Expression Of Lysosome-associated Membrane Protein Research Articles

GLA Mutations Suppress Autophagy and Stimulate Lysosome Generation in Fabry Disease.

Fabry disease (FD) is an X-linked recessive inheritance lysosomal storage disorder caused by pathogenic mutations in the GLA gene leading to a deficiency of the enzyme alpha-galactosidase A (α-Gal A). Multiple organ systems are implicated in FD, most notably the kidney, heart, and central nervous system. In our previous study, we identified four GLA mutations from four independent Fabry disease families with kidney disease or neuropathic pain: c.119C>A (p.P40H), c.280T>C (C94R), c.680G>C (p.R227P) and c.801+1G>A (p.L268fsX3). To reveal the molecular mechanism underlying the predisposition to Fabry disease caused by GLA mutations, we analyzed the effects of these four GLA mutations on the protein structure of α-galactosidase A using bioinformatics methods. The results showed that these mutations have a significant impact on the internal dynamics and structures of GLA, and all these altered amino acids are close to the enzyme activity center and lead to significantly reduced enzyme activity. Furthermore, these mutations led to the accumulation of autophagosomes and impairment of autophagy in the cells, which may in turn negatively regulate autophagy by slightly increasing the phosphorylation of mTOR. Moreover, the overexpression of these GLA mutants promoted the expression of lysosome-associated membrane protein 2 (LAMP2), resulting in an increased number of lysosomes. Our study reveals the pathogenesis of these four GLA mutations in FD and provides a scientific foundation for accurate diagnosis and precise medical intervention for FD.

TSTA3 overexpression promotes malignant characteristics in LUSC by regulating LAMP2-mediated autophagy and tumor microenvironment

BackgroundTSTA3 gene encoding GDP-l-fucose synthase has recently been proved to be closely related to the prognosis of patients with various tumors. However, its role in lung cancer is still unclear. The purpose of this study is to explore the expression level, prognostic effect, potential function and mechanism of TSTA3 in lung cancer.MethodsBased on TCGA database, Kaplan–Meier and COX regression was used to analyze the relationship between TSTA3 expression and prognosis of lung cancer patients. Immunohistochemistry was used to determine the TSTA3 protein expression in lung cancer and normal tissues. The function of TSTA3 in lung squamous cell carcinoma (LUSC) cell was determined by CCK8, colony formation, transwell assay in vitro and subcutaneous xenografts in vivo. Transcriptome analysis, Lyso-Tracker Red staining and rescue experiment were used to explore the possible underlying mechanism.ResultsThe expression of TSTA3 was significantly increased in lung cancer, especially in LUSC, and was significantly correlated with the malignant characteristics of LUSC. COX regression analysis showed that the high expression of TSTA3 was an independent prognostic factor in LUSC patients. This was also confirmed by immunohistochemical staining. Compared with the control group, the proliferation, colony formation, invasion and migration ability of LUSC cells with TSTA3 overexpression was enhanced. Similarly, the ability of cell proliferation, colony formation, invasion and migration were weakened after transient knockdown of TSTA3. In vivo experiment showed that compared with control group, TSTA3 overexpression significantly promoted the growth of tumor and shortened survival time. In addition, transcriptome sequencing analysis showed that the differentially expressed genes between TSTA3 overexpression and control group was mainly concentrated in the lysosome pathway. Further study found that TSTA3 might affect the proliferation, invasion and migration of LUSC by regulating the expression of lysosome-associated membrane protein 2 (LAMP2) in LUSC.ConclusionThe expression level of TSTA3 in LUSC is significantly higher than that in normal tissues. High expression of TSTA3 is associated with poor prognosis of LUSC patients. TSTA3 may affect the proliferation, invasion and migration of LUSC by regulating LAMP2.

IFNT stimulates lysosomal function via type I IFN signaling pathway in pregnant bovine leukocytes.

Interferon tau (IFNT) is important in establishing pregnancy in ruminants. Secreted IFNT in the uterus induces the expression of an interferon-stimulated gene (ISG) in uterine tissues and peripheral blood leukocytes (PBLs). In our previous study, increased lysosome and lysosomal cathepsin (CTS) activity and mRNA expression were observed in PBLs of pregnant cows on day 18 of pregnancy. However, the mechanism of IFNT stimulation in PBLs is unclear. Here, we explored the IFNT-mediated lysosomal activation mechanisms in PBLs during early pregnancy in dairy cows. PBLs collected from the peripheral blood of Holstein cows on day 18 post-artificial insemination (AI), after confirmation of their pregnancy status, were used to detect the expression of lysosomal-associated membrane protein (LAMP) 1, 2, CTSB and CTSK. Expression of all genes was significantly higher in PBLs of pregnant cows than in non-pregnant cows. In vitro IFN-mediated stimulation of PBLs collected from cows that did not undergo AI significantly increased lysosomal acidification and expression of LAMP1 and 2, as well as the activities of CTSB and CTSK. Immunodetection analysis showed an increase in LAMP1 and CTSK levels in the PBLs of day 18 pregnant cows. JAK inhibitor significantly decreased lysosomal acidification, CTSK activity, LAMP1, 2, and CTSK expression in the presence of IFNT. These results suggest that IFNT regulates lysosomal function via a type 1IFN-mediated pathway in PBLs during pregnancy recognition.

Mechanistic Insights into the Role of OPN in Mediating Brain Damage via Triggering Lysosomal Damage in Microglia/Macrophage.

We previously found that osteopontin (OPN) played a role in hypoxia-ischemia (HI) brain damage. However, its underlying mechanism is still unknown. Bioinformatics analysis revealed that the OPN protein was linked to the lysosomal cathepsin B (CTSB) and galectin-3 (GAL-3) proteins after HI exposure. In the present study, we tested the hypothesis that OPN was able to play a critical role in the lysosomal damage of microglia/macrophages following HI insult in neonatal mice. The results showed that OPN expression was enhanced, especially in microglia/macrophages, and colocalized with lysosomal-associated membrane protein 1 (LAMP1) and GAL-3; this was accompanied by increased LAMP1 and GAL-3 expression, CTSB leakage, as well as impairment of autophagic flux in the early stage of the HI process. In addition, the knockdown of OPN expression markedly restored lysosomal function with significant improvements in the autophagic flux after HI insult. Interestingly, cleavage of OPN was observed in the ipsilateral cortex following HI. The wild-type OPN and C-terminal OPN (Leu152-Asn294), rather than N-terminal OPN (Met1-Gly151), interacted with GAL-3 to induce lysosomal damage. Furthermore, the secreted OPN stimulated lysosomal damage by binding to CD44 in microglia in vitro. Collectively, this study demonstrated that upregulated OPN in microglia/macrophages and its cleavage product was able to interact with GAL-3, and secreted OPN combined with CD44, leading to lysosomal damage and exacerbating autophagosome accumulation after HI exposure.

Anti-hepatitis B virus activity of lithospermic acid, a polyphenol from Salvia miltiorrhiza, in vitro and in vivo by autophagy regulation

Ethnopharmacological relevanceSalvia miltiorrhiza (the roots of S. miltiorrhiza Bunge, Danshen in Chinese), a traditional Chinese medicine, has been clinically used to prevent and treat various diseases, such as cardiovascular and cerebrovascular diseases, diabetes, and hepatitis B, in China and some other Asian countries. Lithospermic acid (LA), a polyphenol derived from S. miltiorrhiza, has been reported to exhibit multiple pharmacological properties, such as anti-inflammatory, anti-HIV, and anti-carbon tetrachloride-induced liver injury activities. However, little is known about the anti-hepatitis B virus (HBV) activity of LA. Aim of the studyThe study was projected to investigate the anti-HBV activity of LA in vitro (HepG2.2.15 and pHBV1.3-transfected HepG2 cells) and in vivo (pAAV-HBV1.2 hydrodynamic injection [HBV-HDI] mice) and explore the potential mechanism as well. Materials and methodsHepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) contents were detected by ELISA kits. HBV DNA and hepatitis B core antigen (HBcAg) levels were evaluated by quantitative real-time polymerase chain reaction and immunohistochemistry assay, respectively. The proteins in autophagy process, lysosomal acidic function, and autophagy-related signaling pathways were examined by Western blot. Transmission electron microscopy was used to observe the number of autophagosomes and autolysosomes. Confocal microscopy was applied to analyze the autophagic flux and lysosomal acidification, using mCherry-enhanced green fluorescent protein (EGFP)-microtubule-associated protein light chain (LC)3 and lysosomal probes, respectively. ResultsLA exhibited anti-HBV activity by inhibiting HBV DNA replication in HepG2.2.15 and pHBV-transfected HepG2 cells in dose- and time-dependent manners and hampering HBsAg and HBeAg levels in HepG2.2.15 cells to a certain extent. LA reduced HBV DNA, HBsAg/HBeAg, and HBcAg levels in the serum/liver tissues of HBV-HDI C57BL/6 mice during the 3-week treatment and suppressed the withdrawal rebound of HBV DNA and HBsAg in the mice serum. LA increased LC3-II protein expression and the number of autolysosomes/autophagosomes and promoted the degradation of sequestosome 1(p62) protein in vitro and in vivo. LA enhanced the co-localization of LC3 protein with autolysosomes, further confirming the ability of LA to induce a complete autophagy. Knockdown of autophagy-related gene (Atg) 7 or 5 in vitro and administration of 3-methyladenine (an autophagic inhibitor) in vivo disabled the inhibitory efficacy of LA on HBV DNA replication, suggesting that the anti-HBV efficacy of LA depended on its ability of inducing autophagy. LA could enhance lysosomal acidification and improve the function of lysosomes by promoting the protein expression of lysosomal-associated membrane protein (LAMP)-1, LAMP-2, and mature cathepsin D, which may contribute to the autophagic induction of LA. LA inhibited the activation of AKT and mammalian target of rapamycin (mTOR) induced by HBV, which was reversed by IGF-1 (an agonist of the PI3K/AKT/mTOR signaling pathway), indicating that LA elicited autophagy through hampering the PI3K/AKT/mTOR signaling pathway. ConclusionWe revealed the anti-HBV activity and mechanism of LA in vitro and in vivo. This study facilitates a new understanding of the anti-HBV potent components of S. miltiorrhiza and sheds light on LA for further development as an active constituent or candidate used in the therapy against HBV infection.

High Temperature Disrupts Organelle Distribution and Functions Affecting Meiotic Maturation in Porcine Oocytes.

Heat stress (HS) has been known to cause reproductive failure in animals, especially in summer. HS severely affects the developmental potential of oocytes and leads to low fertility rates. Previous studies have reported that HS compromises embryo development in bovine oocytes, and reduces ovarian development in mice, thereby impairing reproductive function in animals. However, the effect of high temperature (HT) on the organelles of porcine oocytes is unknown. In this study, we reported that exposure to HT for 24 h (41°C) significantly decreased meiotic maturation in porcine oocytes (p < 0.05). Further experiments on organelles found that HT induced mitochondrial dysfunction, increased abnormal mitochondrial distribution, and decreased mitochondrial membrane potential (MMP). We also found that HT induced abnormal endoplasmic reticulum (ER) distribution and higher expression of glucose regulatory protein 78 (GRP78), suggesting that HT exposure induces ER stress. Our results also indicated that exposure to HT induced abnormal distribution and dysfunction of the Golgi apparatus, which resulted from a decrease in the expression of the vesicle transporter, Ras-related protein Rab-11A (RAB11A). In addition, we found that HT exposure led to lysosomal damage by increasing the expression of lysosome-associated membrane protein 2 (LAMP2) and microtubule-associated protein 1A/1B-light chain 3 (LC3). In summary, our study revealed that HT exposure disrupts organelle dynamics, which further leads to the failure of meiotic maturation in porcine oocytes.

Autophagy and protein aggregation as a mechanism of dopaminergic degeneration in a primary human dopaminergic neuronal model

The pathophysiology underlying the loss of dopaminergic neurons in Parkinson’s disease (PD) is unclear. A gap of knowledge in the molecular and cellular events leading to degeneration of the nigrostriatal DA system is a major barrier to the development of effective therapies for PD. 1-methyl-4-phenylpyridinium (MPP+) is used as a reliable in vitro model of PD in dopaminergic neurons; however, the molecular mechanisms that lead to cell death with this model are not fully understood. Additionally, there is a lack of translational in vitro models to fully understand progressive dopaminergic neurotoxicity. Here, we propose cultures of primary human dopaminergic neuronal precursor cells (HDNPCs) as a model to study progressive dopaminergic toxicity and neuronal damage in PD. We evaluated the concentration-response of MPP+ (0–10 mM) at 24 h, using cell viability and mitochondrial activity assays (LDH, XTT, Live/Dead staining, and MitoTracker). Based on concentration-response data, we chose two concentrations (1.0 and 2.5 mM) of MPP+ to evaluate markers of autophagy and dopaminergic status [tyrosine hydroxylase (TH)] after a 24-h exposure. Exposure to MPP+ induced cytotoxicity, reduced cell viability, and decreased mitochondrial activity. MPP+ at 1.0 and 2.5 mM also induced expression of lysosome-associated membrane protein 1 (LAMP-1) and increased the ratio of light chain 3 (LC3), LC3BII/LC3BI. The expression of TH also decreased. Furthermore, α-synuclein (α-SYN) and parkin were evaluated by immunofluorescence (IF) at 1.0 and 2.5 mM MPP+ after 24 h. A qualitative analysis revealed decreased parkin expression while α-SYN aggregation was observed in the cytoplasm and the nucleus. These data suggest that in HDNPCs MPP+ can cause cytotoxicity and neuronal damage. This damage may be mediated by autophagy, dopamine synthesis, and protein aggregation. The combination of HDNPCs and MPP+ may serve as valuable in vitro model of progressive dopaminergic neurotoxicity for research into potential treatments for PD.

Overexpression of Lysosome-Associated Membrane Protein 1 in Oral Squamous Cell Carcinoma and its Correlation with Tumor Differentiation and Metastasis.

Introduction:The overexpression of lysosome-associated membrane protein 1 (LAMP1) has been demonstrated in different types of cancers, such as ovarian carcinoma, esophageal squamous cell carcinoma, breast cancer, and colorectal carcinoma. Nonetheless, the expression of LAMP1 in oral squamous cell carcinoma (OSCC) has not been investigated yet.Materials and Methods:This cross-sectional study was conducted on 65 patients with OSCC selected from the Department of Pathology of Shiraz University of Medical Sciences. The control group comprised 55 tissues of normal oral epithelium. The expression of LAMP1 in OSCC tissue samples was assessed using immunohistochemistry (IHC) analysis. The association between LAMP1 and clinicopathological features of patients with OSCC was also evaluated.Results:The expression of LAMP1 was significantly higher in OSCC tissues, as compared to that in normal tissues (P<0.001). The chi-square analysis indicated that the high LAMP1 expression was correlated with the degree of tumor differentiation and metastasis (P=0.014).Conclusions:The obtained results pointed to the overexpression of LAMP1 in OSCC, as well as its correlation with tumor grade and metastasis; therefore, LAMP1 might have a role to play in OSCC pathogenesis and could be regarded as an independent prognostic marker in oral squamous cell carcinoma.

RNA Binding Protein Syncrip Is Required for the Low-Output HSC By Sustaining Proteome Quality

RNA binding proteins (RBPs) have been increasingly recognized as an important class of regulators of normal and malignant hematopoiesis. However, the exact function and underpinning mechanisms of the RBPs that govern hematopoietic stem cells (HSCs) remains poorly characterized. We had previously identified SYNCRIP as a critical RBP that controls leukemia stem cell program in myeloid leukemia. Here, using the novel murine genetic conditional knockout (cKO) model, we delineated the role of SYNCRIP in regulating the low-output HSC. We developed a Syncrip cKO allele and crossed Syncripf/f mice to the interferon (IFN) -a-inducible Mx-1-Cre mice to create Syncripf/f Mx-1-Cre+. We consistently obtained near complete depletion of SYNCRIP 3 weeks after two consecutive Poly(I:C) injections. We observed that SYNCRIP is dispensable for static hematopoiesis and Syncrip KO animals showed equivalent number and frequencies of stem and progenitor cells (Lin-Sca+cKit+ (LSK)- LT-HSC (CD48-CD150+); MPP1 (CD48-CD150-); MPP2 (CD48+CD150+); MPP4 (CD48-CD150-)). However, KO SyncripD/D deficient cells were outcompeted by WT Syncripf/f cells in the transplantation setting (bone marrow (BM) chimerism WT (n=9) 38% ± 7.8% vs. KO (n=9) 2.7% ± 0.8%, p<0.001 at 16 weeks post-transplant) and completely lost their ability to repopulate in secondary recipient animals (WT (n=5) 58% ± 7.4% vs. KO (n=5) 7.2 %± 2.9%, p<0.001 at 16 weeks post-transplant). These data strongly indicate that SYNCRIP is critical for maintenance of long-term self-renewal of HSCs. To decipher the effect of Syncrip deletion on the transcriptomic changes in different cell types upon Syncrip loss, we performed single cell RNA sequencing analysis (scRNA-seq) of sorted LK cells (Lin-cKit+ cells) from KO SyncripD/D (n=3) vs. WT Syncrip f/f (n=3) mice. While there is no significant change in frequencies of stem and progenitor compartments, we found defective trajectory from the HSC that is closely identified as low-output HSC based on previously performed barcoding studies. We observed a strong activation of cellular response to stress and unfolded proteins, in particular the HSF1-dependent pathways upon Syncrip depletion specifically within the HSC population. To further investigate the impacts of SYNCRIP loss in the HSC unfolded protein stress response, we evaluated unfolded proteins in cells using tetraphenylethene maleimide (TMI)-based flow cytometry. The abundance of accessible thiols in unfolded proteins, which is bound by TMI serves as a surrogate measurement for the state of the unfolded proteome. We consistently observed almost 2.5-fold increase in TMI signals specifically in LT-HSC, but not ST-HSCs or MPPs upon SYNCRIP deletion indicating that SYNCRIP is required to maintain high protein quality in HSCs. Similar results were obtained with the epichaperome probe PU-FITC, which consists of HSP90 inhibitor PU-H71 conjugated to FITC. PU-H71 selectively binds to the altered epichaperome, which reflects an accumulation of chaperon networks in an aberrant cellular stress condition. Altogether, these data further confirmed that SYNCRIP depletion tips off the proteostatic balance. To understand the molecular mechanisms underpinning the functional requirement of SYNCRIP in HSPCs, we identified 534 direct mRNA targets of SYNCRIP using hyper-TRIBE method. We performed transcriptomic and proteomic analysis of sorted LT- HSCs and LSKs respectively upon SYNCRIP deletion. We integrated these datasets and found a strong enrichment of SYNCRIP targets in control of cytoskeleton and RHO GTPase related pathways. Using immunofluorescence imaging, we confirmed that SYNCRIP deletion in HSCs resulted in 2-fold reduction in RHO GTPase CDC42 expression coupled with reduced tubulin and a loss of cellular polarity (percentage of tubulin polarized cells 56% WT vs. 40% KO). We also observed that Syncrip deficient HSCs demonstrated reduced expression of lysosomal-associated membrane protein 1 (LAMP-1) and less asymmetric distribution of LAMP1 marked lysosomes during cell division (LAMP1 asymmetric division 25% WT vs. 19% KO). Overexpression of CDC42 restored cell polarity and partly rescued ability of KO SyncripD/D to serially replate. Overall, SYNCRIP is required for maintenance of protein homeostasis and cell polarity of the reserve HSCs. Our study uncovers a new regulatory axis that controls stem cell stress responses to preserve HSC self-renewal. DisclosuresNo relevant conflicts of interest to declare.

Antioxidant Compound, Oxyresveratrol, Inhibits APP Production through the AMPK/ULK1/mTOR-Mediated Autophagy Pathway in Mouse Cortical Astrocytes.

Oxyresveratrol (OxyR), a well-known polyphenolic phytoalexin, possesses a wide range of pharmacological and biological properties, comprising antioxidant, anti-inflammatory, free radical scavenging, anti-cancer, and neuroprotective activities. Autophagy is a cellular self-degradation system that removes aggregated or misfolded intracellular components via the autophagosome-lysosomal pathway. Astrocyte accumulation is one of the earliest neuropathological changes in Alzheimer’s disease (AD), and amyloid precursor protein (APP) is the hallmark of AD. OxyR could affect APP modulation via the autophagy pathway. Here, we have reported that OxyR promotes autophagy signaling and attenuates APP production in primary cortical astrocytes based on immunofluorescence and immunoblotting assay results. Co-treatment with the late-stage autophagy inhibitor chloroquine (CQ) and OxyR caused significantly higher microtubule-associated protein light chain 3 (LC3)-II protein levels and LC3 puncta counts, demonstrating that OxyR stimulated autophagic flux. We also found that OxyR significantly reduced the levels of the autophagy substrate p62/SQSTM1, and p62 levels were significantly augmented by co-treatment with OxyR and CQ, because of the impaired deficiency of p62 in autolysosome. Likewise, pretreatment with the autophagy inhibitor, 3-methyladenine (3-MA), resulted in significantly fewer OxyR-induced LC3 puncta and lower LC3-II expression, suggesting that OxyR-mediated autophagy was dependent on the class III PI3-kinase pathway. In contrast, OxyR caused significantly lower LC3-II protein expression when pretreated with compound C, an AMP-activated protein kinase (AMPK) inhibitor, indicating that AMPK signaling regulated the OxyR-induced autophagic pathway. Additionally, co-treatment with OxyR with rapamycin intended to inhibit the mammalian target of rapamycin (mTOR) caused significantly lower levels of phospho-S6 ribosomal protein (pS6) and higher LC3-II expression, implying that OxyR-mediated autophagy was dependent on the mTOR pathway. Conversely, OxyR treatment significantly upregulated unc-51-like autophagy activating kinase 1 (ULK1) expression, and ULK1 small interfering RNAs (siRNA) caused significantly lower OxyR-induced LC3 puncta counts and LC3-II expression, indicating that ULK1 was essential for initiating OxyR-induced autophagy. However, we found that OxyR treatment astrocytes significantly increased the expression of lysosome-associated membrane protein 1 (LAMP1). Finally, we established a stress-induced APP production model using corticosterone (CORT) in cortical astrocytes, which produced significantly more APP than the equivalent using dexamethasone (DEX). In our experiment we found that CORT-induced APP production was significantly attenuated by OxyR through the autophagy pathway. Therefore, our study reveals that OxyR regulates AMPK/ULK1/mTOR-dependent autophagy induction and APP reduction in mouse cortical astrocytes.

Lysosome-associated membrane protein 3 misexpression in salivary glands induces a Sjögren’s syndrome-like phenotype in mice

ObjectivesSjögren’s syndrome (SS) is an autoimmune sialadenitis with unknown aetiology. Although extensive research implicated an abnormal immune response associated with lymphocytes, an initiating event mediated by salivary gland epithelial cell...

Alcohol-and-HIV-Induced Lysosomal Dysfunction Regulates Extracellular Vesicles Secretion in Vitro and in Liver-Humanized Mice.

Simple SummaryConsumption of alcohol increases liver damage in HIV people; however, the mechanisms remain elusive. By utilizing alcohol (ethanol) exposed HIV-infected human hepatocytes liver cells and ethanol-fed liver humanized mouse model (immunodeficient mice livers harbor human hepatocytes), we show that the combination of alcohol and HIV enhances oxidative stress and impairs lysosome activity, which in turn stimulates pathogenic nanosized extracellular vesicles. These vesicles are of great importance, as manipulating their numbers and contents will eliminate the spread of infection in other cell types.Background: Alcohol abuse is common in people living with HIV-1 and dramatically enhances the severity of HIV-induced liver damage by inducing oxidative stress and lysosomal dysfunction in the liver cells. We hypothesize that the increased release of extracellular vesicles (EVs) in hepatocytes and liver humanized mouse model is linked to lysosome dysfunction. Methods: The study was performed on primary human hepatocytes and human hepatoma RLWXP-GFP (Huh 7.5 cells stably transfected with CYP2E1 and XPack-GFP) cells and validated on ethanol-fed liver-humanized fumarylacetoacetate hydrolase (Fah)-/-, Rag2-/-, common cytokine receptor gamma chain knockout (FRG-KO) mice. Cells and mice were infected with HIV-1ADA virus. Results: We observed an increase in the secretion of EVs associated with a decrease in lysosomal activity and expression of lysosomal-associated membrane protein 1. Next-generation RNA sequencing of primary human hepatocytes revealed 63 differentially expressed genes, with 13 downregulated and 50 upregulated genes in the alcohol–HIV-treated group. Upstream regulator analysis of differentially expressed genes through Ingenuity Pathway Analysis identified transcriptional regulators affecting downstream genes associated with increased oxidative stress, lysosomal associated disease, and function and EVs biogenesis. Our in vitro findings were corroborated by in vivo studies on human hepatocyte-transplanted humanized mice, indicating that intensive EVs’ generation by human hepatocytes and their secretion to serum was associated with increased oxidative stress and reduction in lysosomal activities triggered by HIV infection and ethanol diet. Conclusion: HIV-and-ethanol-metabolism-induced EVs release is tightly controlled by lysosome status in hepatocytes and participates in the development of double-insult-induced liver injury.

Pharmacological Inhibition of O-GlcNAc Transferase Promotes mTOR-Dependent Autophagy in Rat Cortical Neurons.

O-GlcNAc transferase (OGT) is a ubiquitous enzyme that regulates the addition of β-N-acetylglucosamine (O-GlcNAc) to serine and threonine residues of target proteins. Autophagy is a cellular process of self-digestion, in which cytoplasmic resources, such as aggregate proteins, toxic compounds, damaged organelles, mitochondria, and lipid molecules, are degraded and recycled. Here, we examined how three different OGT inhibitors, alloxan, BXZ2, and OSMI-1, modulate O-GlcNAcylation in rat cortical neurons, and their autophagic effects were determined by immunoblot and immunofluorescence assays. We found that the treatment of cortical neurons with an OGT inhibitor decreased O-GlcNAcylation levels and increased LC3-II expression. Interestingly, the pre-treatment with rapamycin, an mTOR inhibitor, further increased the expression levels of LC3-II induced by OGT inhibition, implicating the involvement of mTOR signaling in O-GlcNAcylation-dependent autophagy. In contrast, OGT inhibitor-mediated autophagy was significantly attenuated by 3-methyladenine (3-MA), a blocker of autophagosome formation. However, when pre-treated with chloroquine (CQ), a lysosomotropic agent and a late-stage autophagy inhibitor, OGT inhibitors significantly increased LC3-II levels along with LC3 puncta formation, indicating the stimulation of autophagic flux. Lastly, we found that OGT inhibitors significantly decreased the levels of the autophagy substrate p62/SQSTM1 while increasing the expression of lysosome-associated membrane protein 1 (LAMP1). Together, our study reveals that the modulation of O-GlcNAcylation by OGT inhibition regulates mTOR-dependent autophagy in rat cortical neurons.

Dysregulation of endocytic machinery and ACE2 in small airways of smokers and COPD patients can augment their susceptibility to SARS-CoV-2 (COVID-19) infections.

Lungs of smokers and chronic obstructive pulmonary disease (COPD) are severely compromised and are susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) attack. The dangerous combination of enhanced SARS-CoV-2 attachment receptor protein ACE2 along with an increase in endocytic vacuoles will enable viral attachment, entry, and replication. The objective of the study was to identify the presence of SARS-CoV-2 host attachment receptor angiotensin-converting enzyme-2 (ACE2) along with endocytic vacuoles, early endosome antigen-1 (EEA1), late endosome marker RAB7, cathepsin-L, and lysosomal associated membrane protein-1 (LAMP-1) as lysosome markers in the airways of smokers and COPD patients. The study design was cross-sectional and involved lung resections from 39 patients in total, which included 19 patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I or GOLD stage II COPD, of which 9 were current smokers with COPD (COPD-CS) and 10 were ex-smokers with COPD (COPD-ES), 10 were normal lung function smokers, and 10 were never-smoking normal controls. Immunostaining for ACE2, EEA1, RAB7, and cathepsin-L was done. A comparative description for ACE2, EEA1, RAB7, and cathepsin-L expression pattern is provided for the patient groups. Furthermore, staining intensity for LAMP-1 lysosomes was measured as the ratio of the LAMP-1-stained areas per total area of epithelium or subepithelium, using Image ProPlus v7.0 software. LAMP-1 expression showed a positive correlation to patient smoking history while in COPD LAMP-1 negatively correlated to lung function. The active presence of ACE2 protein along with endocytic vacuoles such as early/late endosomes and lysosomes in the small airways of smokers and COPD patients provides evidence that these patient groups could be more susceptible to COVID-19.

LAMP3 induces apoptosis and autoantigen release in Sjögren’s syndrome patients

Primary Sjögren’s syndrome (pSS) is a complex autoimmune disease characterized by dysfunction of secretory epithelia with only palliative therapy. Patients present with a constellation of symptoms, and the diversity of symptomatic presentation has made it difficult to understand the underlying disease mechanisms. In this study, aggregation of unbiased transcriptome profiling data sets of minor salivary gland biopsies from controls and Sjögren’s syndrome patients identified increased expression of lysosome-associated membrane protein 3 (LAMP3/CD208/DC-LAMP) in a subset of Sjögren’s syndrome cases. Stratification of patients based on their clinical characteristics suggested an association between increased LAMP3 expression and the presence of serum autoantibodies including anti-Ro/SSA, anti-La/SSB, anti-nuclear antibodies. In vitro studies demonstrated that LAMP3 expression induces epithelial cell dysfunction leading to apoptosis. Interestingly, LAMP3 expression resulted in the accumulation and release of intracellular TRIM21 (one component of SSA), La (SSB), and α-fodrin protein, common autoantigens in Sjögren’s syndrome, via extracellular vesicles in an apoptosis-independent mechanism. This study defines a clear role for LAMP3 in the initiation of apoptosis and an independent pathway for the extracellular release of known autoantigens leading to the formation of autoantibodies associated with this disease.ClinicalTrials.gov Identifier: NCT00001196, NCT00001390, NCT02327884.

Regulation of Autophagy Progress via Lysosomal Depletion by Fluvastatin Nanoparticle Treatment in Breast Cancer Cells.

Fluvastatin (FLV) is a statin family member that may play a role in modulating a variety of medical disorders such as atherosclerosis and breast cancer. The present study addresses the ability of FLV to modulate the cellular immune response and provides a new nanosized FLV formula (self-nanoemulsifying delivery system, SNED) potentially more effective for suppression of breast cancer development. We monitored autophagic machinery through the expression of microtubule-associated protein 1A/1B-light chain 3 (LC3I/II). Lysosomal activity upon treatment was evaluated by mRNA and protein expression of lysosomal-associated membrane protein 1 (LAMP-1). Mitogen-activated protein kinase (MAPK) signaling and its association with proinflammatory cytokine secretion were assessed in treated cells. Autophagosome formation was significantly increased in cells that were pretreated with FLV-SNED in comparison to FLV-treated cells. Activation of autophagy was accompanied with arrest of LAMP-1 expression, which correlates with lysosomal activity. Simultaneously, both FLV and FLV-SNED activated MAPK signaling and modified interleukin-6 and tumor necrosis factor-α levels in treated cells. These findings indicate that FLV reduces cell viability via depletion of lysosomal activities along with accumulation of autophagosomes leading to disturbance of autophagosome-lysosomal fusion in treated cells. Furthermore, our data reveal the effectiveness of both FLV agents in the modulation of proinflammatory cytokine secretion from treated cells via regulation of MAPK signaling cascades and indicate that FLV-SNED is more efficient than FLV. This study provides new insights into how FLV regulates breast cancer cell viability via modulation of AMPK-mTOR and ERK-mTOR signaling, and through autophagosome formation accompanied by lysosomal degradation.

Dysregulated FAM215A Stimulates LAMP2 Expression to Confer Drug-Resistant and Malignant in Human Liver Cancer.

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human malignancies worldwide. Long non-coding (lnc) RNAs regulate complex cellular functions, such as cell growth, differentiation, metabolism, and metastasis. Although deregulation of lncRNA expression has been detected in HCC, many of the hepato-carcinogenesis-associated lncRNAs remain yet unidentified. Here, we aimed to investigate the involvement of a specific HCC-dysregulated lncRNA, FAM215A, and characterize its molecular regulation mechanism. We show for the first time that FAM215A is overexpressed in HCC, and its expression level correlates with tumor size, vascular invasion, and pathology stage. Overexpression of FAM215A accelerates cell proliferation and metastasis in HCC cells. According to Gene Expression Omnibus Dataset analysis, FAM215A is induced in doxorubicin (DOX)-resistant HCC cells. Overexpression of FAM215A increases DOX resistance in two HCC cell lines, and this is associated with enhanced expression of lysosome-associated membrane protein 2 (LAMP2). FAM215A interacts with LAMP2 to protect it from ubiquitination. Together, our results show that the lncRNA, FAM215A, is highly expressed in HCC, where it interacts with and stabilizes LAMP2 to increase tumor progression while decreasing doxorubicin sensitivity.

Cadmium-induced cytotoxicity in mouse liver cells is associated with the disruption of autophagic flux via inhibiting the fusion of autophagosomes and lysosomes

Cadmium (Cd) is an important environmental pollutant. Previous studies have shown that Cd can induce liver cell injury; however, the toxicity mechanisms of Cd have not been fully elucidated. This study aimed to further confirm the hepatotoxic effects of Cd in mouse liver cells by various methods both in vivo and in vitro. In addition, it found that Cd induced autophagy but also caused autophagy blockade, and autophagy blockade intensified Cd-induced injury in liver cells. Subsequently, the study investigated the effects of Cd on lysosomes and found that Cd induced lysosomal acidification, promoted the expression of lysosomal-associated membrane protein 2 and lysosomal hydrolase cathepsin B both in vivo and in vitro, and enhanced the lysosomal degradation capacity. It indicated that Cd triggered lysosomal activation. However, the fusion of autophagosomes with lysosomes was inhibited by Cd both in vivo and in vitro. Next, the expression of Rab7, a key protein that regulates autophagosome–lysosome fusion, was examined. Cd was found to inhibit Rab7 expression both in vivo and in vitro. In conclusion, the results indicated that Cd obstructed the autophagic flux by inhibiting the fusion of autophagosomes with lysosomes, thus exacerbating the Cd-induced hepatotoxicity. Moreover, the molecular mechanism of Cd-induced inhibition of autophagosome–lysosome fusion is probably related to the Cd-induced downregulation of Rab7.

MiR-207 inhibits autophagy and promotes apoptosis of cardiomyocytes by directly targeting LAMP2 in type 2 diabetic cardiomyopathy

Autophagy dysfunction plays a critical role in diabetic cardiomyopathy (DCM). MiR-207 regulates the expression of lysosomal-associated membrane protein 2 (LAMP2), an autophagy-related protein, following ischemic stroke in neurocytes. However, the roles and mechanisms of miR-207 in DCM remain unknown. Therefore, in this study, we aim to investigate the roles and mechanisms of miR-207 in type 2 DCM. The results showed that autophagic dysfunction with increased LC3II and P62 expression and decreased LAMP2 expression, and increased cell apoptosis with up-regulated cleaved-caspase3 expression were noted in the myocardium of type 2 DCM mice and neonatal mouse cardiac myocytes (NMCMs) stimulated with PA. In addition, miR-207 was significantly upregulated in the myocardium of DCM mice and NMCMs stimulated with PA. In NMCMs, miR-207 inhibited LAMP2 mRNA and protein expression. MiR-207 mimics significantly inhibited autophagy by increasing P62 and LC3II expression and promoted cell apoptosis by increasing cleaved-caspase3 expression, and these effects were reversed by LAMP2 overexpression. In conclusion, miR-207 inhibited autophagy and promoted apoptosis of cardiomyocytes by directly targeting LAMP2, which participated in the development of type 2 diabetic cardiomyopathy.

Lysosome imaging in cancer cells by pyrene-benzothiazolium dyes: An alternative imaging approach for LAMP-1 expression based visualization methods to avoid background interference

A series of pyrene-benzothiazolium dyes (1a–1d) were experimentally investigated to study their internalization mechanism into cellular lysosomes as well as their potential imaging applications for live cell imaging. The lysosome selectivity of the probes was further compared by using fluorescently tagged lysosome associated membrane protein-1 (LAMP-1) expression-dependent visualization in both normal (COS-7, HEK293) and cancer (A549, Huh 7.5) cell lines. These probes were successfully employed as reliable lysosome markers in tumor cell models, thus providing an attractive alternative to LAMP-1 expression-dependent visualization methods. One advantage of these probes is the elimination of significant background fluorescence arising from fluorescently tagged protein expression on the cell surface when cells were transfected with LAMP-1 expression plasmids. Probes exhibited remarkable ability to stain cellular lysosomes for long-term experiments (up to 24 h) and the highly lipophilic nature of the probe design allowed their accumulation in hydrophobic regions of the cellular lysosomes. Experimental evidences indicated that the probes are likely to be internalized into lysosomes via endocytosis and accumulated in the hydrophobic regions of the lysosomes rather than in the acidic lysosomal lumen. These probes also demonstrated significant stability and lysosome staining for fixed cell imaging applications as well. Lastly, the benzothiazolium moiety of the probes was identified as the key component for lysosome selectivity.