USP32-regulated LAMTOR1 ubiquitination impacts mTORC1 activation and autophagy induction

Lycobetaine Has Therapeutic Efficacy in Lung Squamous Cell Carcinoma by Targeting USP32 to Trigger Ferroptosis

Ubiquitin-specific protease 32 (USP32), a deubiquitylating enzyme that controls the ubiquitin process, is overexpressed in multiple cancers and serves as a promising therapeutic target for cancer therapy. Drugs targeting ferroptosis have exhibited promising anticancer activity. Lycobetaine (LBT), a natural alkaloid, holds promise against various cancers, yet its specific targets and anticancer mechanisms remain unclear. In this study, we show that LBT induced ferroptosis in lung squamous cell carcinoma (LUSC) cells, accompanied by glutathione depletion and the accumulation of lipid peroxidation, malondialdehyde, and ferrous iron. Mechanistically, drug affinity responsive target stability-based mass spectrometry analysis, molecular dynamics simulations, and a cellular thermal shift assay confirmed that USP32 is a potential target of LBT in LUSC cells. Moreover, a strong interaction between USP32 and nuclear factor erythroid 2-related factor 2 (NRF2) was found via immunoprecipitation-mass spectrometry and co-immunoprecipitation. In addition, the ubiquitination assay results demonstrated that LBT treatment significantly increased NRF2 ubiquitination and degradation by targeting USP32. Importantly, USP32 overexpression effectively attenuated the effects of LBT on proliferation and ferroptosis in LUSC cells. In orthotopic LUSC xenografts, the administration of LBT significantly inhibited tumor growth and metastasis and induced ferroptosis by targeting the USP32-NRF2 signaling axis. Taken together, these data suggest that LBT exerts its anticancer effects by inhibiting USP32-mediated NRF2 deubiquitination to induce ferroptosis and that LBT may serve as a prospective USP32-targeting agent for LUSC treatment.

LAMTOR1/mTORC1 promotes CD276 to induce immunosuppression via PI3K/Akt/MMP signaling pathway in Clostridium perfringens-induced necrotic enteritis of laying hens

Clostridium perfringens (C. perfringens) causes avian necrotic enteritis, leading to huge economic losses to the poultry industry. This pathogen induces host immunosuppression; however, the molecular mechanism is still unclear. Thus, we established a laying hen infection model to explore this mechanism. We randomly divided 20 one-old-day laying hens into the control and infection groups. The infection group was infected intragastrically with 1 × 109 colony-forming units of C. perfringens in 1 mL of sterile phosphate-buffered saline (PBS) once a day from d 17 to 20; the control group received the same volume of PBS without the bacterium. Twenty-four hours after the last challenge, we sacrificed the laying hens and collected the jejunum for analysis. The infection group presented alterations in blood biochemical parameters and necrotic lesion scores as well as damage to the jejunum. Proteomics revealed 427 upregulated and 291 downregulated proteins in the infection group. In the infection group, CD3, CD4, and CD8 messenger RNA expression (mRNA) expression was decreased; LAMTOR1 and mTORC1 mRNA expression was increased; CD276 protein expression was enhanced; and the PI3K/Akt/MMP pathway was activated in jejunum of laying hens. This is the first study to report CD276 expression in the jejunum related to immunosuppression in a laying hen model of necrotic enteritis. It provides some new key targets to potentially control avian necrotic enteritis.

Deubiquitinases as novel therapeutic targets for diseases

Deubiquitinating enzymes (DUBs) regulate substrate ubiquitination by removing ubiquitin or cleaving within ubiquitin chains, thereby maintaining cellular homeostasis. Approximately 100 DUBs in humans counteract E3 ubiquitin ligases, finely balancing ubiquitination and deubiquitination processes to maintain cellular proteostasis and respond to various stimuli and stresses. Given their role in modulating ubiquitination levels of various substrates, DUBs are increasingly linked to human health and disease. Here, we review the DUB family, highlighting their distinctive structural characteristics and chain-type specificities. We show that DUB family members regulate key signaling pathways, such as NF-κB, PI3K/Akt/mTOR, and MAPK, and play crucial roles in tumorigenesis and other diseases (neurodegenerative disorders, cardiovascular diseases, inflammatory disorders, and developmental diseases), making them promising therapeutic targets Our review also discusses the challenges in developing DUB inhibitors and underscores the critical role of the DUBs in cellular signaling and cancer. This comprehensive analysis enhances our understanding of the complex biological functions of the DUBs and underscores their therapeutic potential.

LAMTOR1 decreased exosomal PD-L1 to enhance immunotherapy efficacy in non-small cell lung cancer

Great progress has been made in utilizing immune checkpoint blockade (ICB) for the treatment of non-small-cell lung cancer (NSCLC). Therapies targeting programmed cell death protein 1 (PD-1) and its ligand PD-L1, expressed on tumor cells, have demonstrated potential in improving patient survival rates. An unresolved issue involves immune suppression induced by exosomal PD-L1 within the tumor microenvironment (TME), particularly regarding CD8+ T cells. Our study unveiled the crucial involvement of LAMTOR1 in suppressing the exosomes of PD-L1 and promoting CD8+ T cell infiltration in NSCLC. Through its interaction with HRS, LAMTOR1 facilitates PD-L1 lysosomal degradation, thereby reducing exosomal PD-L1 release. Notably, the ability of LAMTOR1 to promote PD-L1 lysosomal degradation relies on a specific ubiquitination site and an HRS binding sequence. The findings suggest that employing LAMTOR1 to construct peptides could serve as a promising strategy for bolstering the efficacy of immunotherapy in NSCLC. The discovery and comprehension of how LAMTOR1 inhibits the release of exosomal PD-L1 offer insights into potential therapeutic strategies for improving immunotherapy. It is imperative to conduct further research and clinical trials to investigate the feasibility and efficacy of targeting LAMTOR1 in NSCLC treatment.

USP32 facilitates non-small cell lung cancer progression via deubiquitinating BAG3 and activating RAF-MEK-ERK signaling pathway

The regulatory significance of ubiquitin-specific peptidase 32 (USP32) in tumor is significant, nevertheless, the biological roles and regulatory mechanisms of USP32 in non-small cell lung cancer (NSCLC) remain unclear. According to our research, USP32 was strongly expressed in NSCLC cell lines and tissues and was linked to a bad prognosis for NSCLC patients. Interference with USP32 resulted in a significant inhibition of NSCLC cell proliferation, migration potential, and EMT development; on the other hand, USP32 overexpression had the opposite effect. To further elucidate the mechanism of action of USP32 in NSCLC, we screened H1299 cells for interacting proteins and found that USP32 interacts with BAG3 (Bcl2-associated athanogene 3) and deubiquitinates and stabilizes BAG3 in a deubiquitinating activity-dependent manner. Functionally, restoration of BAG3 expression abrogated the antitumor effects of USP32 silencing. Furthermore, USP32 increased the phosphorylation level of the RAF/MEK/ERK signaling pathway in NSCLC cells by stabilizing BAG3. In summary, these findings imply that USP32 is critical to the development of NSCLC and could offer a theoretical framework for the clinical diagnosis and management of NSCLC patients in the future.

Progress in the study of autophagy-related proteins affecting resistance to chemotherapeutic drugs in leukemia

Leukemia is a life-threatening malignant tumor of the hematopoietic system. Currently, the main treatment modalities are chemotherapy and hematopoietic stem cell transplantation. However, increased drug resistance due to decreased sensitivity of leukemia cells to chemotherapeutic drugs presents a major challenge in current treatments. Autophagy-associated proteins involved in autophagy initiation have now been shown to be involved in the development of various types of leukemia cells and are associated with drug resistance. Therefore, this review will explore the roles of autophagy-related proteins involved in four key autophagic processes: induction of autophagy and phagophore formation, phagophore extension, and autophagosome formation, on the development of various types of leukemias as well as drug resistance. Autophagy may become a promising therapeutic target for treating leukemia.

TRAF4-Mediated LAMTOR1 Ubiquitination Promotes mTORC1 Activation and Inhibits the Inflammation-Induced Colorectal Cancer Progression

Mechanistic target of rapamycin complex 1 (mTORC1) is a conserved serine/threonine kinase that integrates various environmental signals to regulate cell growth and metabolism. mTORC1 activation requires tethering to lysosomes by the Ragulator-Rag complex. However, the dynamic regulation of the interaction between Ragulator and Rag guanosine triphosphatase (GTPase) remains unclear. In this study, that LAMTOR1, an essential component of Ragulator, is dynamically ubiquitinated depending on amino acid abundance is reported. It is found that the E3 ligase TRAF4 directly interacts with LAMTOR1 and catalyzes the K63-linked polyubiquitination of LAMTOR1 at K151. Ubiquitination of LAMTOR1 by TRAF4 promoted its binding to Rag GTPases and enhanced mTORC1 activation, K151R knock-in or TRAF4 knock-out blocks amino acid-induced mTORC1 activation and accelerates the development of inflammation-induced colon cancer. This study revealed that TRAF4-mediated LAMTOR1 ubiquitination is a regulatory mechanism for mTORC1 activation and provides a therapeutic target for diseases involving mTORC1 dysregulation.

Post-translational regulation of the mTORC1 pathway: A switch that regulates metabolism-related gene expression

The mechanistic target of rapamycin complex 1 (mTORC1) is a kinase complex that plays a crucial role in coordinating cell growth in response to various signals, including amino acids, growth factors, oxygen, and ATP. Activation of mTORC1 promotes cell growth and anabolism, while its suppression leads to catabolism and inhibition of cell growth, enabling cells to withstand nutrient scarcity and stress. Dysregulation of mTORC1 activity is associated with numerous diseases, such as cancer, metabolic disorders, and neurodegenerative conditions. This review focuses on how post-translational modifications, particularly phosphorylation and ubiquitination, modulate mTORC1 signaling pathway and their consequential implications for pathogenesis. Understanding the impact of phosphorylation and ubiquitination on the mTORC1 signaling pathway provides valuable insights into the regulation of cellular growth and potential therapeutic targets for related diseases.

Methylation of GPRC5A promotes liver metastasis and docetaxel resistance through activating mTOR signaling pathway in triple negative breast cancer

AIMS

This study aims to explore the function and mechanism of G Protein-coupled receptor class C group 5 member A (GPRC5A) in docetaxel-resistance and liver metastasis of breast cancer.

METHODS

Single-cell RNA transcriptomic analysis and bioinformatic analysis are used to screen relevant genes in breast cancer metastatic hepatic specimens. MeRIP, dual-luciferase analysis and bioinformation were used to detect m6A modulation. Mass spectrometry (MS), co-inmunoprecipitation (co-IP) and immunofluorescence colocalization were executed to explore the mechanism of GPRC5A in breast cancer cells.

RESULT

GPRC5A was upregulated in triple-negative breast cancer (TNBC) and was associated with a poor prognosis. In vitro and in vivo experiments demonstrated that knockdown of GPRC5A alleviated metastasis and resistance to docetaxel in TNBC. Overexpression of GPRC5A had the opposite effects. The m6A methylation of GPRC5A mRNA was modulated by METTL3 and YTHDF1, which facilitates its translation. GPRC5A inhibited the ubiquitination-dependent degradation of LAMTOR1, resulting in the recruitment of mTORC1 to lysosomes and activating the mTORC1/p70s6k signaling pathway.

CONCLUSION

METTL3/YTHDF1 axis up-regulates GPRC5A expression by m6A methylation. GPRC5A activates mTORC1/p70s6k signaling pathway by recruiting mTORC1 to lysosomes, consequently promotes docetaxel-resistance and liver metastasis.

An atypical GABARAP binding module drives the pro-autophagic potential of the AML-associated NPM1c variant

The nucleolar scaffold protein NPM1 is a multifunctional regulator of cellular homeostasis, genome integrity, and stress response. NPM1 mutations, known as NPM1c variants promoting its aberrant cytoplasmic localization, are the most frequent genetic alterations in acute myeloid leukemia (AML). A hallmark of AML cells is their dependency on elevated autophagic flux. Here, we show that NPM1 and NPM1c induce the autophagy-lysosome pathway by activating the master transcription factor TFEB, thereby coordinating the expression of lysosomal proteins and autophagy regulators. Importantly, both NPM1 and NPM1c bind to autophagy modifiers of the GABARAP subfamily through an atypical binding module preserved within its N terminus. The propensity of NPM1c to induce autophagy depends on this module, likely indicating that NPM1c exerts its pro-autophagic activity by direct engagement with GABARAPL1. Our data report a non-canonical binding mode of GABARAP family members that drives the pro-autophagic potential of NPM1c, potentially enabling therapeutic options.

USP32 deubiquitinase: cellular functions, regulatory mechanisms, and potential as a cancer therapy target

An essential protein regulatory system in cells is the ubiquitin-proteasome pathway. The substrate is modified by the ubiquitin ligase system (E1-E2-E3) in this pathway, which is a dynamic protein bidirectional modification regulation system. Deubiquitinating enzymes (DUBs) are tasked with specifically hydrolyzing ubiquitin molecules from ubiquitin-linked proteins or precursor proteins and inversely regulating protein degradation, which in turn affects protein function. The ubiquitin-specific peptidase 32 (USP32) protein level is associated with cell cycle progression, proliferation, migration, invasion, and other cellular biological processes. It is an important member of the ubiquitin-specific protease family. It is thought that USP32, a unique enzyme that controls the ubiquitin process, is closely linked to the onset and progression of many cancers, including small cell lung cancer, gastric cancer, breast cancer, epithelial ovarian cancer, glioblastoma, gastrointestinal stromal tumor, acute myeloid leukemia, and pancreatic adenocarcinoma. In this review, we focus on the multiple mechanisms of USP32 in various tumor types and show that USP32 controls the stability of many distinct proteins. Therefore, USP32 is a key and promising therapeutic target for tumor therapy, which could provide important new insights and avenues for antitumor drug development. The therapeutic importance of USP32 in cancer treatment remains to be further proven. In conclusion, there are many options for the future direction of USP32 research.

LAMTOR1 ubiquitination restricts its interaction with the vacuolar-type H+-ATPase, promotes autophagy and is controlled by USP32

Among the various signals governing autophagy, ubiquitination plays a critical role both by controlling the stability of upstream regulators or components of macroautophagy/autophagy pathways and by facilitating the recruitment of cargo to autophagy receptors. As such, modulators of ubiquitin signaling can influence autophagic substrate degradation. Recently, we identified a non-proteolytic ubiquitin signal at the Ragulator complex subunit LAMTOR1 that is reversed by the deubiquitinase USP32. Loss of USP32 promotes ubiquitination within the unstructured N-terminal region of LAMTOR1 and prevents its efficient interaction with the vacuolar-type H+-ATPase, a prerequisite for full activation of MTORC1 at lysosomes. Consequently, MTORC1 activity is decreased and autophagy is upregulated in USP32 knockout cells. This phenotype is conserved in Caenorhabditis elegans. Depletion of USP32 homolog CYK-3 in worms results in LET-363/MTOR inhibition and autophagy induction. Based on our data, we propose an additional control layer of the MTORC1 activation cascade at lysosomes via USP32-regulated LAMTOR1 ubiquitination.