow a more realistic approach to evaluate the consequences of authophagy inhibition as a therapeutic concept and its potential side effects. Here, we present shRNA transgenic mice that via doxycycline (DOX) regulable expression of a highly efficient miR30-E-based shRNA enabled knockdown of Atg7 simultaneously in the majority of organs, with the brain and spleen being noteable exceptions. Induced animals deteriorated rapidly and experienced profound destruction of the exocrine pancreas, severe hypoglycemia and depletion of hepatic glycogen storages. Cessation of DOX application restored apparent health, glucose homeostasis and pancreatic integrity. In a similar Atg5 knockdown model we neither observed loss of pancreatic integrity nor diminished survival after DOX treatment, but identified histological changes consistent with steatohepatitis and hepatic fibrosis in the recovery period after termination of DOX. Regulable Atg7-shRNA mice are valuable tools that will enable further studies on the role of autophagy impairment at various disease stages and thereby help to evaluate the consequences of acute autophagy inhibition as a therapeutic concept.Abbreviations: ACTB: actin, beta; AMY: amylase complex; ATG4B: autophagy related 4B, cysteine peptidase; ATG5: autophagy related 5; ATG7: autophagy related 7; Cag: CMV early enhancer/chicken ACTB promoter; Col1a1: collagen, type I, alpha 1; Cre: cre recombinase; DOX: doxycycline; GCG: glucagon; GFP: green fluorescent protein; INS: insulin; LC3: microtubule-associated protein 1 light chain 3; miR30-E: optimized microRNA backbone; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; PNLIP: pancreatic lipase; rtTA: reverse tetracycline transactivator protein; SQSTM1/p62: sequestome 1; TRE: tetracycline responsive element.

Mitogen Activated Protein Kinase (MAPK) Activation, p53, and Autophagy Inhibition Characterize the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike Protein Induced Neurotoxicity

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and prions use common pathogenic pathways to induce toxicity in neurons. Infectious prions rapidly activate the p38 mitogen activated protein kinase (MAPK) pathway, and SARS-CoV-2 spike proteins rapidly activate both the p38 MAPK and c-Jun NH2-terminal kinase (JNK) pathways through toll-like receptor signaling, indicating the potential for similar neurotoxicity, causing prion and prion-like disease. In this review, we analyze the roles of autophagy inhibition, molecular mimicry, elevated intracellular p53 levels and reduced Wild-type p53-induced phosphatase 1 (Wip1) and dual-specificity phosphatase (DUSP) expression in neurons in the disease process. The pathways induced by the spike protein via toll-like receptor activation induce both the upregulation of PrP^C (the normal isoform of the prion protein, PrP) and the expression of β amyloid. Through the spike-protein-dependent elevation of p53 levels via β amyloid metabolism, increased PrP^C expression can lead to PrP misfolding and impaired autophagy, generating prion disease. We conclude that, according to the age of the spike protein-exposed patient and the state of their cellular autophagy activity, excess sustained activity of p53 in neurons may be a catalytic factor in neurodegeneration. An autoimmune reaction via molecular mimicry likely also contributes to neurological symptoms. Overall results suggest that neurodegeneration is in part due to the intensity and duration of spike protein exposure, patient advanced age, cellular autophagy activity, and activation, function and regulation of p53. Finally, the neurologically damaging effects can be cumulatively spike-protein dependent, whether exposure is by natural infection or, more substantially, by repeated mRNA vaccination.

Glucose Starvation-Caused Oxidative Stress Induces Inflammation and Autophagy in Human Gingival Fibroblasts

Gingival tissue experiences an environment of nutrient shortage, such as low glucose conditions, after periodontal surgery. Our previous studies found that this low glucose condition inhibits normal gingival cell functions. However, the mechanism by which this glucose-deficient environment causes cellular damage to human gingival fibroblasts (HGnFs) remains unclear. This study aimed to investigate the biological effects of ROS induction on HGnFs under low glucose conditions. ROS levels and cellular anti-ROS ability of HGnFs under different glucose concentrations were evaluated by measuring ROS formation and the expression of superoxide dismutase and heme oxygenase 1. Changes in cellular viability were investigated using 5-bromo-2′-deoxyuridine assay and cell survival detection, and the cellular damage was evaluated by the expression of inflammatory cytokines and changes in the expression of autophagy-related protein. ROS formation was then blocked using N-acetyl-L-cysteine (NAC), and the effects of ROS on HGnFs under low glucose conditions were investigated. Low glucose conditions induced ROS accumulation, reduced cellular activity, and induced inflammation and autophagy. After NAC application, the anti-ROS capacity increased, cellular activity improved, and inflammation and autophagy were controlled. This can be effectively controlled by the application of antioxidants such as NAC.

Increased Levels of Phosphorylated ERK Induce CTGF Expression in Autophagy-Deficient Mouse Hepatocytes

Autophagy performs essential cell functions in the liver through an intracellular lysosomal degradation process. Several studies have reported that autophagy deficiency can lead to liver injury, including hepatic fibrosis; however, the mechanisms underlying the relationship between autophagy deficiency and liver pathology are unclear. In this study, we examined the expression levels of fibrosis-associated genes in hepatocyte-specific ATG7-deficient mice. The expression levels of the connective tissue growth factor (CTGF) and phosphorylated ERK (phospho-ERK) proteins were increased significantly in primary hepatocytes isolated from hepatocyte-specific ATG7-deficient mice compared to those isolated from control mice. In addition, the inhibition of autophagy in cultured mammalian hepatic AML12 and LX2 cells increased CTGF and phospho-ERK protein levels without altering CTGF mRNA expression. In addition, the autophagy deficiency-mediated enhancement of CTGF expression was attenuated when ERK was inhibited. Overall, these results suggest that the inhibition of autophagy in hepatocytes increases phospho-ERK expression, which in turn increases the expression of CTGF, a biomarker of fibrosis.

Autophagy Is Possibly Involved in Osteoblast Responses to Mechanical Loadings

Both mechanical loading and autophagy play important roles in regulating bone growth and remodeling, but the relationship between the two remains unclear. In this study, we examined bone structure with micro-CT imaging and measured bone mechanical properties with three-point bending experiments using bones from wild-type (WT) mice and conditional knockout (cKO) mice with Atg7 deletion in their osteoblasts. We found that the knockout mice had significantly less bone volume, bone thickness, bone ultimate breaking force, and bone stiffness compared to wild-type mice. Additionally, bone marrow cells from knockout mice had reduced differentiation and mineralization capacities in terms of alkaline phosphatase and calcium secretion, as well as Runx2 and osteopontin expression. Knockout mice also had significantly less relative bone formation rate due to mechanical loading. Furthermore, we found that the osteoblasts from wild-type mice had stronger responses to mechanical stimulation compared to autophagy-deficient osteoblasts from knockout mice. When inhibiting autophagy with 3 MA in wild-type osteoblasts, we found similar results as we did in autophagy-deficient osteoblasts. We also found that mechanical loading-induced ATP release is able to regulate ERK1/2, Runx2, alkaline phosphatase, and osteopontin activities. These results suggest that the ATP pathway may play an important role in the possible involvement of autophagy in osteoblast mechanobiology.

Autophagy-related genes genetically interact with Pmk1 MAPK signaling in fission yeast

Apart from the highly conserved role in the cellular degradation process, autophagy also appears to play a key role in cellular proliferation. Here, we describe the genetic interaction of autophagy-related genes and Pmk1 MAPK signaling in fission yeast. atg1 deletion cells (Δ atg1 ) exhibit the vic (viable in the presence of immunosuppressant and Cl ^- ) phenotype, indicative of Pmk1 signaling inhibition. Moreover, the Δ atg1 Δ pmk1 double mutant resembles the single Δ pmk1 mutant, suggesting that Atg1 functions in the Pmk1 pathway. In addition, the growth defect induced by overexpression of Pck2, an upstream activator of Pmk1 MAPK was alleviated by the deletion of atg1 ⁺ . Finally, the deletion of autophagy-related genes recapitulates Pmk1 MAPK signaling inhibition. Our data suggest a novel role for autophagy in MAPK signaling regulation.

E4BP4 Coordinates Circadian Control of Cognition in Delirium

Improved understanding of the etiologies of delirium, a common and severe neuropsychiatric syndrome, would facilitate the disease prevention and treatment. Here, the authors invesitgate the role of circadian rhythms in the pathogenesis of delirium. They observe perturbance of circadian rhythms in mouse models of delirium and disrupted clock gene expression in patients with delirium. In turn, physiological and genetic circadian disruptions sensitize mice to delirium with aggravated cognitive impairment. Likewise, global deletion of E4bp4 (E4 promoter-binding protein), a clock gene markedly altered in delirium conditions, results in exacerbated delirium-associated cognitive decline. Cognitive decline in delirium models is attributed to microglial activation and impaired long-term potentiation in the hippocampus. Single-cell RNA-sequencing reveals microglia as the regulatory target of E4bp4. E4bp4 restrains microglial activation via inhibiting the ERK1/2 signaling pathway. Supporting this, mice lacking in microglial E4bp4 are delirious prone, whereas mice with E4bp4 specifically deleted in hippocampal CA1 neurons have a normal phenotype. Mechanistically, E4bp4 inhibits ERK1/2 signaling by trans-repressing Mapk1/3 (genes encoding ERK1/2) via direct binding to a D-box element in the promoter region. These findings define a causal role of clock dysfunction in delirium development and indicate E4bp4 as a regulator of cognition at the crosstalk between circadian clock and delirium.

Cardioprotective effects of chloroquine pretreatment on ischemic and reperfusion injury via activation of ERK1/2 in isolated rat hearts

PURPOSE

Several therapeutic agents have been found to prevent myocardial ischemic and reperfusion (I/R) injury after cardiac surgery; however, no drug is routinely used to afford cardioprotective benefits in clinical settings. Herein, we aimed to determine whether chloroquine (CQ) pretreatment attenuates I/R injury after global ischemia in isolated rat hearts and elucidate mechanisms underlying the effects of CQ.

METHODS

Isolated rat hearts were subjected to 30-min global ischemia, followed by 60-min reperfusion with Krebs-Henseleit buffer (KHB). Immediately before ischemia, 10 mL of pretreatment solutions (KHB, n = 4 or KHB + CQ [100 μM], n = 4) were injected through the aortic root. Cardiac function was examined based on the rate pressure product (RPP). Myocardial apoptosis was evaluated using TUNEL staining. To assess the reperfusion ischemia salvage kinase pathway, protein expression levels of AKT and extracellular signal-regulated kinase (ERK1/2) were determined using western blotting. To investigate the role of ERK1/2, an ERK1/2 selective inhibitor was used in eight additional rats.

RESULTS

The recovery rate of the RPP was higher in the KHB + CQ group than in the KHB group 60 min after I/R (KHB, 44 ± 3% vs. KHB + CQ, 69 ± 7%; P = 0.019, d = 2.2). CQ pretreatment reduced apoptosis and enhanced the phosphorylation of ERK1/2; however, AKT phosphorylation was unaltered. In addition, the ERK1/2 inhibitor abolished CQ-mediated cardioprotective effects.

CONCLUSIONS

CQ pretreatment showed protective effects on cardiac function after I/R by activating ERK1/2.

Autophagy: A Key Player in Pancreatic Cancer Progression and a Potential Drug Target

Pancreatic cancer is known to have the lowest survival outcomes among all major cancers, and unfortunately, this has only been marginally improved over last four decades. The innate characteristics of pancreatic cancer include an aggressive and fast-growing nature from powerful driver mutations, a highly defensive tumor microenvironment and the upregulation of advantageous survival pathways such as autophagy. Autophagy involves targeted degradation of proteins and organelles to provide a secondary source of cellular supplies to maintain cell growth. Elevated autophagic activity in pancreatic cancer is recognized as a major survival pathway as it provides a plethora of support for tumors by supplying vital resources, maintaining tumour survival under the stressful microenvironment and promoting other pathways involved in tumour progression and metastasis. The combination of these features is unique to pancreatic cancer and present significant resistance to chemotherapeutic strategies, thus, indicating a need for further investigation into therapies targeting this crucial pathway. This review will outline the autophagy pathway and its regulation, in addition to the genetic landscape and tumor microenvironment that contribute to pancreatic cancer severity. Moreover, this review will also discuss the mechanisms of novel therapeutic strategies that inhibit autophagy and how they could be used to suppress tumor progression.

Modulation of MAPK- and PI3/AKT-Dependent Autophagy Signaling by Stavudine (D4T) in PBMC of Alzheimer’s Disease Patients

Background: Aβ₄₂ deposition plays a pivotal role in AD pathogenesis by inducing the activation of microglial cells and neuroinflammation. This process is antagonized by microglia-mediated clearance of Aβ plaques. Activation of the NLRP3 inflammasome is involved in neuroinflammation and in the impairments of Aβ-plaque clearance. On the other hand, stavudine (D4T) downregulates the NLRP3 inflammasome and stimulates autophagy-mediated Aβ-clearing in a THP-1-derived macrophages. Methods: We explored the effect of D4T on Aβ autophagy in PBMC from AD patients that were primed with LPS and stimulated with Aβ oligomers in the absence/presence of D4T. We analyzed the NLRP3 activity by measuring NLRP3-ASC complex formation by AMNIS FlowSight and pro-inflammatory cytokine (IL-1β, IL-18 and Caspase-1) production by ELISA. The phosphorylation status of p38, ERK, AKT, p70, and the protein expression of CREB, LAMP2A, beclin-1, Caspase-3 and Bcl2 were analyzed by Western blot. Results: Data showed that D4T: (1) downregulates NLRP3 inflammasome activation and the production of down-stream pro-inflammatory cytokines in PBMC; (2) stimulates the phosphorylation of AKT, ERK and p70 as well as LAMP2A, beclin-1 and Bcl2 expression and reduces Caspase-3 expression, suggesting an effect of this compound on autophagy; (3) increases phospho-CREB, which is a downstream target of p-ERK and p-AKT, inducing anti-inflammatory cytokine production and resulting in a possible decrease of Aβ-mediated cytotoxicity; and (4) reduces the phosphorylation of p38, a protein involved in the production of pro-inflammatory cytokines and tau hyperphosphorylation. Conclusions: D4T reduces the activation of the NLRP3 inflammasome, and it might stimulate autophagy as well as the molecular mechanism that modulates Aβ cytotoxicity, and D4T might reduce inflammation in the cells of AD patients. It could be very interesting to check the possible beneficial effects of D4T in the clinical scenario.

Trehalose decreases mRNA and protein expressions of c-Jun and JunB in human cervical cancer HeLa cells

Increasing evidence suggests that trehalose, a non-reducing disaccharide, ameliorates disease phenotypes by activating autophagy in animal models of various human diseases, including neurodegenerative diseases. Multiple in vitro studies suggest that activation of transcription factor EB, a master regulator of lysosomal biogenesis and autophagy genes, is a major contributor to trehalose-induced autophagy at later stages of exposure. However, underlying causes of trehalose-induced autophagy possibly occur at the early stage of the exposure period. In this study, we investigated the effects of short-term exposure of HeLa cells to trehalose on several signal transduction pathways to elucidate the initial events involved in its beneficial effects. Phospho-protein array analysis revealed that trehalose decreases levels of phosphorylated c-Jun, a component of the transcription factor activator protein-1, after 6 h. Trehalose also rapidly reduced mRNA expression levels of c-Jun and JunB, a member of the Jun family, within 1 h, resulting in a subsequent decrease in their protein levels. Future studies, exploring the interplay between decreased c-Jun and JunB protein levels and beneficial effects of trehalose may provide novel insights into the mechanisms of trehalose action.

Rhinacanthin-C but Not -D Extracted from Rhinacanthus nasutus (L.) Kurz Offers Neuroprotection via ERK, CHOP, and LC3B Pathways

Neurodegenerative diseases present an increasing problem as the world's population ages; thus, the discovery of new drugs that prevent diseases such as Alzheimer's, and Parkinson's diseases are vital. In this study, Rhinacanthin-C and -D were isolated from Rhinacanthus nasustus, using ethyl acetate, followed by chromatography to isolate Rhinacanthin-C and -D. Both compounds were confirmed using NMR and ultra-performance-LCMS. Using glutamate toxicity in HT-22 cells, we measured cell viability and apoptosis, ROS build-up, and investigated signaling pathways. We show that Rhinacanthin-C and 2-hydroxy-1,4-naphthoquinone have neuroprotective effects against glutamate-induced apoptosis in HT-22 cells. Furthermore, we see that Rhinacanthin-C resulted in autophagy inhibition and increased ER stress. In contrast, low concentrations of Rhinacanthin-C and 2-hydroxy-1,4-naphthoquinone prevented ER stress and CHOP expression. All concentrations of Rhinacanthin-C prevented ROS production and ERK1/2 phosphorylation. We conclude that, while autophagy is present in HT-22 cells subjected to glutamate toxicity, its inhibition is not necessary for cryoprotection.

MAP kinase-dependent autophagy controls phorbol myristate acetate-induced macrophage differentiation of HL-60 leukemia cells

We investigated the mechanisms and the role of autophagy in the differentiation of HL-60 human acute myeloid leukemia cells induced by protein kinase C (PKC) activator phorbol myristate acetate (PMA). PMA-triggered differentiation of HL-60 cells into macrophage-like cells was confirmed by cell-cycle arrest accompanied by elevated expression of macrophage markers CD11b, CD13, CD14, CD45, EGR1, CSF1R, and IL-8. The induction of autophagy was demonstrated by the increase in intracellular acidification, accumulation/punctuation of autophagosome marker LC3-II, and the increase in autophagic flux. PMA also increased nuclear translocation of autophagy transcription factors TFEB, FOXO1, and FOXO3, as well as the expression of several autophagy-related (ATG) genes in HL-60 cells. PMA failed to activate autophagy inducer AMP-activated protein kinase (AMPK) and inhibit autophagy suppressor mechanistic target of rapamycin complex 1 (mTORC1). On the other hand, it readily stimulated the phosphorylation of mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) via a protein kinase C-dependent mechanism. Pharmacological or genetic inhibition of ERK or JNK suppressed PMA-triggered nuclear translocation of TFEB and FOXO1/3, ATG expression, dissociation of pro-autophagic beclin-1 from its inhibitor BCL2, autophagy induction, and differentiation of HL-60 cells into macrophage-like cells. Pharmacological or genetic inhibition of autophagy also blocked PMA-induced macrophage differentiation of HL-60 cells. Therefore, MAP kinases ERK and JNK control PMA-induced macrophage differentiation of HL-60 leukemia cells through AMPK/mTORC1-independent, TFEB/FOXO-mediated transcriptional and beclin-1-dependent post-translational activation of autophagy.

S-20, a steroidal saponin from the berries of black nightshade, exerts anti-multidrug resistance activity in K562/ADR cells through autophagic cell death and ERK activation

Multidrug resistance (MDR) is a major cause of chemotherapy failure. Adriamycin (ADR) has been widely used to treat cancer, however, as a substrate of the adenosine triphosphate binding cassette (ABC) transporter, it is easy to develop drug resistance during the treatment. Here, we demonstrated that steroidal saponin S-20 isolated from the berries of black nightshade has comparable cytotoxicity in ADR-sensitive and resistant K562 cell lines. Autophagy is generally considered to be a protective mechanism to mediate MDR during treatment. However, we found that S-20-induced cell death in K562/ADR is associated with autophagy. We further explored the underlying mechanisms and found that S-20 induces caspase-dependent apoptosis in ADR-sensitive and resistant K562 cell lines. Most importantly, S-20-induced autophagy activates the ERK pathway and then inhibits the expression of drug resistance protein, which is the main reason to overcome K562/ADR resistance, rather than apoptosis. Taken together, our findings emphasize that S-20 exerts anti-multidrug resistance activity in K562/ADR cells through autophagic cell death and ERK activation, which may be considered as an effective strategy.