Regulation of membrane traffic by phosphoinositide 3-kinases

Genome-wide identification of PAR domain protein 1 (PDP1) targets through ChIP-seq reveals the regulation of diapause-specific characteristics in Culex pipiens

Insects use seasonal diapause as an alternative strategy to endure adverse seasons. This developmental trajectory is induced by environmental cues like short-day lengths in late summer and early fall, but how insects measure day length is unknown. The circadian clock has been implicated in regulating photoperiodic or seasonal responses in many insects, including the Northern house mosquito, Culex pipiens, which enters adult diapause. To investigate the potential control of diapause by circadian control, we employed ChIP-sequencing to identify the downstream targets of a circadian transcription factor, PAR domain protein 1 (PDP1), that contribute to the hallmark features of diapause. We identified the nearest genes in a 10 kb region of the anticipated PDP1 binding sites, listed prospective targets and searched for PDP1-specific binding sites. By examining the functional relevance to diapause-specific behaviours and modifications such as metabolic pathways, lifespan extension, cell cycle regulation and stress tolerance, eight genes were selected as targets and validated using ChIP-qPCR. In addition, qRT-PCR demonstrated that the mRNA abundance of PDP1 targets increased in the heads of diapausing females during the middle of the scotophase (ZT17) compared with the early photophase (ZT1), in agreement with the peak and trough of PDP1 abundance. Thus, our investigation uncovered the mechanism by which PDP1 might generate a diapause phenotype in insects.

Pik3c3 expression profiling in the mouse kidney and its role in proximal tubule cell physiology

The class 3 phosphatidylinositol 3-kinase (Pik3c3) plays critical roles in regulating autophagy, endocytosis, and nutrient sensing, but its expression profile in the kidney remains undefined. Recently, we validated a Pik3c3 antibody through immunofluorescence staining of kidney tissues from cell type-specific Pik3c3 knockout mice. Immunohistochemistry unveiled significant disparities in Pik3c3 expression levels across various kidney cell types. Notably, renal interstitial cells exhibit minimal Pik3c3 expression. Further, coimmunofluorescence staining, utilizing nephron segment- or cell type-specific markers, revealed nearly undetectable levels of Pik3c3 expression in glomerular mesangial cells and endothelial cells. Intriguingly, although podocytes exhibit the highest Pik3c3 expression levels among all kidney cell types, the renal proximal tubule cells (RPTCs) express the highest level of Pik3c3 among all renal tubules. RPTCs are known to express the highest level of the epidermal growth factor receptor (EGFR) in adult kidneys; however, the role of Pik3c3 in EGFR signaling within RPTCs remains unexplored. Therefore, we conducted additional cell culture studies. The results demonstrated that Pik3c3 inhibition significantly delayed EGF-stimulated EGFR degradation and the termination of EGFR signaling in RPTCs. Mechanistically, Pik3c3 inhibition surprisingly did not affect the initial endocytosis process but instead impeded the lysosomal degradation of EGFR. In summary, this study defines, for the first time, the expression profile of Pik3c3 in the mouse kidney and also highlights a pivotal role of Pik3c3 in the proximal tubule cells. These findings shed light on the intricate mechanisms underlying Pik3c3-mediated regulation of EGFR signaling, providing valuable insights into the role of Pik3c3 in renal cell physiology. NEW & NOTEWORTHY This is the first report defining the class 3 phosphatidylinositol 3-kinase (Pik3c3) expression profile in the kidney. Pik3c3 is nearly absent in renal interstitial cells, glomerular mesangial cells, and endothelial cells. Remarkably, glomerular podocytes express the highest Pik3c3 level in the kidney. However, the proximal tubule exhibits the highest expression level among all renal tubules. This study also unveils the pivotal role of Pik3c3 in regulating EGFR degradation and signaling termination in RPTCs, furthering our understanding of Pik3c3 in renal cell physiology.

Autophagy-related miRNAs, exosomal miRNAs, and circRNAs in tumor progression and drug-and radiation resistance in colorectal cancer

Targeted therapies are often more tolerable than traditional cytotoxic ones. Nurses play a critical role in providing patients and caregivers with information about the disease, available therapies, and the kind, severity, and identification of any potential adverse events. By doing this, it may be possible to ensure that any adverse effects are managed quickly, maximizing the therapeutic benefit. In colorectal cancer (CRC), autophagy-related activities are significantly influenced by miRNAs and exosomal miRNAs. CRC development and treatment resistance have been associated with the cellular process of autophagy. miRNAs, which are short non-coding RNA molecules, have the ability to control the expression of genes by binding to the 3' untranslated region (UTR) of target mRNAs and either preventing or suppressing translation. It has been discovered that several miRNAs are significant regulators of CRC autophagy. By preventing autophagy, these miRNAs enhance the survival and growth of cancer cells. Exosomes are small membrane vesicles that are released by cells and include miRNAs among other bioactive compounds. Exosomes have the ability to modify recipient cells' biological processes by delivering their cargo, which includes miRNAs. It has been demonstrated that exosomal miRNAs control autophagy in CRC in both autocrine and paracrine ways. We will discuss the potential roles of miRNAs, exosomal miRNAs, and circRNAs in CRC autophagy processes and how nursing care can reduce unfavorable outcomes.

Blockage of Autophagy for Cancer Therapy: A Comprehensive Review

The incidence and mortality of cancer are increasing, making it a leading cause of death worldwide. Conventional treatments such as surgery, radiotherapy, and chemotherapy face significant limitations due to therapeutic resistance. Autophagy, a cellular self-degradation mechanism, plays a crucial role in cancer development, drug resistance, and treatment. This review investigates the potential of autophagy inhibition as a therapeutic strategy for cancer. A systematic search was conducted on Embase, PubMed, and Google Scholar databases from 1967 to 2024 to identify studies on autophagy inhibitors and their mechanisms in cancer therapy. The review includes original articles utilizing in vitro and in vivo experimental methods, literature reviews, and clinical trials. Key terms used were "Autophagy", "Inhibitors", "Molecular mechanism", "Cancer therapy", and "Clinical trials". Autophagy inhibitors such as chloroquine (CQ) and hydroxychloroquine (HCQ) have shown promise in preclinical studies by inhibiting lysosomal acidification and preventing autophagosome degradation. Other inhibitors like wortmannin and SAR405 target specific components of the autophagy pathway. Combining these inhibitors with chemotherapy has demonstrated enhanced efficacy, making cancer cells more susceptible to cytotoxic agents. Clinical trials involving CQ and HCQ have shown encouraging results, although further investigation is needed to optimize their use in cancer therapy. Autophagy exhibits a dual role in cancer, functioning as both a survival mechanism and a cell death pathway. Targeting autophagy presents a viable strategy for cancer therapy, particularly when integrated with existing treatments. However, the complexity of autophagy regulation and the potential side effects necessitate further research to develop precise and context-specific therapeutic approaches.

Cand2 inhibits CRL-mediated ubiquitination and suppresses autophagy to facilitate pathogenicity of phytopathogenic fungi

The ubiquitin-proteasome system and the autophagy system are the two primary mechanisms used by eukaryotes to maintain protein homeostasis, and both are closely related to the pathogenicity of the rice blast fungus. In this research, we identified MoCand2 as an inhibitor of ubiquitination in Magnaporthe oryzae. Through this role, MoCand2 participates in the regulation of autophagy and pathogenicity. Specifically, we found that deletion of MoCand2 increased the ubiquitination level in M. oryzae, whereas overexpression of MoCand2 inhibited the accumulation of ubiquitinated proteins. Interaction analyses showed that MoCand2 is a subunit of Cullin-RING ligases (CRLs). It suppresses ubiquitination by blocking the assembly of CRLs and downregulating the expression of key CRL subunits. Further research indicated that MoCand2 regulates autophagy through ubiquitination. MoCand2 knockout led to over-ubiquitination and over-degradation of MoTor, and we confirmed that MoTor content was negatively correlated with autophagy level. In addition, MoCand2 knockout accelerated the K63 ubiquitination of MoAtg6 and strengthened the assembly and activity of the phosphatidylinositol-3-kinase class 3 complex, thus enhancing autophagy. Abnormal ubiquitination and autophagy in ΔMocand2 resulted in defects in growth, conidiation, stress resistance, and pathogenicity. Finally, sequence alignment and functional analyses in other phytopathogenic fungi confirmed the high conservation of fungal Cand2s. Our research thus reveals a novel mechanism by which ubiquitination regulates autophagy and pathogenicity in phytopathogenic fungi.

The Regulation of Exosome Generation and Function in Physiological and Pathological Processes

Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.

Deterministic early endosomal maturations emerge from a stochastic trigger-and-convert mechanism

Endosomal maturation is critical for robust and timely cargo transport to specific cellular compartments. The most prominent model of early endosomal maturation involves a phosphoinositide-driven gain or loss of specific proteins on individual endosomes, emphasising an autonomous and stochastic description. However, limitations in fast, volumetric imaging long hindered direct whole cell-level measurements of absolute numbers of maturation events. Here, we use lattice light-sheet imaging and bespoke automated analysis to track individual very early (APPL1-positive) and early (EEA1-positive) endosomes over the entire population, demonstrating that direct inter-endosomal contact drives maturation between these populations. Using fluorescence lifetime, we show that this endosomal interaction is underpinned by asymmetric binding of EEA1 to very early and early endosomes through its N- and C-termini, respectively. In combination with agent-based simulation which supports a 'trigger-and-convert' model, our findings indicate that APPL1- to EEA1-positive maturation is driven not by autonomous events but by heterotypic EEA1-mediated interactions, providing a mechanism for temporal and population-level control of maturation.

Novel variants in genes related to vesicle-mediated-transport modify Parkinson's disease risk

OBJECTIVES

VPS35 and VPS13 have been associated with Parkinson's disease (PD), and their shared phenotype in yeast when reduced in function is abnormal vacuolar transport. We aim to test if additional potentially deleterious variants in other genes that share this phenotype can modify the risk for PD.

METHODS

77 VPS and VPS-related genes were analyzed using whole-genome-sequencing data from 202 PD patients of Ashkenazi Jewish (AJ) ancestry. Filtering was done based on quality and functionality scores. Ten variants in nine genes were further genotyped in 1200 consecutively recruited unrelated AJ-PD patients, and allele frequencies and odds ratio calculated compared to gnomAD-AJ-non-neuro database, in un-stratified (n = 1200) and stratified manner (LRRK2-G2019S-PD patients (n = 145), GBA-PD patients (n = 235), and non-carriers of these mutations (NC, n = 787)).

RESULTS

Five variants in PIK3C3, VPS11, AP1G2, HGS and VPS13D were significantly associated with PD-risk. PIK3C3-R768W showed a significant association in an un-stratified (all PDs) analysis, as well as in stratified (LRRK2, GBA, and NC) analyses (Odds ratios = 2.71, 5.32, 3.26. and 2.19 with p = 0.0015, 0.002, 0.0287, and 0.0447, respectively). AP1G2-R563W was significantly associated in LRRK2-carriers (OR = 3.69, p = 0.006) while VPS13D-D2932N was significantly associated in GBA-carriers (OR = 5.45, p = 0.0027). VPS11-C846G and HGS-S243Y were significantly associated in NC (OR = 2.48 and 2.06, with p = 0.022 and 0.0163, respectively).

CONCLUSIONS

Variants in genes involved in vesicle-mediated protein transport and recycling pathways, including autophagy and mitophagy, may differentially modify PD-risk in LRRK2-carriers, GBA carriers, or NC. Specifically, PIK3C3-R768W is a PD-risk allele, with the highest effect size in LRRK2-G2019S carriers. These results suggest oligogenic effect that may depends on the genetic background of the patient. An unbiased burden of mutations approach in these genes should be evaluated in additional PD and control groups. The mechanisms by which these novel variants interact and increase PD-risk should be researched in depth for better tailoring therapeutic intervention for PD prevention or slowing disease progression.

SARS-CoV-2 pandemics: an update of CRISPR in diagnosis and host-virus interaction studies

Since December 2019, the Coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has spread rapidly around the world, overburdening healthcare systems and creating significant global health concerns. Rapid detection of infected individuals via early diagnostic tests and administration of effective therapy remains vital in pandemic control, and recent advances in the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated proteins) system may support the development of novel diagnostic and therapeutic approaches. Cas-based SARS-CoV-2 detection methods (FELUDA, DETECTR, and SHERLOCK) have been developed for easier handling compared to quantitative polymerase chain reaction (qPCR) assays, with good rapidity, high specificity, and reduced need for complex instrumentation. Cas-CRISPR-derived RNA (Cas-crRNA) complexes have been shown to reduce viral loads in the lungs of infected hamsters, by degrading virus genomes and limiting viral replication in host cells. Viral-host interaction screening platforms have been developed using the CRISPR-based system to identify essential cellular factors involved in pathogenesis, and CRISPR knockout and activation screening results have revealed vital pathways in the life cycle of coronaviruses, including host cell entry receptors (ACE2, DPP4, and ANPEP), proteases involved in spike activation and membrane fusion (CTSL and TMPRSS2), intracellular traffic control routes for virus uncoating and budding, and membrane recruitment for viral replication. Several novel genes (SMARCA4, ARIDIA, and KDM6A) have also been identified via systematic data mining analysis as pathogenic factors for severe CoV infection. This review highlights how CRISPR-based systems can be applied to investigate the viral life cycle, detect viral genomes, and develop therapies against SARS-CoV-2 infection.

Evaluation of the Effectiveness of Various Autophagy Inhibitors in A549 Cancer Stem Cells

Numerous studies have already established that autophagy plays a central role in the survival of all cells, including malignant ones. Autophagy is a central cog in the general mechanism that provides the intracellular proteostasis determining cellular physiological and phenotypic characteristics. The accumulated data show that autophagy largely contributes to cancer cell stemness. Thus, autophagy modulation is considered one of the promising pharmacological targets in therapy aimed at cancer stem cell elimination. However, autophagy is a multi-stage intracellular process that involves numerous protein participants. In addition, the process can be activated simultaneously by various signaling modules. Therefore, it is no small feat to select an effective pharmacological drug against autophagy. What's more, the search for potential chemotherapeutic agents that could eliminate cancer stem cells through pharmacological inhibition of autophagy is still under way. In the present work, we selected a panel of autophagy inhibitors (Autophinib, SBI-0206965, Siramesine, MRT68921, and IITZ-01), some of whom have been recently identified as effective autophagy inhibitors in cancer cells. Using A549 cancer cells, which express the core stem factors Oct4 and Sox2, we evaluated the effect of these drugs on the survival and preservation of the original properties of cancer stem cells. Among the agents selected, only Autophinib demonstrated a significant toxic effect on cancer stem cells. The obtained results demonstrate that autophagy inhibition by Autophinib downregulates the expression of the Sox2 protein in A549 cells, and that this downregulation correlates with a pronounced induction of apoptosis. Moreover, Autophinib-treated A549 cells are unable to form spheroids, which indicates a reduction in stemness. Thus, among the drugs studied, only Autophinib can be considered a potential agent against cancer stem cells.

Myotubularin functions through actomyosin to interact with the Hippo pathway

The Hippo pathway is an evolutionarily conserved developmental pathway that controls organ size by integrating diverse regulatory inputs, including actomyosin-mediated cytoskeletal tension. Despite established connections between the actomyosin cytoskeleton and the Hippo pathway, the upstream regulation of actomyosin in the Hippo pathway is less defined. Here, we identify the phosphoinositide-3-phosphatase Myotubularin (Mtm) as a novel upstream regulator of actomyosin that functions synergistically with the Hippo pathway during growth control. Mechanistically, Mtm regulates membrane phospholipid PI(3)P dynamics, which, in turn, modulates actomyosin activity through Rab11-mediated vesicular trafficking. We reveal PI(3)P dynamics as a novel mode of upstream regulation of actomyosin and establish Rab11-mediated vesicular trafficking as a functional link between membrane lipid dynamics and actomyosin activation in the context of growth control. Our study also shows that MTMR2, the human counterpart of Drosophila Mtm, has conserved functions in regulating actomyosin activity and tissue growth, providing new insights into the molecular basis of MTMR2-related peripheral nerve myelination and human disorders.

Influence of protein corona on the interaction of glycogen-siRNA constructs with ex vivo human blood immune cells

Glycogen-nucleic acid constructs i.e., glycoplexes are emerging promising platforms for the alteration of gene expression and transcription. Understanding the interaction of glycoplexes with human blood components, such as serum proteins and peripheral blood mononuclear cells (PBMCs), is important to overcome immune cell activation and control biodistribution upon administration of the glycoplexes in vivo. Herein, we investigated the interactions of polyethylene glycol (PEG)ylated and non-PEGylated glycoplexes carrying siRNA molecules with PBMCs isolated from the blood of healthy donors. We found that both types of glycoplexes were non-toxic and were primarily phagocytosed by monocytes without triggering a pro-inflammatory interleukin 6 cytokine production. Furthermore, we investigated the role of the protein corona on controlling the internalization efficiency in immune cells - we found that the adsorption of serum proteins, in particular haptoglobin, alpha-1-antitrypsin and apolipoprotein A-II, onto the non-PEGylated glycoplexes, significantly reduced the uptake of the glycoplexes by PBMCs. Moreover, the non-PEGylated glycoplexes were efficient in the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) knockdown in monocytic THP-1 cell line. This study provides an insight into the rational design of glycogen-based nanocarriers for the safe delivery of siRNA without eliciting unwanted immune cell activation and efficient siRNA activity upon its delivery.

Albumin Stimulates Epithelial Na+ Transport and Barrier Integrity by Activating the PI3K/AKT/SGK1 Pathway

Albumin is a major serum protein and is frequently used as a cell culture supplement. It is crucially involved in the regulation of osmotic pressure and distribution of fluid between different compartments. Alveolar epithelial Na⁺ transport drives alveolar fluid clearance (AFC), enabling air breathing. Whether or not albumin affects AFC and Na⁺ transport is yet unknown. We therefore determined the acute and chronic effects of albumin on Na⁺ transport in fetal distal lung epithelial (FDLE) cells and the involved kinase pathways. Chronic BSA treatment strongly increased epithelial Na⁺ transport and barrier integrity in Ussing chambers. BSA did not elevate mRNA expression of Na⁺ transporters in FDLE cells after 24 h. Moreover, acute BSA treatment for 45 min mimicked the chronic effects. The elevated Na⁺ transport was caused by an increased maximal ENaC activity, while Na,K-ATPase activity remained unchanged. Acute and chronic BSA treatment lowered membrane permeability, confirming the increased barrier integrity observed in Ussing chambers. Western blots demonstrated an increased phosphorylation of AKT and SGK1, and PI3K inhibition abolished the stimulating effect of BSA. BSA therefore enhanced epithelial Na⁺ transport and barrier integrity by activating the PI3K/AKT/SGK1 pathway.

Molecular Mechanisms of Autophagy in Cancer Development, Progression, and Therapy

Autophagy is an evolutionarily conserved and tightly regulated process that plays an important role in maintaining cellular homeostasis. It involves regulation of various genes that function to degrade unnecessary or dysfunctional cellular components, and to recycle metabolic substrates. Autophagy is modulated by many factors, such as nutritional status, energy level, hypoxic conditions, endoplasmic reticulum stress, hormonal stimulation and drugs, and these factors can regulate autophagy both upstream and downstream of the pathway. In cancer, autophagy acts as a double-edged sword depending on the tissue type and stage of tumorigenesis. On the one hand, autophagy promotes tumor progression in advanced stages by stimulating tumor growth. On the other hand, autophagy inhibits tumor development in the early stages by enhancing its tumor suppressor activity. Moreover, autophagy drives resistance to anticancer therapy, even though in some tumor types, its activation induces lethal effects on cancer cells. In this review, we summarize the biological mechanisms of autophagy and its dual role in cancer. In addition, we report the current understanding of autophagy in some cancer types with markedly high incidence and/or lethality, and the existing therapeutic strategies targeting autophagy for the treatment of cancer.

Endosomal cargo recycling mediated by Gpa1 and phosphatidylinositol 3-kinase is inhibited by glucose starvation

Cell surface protein trafficking is regulated in response to nutrient availability, with multiple pathways directing surface membrane proteins to the lysosome for degradation in response to suboptimal extracellular nutrients. Internalized protein and lipid cargoes recycle back to the surface efficiently in glucose-replete conditions, but this trafficking is attenuated following glucose starvation. We find that cells with either reduced or hyperactive phosphatidylinositol 3-kinase (PI3K) activity are defective for endosome to surface recycling. Furthermore, we find that the yeast Gα subunit Gpa1, an endosomal PI3K effector, is required for surface recycling of cargoes. Following glucose starvation, mRNA and protein levels of a distinct Gα subunit Gpa2 are elevated following nuclear translocation of Mig1, which inhibits recycling of various cargoes. As Gpa1 and Gpa2 interact at the surface where Gpa2 concentrates during glucose starvation, we propose that this disrupts PI3K activity required for recycling, potentially diverting Gpa1 to the surface and interfering with its endosomal role in recycling. In support of this model, glucose starvation and overexpression of Gpa2 alter PI3K endosomal phosphoinositide production. Glucose deprivation therefore triggers a survival mechanism to increase retention of surface cargoes in endosomes and promote their lysosomal degradation.

The role of PI3'-lipid signalling in melanoma initiation, progression and maintenance

Phosphatidylinositol-3'-kinases (PI3Ks) are a family of lipid kinases that phosphorylate the 3' hydroxyl (OH) of the inositol ring of phosphatidylinositides (PI). Through their downstream effectors, PI3K generated lipids (PI3K-lipids hereafter) such as PI(3,4,5)P3 and PI(3,4)P2 regulate myriad biochemical and biological processes in both normal and cancer cells including responses to growth hormones and cytokines; the cell division cycle; cell death; cellular growth; angiogenesis; membrane dynamics; and autophagy and many aspects of cellular metabolism. Engagement of receptor tyrosine kinase by their cognate ligands leads to activation of members of the Class I family of PI3'-kinases (PI3Kα, β, δ & γ) leading to accumulation of PI3K-lipids. Importantly, PI3K-lipid accumulation is antagonized by the hydrolytic action of a number of PI3K-lipid phosphatases, most notably the melanoma suppressor PTEN (lipid phosphatase and tensin homologue). Downstream of PI3K-lipid production, the protein kinases AKT1-3 are believed to be key effectors of PI3'-kinase signalling in cells. Indeed, in preclinical models, activation of the PI3K→AKT signalling axis cooperates with alterations such as expression of the BRAFV600E oncoprotein kinase to promote melanoma progression and metastasis. In this review, we describe the different classes of PI3K-lipid effectors, and how they may promote melanomagenesis, influence the tumour microenvironment, melanoma maintenance and progression to metastatic disease. We also provide an update on both FDA-approved or experimental inhibitors of the PI3K→AKT pathway that are currently being evaluated for the treatment of melanoma either in preclinical models or in clinical trials.

Secretion of pro-angiogenic extracellular vesicles during hypoxia is dependent on the autophagy-related protein GABARAPL1

Tumour hypoxia is a hallmark of solid tumours and contributes to tumour progression, metastasis development and therapy resistance. In response to hypoxia, tumour cells secrete pro-angiogenic factors to induce blood vessel formation and restore oxygen supply to hypoxic regions. Extracellular vesicles (EVs) are emerging as mediators of intercellular communication in the tumour microenvironment. Here we demonstrate that increased expression of the LC3/GABARAP protein family member GABARAPL1, is required for endosomal maturation, sorting of cargo to endosomes and the secretion of EVs. Silencing GABARAPL1 results in a block in the early endosomal pathway and impaired secretion of EVs with pro-angiogenic properties. Tumour xenografts of doxycycline inducible GABARAPL1 knockdown cells display impaired vascularisation that results in decreased tumour growth, elevated tumour necrosis and increased therapy efficacy. Moreover, our data show that GABARAPL1 is expressed on the EV surface and targeting GABARAPL1+ EVs with GABARAPL1 targeting antibodies results in blockade of pro-angiogenic effects in vitro. In summary, we reveal that GABARAPL1 is required for EV cargo loading and secretion. GABARAPL1+ EVs are detectable and targetable and are therefore interesting to pursue as a therapeutic target.

Entry of the Varicellovirus Canid herpesvirus 1 into Madin-Darby canine kidney epithelial cells is pH-independent and occurs via a macropinocytosis-like mechanism but without increase in fluid uptake

Canid herpesvirus 1 (CHV-1) is a Varicellovirus that causes self-limiting infections in adult dogs but morbidity and mortality in puppies. Using a multipronged approach, we discovered the CHV-1 entry pathway into Madin-Darby canine kidney (MDCK) epithelial cells. We found that CHV-1 triggered extensive host cell membrane lamellipodial ruffling and rapid internalisation of virions in large, uncoated vacuoles, suggestive of macropinocytosis. Treatment with inhibitors targeting key macropinocytosis factors, including inhibitors of Na⁺ /H⁺ exchangers, F-actin, myosin light-chain kinase, protein kinase C, p21-activated kinase, phosphatidylinositol-3-kinase and focal adhesion kinase, significantly reduced viral replication. Moreover, the effect was restricted to exposure to the inhibitors early in infection, confirming a role for the macropinocytic machinery during entry. The profile of inhibitors also suggested a role for signalling via integrins and receptor tyrosine kinases in viral entry. In contrast, inhibitors of clathrin, caveolin, microtubules and endosomal acidification did not affect CHV-1 entry into MDCK cells. We found that the virus colocalised with the fluid-phase uptake marker dextran; however, surprisingly, CHV-1 infection did not enhance the uptake of dextran. Thus, our results indicate that CHV-1 uses a macropinocytosis-like, pH-independent entry pathway into MDCK cells, which nevertheless is not based on stimulation of fluid uptake. TAKE AWAYS: CHV-1 enters epithelial cells via a macropinocytosis-like mechanism. CHV-1 induces extensive lamellipodial ruffling. CHV-1 entry into MDCK cells is pH-independent.

WW, PH and C-Terminal Domains Cooperate to Direct the Subcellular Localizations of PLEKHA5, PLEKHA6 and PLEKHA7

PLEKHA5, PLEKHA6, and PLEKHA7 (WW-PLEKHAs) are members of the PLEKHA family of proteins that interact with PDZD11 through their tandem WW domains. WW-PLEKHAs contribute to the trafficking and retention of transmembrane proteins, including nectins, Tspan33, and the copper pump ATP7A, at cell-cell junctions and lateral membranes. However, the structural basis for the distinct subcellular localizations of PLEKHA5, PLEKHA6, and PLEKHA7 is not clear. Here we expressed mutant and chimeric proteins of WW-PLEKHAs in cultured cells to clarify the role of their structural domains in their localization. We found that the WW-mediated interaction between PLEKHA5 and PDZD11 is required for their respective association with cytoplasmic microtubules. The PH domain of PLEKHA5 is required for its localization along the lateral plasma membrane and promotes the lateral localization of PLEKHA7 in a chimeric molecule. Although the PH domain of PLEKHA7 is not required for its localization at the adherens junctions (AJ), it promotes a AJ localization of chimeric proteins. The C-terminal region of PLEKHA6 and PLEKHA7 and the coiled-coil region of PLEKHA7 promote their localization at AJ of epithelial cells. These observations indicate that the localizations of WW-PLEKHAs at specific subcellular sites, where they recruit PDZD11, are the result of multiple cooperative protein-lipid and protein-protein interactions and provide a rational basis for the identification of additional proteins involved in trafficking and sorting of WW-PLEKHAs.

Taspine is a natural product that suppresses P2X4 receptor activity via phosphoinositide 3-kinase inhibition

BACKGROUND & PURPOSE

P2X4 is a ligand-gated cation channel activated by extracellular ATP, involved in neuropathic pain, inflammation and arterial tone.

EXPERIMENTAL APPROACH

Natural products were screened against human or mouse P2X4 activity using fura-2 loaded 1321N1 cells for measurement of intracellular Ca²⁺ responses; whole-cell currents were measured by patch clamp electrophysiological. Human primary macrophage chemokine release was used to assess effect of taspine on inflammatory cell function. An enzymatic assay was performed to assess the effect of taspine on recombinant PI3-kinase.

KEY RESULTS

A natural product screen identified taspine as an inhibitor of human P2X4 activity. Taspine inhibits human and mouse P2X4-mediated Ca²⁺ influx in 1321N1 cells expressing receptors (IC₅₀ 1.6±0.4 μM and 1.6±0.3 μM, respectively), but lacked activity at human P2X2, P2X3, P2X2/3 and P2X7 receptors. Taspine inhibited the maximal response at human and mouse P2X4 but had no effect on ATP potency. Taspine has a slow onset rate (~15 mins for half-maximal inhibition), irreversible over 30 minutes of washout. Taspine inhibits P2X4-mediated Ca²⁺ signalling in mouse BV-2 microglia cells and human primary macrophage. Taspine inhibited P2X4-mediated CXCL5 secretion in human primary macrophage. Taspine reversed ivermectin-induced potentiation of P2X4 currents in 1321N1 stably expressing cells. The known PI3-kinase inhibitor LY294002 mimicked the properties of taspine on P2X4-mediated Ca²⁺ influx and whole-cell currents. Taspine directly inhibited the enzymatic activity of recombinant PI3-kinase in a competitive manner.

CONCLUSIONS AND IMPLICATIONS

Taspine is a novel natural product P2X4 inhibitor, mediating its effect through PI3-kinase inhibitor rather than receptor antagonism. Taspine can inhibit the pro-inflammatory signalling by P2X4 in human primary macrophage.

SNX19 restricts endolysosome motility through contacts with the endoplasmic reticulum

The ability of endolysosomal organelles to move within the cytoplasm is essential for the performance of their functions. Long-range movement involves coupling of the endolysosomes to motor proteins that carry them along microtubule tracks. This movement is influenced by interactions with other organelles, but the mechanisms involved are incompletely understood. Herein we show that the sorting nexin SNX19 tethers endolysosomes to the endoplasmic reticulum (ER), decreasing their motility and contributing to their concentration in the perinuclear area of the cell. Tethering depends on two N-terminal transmembrane domains that anchor SNX19 to the ER, and a PX domain that binds to phosphatidylinositol 3-phosphate on the endolysosomal membrane. Two other domains named PXA and PXC negatively regulate the interaction of SNX19 with endolysosomes. These studies thus identify a mechanism for controlling the motility and positioning of endolysosomes that involves tethering to the ER by a sorting nexin.

A Structural Approach into Drug Discovery Based on Autophagy

Autophagy is a lysosome-dependent intracellular degradation machinery that plays an essential role in the regulation of cellular homeostasis. As many studies have revealed that autophagy is related to cancer, neurodegenerative diseases, metabolic diseases, and so on, and it is considered as a promising drug target. Recent advances in structural determination and computational technologies provide important structural information on essential autophagy-related proteins. Combined with high-throughput screening methods, structure-activity relationship studies have led to the discovery of molecules that modulate autophagy. In this review, we summarize the recent structural studies on autophagy-related proteins and the discovery of modulators, indicating that targeting autophagy can be utilized as an effective strategy for novel drug development.

Group V Secretory Phospholipase A2 Regulates Endocytosis of Acetylated LDL by Transcriptional Activation of PGK1 in RAW264.7 Macrophage Cell Line

AIMS

It was suggested that group V secretory phospholipase A₂ (sPLA2-V) existed in the nucleus. This study examined whether nuclear sPLA₂-V plays a role in endocytosis of acetylated low-density lipoprotein (AcLDL) in monocyte/macrophage-like cell line RAW264.7 cells.

METHODS

RAW264.7 cells were transfected with shRNA vector targeting sPLA₂-V (sPLA₂-V-knockdown [KD] cells) or empty vector (sPLA₂-V-wild-type [WT] cells). AcLDL endocytosis was assessed by incubation with ¹²⁵I-AcLDL or AcLDL conjugated with pHrodo. Actin polymerization was assessed by flow cytometry using Alexa Fluor 546-phalloidin.

RESULTS

In immunofluorescence microscopic studies, sPLA₂-V was detected in the nucleus. ChIP-Seq and ChIP-qPCR analyses showed binding of sPLA₂-V to the promoter region of the phosphoglycerate kinase 1 (Pgk1) gene. In the promoter assay, sPLA₂-V-KD cells had lower promoter activity of the Pgk1 gene than sPLA₂-V-WT cells, and this decrease could be reversed by transfection with a vector encoding sPLA₂-V-H48Q that lacks enzymatic activity. Compared with sPLA₂-V-WT cells, sPLA₂-V-KD cells had decreased PGK1 protein expression, beclin 1 (Beclin1) phosphorylation at S30, and class III PI3-kinase activity that could also be restored by transfection with sPLA₂-V-H48Q. sPLA₂-V-KD cells had impaired actin polymerization and endocytosis, which was reversed by introduction of sPLA₂-V-H48Q or PGK1 overexpression. In sPLA₂-V-WT cells, siRNA-mediated depletion of PGK1 suppressed Beclin1 phosphorylation and impaired actin polymerization and intracellular trafficking of pHrodo-conjugated AcLDL.

CONCLUSIONS

Nuclear sPLA₂-V binds to the Pgk1 gene promoter region and increases its transcriptional activity. sPLA₂-V regulates AcLDL endocytosis through PGK1-Beclin1 in a manner that is independent of its enzymatic activity in RAW264.7 cells.

Vps34 Inhibits Hepatocellular Carcinoma Invasion by Regulating Endosome-Lysosome Trafficking via Rab7-RILP and Rab11

Purpose

The role of vacuolar protein sorting 34 (Vps34), an indispensable protein required for cell vesicular trafficking, in the biological behavior of hepatocellular carcinoma (HCC) has yet to be studied.

Materials and Methods

In the present study, the expression of Vps34 in HCC and the effect of Vps34 on HCC cell invasion was detected both in vivo and in vitro. Furthermore, by modulating the RILP and Rab11, which regulate juxtanuclear lysosome aggregation and recycling endosome respectively, the underlying mechanism was investigated.

Results

Vps34 was significantly decreased in HCC and negatively correlated with the HCC invasiveness both in vivo and in vitro. Moreover, Vps34 could promote lysosomal juxtanuclear accumulation, reduce the invasive ability of HCC cells via the Rab7-RILP pathway. In addition, the deficiency of Vps34 in HCC cells affected the endosome-lysosome system, resulting in enhanced Rab11 mediated endocytic recycling of cell surface receptor and increased invasion of HCC cells.

Conclusion

Our study reveals that Vps34 acts as an invasion suppressor in HCC cells, and more importantly, the endosome-lysosome trafficking regulated by Vps34 has the potential to become a target pathway in HCC treatment.

VPS34 regulates dynamin to determine the endocytosis of mitochondria-targeted zinc oxide nanoparticles in human osteosarcoma cells

In our previous study, zinc oxide nanoparticles (ZnO NPs) presented satisfying therapeutic effects with cancer cell selectivity in osteosarcoma cells and, thus, have been considered as a potential nanomedicine for human osteosarcoma treatment. However, the poorly investigated internalization process, including their endocytic pathway into tumor cells and intracellular fate, limits the clinical application. Here, we further clarified these aspects. First, ZnO NPs were rapidly internalized by osteosarcoma cells and accumulated in mitochondria, before being entrapped into lysosomes. Second, dynasore (a dynamin inhibitor) was demonstrated to be the most effective in blocking ZnO NP uptake and rescuing ZnO NP-induced osteosarcoma cell autophagic death and apoptosis. Third, we confirmed the key role of dynamin 2 in ZnO NP endocytosis and subsequent autophagic cell death in vitro and in vivo. Furthermore, we proved that VPS34 transferred from cell cytoplasm to cell membrane to interact with dynamin under ZnO NP treatment. Altogether, combined with our previous study, the current research further revealed that ZnO NPs entered human osteosarcoma cells through the VPS34/dynamin 2-dependent endocytic pathway, directly targeting and damaging the mitochondria before being entrapped into the lysosomes, thereby initiating mitophagy-Zn²⁺-reactive oxygen species-mitophagy axis mediated cell apoptosis.

Phosphatidylinositol 3-Phosphate Mediates the Establishment of Infectious Bursal Disease Virus Replication Complexes in Association with Early Endosomes

Infectious bursal disease virus (IBDV) is the archetypal member of the family Birnaviridae and the etiological agent of Gumboro disease, a highly contagious immunosuppressive infection of concern to the global poultry sector for its adverse health effects in chicks. Unlike most double-stranded RNA (dsRNA) viruses, which enclose their genomes within specialized cores throughout their viral replication cycle, birnaviruses organize their bisegmented dsRNA genome in ribonucleoprotein (RNP) structures. Recently, we demonstrated that IBDV exploits endosomal membranes for replication. The establishment of IBDV replication machinery on the cytosolic leaflet of endosomal compartments is mediated by the viral protein VP3 and its intrinsic ability to target endosomes. In this study, we identified the early endosomal phosphatidylinositol 3-phosphate [PtdIns(3)P] as a key host factor of VP3 association with endosomal membranes and consequent establishment of IBDV replication complexes in early endosomes. Indeed, our data reveal a crucial role for PtdIns(3)P in IBDV replication. Overall, our findings provide new insights into the replicative strategy of birnaviruses and strongly suggest that it resembles those of positive-strand RNA (+ssRNA) viruses, which replicate in association with host membranes. Furthermore, our findings support the role of birnaviruses as evolutionary intermediaries between +ssRNA and dsRNA viruses and, importantly, demonstrate a novel role for PtdIns(3)P in the replication of a dsRNA virus.IMPORTANCE Infectious bursal disease virus (IBDV) infects chicks and is the causative agent of Gumboro disease. During IBDV outbreaks in recent decades, the emergence of very virulent variants and the lack of effective prevention/treatment strategies to fight this disease have had devastating consequences for the poultry industry. IBDV belongs to the peculiar family Birnaviridae Unlike most dsRNA viruses, birnaviruses organize their genomes in ribonucleoprotein complexes and replicate in a core-independent manner. We recently demonstrated that IBDV exploits host cell endosomes as platforms for viral replication, a process that depends on the VP3 viral protein. In this study, we delved deeper into the molecular characterization of IBDV-endosome association and investigated the role of host cell phosphatidylinositide lipids in VP3 protein localization and IBDV infection. Together, our findings demonstrate that PtdIns(3)P serves as a scaffold for the association of VP3 to endosomes and reveal its essential role for IBDV replication.

Gene commander in the trash heap: Transcriptional regulation and ubiquitination modification mediated by RNF6 in carcinogenesis

RING finger protein 6 (RNF6), a RING finger protein, has been identified as a potential tumor promoter in several cancers. However, the exact mechanism of RNF6 in cancer remains elusive. As in various diseases, RNF6 may be involved in regulating cell growth, cell proliferation, invasion, cell cycle progression, apoptosis and cell adhesion through E3 ligase-mediated ubiquitination. Thus, the research on RNF6 is mainly focused on the ubiquitination of RNF6 in recent years. This article summarizes the role of RNF6 ubiquitination in various physiological and pathological mechanisms, such as Akt/mTOR signaling pathway, Wnt/β-catenin pathway, RNF6/ERα/Bcl-xL axis, and provides knowledge and understanding for the treatment of diseases.

Rag GTPases and phosphatidylinositol 3-phosphate mediate recruitment of the AP-5/SPG11/SPG15 complex

Adaptor protein complex 5 (AP-5) and its partners, SPG11 and SPG15, are recruited onto late endosomes and lysosomes. Here we show that recruitment of AP-5/SPG11/SPG15 is enhanced in starved cells and occurs by coincidence detection, requiring both phosphatidylinositol 3-phosphate (PI3P) and Rag GTPases. PI3P binding is via the SPG15 FYVE domain, which, on its own, localizes to early endosomes. GDP-locked RagC promotes recruitment of AP-5/SPG11/SPG15, while GTP-locked RagA prevents its recruitment. Our results uncover an interplay between AP-5/SPG11/SPG15 and the mTORC1 pathway and help to explain the phenotype of AP-5/SPG11/SPG15 deficiency in patients, including the defect in autophagic lysosome reformation.

Antibiotics and resistance: the two-sided coin of the mycobacterial cell wall

Mycobacterium tuberculosis, the bacterium responsible for tuberculosis, is the global leading cause of mortality from an infectious agent. Part of this success relies on the unique cell wall, which consists of a thick waxy coat with tightly packed layers of complexed sugars, lipids and peptides. This coat provides a protective hydrophobic barrier to antibiotics and the host's defences, while enabling the bacterium to spread efficiently through sputum to infect and survive within the macrophages of new hosts. However, part of this success comes at a cost, with many of the current first- and second-line drugs targeting the enzymes involved in cell wall biosynthesis. The flip side of this coin is that resistance to these drugs develops either in the target enzymes or the activation pathways of the drugs, paving the way for new resistant clinical strains. This review provides a synopsis of the structure and synthesis of the cell wall and the major current drugs and targets, along with any mechanisms of resistance.

Porcine Reproductive and Respiratory Syndrome Virus Utilizes Viral Apoptotic Mimicry as an Alternative Pathway To Infect Host Cells

PRRS has caused huge economic losses to pig farming worldwide. Its causative agent, PRRSV, infects host cells through low pH-dependent clathrin-mediated endocytosis and CD163 is indispensable during the process. Whether there exist alternative infection pathways for PRRSV arouses our interest. Here, we found that PRRSV exposed PS on its envelope and disguised as apoptotic debris. The PS receptor TIM-1/4 recognized PRRSV and induced the downstream signaling pathway to mediate viral infection via CD163-dependent macropinocytosis. The current work deepens our understanding of PRRSV infection and provides clues for the development of drugs and vaccines against the virus.

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), has led to enormous economic losses in global swine industry. Infection by PRRSV is previously shown to be via low pH-dependent clathrin-mediated endocytosis, and CD163 functions as an essential receptor during viral infection. Despite much research focusing on it, PRRSV infection remains to be fully elucidated. In this study, we demonstrated that PRRSV externalized phosphatidylserine (PS) on the envelope as viral apoptotic mimicry and infected host cells through T-cell immunoglobulin and mucin domain (TIM)-induced and CD163-involved macropinocytosis as an alternative pathway. In detail, we identified that PS receptor TIM-1/4 recognized and interacted with PRRSV as viral apoptotic mimicry and subsequently induced macropinocytosis by the downstream Rho GTPases Rac1, cell division control protein 42 (Cdc42), and p21-activated kinase 1 (Pak1). Altogether, these results expand our knowledge of PRRSV infection, which will support implications for the prevention and control of PRRS.

IMPORTANCE PRRS has caused huge economic losses to pig farming worldwide. Its causative agent, PRRSV, infects host cells through low pH-dependent clathrin-mediated endocytosis and CD163 is indispensable during the process. Whether there exist alternative infection pathways for PRRSV arouses our interest. Here, we found that PRRSV exposed PS on its envelope and disguised as apoptotic debris. The PS receptor TIM-1/4 recognized PRRSV and induced the downstream signaling pathway to mediate viral infection via CD163-dependent macropinocytosis. The current work deepens our understanding of PRRSV infection and provides clues for the development of drugs and vaccines against the virus.

Inhibiting fusion with cellular membrane system: therapeutic options to prevent severe acute respiratory syndrome coronavirus-2 infection

Severe acute respiratory syndrome coronavirus (SARS-CoV), an enveloped virus with a positive-sense single-stranded RNA genome, facilitates the host cell entry through intricate interactions with proteins and lipids of the cell membrane. The detailed molecular mechanism involves binding to the host cell receptor and fusion at the plasma membrane or after being trafficked to late endosomes under favorable environmental conditions. A crucial event in the process is the proteolytic cleavage of the viral spike protein by the host's endogenous proteases that releases the fusion peptide enabling fusion with the host cellular membrane system. The present review details the mechanism of viral fusion with the host and highlights the therapeutic options that prevent SARS-CoV-2 entry in humans.

Toxoplasma gondii Mechanisms of Entry Into Host Cells

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan parasite. Toxoplasma can invade and multiply inside any nucleated cell of a wide range of homeothermic hosts. The canonical process of internalization involves several steps: an initial recognition of the host cell surface and a sequential secretion of proteins from micronemes followed by rhoptries that assemble a macromolecular complex constituting a specialized and transient moving junction. The parasite is then internalized via an endocytic process with the establishment of a parasitophorous vacuole (PV), that does not fuse with lysosomes, where the parasites survive and multiply. This process of host cell invasion is usually referred to active penetration. Using different cell types and inhibitors of distinct endocytic pathways, we show that treatment of host cells with compounds that interfere with clathrin-mediated endocytosis (hypertonic sucrose medium, chlorpromazine hydrochloride, and pitstop 2 inhibited the internalization of tachyzoites). In addition, treatments that interfere with macropinocytosis, such as incubation with amiloride or IPA-3, increased parasite attachment to the host cell surface but significantly blocked parasite internalization. Immunofluorescence microscopy showed that markers of macropinocytosis, such as the Rab5 effector rabankyrin 5 and Pak1, are associated with parasite-containing cytoplasmic vacuoles. These results indicate that entrance of T. gondii into mammalian cells can take place both by the well-characterized interaction of parasite and host cell endocytic machinery and other processes, such as the clathrin-mediated endocytosis, and macropinocytosis.

Host membrane lipids are trafficked to membranes of intravacuolar bacterium Ehrlichia chaffeensis

Ehrlichia chaffeensis, a cholesterol-rich and cholesterol-dependent obligate intracellular bacterium, partially lacks genes for glycerophospholipid biosynthesis. We found here that E. chaffeensis is dependent on host glycerolipid biosynthesis, as an inhibitor of host long-chain acyl CoA synthetases, key enzymes for glycerolipid biosynthesis, significantly reduced bacterial proliferation. E. chaffeensis cannot synthesize phosphatidylcholine or cholesterol but encodes enzymes for phosphatidylethanolamine (PE) biosynthesis; however, exogenous NBD-phosphatidylcholine, Bodipy-PE, and TopFluor-cholesterol were rapidly trafficked to ehrlichiae in infected cells. DiI (3,3'-dioctadecylindocarbocyanine)-prelabeled host-cell membranes were unidirectionally trafficked to Ehrlichia inclusion and bacterial membranes, but DiI-prelabeled Ehrlichia membranes were not trafficked to host-cell membranes. The trafficking of host-cell membranes to Ehrlichia inclusions was dependent on both host endocytic and autophagic pathways, and bacterial protein synthesis, as the respective inhibitors blocked both infection and trafficking of DiI-labeled host membranes to Ehrlichia In addition, DiI-labeled host-cell membranes were trafficked to autophagosomes induced by the E. chaffeensis type IV secretion system effector Etf-1, which traffic to and fuse with Ehrlichia inclusions. Cryosections of infected cells revealed numerous membranous vesicles inside inclusions, as well as multivesicular bodies docked on the inclusion surface, both of which were immunogold-labeled by a GFP-tagged 2×FYVE protein that binds to phosphatidylinositol 3-phosphate. Focused ion-beam scanning electron microscopy of infected cells validated numerous membranous structures inside bacteria-containing inclusions. Our results support the notion that Ehrlichia inclusions are amphisomes formed through fusion of early endosomes, multivesicular bodies, and early autophagosomes induced by Etf-1, and they provide host-cell glycerophospholipids and cholesterol that are necessary for bacterial proliferation.

Use of human neuroblastoma SH-SY5Y cells to evaluate glyphosate-induced effects on oxidative stress, neuronal development and cell death signaling pathways

Glyphosate-containing herbicides are the most used agrochemicals in the world. Their indiscriminate application raises some concerns regarding the possible health and environmental hazards. In this study, we investigated in human neuroblastoma cell line SH-SY5Y if oxidative stress, altered neurodevelopment and cell death pathways are involved in response to glyphosate and its metabolite aminomethylphosphonic acid (AMPA) exposures. MTT and LDH assays were carried out to assess the glyphosate and AMPA cytotoxicity. Lipid peroxides measured as malondialdehyde (MDA), nitric oxide (NO) and reactive oxygen species (ROS) production, and caspase-Glo 3/7 activity were evaluated. The neuroprotective role of melatonin (MEL), Trolox, N-acetylcysteine (NAC) and Sylibin against glyphosate- and AMPA-induced oxidative stress was examined. Glyphosate and AMPA effects on neuronal development related gene transcriptions, and gene expression profiling of cell death pathways by Real-Time PCR array were also investigated. Glyphosate (5 mM) and AMPA (10 mM) induced a significant increase in MDA levels, NO and ROS production and caspase 3/7 activity. Glyphosate exposure induced up-regulation of Wnt3a, Wnt5a, Wnt7a, CAMK2A, CAMK2B and down-regulation of GAP43 and TUBB3 mRNA expression involved in normal neural cell development. In relation to gene expression profiling of cell death pathways, of the 84 genes examined in cells a greater than 2-fold change was observed for APAF1, BAX, BCL2, CASP3, CASP7, CASP9, SYCP2, TNF, TP53, CTSB, NFκB1, PIK3C3, SNCA, SQSTMT, HSPBAP1 and KCNIPI mRNA expression for glyphosate and AMPA exposures. These gene expression data can help to define neurotoxic mechanisms of glyphosate and AMPA. Our results demonstrated that glyphosate and AMPA induced cytotoxic effects on neuronal development, oxidative stress and cell death via apoptotic, autophagy and necrotic pathways and confirmed that glyphosate environmental exposure becomes a concern. This study demonstrates that SH-SY5Y cell line could be considered an in vitro system for pesticide screening.

PI3KC2α-dependent and VPS34-independent generation of PI3P controls primary cilium-mediated autophagy in response to shear stress

Cells subjected to stress situations mobilize specific membranes and proteins to initiate autophagy. Phosphatidylinositol-3-phosphate (PI3P), a crucial lipid in membrane dynamics, is known to be essential in this context. In addition to nutriments deprivation, autophagy is also triggered by fluid-flow induced shear stress in epithelial cells, and this specific autophagic response depends on primary cilium (PC) signaling and leads to cell size regulation. Here we report that PI3KC2α, required for ciliogenesis and PC functions, promotes the synthesis of a local pool of PI3P upon shear stress. We show that PI3KC2α depletion in cells subjected to shear stress abolishes ciliogenesis as well as the autophagy and related cell size regulation. We finally show that PI3KC2α and VPS34, the two main enzymes responsible for PI3P synthesis, have different roles during autophagy, depending on the type of cellular stress: while VPS34 is clearly required for starvation-induced autophagy, PI3KC2α participates only in shear stress-dependent autophagy.

The primary cilium is required for the autophagic response to shear stress. Here, the authors show that PI3KC2α has a role in ciliogenesis and promotes local PI3P production upon shear stress to induce autophagy that is distinct from VPS34-driven starvation-induced autophagy.

Autophagy protects PC12 cells against deoxynivalenol toxicity via the Class III PI3K/beclin 1/Bcl-2 pathway

Deoxynivalenol (DON) is a major mycotoxin from the trichothecene family of mycotoxins produced by Fusarium fungi. It can cause a variety of adverse effects on human and farm animal health. Here, we determined the effect of DON on the Class III phosphatidylinositol 3-kinase (PIK3C3)/beclin 1/B cell lymphoma-2 (Bcl-2) pathway in PC12 cells and the relationship between autophagy and apoptosis. The effects of DON were evaluated based on the apoptosis ratio; the typical indicators of autophagy, including cellular morphology, acridine orange- and monodansylcadaverine-labeled vacuoles, green fluorescent protein-microtubule associated protein 1 light chain 3 (LC3) localization, and LC3 immunofluorescence; and the expression of key autophagy-related genes and proteins, that is, PIK3C3, beclin 1, Bcl-2, LC3, and p62. The relationship between autophagy and apoptosis was analyzed by western blot analysis and flow cytometry. DON-induced PC12 cell morphological changes and autophagy significantly. PIK3C3, beclin 1, and LC3 increased in tandem with the DON concentration used; Bcl-2 and p62 expression decreased as DON concentrations increased. Moreover, the PIK3C3/beclin 1/Bcl-2 signaling pathway played a role in DON-induced autophagy. Our findings suggest that DON can induce autophagy by activating the PIK3C3/beclin 1/Bcl-2 signaling pathway and that autophagy may play a positive role in reducing DON-induced apoptosis.

Class III PI3K Vps34 Controls Thyroid Hormone Production by Regulating Thyroglobulin Iodination, Lysosomal Proteolysis, and Tissue Homeostasis

Background: The production of thyroid hormones [triiodothyronine (T3), thyroxine (T4)] depends on the organization of the thyroid in follicles, which are lined by a monolayer of thyrocytes with strict apicobasal polarity. This polarization supports vectorial transport of thyroglobulin (Tg) for storage into, and recapture from, the colloid. It also allows selective addressing of channels, transporters, ion pumps, and enzymes to their appropriate basolateral [Na⁺/I^- symporter (NIS), SLC26A7, and Na⁺/K⁺-ATPase] or apical membrane domain (anoctamin, SLC26A4, DUOX2, DUOXA2, and thyroperoxidase). How these actors of T3/T4 synthesis reach their final destination remains poorly understood. The PI 3-kinase isoform Vps34/PIK3C3 is now recognized as a main component in the general control of vesicular trafficking and of cell homeostasis through the regulation of endosomal trafficking and autophagy. We recently reported that conditional Vps34 inactivation in proximal tubular cells in the kidney prevents normal addressing of apical membrane proteins and causes abortive macroautophagy. Methods:Vps34 was inactivated using a Pax8-driven Cre recombinase system. The impact of Vps34 inactivation in thyrocytes was analyzed by histological, immunolocalization, and messenger RNA expression profiling. Thyroid hormone synthesis was assayed by ¹²⁵I injection and plasma analysis. Results:Vps34 conditional knockout (Vps34^cKO) mice were born at the expected Mendelian ratio and showed normal growth until postnatal day 14 (P14), then stopped growing and died at ∼1 month of age. We therefore analyzed thyroid Vps34^cKO at P14. We found that loss of Vps34 in thyrocytes causes (i) disorganization of thyroid parenchyma, with abnormal thyrocyte and follicular shape and reduced PAS⁺ colloidal spaces; (ii) severe noncompensated hypothyroidism with extremely low T4 levels (0.75 ± 0.62 μg/dL) and huge thyrotropin plasma levels (19,300 ± 10,500 mU/L); (iii) impaired ¹²⁵I organification at comparable uptake and frequent occurrence of follicles with luminal Tg but nondetectable T4-bearing Tg; (iv) intense signal in thyrocytes for the lysosomal membrane marker, LAMP-1, as well as Tg and the autophagy marker, p62, indicating defective lysosomal proteolysis; and (v) presence of macrophages in the colloidal space. Conclusions: We conclude that Vps34 is crucial for thyroid hormonogenesis, at least by controlling epithelial organization, Tg iodination as well as proteolytic T3/T4 excision in lysosomes.

Angiotensin II inhibits P-glycoprotein in intestinal epithelial cells

AIM

P-glycoprotein (Pgp/MDR1) plays a major role in intestinal homeostasis. Decrease in Pgp function and expression has been implicated in the pathogenesis of IBD. However, inhibitory mechanisms involved in the decrease of Pgp in inflammation are not fully understood. Angiotensin II (Ang II), a peptide hormone predominantly expressed in the epithelial cells of the crypt-villus junction of the intestine, has been shown to exert pro-inflammatory effects in the gut. It is increased in IBD patients and animals with experimental colitis. Whether Ang II directly influences Pgp is not known.

METHODS

Pgp activity was measured as verapamil-sensitive 3 H-digoxin flux. Pgp surface expression and exocytosis were measured by cell surface biotinylation studies. Signalling pathways were elucidated by Western blot analysis and pharmacological approaches.

RESULTS

Ang II (10 nM) significantly inhibited Pgp activity at 60 minutes. Ang II-mediated effects on Pgp function were receptor-mediated as the Ang II receptor 1 (ATR1) antagonist, losartan, blocked Pgp inhibition. Ang II effects on Pgp activity appeared to be mediated via PI3 kinase, p38 MAPK and Akt signalling. Ang II-mediated inhibition of Pgp activity was associated with a decrease in the surface membrane expression of Pgp protein via decreased exocytosis and was found to be dependent on the Akt pathway. Short-term treatment of Ang II (2 mg/kg b.wt., 2 hours) to mice also decreased the membrane expression of Pgp protein levels in ileum and colon.

CONCLUSION

Our findings provide novel insights into the role of Ang II and ATR1 in decreasing Pgp expression in intestinal inflammation.

Critical Role for Phosphatidylinositol-3 Kinase Vps34/PIK3C3 in ON-Bipolar Cells

Purpose

Phosphatidylinositol-3-phosphate (PI(3)P), and Vps34, the type III phosphatidylinositol 3-kinase primarily responsible for its production, are important for function and survival of sensory neurons, where they have key roles in membrane processing events, such as autophagy, endosome processing, and fusion of membranes bearing ubiquitinated cargos with lysosomes. We examined their roles in the most abundant class of secondary neurons in the vertebrate retina, the ON-bipolar cells (ON-BCs).

Methods

A conditional Vps34 knockout mouse line was generated by crossing Vps34 floxed mice with transgenic mice expressing Cre recombinase in ON-BCs. Structural changes in the retina were determined by immunofluorescence and electron microscopy, and bipolar cell function was determined by electroretinography.

Results

Vps34 deletion led to selective death of ON-BCs, a thinning of the inner nuclear layer, and a progressive decline of electroretinogram b-wave amplitudes. There was no evidence for loss of other retinal neurons, or disruption of rod-horizontal cell contacts in the outer plexiform layer. Loss of Vps34 led to aberrant accumulation of membranes positive for autophagy markers LC3, p62, and ubiquitin, accumulation of endosomal membranes positive for Rab7, and accumulation of lysosomes. Similar effects were observed in Purkinje cells of the cerebellum, leading to severe and progressive ataxia.

Conclusions

These results support an essential role for PI(3)P in fusion of autophagosomes with lysosomes and in late endosome maturation. The cell death resulting from Vps34 knockout suggests that these processes are essential for the health of ON-BCs.

Particles from the Echinococcus granulosus Laminated Layer Inhibit CD40 Upregulation in Dendritic Cells by Interfering with Akt Activation

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS).

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS). We also reported that the presence of pLL inhibited the activating phosphorylation of the phosphatidylinositol 3-kinase (PI3K) effector Akt induced by granulocyte-macrophage colony-stimulating factor or interleukin-4. We now show that the inhibitory effect of pLL extends to LPS as a PI3K activator, and results in diminished phosphorylation of GSK3 downstream from Akt. Functionally, the inhibition of Akt and GSK3 phosphorylation are linked to the blunted upregulation of CD40, a major feature of the unconventional maturation phenotype. Paradoxically, all aspects of unconventional maturation induced by pLL depend on PI3K class I. Additional components of the phagocytic machinery are needed, but phagocytosis of pLL particles is not required. These observations hint at a DC response mechanism related to receptor-independent mechanisms proposed for certain crystalline and synthetic polymer-based particles; this would fit the previously reported lack of detection of molecular-level motifs necessary of the effects of pLL on DCs. Finally, we report that DCs exposed to pLL are able to condition DCs not exposed to the material so that these cannot upregulate CD40 in full in response to LPS.

Targeting Autophagy for Cancer Treatment and Tumor Chemosensitization

Autophagy is a tightly regulated catabolic process that facilitates nutrient recycling from damaged organelles and other cellular components through lysosomal degradation. Deregulation of this process has been associated with the development of several pathophysiological processes, such as cancer and neurodegenerative diseases. In cancer, autophagy has opposing roles, being either cytoprotective or cytotoxic. Thus, deciphering the role of autophagy in each tumor context is crucial. Moreover, autophagy has been shown to contribute to chemoresistance in some patients. In this regard, autophagy modulation has recently emerged as a promising therapeutic strategy for the treatment and chemosensitization of tumors, and has already demonstrated positive clinical results in patients. In this review, the dual role of autophagy during carcinogenesis is discussed and current therapeutic strategies aimed at targeting autophagy for the treatment of cancer, both under preclinical and clinical development, are presented. The use of autophagy modulators in combination therapies, in order to overcome drug resistance during cancer treatment, is also discussed as well as the potential challenges and limitations for the use of these novel therapeutic strategies in the clinic.

Autophagy in Neurons

Autophagy is the major cellular pathway to degrade dysfunctional organelles and protein aggregates. Autophagy is particularly important in neurons, which are terminally differentiated cells that must last the lifetime of the organism. There are both constitutive and stress-induced pathways for autophagy in neurons, which catalyze the turnover of aged or damaged mitochondria, endoplasmic reticulum, other cellular organelles, and aggregated proteins. These pathways are required in neurodevelopment as well as in the maintenance of neuronal homeostasis. Here we review the core components of the pathway for autophagosome biogenesis, as well as the cell biology of bulk and selective autophagy in neurons. Finally, we discuss the role of autophagy in neuronal development, homeostasis, and aging and the links between deficits in autophagy and neurodegeneration.

Oridonin prevents insulin resistance-mediated cognitive disorder through PTEN/Akt pathway and autophagy in minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) was characterized for cognitive dysfunction. Insulin resistance (IR) has been identified to be correlated with the pathogenesis of MHE. Oridonin (Ori) is an active terpenoid, which has been reported to rescue synaptic loss and restore insulin sensitivity. In this study, we found that intraperitoneal injection of Ori rescued IR, reduced the autophagosome formation and synaptic loss and improved cognitive dysfunction in MHE rats. Moreover, in insulin‐resistant PC12 cells and N2a cells, we found that Ori blocked IR‐induced synaptic deficits via the down‐regulation of PTEN, the phosphorylation of Akt and the inhibition of autophagy. Taken together, these results suggested that Ori displays therapeutic efficacy towards memory deficits via improvement of IR in MHE and represents a novel bioactive therapeutic agent for treating MHE.

Astaxanthin Modulation of Signaling Pathways That Regulate Autophagy

Autophagy is a lysosomal pathway that degrades and recycles unused or dysfunctional cell components as well as toxic cytosolic materials. Basal autophagy favors cell survival. However, the aberrant regulation of autophagy can promote pathological conditions. The autophagy pathway is regulated by several cell-stress and cell-survival signaling pathways that can be targeted for the purpose of disease control. In experimental models of disease, the carotenoid astaxanthin has been shown to modulate autophagy by regulating signaling pathways, including the AMP-activated protein kinase (AMPK), cellular homolog of murine thymoma virus akt8 oncogene (Akt), and mitogen-activated protein kinase (MAPK), such as c-Jun N-terminal kinase (JNK) and p38. Astaxanthin is a promising therapeutic agent for the treatment of a wide variety of diseases by regulating autophagy.

Novel role of autophagy-associated Pik3c3 gene in gonadal white adipose tissue browning in aged C57/Bl6 male mice

Adipose tissue dysfunction is associated with inflammation, metabolic syndrome and other diseases in aging. Recent work has demonstrated that compromised autophagy activity in aging adipose tissue promotes ER stress responses, contributing to adipose tissue and systemic inflammation in aging. Phosphatidylinositol 3-kinase catalytic subunit type 3 (Pik3c3) is an 887 amino acid lipid kinase that regulates intracellular membrane trafficking and autophagy activity. To address the mechanistic link between autophagy and ER stress response in aging adipose tissue, we generated a line of adipose tissue-specific Pik3c3 knock out (~mutant mice) with the Fabp4 (Fatty acid binding protein 4) promoter driven Cre recombinase system. We found elevated ER stress response signaling with reduced autophagy activity without any significant change on adiposity or glucose tolerance in early life of Pik3c3 mutant mice. Interestingly, middle- and old-aged mutant mice exhibited improved glucose tolerance (GTT) and reduced adiposity compared to age and sex-matched littermates. In addition, adipose tissue-specific Pik3c3 mutants display reduced expression of adiposity-associated genes with the signature of adipose tissue browning phenotypes in old age. Overall, the results suggest that altered adipose tissue characteristics due to autophagy inhibition early in life has beneficial effects that promote adipose tissue browning and improves glucose tolerance in late-life.

Vrl1 relies on its VPS9-domain to play a role in autophagy in Saccharomyces cerevisiae

Autophagy is an intracellular degradation process involving many Atg proteins, which are recruited hierarchically to regulate this process. Rab/Ypt GTPases and their activators, guanine nucleotide exchange factors (GEFs), which are critical for regulating vesicle trafficking, are also involved in autophagy. Previously, we reported that yeast Vps21 and its GEF Vps9 are required for autophagy. Later, a third yeast VPS9-domain-containing protein, VARP-like 1 (Vrl1), which was identified as a mutant in major laboratory strains, had partially overlapping functions with Vps9 in trafficking. In this study, we showed that Vrl1 performed roles in autophagy, and its VPS9-domain was crucial for its role in autophagy. We found that localization of Vrl1 differed from the other two VPS9-domain-containing proteins, Vps9 and Muk1, and only Vrl1 changed from multipoint to diffusion after starvation. Like Vps9, Vrl1 suppressed autophagic defects caused by the VPS9 deletion. We further showed that these VPS9-domain-containing proteins, Vps9, Muk1, and Vrl1, all co-localized with Atg8 on autophagosomes in cells blocked in any late step of starvation-induced autophagy, with Vrl1 most often co-localizing with Atg8. A small portion (<25%) of these VPS9-domain-containing proteins were degraded through autophagy. However, a large portion (>60%) of Vrl1 decreased independently of autophagy. We propose that Vrl1 may regulate autophagy in a similar way as Vps9, and the level of Vrl1 partly decreases through both autophagy-dependent and -independent routes.

MiR-338-5p promotes metastasis of colorectal cancer by inhibition of phosphatidylinositol 3-kinase, catalytic subunit type 3-mediated autophagy pathway

Background

In our preliminary screening, expression of miR-338-5p was found to be higher in primary colorectal cancer (CRC) with metastasis. The autophagy related gene- phosphatidylinositol 3-kinase, catalytic subunit type 3 (PIK3C3) appeared to be targeted by miR-338-5p. Here, we provide solid evidence in support of PIK3C3 involved in miR-338-5p related metastasis of CRC in vitro and in vivo.

Methods

The potential clinical relevance of miR-338-5p and its target gene was analysed on benign colorectal polyps and primary CRCs by QPCR. Mouse spleen xenograft experiment was performed to examine the importance of miR-338-5p for metastasis.

Findings

PIK3C3 was one of target genes of miR-338-5p. In primary CRCs, expression of miR-338-5p is positively related to tumour staging, distant metastasis and poor patient survival. Patients with higher ratios of miR-338-5p/PIK3C3 also had significantly poor overall survival, supporting their significance in the progression of CRC. Over-expression of miR-338-5p promotes CRC metastasis to the liver and lung in vivo, in which PIK3C3 was down-regulated in the metastatic tumours. In contrast, overexpression of PIK3C3 in miR-338-5p stable cells inhibited the growth of metastatic tumours. Both migration and invasion of CRC in vitro induced by miR-338-5p are mediated by suppression of PIK3C3. Using forward and reverse approaches, autophagy was proved to involve in CRC migration and invasion induced by miR-338-5p.

Interpretation

MiR-338-5p induces migration, invasion and metastasis of CRC in part through PIK3C3-related autophagy pathway. The miR-338-5p/PIK3C3 ratio may become a prognostic biomarker for CRC patients.

Fund

NCKU Hospital, Taiwan, Ministry of Science and Technology, Taiwan.