Pros and cons of different ways to address dysfunctional autophagy in Pompe disease

CARM1 promotes gastric cancer progression by regulating TFE3 mediated autophagy enhancement through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways

BACKGROUND

The role of CARM1 in tumors is inconsistent. It acts as an oncogene in most cancers but it inhibits the progression of liver and pancreatic cancers. CARM1 has recently been reported to regulate autophagy, but this function is also context-dependent. However, the effect of CARM1 on gastric cancer (GC) has not been studied. We aimed to explore whether CARM1 was involved in the progression of GC by regulating autophagy.

METHODS

The clinical values of CARM1 and autophagy in GC were evaluated by immunohistochemistry and qRT-PCR. Transmission electron microscopy, immunofluorescence and western blotting were employed to identify autophagy. The role of CARM1 in GC was investigated by CCK-8, colony formation and flow cytometry assays in vitro and a xenograft model in vivo. Immunoprecipitation assays were performed to determine the interaction of CARM1 and TFE3.

RESULTS

CARM1 was upregulated in clinical GC tissues and cell lines, and higher CARM1 expression predicted worse prognosis. CARM1 enhanced GC cell proliferation, facilitated G1-S transition and inhibited ER stress-induced apoptosis by regulating autophagy. Importantly, treatment with a CARM1 inhibitor rescued the tumor-promoting effects of CARM1 both in vitro and in vivo. Furthermore, we demonstrated that CARM1 promoted TFE3 nuclear translocation to induce autophagy through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways.

CONCLUSION

CARM1 promoted GC cell proliferation, accelerated G1-S transition and reduced ER stress-induced apoptosis by regulating autophagy. Mechanistically, CARM1 triggered autophagy by facilitating TFE3 nuclear translocation through the AMPK-mTOR and AMPK-CARM1-TFE3 signaling pathways.

LAMP2 Cardiomyopathy: Consequences of Impaired Autophagy in the Heart

Background

Human mutations in the X‐linked lysosome‐associated membrane protein‐2 (LAMP2) gene can cause a multisystem Danon disease or a primary cardiomyopathy characterized by massive hypertrophy, conduction system abnormalities, and malignant ventricular arrhythmias. We introduced an in‐frame LAMP2 gene exon 6 deletion mutation (denoted L2^Δ6) causing human cardiomyopathy, into mouse LAMP2 gene, to elucidate its consequences on cardiomyocyte biology. This mutation results in in‐frame deletion of 41 amino acids, compatible with presence of some defective LAMP2 protein.

Methods and Results

Left ventricular tissues from L2^Δ6 and wild‐type mice had equivalent amounts of LAMP2 RNA, but a significantly lower level of LAMP2 protein. By 20 weeks of age male mutant mice developed left ventricular hypertrophy which was followed by left ventricular dilatation and reduced systolic function. Cardiac electrophysiology and isolated cardiomyocyte studies demonstrated ventricular arrhythmia, conduction disturbances, abnormal calcium transients and increased sensitivity to catecholamines. Myocardial fibrosis was strikingly increased in 40‐week‐old L2^Δ6 mice, recapitulating findings of human LAMP2 cardiomyopathy. Immunofluorescence and transmission electron microscopy identified mislocalization of lysosomes and accumulation of autophagosomes between sarcomeres, causing profound morphological changes disrupting the cellular ultrastructure. Transcription profile and protein expression analyses of L2^Δ6 hearts showed significantly increased expression of genes encoding activators and protein components of autophagy, hypertrophy, and apoptosis.

Conclusions

We suggest that impaired autophagy results in cardiac hypertrophy and profound transcriptional reactions that impacted metabolism, calcium homeostasis, and cell survival. These responses define the molecular pathways that underlie the pathology and aberrant electrophysiology in cardiomyopathy of Danon disease.

Exenatide improves random-pattern skin flap survival via TFE3 mediated autophagy augment

Random-pattern skin flaps are widely applied to rebuild and restore soft-tissue damage in reconstructive surgery; however, ischemia and subsequent ischemia-reperfusion injury lead to flap necrosis and are major complications. Exenatide, a glucagon-like peptide-1 analog, exerts therapeutic benefits for diabetic wounds, cardiac injury, and nonalcoholic fatty liver disease. Furthermore, Exenatide is a known activator of autophagy, which is a complex process of subcellular degradation that may enhance the viability of random skin flaps. In this study, we explored whether exenatide can improve skin flap survival. Our results showed that exenatide augments autophagy, increases flap viability, enhances angiogenesis, reduces oxidative stress, and alleviates pyroptosis. Coadministration of exenatide with 3-methyladenine and chloroquine, potent inhibitors of autophagy, reversed the beneficial effects, suggesting that the therapeutic benefits of exenatide for skin flaps are due largely to autophagy activation. Mechanistically, we identified that exenatide enhanced activation and nuclear translocation of TFE3, which leads to autophagy activation. Furthermore, we found that exenatide activates the AMPK-SKP2-CARM1 and AMPK-mTOR signaling pathways, which likely lead to exenatide's effects on activating TFE3. Overall, our findings suggest that exenatide may be a potent therapy to prevent flap necrosis, and we also reveal novel mechanistic insight into exenatide's effect on flap survival.

Evaluation of HIV-1 derived lentiviral vectors as transductors of Mucopolysaccharidosis type IV a fibroblasts

Mucopolysaccharidosis type IVA (MPS IVA) is a lysosomal storage disease produced by the deficiency of the N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme, leading to glycosaminoglycans (GAGs) accumulation. Since currently available treatments remain limited and unspecific, novel therapeutic approaches are essential for the disease treatment. In an attempt to reduce treatment limitations, gene therapy rises as a more effective and specific alternative. We present in this study the delivery assessment of GALNS and sulfatase-modifying factor 1 (SUMF1) genes via HIV-1 derived lentiviral vectors into fibroblasts from MPS IVA patients. After transduction, we determined GALNS enzymatic activity, lysosomal mass change, and autophagy pathway impairment. Additionally, we computationally assessed the effect of mutations over the enzyme-substrate interaction and phenotypic effects. The results showed that the co-transduction of MPS IVA fibroblasts with GALNS and SUMF1 cDNAs led to a significant increase in GALNS enzyme activity and a reduction of lysosomal mass. We show that patient-specific differences in cellular response are directly associated with the set of mutations on each patient. Lastly, we present new evidence supporting autophagy impairment in MPS IVA due to the presence and changes in autophagy proteins in treated MPS IVA fibroblasts. Our results offer new evidence that demonstrate the potential of lentiviral vectors as a strategy to correct GALNS deficiency.

Enzyme Replacement Therapy Can Reverse Pathogenic Cascade in Pompe Disease

Pompe disease, a deficiency of glycogen-degrading lysosomal acid alpha-glucosidase (GAA), is a disabling multisystemic illness that invariably affects skeletal muscle in all patients. The patients still carry a heavy burden of the disease, despite the currently available enzyme replacement therapy. We have previously shown that progressive entrapment of glycogen in the lysosome in muscle sets in motion a whole series of “extra-lysosomal” events including defective autophagy and disruption of a variety of signaling pathways. Here, we report that metabolic abnormalities and energy deficit also contribute to the complexity of the pathogenic cascade. A decrease in the metabolites of the glycolytic pathway and a shift to lipids as the energy source are observed in the diseased muscle. We now demonstrate in a pre-clinical study that a recently developed replacement enzyme (recombinant human GAA; AT-GAA; Amicus Therapeutics) with much improved lysosome-targeting properties reversed or significantly improved all aspects of the disease pathogenesis, an outcome not observed with the current standard of care. The therapy was initiated in GAA-deficient mice with fully developed muscle pathology but without obvious clinical symptoms; this point deserves consideration.

MicroRNA-7 inhibits hepatocellular carcinoma cell invasion and metastasis by regulating Atg5-mediated autophagy

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors of the digestive system, with a low 5-year survival rate (5-9%). The abnormal expression of miRNA in liver cancer cells may play an important role in the pathophysiology of liver cancer. The ability of tumor invasion and metastasis is an important indicator to evaluate the degree of malignancy of HCC. Autophagy may affect the ability of tumor cells to invade and metastasize. Autophagy-related genes and proteins (Atg) are the core and key to regulating autophagy. The purpose of this study was to investigate the effect of microRNA-7 (miR-7) on targeting autophagy-related protein Atg5 to inhibit the effect of autophagy on the invasion and metastasis ability of liver cancer cells.

METHODS

The content of miR-7 and Atg5 in normal liver tissue and HCC tissues was detected by quantitative real-time polymerase chain (qRT-PCR). SMMC-7721 hepatoma cells were cultured in vitro, a starvation environment was simulated to activate autophagy, and transfection of cells was carried out by using miR-7 mimic, inhibitor, and autophagic inhibitor 3-MA. The RFP-GFP-LC3 double-labeled adenovirus infected hepatoma cells, and autophagy was detected by fluorescence microscopy. Western blot was used to detect the expression of LC3, Atg5, and the epithelial-mesenchymal transition (EMT)-related proteins (N-cadherin, vimentin, and snail). Transwell and plate cloning were used to detect the proliferation, invasion, and metastasis of hepatocarcinoma cells.

RESULTS

Expression of miR-7 (16.72±4.71, P<0.05) in HCC tissues was low, but the expression of Atg5 (13.70±2.80, P<0.05)was high. MiR-7 and Atg5 were highly negatively correlated in hepatoma tissues (r=-0.97). With the overexpression of hepatoma cells, the expression of Atg5 (0.49±0.07, F=395.26) and LC3II (0.51±0.06, F=23.58) was increased (P<0.05), and the autophagy was enhanced. As a result, the proliferation of hepatocarcinoma cells was decreased (t=3.22, P<0.05), the expression of EMT-related protein [N-cadherin (0.37±0.04), vimentin (0.60±0.07), snail (0.54±0.07)] was decreased (P<0.05), and hepatoma cell invasion and metastasis were decreased (n=6, F=162.28, P<0.05).

CONCLUSIONS

MiR-7 can inhibit the invasion and metastasis of hepatoma cells by targeting Atg5 to regulate autophagy.

An integrative correlation of myopathology, phenotype and genotype in late onset Pompe disease

AIMS

Pompe disease is caused by pathogenic mutations in the alpha 1,4-glucosidase (GAA) gene and in patients with late onset Pome disease (LOPD), genotype-phenotype correlations are unpredictable. Skeletal muscle pathology includes glycogen accumulation and altered autophagy of various degrees. A correlation of the muscle morphology with clinical features and the genetic background in GAA may contribute to the understanding of the phenotypic variability.

METHODS

Muscle biopsies taken before enzyme replacement therapy were analysed from 53 patients with LOPD. On resin sections, glycogen accumulation, fibrosis, autophagic vacuoles and the degree of muscle damage (morphology-score) were analysed and the results were compared with clinical findings. Additional autophagy markers microtubule-associated protein 1A/1B-light chain 3, p62 and Bcl2-associated athanogene 3 were analysed on cryosections from 22 LOPD biopsies.

RESULTS

The myopathology showed a high variability with, in most patients, a moderate glycogen accumulation and a low morphology-score. High morphology-scores were associated with increased fibrosis and autophagy highlighting the role of autophagy in severe stages of skeletal muscle damage. The morphology-score did not correlate with the patient's age at biopsy, disease duration, nor with the residual GAA enzyme activity or creatine-kinase levels. In 37 patients with LOPD, genetic analysis identified the most frequent mutation, c.-32-13T>G, in 95%, most commonly in combination with c.525delT (19%). No significant correlation was found between the different GAA genotypes and muscle morphology type.

CONCLUSIONS

Muscle morphology in LOPD patients shows a high variability with, in most cases, moderate pathology. Increased pathology is associated with more fibrosis and autophagy.