TMEM189 negatively regulates the stability of ULK1 protein and cell autophagy

Molecular cloning, expression, and functional analyses of plasmanylethanolamine desaturase gene of Takifugu rubripes

The aging population has led to a significant increase in neurodegenerative diseases, particularly Alzheimer's disease (AD), which adversely affects the quality of life and longevity of the elderly. Abnormal plasmalogen metabolism plays a crucial role in the pathogenesis of AD. This study focused on tmem189, a key gene involved in plasmalogen synthesis. We successfully cloned and characterized the open reading frame (ORF) of tmem189 in Takifugu rubripes, revealing that it encodes a protein consisting of 275 amino acids. Notably, tmem189 expression was found to be higher in brain compared to other tissues. We transfected a GFP-tagged eukaryotic expression vector into 293 T cells, confirming successful expression of tmem189 with increased expression  levels. Additionally, liquid chromatography-mass spectrometry (LC-MS) analysis demonstrated that tmem189 promotes plasmalogen synthesis in the transfected 293T cells. Our findings suggest that tmem189 could serve as a potential target for the treatment of neurodegenerative diseases, providing new insights into the promotion of plasmalogen synthesis.

GPX4 knockdown suppresses M2 macrophage polarization in gastric cancer by modulating kynurenine metabolism

Background: Glutathione peroxidase 4 (GPX4), an important factor regulating redox homeostasis, plays an important role in tumor microenvironment and progression. However, the role of GPX4 in gastric cancer (GC) is unclear. Methods: Spectral flow cytometry and multiplex immunohistochemistry were employed to assess the correlation between GPX4 expression and immune cell infiltration. Metabolomics analysis of conditioned media from GPX4 knockdown NUGC3 cells identified metabolic alterations. Additionally, both in vitro and in vivo functional studies were conducted to elucidate the mechanistic role of GPX4 in regulating the tumor microenvironment and progression. Results: Knockdown of GPX4 in GC cells inhibited tumor growth, enhanced CD8+ T cell infiltration, and suppressed the polarization of tumor-associated macrophages (TAMs) toward the pro-tumor M2 phenotype. Multiplex immunohistochemistry revealed a positive correlation between GPX4 expression and M2 macrophage infiltration in clinical samples from patients with GC. Metabolomics revealed that GPX4 knockdown regulate kynurenine metabolism pathway. Furthermore, mechanistic studies reveal that GPX4 silencing elevates lipid peroxidation, triggering the conversion of KYNU ubiquitin chain modifications from K48 to K63. Such ubiquitination remodeling stabilizes KYNU expression (a key kynurenine-metabolizing enzyme), reduces kynurenine accumulation, and ultimately reprograms TAM polarization to enhance antitumor immunity. We also identified that the K96 and K163 sites are important for KYNU's modification by K48 and K63 ubiquitin chains. Conclusion: Our study not only affirm the role of GPx4 in GC progression but also highlight it as a promising target for reshaping the immune microenvironment.

ANXA2 in cancer: aberrant regulation of tumour cell apoptosis and its immune interactions

Annexin A2 (ANXA2) is a multifunctional protein that binds to calcium and phospholipids and plays a critical role in various pathological conditions, including cancer and inflammation. Recently, there has been increasing recognition of the significant role of ANXA2 in inhibiting apoptosis and promoting immune evasion in tumour cells. Therefore, a deep understanding of the regulatory mechanisms of ANXA2 in tumour cell apoptosis and its relationship with immune evasion can provide new targets for cancer therapy. This review summarizes the role and mechanisms of ANXA2 in regulating apoptosis in tumour cells, the connection between apoptosis regulation and tumour immunity, and the potential role of ANXA2 in therapy resistance.

Chemoproteomics-Enabled De Novo Proteolysis Targeting Chimera Discovery Platform Identifies a Metallothionein Degrader to Probe Its Role in Cancer

Proteolysis targeting chimeras (PROTACs) represent powerful tools to modulate the activity of classically "undruggable" proteins, but their application has been limited to known ligands and a few select protein classes. Herein, we present our chemoproteomic strategy for simultaneous de novo discovery of novel degraders and ligands for challenging and previously "undruggable" targets. Using comparative PROTAC versus ligand global proteomics analyses, we rapidly identify proteins selectively downregulated by several "untargeted" PROTACs containing a VHL E3 ligase recruiter and various covalent and noncovalent ligands. We showcase our approach by identifying a first-in-class PROTAC for metallothionein 2A (MT2A), a small, cysteine-rich, metal-binding protein implicated in heavy metal detoxification, zinc homeostasis, and cellular invasion. Notably, isoform-specific MT overexpression has been shown to augment cellular migration and invasion across several cancer cell lines, although the precise mechanisms are unknown due to insufficient tools to study MTs. We show that optimized PROTAC AA-BR-157 covalently binds conserved C44, degrades overexpressed MT2A with nanomolar potency, and reduces the migration and invasion of MDA-MB-231 cells. We further demonstrate a time-dependent increase in intracellular zinc levels following MT2A degradation as well as downregulation of protein diaphanous homolog 3 (DIAPH3), a positive regulator of actin and cell motility. Super-resolution imaging of MDA-MB-231 cells shows that the downregulation of MT2A and DIAPH3 inhibits cell polarization and thereby migration, suggesting that MT2A may regulate motility via DIAPH3-dependent cytoskeletal remodeling. In summary, our strategy enables the de novo discovery of PROTACs and ligands for novel disease-related targets and lays the groundwork for expansion of the druggable proteome.

Decoding the Expressions, Immune Relevance, and Prognostic Values of Ferroptosis Gene TMEM189: A Pan-cancer Analysis

BACKGROUND

TMEM189 is a recently discovered transmembrane protein involved in ether glycerophospholipid synthesis and ferroptosis regulation. However, its role in tumors is not well understood.

OBJECTIVE

This study aimed to elucidate the oncogenic effects and prognostic values of TMEM189 in tumors.

METHODS

We performed a pan-cancer analysis of TMEM189 using various databases, bioinformatics and statistical tools, and tissue microarray analysis.

RESULTS

TMEM189 was upregulated in tumors compared to normal tissues. High TMEM189 expression was found to be linked to reduced promoter methylation. Moreover, TMEM189 exhibited a negative correlation with immunogenic markers, immune cell infiltration, and expression of Immune Checkpoint Genes (ICGs) in most cancers, implicating its immunosuppressive role in tumor microenvironments (TME). The genes that interact and are similar to TMEM189 were involved in hotspot signaling pathways in pan-cancer. TMEM189 overexpression was found to be usually associated with poor prognosis, especially an independent prognostic risk factor for BLCA, BRCA, LUAD, MESO, LIHC, and SKCM.

CONCLUSION

TMEM189 is overexpressed and exerts immunosuppressive effects in many tumors with a significant association with poor prognosis, suggesting its potential as a therapeutic target in cancer treatment.

Peds1 deficiency in zebrafish results in myeloid cell apoptosis and exacerbated inflammation

Plasmalogens are glycerophospholipids with a vinyl ether bond that confers unique properties. Recent identification of the gene encoding PEDS1, the desaturase generating the vinyl ether bond, enables evaluation of the role of plasmalogens in health and disease. Here, we report that Peds1-deficient zebrafish larvae display delayed development, increased basal inflammation, normal hematopoietic stem and progenitor cell emergence, and cell-autonomous myeloid cell apoptosis. In a sterile acute inflammation model, Peds1-deficient larvae exhibited impaired inflammation resolution and tissue regeneration, increased interleukin-1β and NF-κB expression, and elevated ROS levels at the wound site. Abnormal immune cell recruitment, neutrophil persistence, and fewer but predominantly pro-inflammatory macrophages were observed. Chronic skin inflammation worsened in Peds1-deficient larvae but was mitigated by exogenous plasmalogen, which also alleviated hyper-susceptibility to bacterial infection, as did pharmacological inhibition of caspase-3 and colony-stimulating factor 3-induced myelopoiesis. Overall, our results highlight an important role for plasmalogens in myeloid cell biology and inflammation.

PRRSV GP5 inhibits the antivirus effects of chaperone-mediated autophagy by targeting LAMP2A

Autophagy is an important biological process in host defense against viral infection. However, many viruses have evolved various strategies to disrupt the host antiviral system. Porcine reproductive and respiratory syndrome virus (PRRSV) is a typical immunosuppressive virus with a large economic impact on the swine industry. At present, studies on the escape mechanism of PRRSV in the autophagy process, especially through chaperone-mediated autophagy (CMA), are limited. This study confirmed that PRRSV glycoprotein 5 (GP5) could disrupt the formation of the GFAP-LAMP2A complex by inhibiting the MTORC2/PHLPP1/GFAP pathway, promoting the dissociation of the pGFAP-EF1α complex, and blocking the K63-linked polyubiquitination of LAMP2A to inhibit the activity of CMA. Further research demonstrated that CMA plays an anti-PRRSV role by antagonizing nonstructural protein 11 (NSP11)-mediated inhibition of type I interferon (IFN-I) signaling. Taken together, these results indicate that PRRSV GP5 inhibits the antiviral effect of CMA by targeting LAMP2A. This research provides new insight into the escape mechanism of immunosuppressive viruses in CMA.

IMPORTANCE

Viruses have evolved sophisticated mechanisms to manipulate autophagy to evade degradation and immune responses. Porcine reproductive and respiratory syndrome virus (PRRSV) is a typical immunosuppressive virus that causes enormous economic losses in the swine industry. However, the mechanism by which PRRSV manipulates autophagy to defend against host antiviral effects remains unclear. In this study, we found that PRRSV GP5 interacts with LAMP2A and disrupts the formation of the GFAP-LAMP2A complex, thus inhibiting the activity of CMA and subsequently enhancing the inhibitory effect of the NSP11-mediated IFN-I signaling pathway, ultimately facilitating PRRSV replication. Our study revealed a novel mechanism by which PRRSV escapes host antiviral effects through CMA, providing a potential host target, LAMP2A, for developing antiviral drugs and contributing to understanding the escape mechanism of immunosuppressive viruses.

Blockage of TMEM189 induces G2/M arrest and inhibits the growth of breast tumors

Cancer is the major cause of premature death in humans worldwide, demanding more efficient therapeutics. Aberrant cell proliferation resulting from the loss of cell cycle regulation is the major hallmark of cancer, so targeting cell cycle is a promising strategy to combat cancer. However, the molecular mechanism underlying the dysregulation of cell cycle of cancer cells remains poorly understood. TMEM189, a newly identified protein, plays roles in the biosynthesis of ethanolamine plasmalogen and the regulation of autophagy. Here, we demonstrated that the expression level of TMEM189 was negatively correlated with the survival rate of the cancer patients. TMEM189 deficiency significantly suppresses the cancer cell proliferation and migration, and causes cell cycle G2/M arrest both in vitro and in vivo. Furthermore, TMEM189 depletion suppressed the growth of breast tumors in vivo. Taken together, our work indicated that TMEM189 promotes cancer progression by regulating cell cycle G2/M transition, suggesting that it is a promising target in cancer therapy.

Ether-lipids and cellular signaling: A differential role of alkyl- and alkenyl-ether-lipids?

Ether-lipids (EL) are specific lipids bearing a characteristic sn-1 ether bond. Depending on the ether or vinyl-ether nature of this bond, they are present as alkyl- or alkenyl-EL, respectively. Among EL, alkenyl-EL, also referred as plasmalogens in the literature, attract most of the scientific interest as they are the predominant EL species in eukaryotic cells, thus less is known about alkyl-EL. EL have been implicated in various signaling pathways and alterations in their quantity are frequently observed in pathologies such as neurodegenerative and cardiovascular diseases or cancer. However, it remains unknown whether both alkyl- and alkenyl-EL play the same roles in these processes. This review summarizes the roles and mechanisms of action of EL in cellular signaling and tries to discriminate between alkyl- and alkenyl-EL. We also focus on the involvement of EL-mediated alterations of cellular signaling in diseases and discuss the potential interest for EL in therapy.

Ubiquitination in the regulation of autophagy

Autophagy, an efficient and effective approach to clear rapidly damaged organelles, macromolecules, and other harmful cellular components, enables the recycling of nutrient materials and supply of nutrients to maintain cellular homeostasis. Ubiquitination plays an important regulatory role in autophagy. This paper summarizes the most recent progress in ubiquitin modification in various stages of autophagy, including initiation, elongation, and termination. Moreover, this paper shows that ubiquitination is an important way through which selective autophagy achieves substrate specificity. Furthermore, we note the distinction between monoubiquitination and polyubiquitination in the regulation of autophagy. Compared with monoubiquitination, polyubiquitination is a more common strategy to regulate the activity of the autophagy molecular machinery. In addition, the role of ubiquitination in the closure and fusion of autophagosomes warrants further study. This article not only clarifies the regulatory mechanism of autophagy but also contributes to a deeper understanding of the importance of ubiquitination modification.

Autophagy/Mitophagy Regulated by Ubiquitination: A Promising Pathway in Cancer Therapeutics

Autophagy is essential for organismal development, maintenance of energy homeostasis, and quality control of organelles and proteins. As a selective form of autophagy, mitophagy is necessary for effectively eliminating dysfunctional mitochondria. Both autophagy and mitophagy are linked with tumor progression and inhibition. The regulation of mitophagy and autophagy depend upon tumor type and stage. In tumors, mitophagy has dual roles: it removes damaged mitochondria to maintain healthy mitochondria and energy production, which are necessary for tumor growth. In contrast, mitophagy has been shown to inhibit tumor growth by mitigating excessive ROS production, thus preventing mutation and chromosomal instability. Ubiquitination and deubiquitination are important modifications that regulate autophagy. Multiple E3 ubiquitin ligases and DUBs modulate the activity of the autophagy and mitophagy machinery, thereby influencing cancer progression. In this review, we summarize the mechanistic association between cancer development and autophagy/mitophagy activities regulated by the ubiquitin modification of autophagic proteins. In addition, we discuss the function of multiple proteins involved in autophagy/mitophagy in tumors that may represent potential therapeutic targets.

Lipidomic markers of breast cancer malignant tumor histological types

The molecular profile of a tumor is associated with its histological type and can be used both to study the mechanisms of tumor progression and to diagnose it. In this work, changes in the lipid profile of a malignant breast tumor and the adjacent tissue were studied. The potential possibility of determining the histological type of the tumor by its lipid profile was evaluated. Lipid profiling was performed by reverse-phase chromato-mass-spectrometric analysis the tissue of lipid extract with identification of lipids by characteristic fragments. Potential lipid markers of the histological type of tumor were determined using the Kruskal-Wallis test. Impact of lipid markers was calculated by MetaboAnalyst. Classification models were built by support vector machines with linear kernel and 1-vs-1 architecture. Models were validated by leave-one out cross-validation. Accuracy of models based on microenvironment tissue, were 99% and 75%, accuracy of models, based on tumor tissue, were 90% and 40% for the positive ion mode and negative ion mode respectively. The lipid profile of marginal (adjacent) tissue can be used for identification histological types of breast cancer. Glycerophospholipid metabolism pathway changes were statistically significant in the adjacent tissue and tumor tissue.

Function and regulation of ULK1: From physiology to pathology

The expression of ULK1, a core protein of autophagy, is closely related to autophagic activity. Numerous studies have shown that pathological abnormal expression of ULK1 is associated with various human diseases such as neurological disorders, infections, cardiovascular diseases, liver diseases and cancers. In addition, new advances in the regulation of ULK1 have been identified. Furthermore, targeting ULK1 as a therapeutic strategy for diseases is gaining attention as new corresponding activators or inhibitors are being developed. In this review, we describe the structure and regulation of ULK1 as well as the current targeted activators and inhibitors. Moreover, we highlight the pathological disorders of ULK1 expression and its critical role in human diseases.