Gamma-glutamyltransferase 7 suppresses gastric cancer by cooperating with RAB7 to induce mitophagy
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ABSTRACT: We identified gamma-glutamyltransferase 7 (GGT7) to be frequently downregulated in gastric cancer, but its role remains unknown. Here we elucidated the clinical significance, functional roles and molecular mechanism of GGT7 in gastric cancer. GGT7 was downregulated by promoter methylation and restored by demethylation treatment in gastric cancer cells. GGT7 methylation inversely correlated with mRNA expression in gastric tumors (n=221; r=-0.686, P<0.0001). High-expression of GGT7 in adjacent non-tumor tissues was significantly associated with favorable survival in gastric cancer patients (n=138; P=0.009), and was an independent prognostic factor by multivariate Cox regression (HR=0.381, P<0.05). GGT7 significantly inhibited gastric cancer cell growth, G1-S transition, and migration and invasion abilities. GGT7 also significantly attenuated the growth of subcutaneous xenograft tumors and reduced metastasis to the lung in nude mice. The mitophagy regulator RAB7 was identified as a direct downstream co-player of GGT7 by co-immunoprecipitation followed by mass spectrometry. Growth suppression effect of GGT7 was at least partly dependent on RAB7 by rescue experiments. GGT7 induced autophagy as shown by electron microscopy and confirmed by the increased LC3B and decreased p62. GGT7 recruited RAB7 by direct binding and drove RAB7 to translocate from nucleus to cytoplasm, subsequently mediating mitophagy by increasing mitophagy mediators/inducers. GGT7 inhibited intracellular ROS, which was associated with increased mitophagy, and subsequently suppressed MAPK signaling. Collectively, GGT7 plays a pivotal tumor-suppressing role in gastric cancer by directly binding with RAB7 to induce mitophagy and inhibit ROS and MAPK cascades. GGT7 is an independent prognostic factor for gastric cancer patients.
Project description:Pulmonary arterial hypertension (PAH) is a devastating and progressive disease with limited treatment options. Endothelial dysfunction plays a central role in development and progression of PAH, yet the underlying mechanisms are incompletely understood. The endosome-lysosome system is important to maintain cellular health and the small GTPase RAB7 regulates many functions of this system. Here, we explored the role of RAB7 in endothelial cell (EC) function and lung vascular homeostasis. We found reduced expression of RAB7 in ECs from PAH patients. Endothelial haploinsufficiency of RAB7 caused spontaneous PH in mice. Silencing of RAB7 in ECs induced broad changes in gene expression revealed via RNA sequencing and RAB7 silenced ECs showed impaired angiogenesis, expansion of a senescent cell fraction, combined with impaired endolysosomal trafficking and degradation, which suggests inhibition of autophagy at the pre-degradation level.
Project description:Purpose: Assess the transcriptional changes induced upon RAB7 knock-down in melanoma (SK-Mel-28 and UACC-62) and in colon cancer (HCT-116) cell lines. Methods: mRNA profiles of tumor cell lines (SK-Mel-28, UACC-62, HCT-116) stably expressing scrambled shRNA or RAB7 shRNA (harvested at day 3 after lentiviral infection) were generated by deep sequencing, using three biological replicates per condition. The sequence reads that passed quality filters were analyzed with TopHat and Cufflinks. Validation of induced / silenced genes was performed by western blot. Results show a differential impact of RAB7 expression in the transcriptomic profile of melanoma vs non-melanoma cell lines, and support a lineage-specific role of this small GTPase in melanoma. Examination of the mRNA profiles RAB7-depleted vs wild type cells, performed in parallel in 3 different tumor cell lines (Melanomas: SK-Mel-28 and UACC-62, Non-melanoma: HCT-116) harvested at day 3 after lentiviral infection.
Project description:Purpose: Asess the transcritpional changes induced upon RAB7 knock-down in melanoma (SK-Mel-28 and UACC-62) and in colon cancer (HCT-116) cell lines. Methods: mRNA profiles of tumor cell lines (SK-Mel-28, UACC-62, HCT-116) stably expressing scrambled shRNA or RAB7 shRNA (harvested at day 3 after lentiviral infection) were generated by deep sequencing, using three biological replicates per condition. The sequence reads that passed quality filters were analyzed with TopHat and Cufflinks. Validation of induced / silenced genes was performed by western blot. Results show a differential impact of RAB7 expression in the transcriptomic profile of melanoma vs non-melanoma cell lines, and support a lineage-specific role of this small GTPase in melanoma.
Project description:We purified by magnet assisted cell sorting microglial cells from brains of adult Rab7 null mutant, aged mice and respective controls, isolated total RNA and performed RNAseq to determine the transciptome profiles.
Project description:The paper "Metabolomic Machine Learning Predictor for Diagnosis and Prognosis of Gastric Cancer" addresses the need for non-invasive diagnostic tools for gastric cancer (GC). Traditional methods like endoscopy are invasive and expensive. The authors conducted a targeted metabolomics analysis of 702 plasma samples to develop machine learning models for GC diagnosis and prognosis. The diagnostic model, using 10 metabolites, achieved a sensitivity of 0.905, outperforming conventional protein marker-based methods. The prognostic model effectively stratified patients into risk groups, surpassing traditional clinical models.
I have successfully reproduced the diagnosis model from the paper. This machine learning-based system differentiates GC patients from non-GC controls using metabolomics data from plasma samples analyzed by liquid chromatography-mass spectrometry (LC-MS). The model focuses on 10 metabolites, including succinate, uridine, lactate, and serotonin. Employing LASSO regression and a random forest classifier, the model achieved an AUROC of 0.967, with a sensitivity of 0.854 and specificity of 0.926. This model significantly outperforms traditional diagnostic methods and underscores the potential of integrating machine learning with metabolomics for early GC detection and treatment.
Project description:Cholesterol import in mammalian cells is mediated by the LDL receptor pathway. Here, we perform a genome-wide CRISPR screen using an endogenous cholesterol reporter and identify >100 genes involved in LDL-cholesterol import. We characterise C18orf8 as a core subunit of the mammalian Mon1-Ccz1 guanidine exchange factor (GEF) for Rab7, required for complex stability and function. C18orf8-deficient cells lack Rab7 activation and show severe defects in late endosome morphology and endosomal LDL trafficking, resulting in cellular cholesterol deficiency. Unexpectedly, free cholesterol accumulates within swollen lysosomes, suggesting a critical defect in lysosomal cholesterol export. We find that active Rab7 interacts with the NPC1 cholesterol transporter and licenses lysosomal cholesterol export. This process is abolished in C18orf8-, Ccz1- and Mon1A/B-deficient cells and restored by a constitutively active Rab7. The trimeric Mon1-Ccz1-C18orf8 (MCC) GEF therefore plays a central role in cellular cholesterol homeostasis coordinating Rab7 activation, endosomal LDL trafficking and NPC1-dependent lysosomal cholesterol export.
Project description:Bladder cancer is one of the most common malignancy in the urinary tract with high recurrence and drug resistance in clinics. Alternative treatments from existing drugs might be a promising strategy. Nitazoxanide (NTZ), an FDA-approved antiprotozoal drug, has got increasingly noticed because of its favorable safety profile and antitumor potential, yet the effects in bladder cancer and underlying mechanisms remain poorly understood. Herein, we find that NTZ induces mitochondrial damage and mitophagy initiation through PINK1-generated phospho-ubiquitin(pS65-Ub) and autophagy receptor-mediated pathway even in the absence of Atg5/Beclin1. Meanwhile, NTZ inhibits lysosomal degradation activity, leading to mitophagy flux impairment at late stage. Mitochondrial reactive oxygen species (ROS) production is critical in this process, as eliminating ROS with N-acetylcysteine (NAC) efficiently inhibits PINK1 signaling-mediated mitophagy initiation and alleviates lysosomal dysfunction. Co-treatment with NTZ and autophagy inhibitor Chloroquine (CQ) to aggravate mitophagy flux impairment promotes NTZ-induced apoptosis, while alleviation of mitophagy flux impairment with ROS scavenger reduced cell death. Moreover, we also discover a similar signaling response in the 3D bladder tumor spheroid after NTZ exposure. In vivo study reveals a significant inhibition of orthotopic bladder tumors with no obvious systemic toxicity. Together, our results uncover the anti-tumor activities of NTZ with the involvement of ROS-mediated mitophagy modulation at different stages and demonstrate it as a potential drug candidate for fighting against bladder tumors.
Project description:The endosomal system is a highly dynamic multifunctional organelle, whose complexity is regulated in part by reversible ubiquitylation. Despite the wide-ranging influence of ubiquitin in endosomal processes, relatively few enzymes utilizing ubiquitin have been described to control endosome integrity and function. Here we reveal the deubiquitylating enzyme (DUB) ubiquitin-specific protease 32 (USP32) as a powerful new player in this context. Loss of USP32 inhibits late endosome (LE) transport and recycling of LE cargos to the TGN, resulting in dispersion and swelling of the late compartment. Using SILAC-based ubiquitome profiling we identify the small GTPase Rab7—the logistical centerpiece of LE biology—as a substrate of USP32. Mechanistic studies reveal that LE transport effector RILP prefers ubiquitylation-deficient Rab7, while retromer-mediated LE recycling benefits from an intact cycle of Rab7 ubiquitylation. Collectively, our observations suggest that reversible ubiquitylation helps switch Rab7 between its various functions, thereby maintaining global spatiotemporal order in the endosomal system.