NIPSNAP protein family emerges as a sensor of mitochondrial health

Mitochondrial quality control pathways sense mitochondrial protein import

Mitochondrial quality control (MQC) mechanisms are required to maintain a functional proteome, which enables mitochondria to perform a myriad of important cellular functions from oxidative phosphorylation to numerous other metabolic pathways. Mitochondrial protein homeostasis begins with the import of over 1000 nuclear-encoded mitochondrial proteins and the synthesis of 13 mitochondrial DNA-encoded proteins. A network of chaperones and proteases helps to fold new proteins and degrade unnecessary, damaged, or misfolded proteins, whereas more extensive damage can be removed by mitochondrial-derived vesicles (MDVs) or mitochondrial autophagy (mitophagy). Here, focusing on mechanisms in mammalian cells, we review the importance of mitochondrial protein import as a sentinel of mitochondrial function that activates multiple MQC mechanisms when impaired.

Exploring the potential link between MitoEVs and the immune microenvironment of periodontitis based on machine learning and bioinformatics methods

BACKGROUND

Periodontitis is a chronic inflammatory condition triggered by immune system malfunction. Mitochondrial extracellular vesicles (MitoEVs) are a group of highly heterogeneous extracellular vesicles (EVs) enriched in mitochondrial fractions. The objective of this research was to examine the correlation between MitoEVs and the immune microenvironment of periodontitis.

METHODS

Data from MitoCarta 3.0, GeneCards, and GEO databases were utilized to identify differentially expressed MitoEV-related genes (MERGs) and conduct functional enrichment and pathway analyses. The random forest and LASSO algorithms were employed to identify hub MERGs. Infiltration levels of immune cells in periodontitis and healthy groups were estimated using the CIBERSORT algorithm, and phenotypic subgroups of periodontitis based on hub MERG expression levels were explored using a consensus clustering method.

RESULTS

A total of 44 differentially expressed MERGs were identified. The random forest and LASSO algorithms identified 9 hub MERGs (BCL2L11, GLDC, CYP24A1, COQ2, MTPAP, NIPSNAP3A, FAM162A, MYO19, and NDUFS1). ROC curve analysis showed that the hub gene and logistic regression model presented excellent diagnostic and discriminating abilities. Immune infiltration and consensus clustering analysis indicated that hub MERGs were highly correlated with various types of immune cells, and there were significant differences in immune cells and hub MERGs among different periodontitis subtypes.

CONCLUSION

The periodontitis classification model based on MERGs shows excellent performance and can offer novel perspectives into the pathogenesis of periodontitis. The high correlation between MERGs and various immune cells and the significant differences between immune cells and MERGs in different periodontitis subtypes can clarify the regulatory roles of MitoEVs in the immune microenvironment of periodontitis. Future research should focus on elucidating the functional mechanisms of hub MERGs and exploring potential therapeutic interventions based on these findings.

The clarithromycin-binding proteins NIPSNAP1 and 2 regulate cytokine production through mitochondrial quality control

The mechanism underlying the anti-inflammatory effect of macrolide antibiotics, such as clarithromycin (CAM), remains to be clarified. The CAM-binding proteins 4-nitrophenylphosphatase domain and non-neuronal synaptosomal associated protein 25 (SNAP25)-like protein homolog (NIPSNAP) 1 and 2 are involved in the immune response and mitochondrial homeostasis. However, the axis between CAM-NIPSNAP-mitochondria and Toll-like receptor (TLR) and their molecular mechanisms remain unknown. In this study, we sought to elucidate the relationship between mitochondrial homeostasis mediated by NIPSNAP1 and 2 and the immunomodulatory effect of CAM. NIPSNAP1 or 2 knockdown (KD) by RNA interference impaired TLR4-mediated interleukin-8 (IL-8) production. Similar impairment was observed upon treatment with mitochondrial function inhibitors. However, IL-8 secretion was not impaired in NIPSNAP1 and 2 individual knockout (KO) and double KO (DKO) cells. Moreover, the oxygen consumption rate (OCR) in mitochondria measured using a flex analyzer was significantly reduced in NIPSNAP1 or 2 KD cells, but not in DKO cells. CAM also dose-dependently reduced the OCR. These results indicate that CAM suppresses the IL-8 production via the mitochondrial quality control regulated by temporary functional inhibition of NIPSNAP1 and 2. Our findings provide new insight into the mechanisms underlying cytokine production, including the TLR-mitochondria axis, and the immunomodulatory effects of macrolides.

Advancing Biomarker Discovery and Therapeutic Targets in Duchenne Muscular Dystrophy: A Comprehensive Review

Mounting evidence underscores the intricate interplay between the immune system and skeletal muscles in Duchenne muscular dystrophy (DMD), as well as during regular muscle regeneration. While immune cell infiltration into skeletal muscles stands out as a prominent feature in the disease pathophysiology, a myriad of secondary defects involving metabolic and inflammatory pathways persist, with the key players yet to be fully elucidated. Steroids, currently the sole effective therapy for delaying onset and symptom control, come with adverse side effects, limiting their widespread use. Preliminary evidence spotlighting the distinctive features of T cell profiling in DMD prompts the immuno-characterization of circulating cells. A molecular analysis of their transcriptome and secretome holds the promise of identifying a subpopulation of cells suitable as disease biomarkers. Furthermore, it provides a gateway to unraveling new pathological pathways and pinpointing potential therapeutic targets. Simultaneously, the last decade has witnessed the emergence of novel approaches. The development and equilibrium of both innate and adaptive immune systems are intricately linked to the gut microbiota. Modulating microbiota-derived metabolites could potentially exacerbate muscle damage through immune system activation. Concurrently, genome sequencing has conferred clinical utility for rare disease diagnosis since innovative methodologies have been deployed to interpret the functional consequences of genomic variations. Despite numerous genes falling short as clinical targets for MD, the exploration of Tdark genes holds promise for unearthing novel and uncharted therapeutic insights. In the quest to expedite the translation of fundamental knowledge into clinical applications, the identification of novel biomarkers and disease targets is paramount. This initiative not only advances our understanding but also paves the way for the design of innovative therapeutic strategies, contributing to enhanced care for individuals grappling with these incapacitating diseases.

Nipsnap1-A regulatory factor required for long-term maintenance of non-shivering thermogenesis

OBJECTIVE

The activation of non-shivering thermogenesis (NST) has strong potential to combat obesity and metabolic disease. The activation of NST however is extremely temporal and the mechanisms surrounding how the benefits of NST are sustained once fully activated, remain unexplored. The objective of this study is to investigate the role of 4-Nitrophenylphosphatase Domain and Non-Neuronal SNAP25-Like 1 (Nipsnap1) in NST maintenance, which is a critical regulator identified in this study.

METHODS

The expression of Nipsnap1 was profiled by immunoblotting and RT-qPCR. We generated Nipsnap1 knockout mice (N1-KO) and investigated the function of Nipsnap1 in NST maintenance and whole-body metabolism using whole body respirometry analyses. We evaluate the metabolic regulatory role of Nipsnap1 using cellular and mitochondrial respiration assay.

RESULTS

Here, we show Nipsnap1 as a critical regulator of long-term thermogenic maintenance in brown adipose tissue (BAT). Nipsnap1 localizes to the mitochondrial matrix and increases its transcript and protein levels in response to both chronic cold and β3 adrenergic signaling. We demonstrated that these mice are unable to sustain activated energy expenditure and have significantly lower body temperature in the face of an extended cold challenge. Furthermore, when mice are exposed to the pharmacological β3 agonist CL 316, 243, the N1-KO mice exhibit significant hyperphagia and altered energy balance. Mechanistically, we demonstrate that Nipsnap1 integrates with lipid metabolism and BAT-specific ablation of Nipsnap1 leads to severe defects in beta-oxidation capacity when exposed to a cold environmental challenge.

CONCLUSION

Our findings identify Nipsnap1 as a potent regulator of long-term NST maintenance in BAT.

NIPSNAP1 directs dual mechanisms to restrain senescence in cancer cells

BACKGROUND

Although the executive pathways of senescence are known, the underlying control mechanisms are diverse and not fully understood, particularly how cancer cells avoid triggering senescence despite experiencing exacerbated stress conditions within the tumor microenvironment.

METHODS

Mass spectrometry (MS)-based proteomic screening was used to identify differentially regulated genes in serum-starved hepatocellular carcinoma cells and RNAi employed to determine knockdown phenotypes of prioritized genes. Thereafter, gene function was investigated using cell proliferation assays (colony-formation, CCK-8, Edu incorporation and cell cycle) together with cellular senescence assays (SA-β-gal, SAHF and SASP). Gene overexpression and knockdown techniques were applied to examine mRNA and protein regulation in combination with luciferase reporter and proteasome degradation assays, respectively. Flow cytometry was applied to detect changes in cellular reactive oxygen species (ROS) and in vivo gene function examined using a xenograft model.

RESULTS

Among the genes induced by serum deprivation, NIPSNAP1 was selected for investigation. Subsequent experiments revealed that NIPSNAP1 promotes cancer cell proliferation and inhibits P27-dependent induction of senescence via dual mechanisms. Firstly, NIPSNAP1 maintains the levels of c-Myc by sequestering the E3 ubiquitin ligase FBXL14 to prevent the proteasome-mediated turnover of c-Myc. Intriguingly, NIPSNAP1 levels are restrained by transcriptional repression mediated by c-Myc-Miz1, with repression lifted in response to serum withdrawal, thus identifying feedback regulation between NIPSNAP1 and c-Myc. Secondly, NIPSNAP1 was shown to modulate ROS levels by promoting interactions between the deacetylase SIRT3 and superoxide dismutase 2 (SOD2). Consequent activation of SOD2 serves to maintain cellular ROS levels below the critical levels required to induce cell cycle arrest and senescence. Importantly, the actions of NIPSNAP1 in promoting cancer cell proliferation and preventing senescence were recapitulated in vivo using xenograft models.

CONCLUSIONS

Together, these findings reveal NIPSNAP1 as an important mediator of c-Myc function and a negative regulator of cellular senescence. These findings also provide a theoretical basis for cancer therapy where targeting NIPSNAP1 invokes cellular senescence.

Genomic, transcriptomic, and metabolomic analysis of Oldenlandia corymbosa reveals the biosynthesis and mode of action of anti-cancer metabolites

Plants accumulate a vast array of secondary metabolites, which constitute a natural resource for pharmaceuticals. Oldenlandia corymbosa belongs to the Rubiaceae family, and has been used in traditional medicine to treat different diseases, including cancer. However, the active metabolites of the plant, their biosynthetic pathway and mode of action in cancer are unknown. To fill these gaps, we exposed this plant to eight different stress conditions and combined different omics data capturing gene expression, metabolic profiles, and anti-cancer activity. Our results show that O. corymbosa extracts are active against breast cancer cell lines and that ursolic acid is responsible for this activity. Moreover, we assembled a high-quality genome and uncovered two genes involved in the biosynthesis of ursolic acid. Finally, we also revealed that ursolic acid causes mitotic catastrophe in cancer cells and identified three high-confidence protein binding targets by Cellular Thermal Shift Assay (CETSA) and reverse docking. Altogether, these results constitute a valuable resource to further characterize the biosynthesis of active metabolites in the Oldenlandia group, while the mode of action of ursolic acid will allow us to further develop this valuable compound.

Rabbit Antidiethoxyphosphotyrosine Antibody, Made by Single B Cell Cloning, Detects Chlorpyrifos Oxon-Modified Proteins in Cultured Cells and Immunopurifies Modified Peptides for Mass Spectrometry

Chronic low-dose exposure to organophosphorus pesticides is associated with the risk of neurodegenerative disease. The mechanism of neurotoxicity is independent of acetylcholinesterase inhibition. Adducts on tyrosine, lysine, threonine, and serine can occur after exposure to organophosphorus pesticides, the most stable being adducts on tyrosine. Rabbit monoclonal 1C6 to diethoxyphosphate-modified tyrosine (depY) was created by single B cell cloning. The amino acid sequence and binding constant (K_d 3.2 × 10^–8 M) were determined. Cultured human neuroblastoma SH-SY5Y and mouse neuroblastoma N2a cells incubated with a subcytotoxic dose of 10 μM chlorpyrifos oxon contained depY-modified proteins detected by monoclonal 1C6 on Western blots. depY-labeled peptides from tryptic digests of cell lysates were immunopurified by binding to immobilized 1C6. Peptides released with 50% acetonitrile and 1% formic acid were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) on an Orbitrap Fusion Lumos mass spectrometer. Protein Prospector database searches identified 51 peptides modified on tyrosine by diethoxyphosphate in SH-SY5Y cell lysate and 73 diethoxyphosphate-modified peptides in N2a cell lysate. Adducts appeared most frequently on the cytoskeleton proteins tubulin, actin, and vimentin. It was concluded that rabbit monoclonal 1C6 can be useful for studies that aim to understand the mechanism of neurotoxicity resulting from low-dose exposure to organophosphorus pesticides.