A mitochondrial unfolded protein response inhibitor suppresses prostate cancer growth in mice via HSP60

The interconnective role of the UPS and autophagy in the quality control of cancer mitochondria

Uncontrollable cancer cell growth is characterized by the maintenance of cellular homeostasis through the continuous accumulation of misfolded proteins and damaged organelles. This review delineates the roles of two complementary and synergistic degradation systems, the ubiquitin-proteasome system (UPS) and the autophagy-lysosome system, in the degradation of misfolded proteins and damaged organelles for intracellular recycling. We emphasize the interconnected decision-making processes of degradation systems in maintaining cellular homeostasis, such as the biophysical state of substrates, receptor oligomerization potentials (e.g., p62), and compartmentalization capacities (e.g., membrane structures). Mitochondria, the cellular hubs for respiration and metabolism, are implicated in tumorigenesis. In the subsequent sections, we thoroughly examine the mechanisms of mitochondrial quality control (MQC) in preserving mitochondrial homeostasis in human cells. Notably, we explored the relationships between mitochondrial dynamics (fusion and fission) and various MQC processes-including the UPS, mitochondrial proteases, and mitophagy-in the context of mitochondrial repair and degradation pathways. Finally, we assessed the potential of targeting MQC (including UPS, mitochondrial molecular chaperones, mitochondrial proteases, mitochondrial dynamics, mitophagy and mitochondrial biogenesis) as cancer therapeutic strategies. Understanding the mechanisms underlying mitochondrial homeostasis may offer novel insights for future cancer therapies.

Mitochondrial unfolded protein response-dependent β-catenin signaling promotes neuroendocrine prostate cancer

The mitochondrial unfolded protein response (UPRmt) maintains mitochondrial quality control and proteostasis under stress conditions. However, the role of UPRmt in aggressive and resistant prostate cancer is not clearly defined. We show that castration-resistant neuroendocrine prostate cancer (CRPC-NE) harbored highly dysfunctional oxidative phosphorylation (OXPHOS) Complexes. However, biochemical and protein analyses of CRPC-NE tumors showed upregulation of nuclear-encoded OXPHOS proteins and UPRmt in this lethal subset of prostate cancer suggestive of compensatory upregulation of stress signaling. Genetic deletion and pharmacological inhibition of the main chaperone of UPRmt heat shock protein 60 (HSP60) reduced neuroendocrine prostate cancer (NEPC) growth in vivo as well as reverted NEPC cells to a more epithelial-like state. HSP60-dependent aggressive NEPC phenotypes was associated with upregulation of β-catenin signaling both in cancer cells and in vivo tumors. HSP60 expression rendered enrichment of aggressive prostate cancer signatures and metastatic potential were inhibited upon suppression of UPRmt. We discovered that UPRmt promoted OXPHOS functions including mitochondrial bioenergetics in CRPC-NE via regulation of β-catenin signaling. Mitochondrial biogenesis facilitated cisplatin resistance and inhibition of UPRmt resensitizes CRPC-NE cells to cisplatin. Together, our findings demonstrated that UPRmt promotes mitochondrial health via upregulating β-catenin signaling and UPRmt represents viable therapeutic target for NEPC.

Fluoride stimulates the MAPK pathway to regulate endoplasmic reticulum stress and heat shock proteins to induce duodenal toxicity in chickens

Fluoride is one of the essential trace elements for body. However, excessive fluoride poses a major threat to human and animal health. Fluorosis may cause pathological damage of the duodenum, but the underlying mechanism needs to be further studied. This study was to investigate the effects of long-term exposure to sodium fluoride (0, 500, 1,000, 2,000 mg/kg) on the duodenum of chickens. The results showed that after NaF exposure, intestinal epithelial cells were disarranged, necrotic or even exfoliated, goblet cells and mucus secretion were increased, and inflammatory response was induced in duodenal tissue. Oxidative stress, endoplasmic reticulum stress (ERs), and heat shock proteins (HSPs) are an adaptive response, however long-term, excessive changes are detrimental. Fluorosis activates ERs through IRE1, PERK and ATF6 pathways, increases the expression of HSP60, HSP70 and HSP90, and causes apoptosis and oxidative damage in duodenal tissue. In addition, fluorosis can activate the MAPK signaling pathway. This article can provide a reference for exploring the potential duodenal toxicity of sodium fluoride.

Patenting perspective of modulators of ClpP endopeptidase: 2019-present

INTRODUCTION

ClpP is a highly conserved serine protease that plays a crucial role in maintaining protein homeostasis in both bacterial cells and human mitochondria. Several studies have demonstrated the potential of ClpP as a drug target, with ClpP modulators, including both inhibitors and activators, showing promise in treating a range of conditions such as drug-resistant bacteria, malignant cancers, and fatty liver disease.

AREA COVERED

This review provides an overview of patents related to ClpP modulators filed over the last five years, detailing their claims and therapeutic applications. The sources of patent information included databases of the European Patent Office, the China Patent Office and the U.S.A. patent Office, while relevant research articles were accessed through PubMed.

EXPERT OPINION

The number of patents concerning ClpP modulators is on the rise, reflecting advancements in related research. By summarizing and outlining relevant patents, we aim to stimulate further interest among researchers, ultimately leading to the development of effective drugs based on ClpP modulators. The broad spectrum of diseases associated with ClpP dysfunction underscores the potential for ClpP modulators to address a wide range of therapeutic needs.

Salvianolic acid B improves mitochondrial dysfunction of septic cardiomyopathy via enhancing ATF5-mediated mitochondrial unfolded protein response

AIMS

Septic cardiomyopathy is characterized by impaired contractile function and mitochondrial activity dysregulation. Salvianolic acid B (Sal B) is a potent therapeutic compound derived from the traditional Chinese medicine Salvia miltiorrhiza. This study explored the protective effects of Sal B on septic heart injury, emphasizing the mitochondrial unfolded protein response (UPRmt).

MATERIALS AND METHODS

An in vivo mouse model of lipopolysaccharide (LPS)-induced heart injury was utilized to assess Sal B's protective role in septic cardiomyopathy. Additionally, cell models stimulated by LPS were developed to investigate the mechanisms of Sal B on UPRmt. Quantitative polymerase chain reaction, western blotting, immunohistochemistry, and immunofluorescence were employed for molecular analysis.

RESULTS

Sal B, administered at doses of 10, 30, and 60 mg/kg, demonstrated protective effects on cardiac contractile function, reduced heart inflammation, and mitigated cardiac injury in LPS-exposed mice. In cardiomyocytes, LPS induced apoptosis, elevated mitochondrial ROS levels, promoted mitochondrial fission, and decreased mitochondrial membrane potential, all of which were alleviated by Sal B. Mechanistically, Sal B was found to induce UPRmt both in vivo and in vitro. ATF5, identified as a UPRmt activator, was modulated by LPS and Sal B, resulting in increased ATF5 expression and its translocation from the cytosol to the nucleus. ATF5-siRNA delivery reversed UPRmt upregulation, exacerbating mitochondrial dysfunction in LPS-stimulated cardiomyocytes and counteracting the mitochondrial function enhancement in Sal B-treated cardiomyocytes.

CONCLUSIONS

This study provides evidence that Sal B confers cardiac protection by enhancing UPRmt, highlighting its potential as a therapeutic approach for mitigating mitochondrial dysfunction in septic cardiomyopathy.

HSPD1 Supports Osteosarcoma Progression through Stabilizing ATP5A1 and thus Activation of AKT/mTOR Signaling

Malignant transformation is concomitant with excessive activation of stress response pathways. Heat shock proteins (HSPs) are stress-inducible proteins that play a role in folding and processing proteins, contributing to the non-oncogene addiction of stressed tumor cells. However, the detailed role of the HSP family in osteosarcoma has not been investigated. Bulk and single-cell transcriptomic data from the GEO and TARGET databases were used to identify HSPs associated with prognosis in osteosarcoma patients. The expression level of HSPD1 was markedly increased in osteosarcoma, correlating with a negative prognosis. Through in vitro and in vivo experiments, we systematically identified HSPD1 as an important contributor to the regulation of proliferation, metastasis, and apoptosis in osteosarcoma by promoting the epithelial-mesenchymal transition (EMT) and activating AKT/mTOR signaling. Subsequently, ATP5A1 was determined as a potential target of HSPD1 using immunoprecipitation followed by mass spectrometry. Mechanistically, HSPD1 may interact with ATP5A1 to reduce the K48-linked ubiquitination and degradation of ATP5A1, which ultimately activates the AKT/mTOR pathway to ensure osteosarcoma progression and EMT process. These findings expand the potential mechanisms by which HSPD1 exerts biological effects and provide strong evidence for its inclusion as a potential therapeutic target in osteosarcoma.

Targeting PRMT3 impairs methylation and oligomerization of HSP60 to boost anti-tumor immunity by activating cGAS/STING signaling

Immune checkpoint blockade (ICB) has emerged as a promising therapeutic option for hepatocellular carcinoma (HCC), but resistance to ICB occurs and patient responses vary. Here, we uncover protein arginine methyltransferase 3 (PRMT3) as a driver for immunotherapy resistance in HCC. We show that PRMT3 expression is induced by ICB-activated T cells via an interferon-gamma (IFNγ)-STAT1 signaling pathway, and higher PRMT3 expression levels correlate with reduced numbers of tumor-infiltrating CD8+ T cells and poorer response to ICB. Genetic depletion or pharmacological inhibition of PRMT3 elicits an influx of T cells into tumors and reduces tumor size in HCC mouse models. Mechanistically, PRMT3 methylates HSP60 at R446 to induce HSP60 oligomerization and maintain mitochondrial homeostasis. Targeting PRMT3-dependent HSP60 methylation disrupts mitochondrial integrity and increases mitochondrial DNA (mtDNA) leakage, which results in cGAS/STING-mediated anti-tumor immunity. Lastly, blocking PRMT3 functions synergize with PD-1 blockade in HCC mouse models. Our study thus identifies PRMT3 as a potential biomarker and therapeutic target to overcome immunotherapy resistance in HCC.

Mitochondrial Chaperone Code: Just warming up

More than 99% of the mitochondrial proteome is encoded by the nucleus and requires refolding following import. Therefore, mitochondrial proteins require the coordinated action of molecular chaperones for their folding and activation. Several heat shock protein (Hsp) molecular chaperones, including members of the Hsp27, Hsp40/70, and Hsp90 families, as well as the chaperonin complex Hsp60/10 have an established role in mitochondrial protein import and folding. The "Chaperone Code" describes the regulation of chaperone activity by dynamic post-translational modifications; however, little is known about the post-translational regulation of mitochondrial chaperones. Dissecting the regulation of chaperone function is essential for understanding their differential regulation in pathogenic conditions and the potential development of efficacious therapeutic strategies. Here, we summarize the recent literature on post-translational regulation of mitochondrial chaperones, the consequences for mitochondrial function, and potential implications for disease.

Mitochondrial unfolded protein response (UPRmt): what we know thus far

Mitochondria are key organelles for the optimal function of the cell. Among their many functions, they maintain protein homeostasis through their own proteostatic machinery, which involves proteases and chaperones that regulate protein import and folding inside mitochondria. In the early 2000s, the mitochondrial unfolded protein response (UPRmt) was first described in mammalian cells. This stress response is activated by the accumulation of unfolded/misfolded proteins within the mitochondrial matrix, which results in the transmission of a signal to the nucleus to increase the expression of proteases and chaperones to address the abnormal mitochondrial protein load. After its discovery, this retrograde signaling pathway has also been described in other organisms of different complexities, suggesting that it is a conserved stress response. Although there are some specific differences among organisms, the mechanism of this stress response is mostly similar and involves the transmission of a signal from mitochondria to the nucleus that induces chromatin remodeling to allow the binding of specific transcription factors to the promoters of chaperones and proteases. In the last decade, proteins and signaling pathways that could be involved in the regulation of the UPRmt, including the Wnt signaling pathway, have been described. This minireview aims to summarize what is known about the mechanism of the UPRmt and its regulation, specifically in mammals and C. elegans.

Knockout Mouse Studies Show That Mitochondrial CLPP Peptidase and CLPX Unfoldase Act in Matrix Condensates near IMM, as Fast Stress Response in Protein Assemblies for Transcript Processing, Translation, and Heme Production

LONP1 is the principal AAA+ unfoldase and bulk protease in the mitochondrial matrix, so its deletion causes embryonic lethality. The AAA+ unfoldase CLPX and the peptidase CLPP also act in the matrix, especially during stress periods, but their substrates are poorly defined. Mammalian CLPP deletion triggers infertility, deafness, growth retardation, and cGAS-STING-activated cytosolic innate immunity. CLPX mutations impair heme biosynthesis and heavy metal homeostasis. CLPP and CLPX are conserved from bacteria to humans, despite their secondary role in proteolysis. Based on recent proteomic-metabolomic evidence from knockout mice and patient cells, we propose that CLPP acts on phase-separated ribonucleoprotein granules and CLPX on multi-enzyme condensates as first-aid systems near the inner mitochondrial membrane. Trimming within assemblies, CLPP rescues stalled processes in mitoribosomes, mitochondrial RNA granules and nucleoids, and the D-foci-mediated degradation of toxic double-stranded mtRNA/mtDNA. Unfolding multi-enzyme condensates, CLPX maximizes PLP-dependent delta-transamination and rescues malformed nascent peptides. Overall, their actions occur in granules with multivalent or hydrophobic interactions, separated from the aqueous phase. Thus, the role of CLPXP in the matrix is compartment-selective, as other mitochondrial peptidases: MPPs at precursor import pores, m-AAA and i-AAA at either IMM face, PARL within the IMM, and OMA1/HTRA2 in the intermembrane space.

Molecular Chaperonin HSP60: Current Understanding and Future Prospects

Molecular chaperones are highly conserved across evolution and play a crucial role in preserving protein homeostasis. The 60 kDa heat shock protein (HSP60), also referred to as chaperonin 60 (Cpn60), resides within mitochondria and is involved in maintaining the organelle's proteome integrity and homeostasis. The HSP60 family, encompassing Cpn60, plays diverse roles in cellular processes, including protein folding, cell signaling, and managing high-temperature stress. In prokaryotes, HSP60 is well understood as a GroEL/GroES complex, which forms a double-ring cavity and aids in protein folding. In eukaryotes, HSP60 is implicated in numerous biological functions, like facilitating the folding of native proteins and influencing disease and development processes. Notably, research highlights its critical involvement in sustaining oxidative stress and preserving mitochondrial integrity. HSP60 perturbation results in the loss of the mitochondria integrity and activates apoptosis. Currently, numerous clinical investigations are in progress to explore targeting HSP60 both in vivo and in vitro across various disease models. These studies aim to enhance our comprehension of disease mechanisms and potentially harness HSP60 as a therapeutic target for various conditions, including cancer, inflammatory disorders, and neurodegenerative diseases. This review delves into the diverse functions of HSP60 in regulating proteo-homeostasis, oxidative stress, ROS, apoptosis, and its implications in diseases like cancer and neurodegeneration.

Endoplasmic reticulum stress responses and epigenetic alterations in arsenic carcinogenesis

Arsenic is a well-known human carcinogen whose environmental exposure via drinking water, food, and air impacts millions of people across the globe. Various mechanisms of arsenic carcinogenesis have been identified, ranging from damage caused by excessive production of free radicals and epigenetic alterations to the generation of cancer stem cells. A growing body of evidence supports the critical involvement of the endoplasmic stress-activated unfolded protein response (UPR) in promoting as well as suppressing cancer development/progression. Various in vitro and in vivo models have also demonstrated that arsenic induces the UPR via activation of the PERK, IRE1α, and ATF6 proteins. In this review, we discuss the mechanisms of arsenic-induced endoplasmic reticulum stress and the role of each UPR pathway in the various cancer types with a focus on the epigenetic regulation and function of the ATF6 protein. The importance of UPR in arsenic carcinogenesis and cancer stem cells is a relatively new area of research that requires additional investigations via various omics-based and computational tools. These approaches will provide interesting insights into the mechanisms of arsenic-induced cancers for prospective target identification and development of novel anti-cancer therapies.

Mitochondrial dysfunction and quality control lie at the heart of subarachnoid hemorrhage

The dramatic increase in intracranial pressure after subarachnoid hemorrhage leads to a decrease in cerebral perfusion pressure and a reduction in cerebral blood flow. Mitochondria are directly affected by direct factors such as ischemia, hypoxia, excitotoxicity, and toxicity of free hemoglobin and its degradation products, which trigger mitochondrial dysfunction. Dysfunctional mitochondria release large amounts of reactive oxygen species, inflammatory mediators, and apoptotic proteins that activate apoptotic pathways, further damaging cells. In response to this array of damage, cells have adopted multiple mitochondrial quality control mechanisms through evolution, including mitochondrial protein quality control, mitochondrial dynamics, mitophagy, mitochondrial biogenesis, and intercellular mitochondrial transfer, to maintain mitochondrial homeostasis under pathological conditions. Specific interventions targeting mitochondrial quality control mechanisms have emerged as promising therapeutic strategies for subarachnoid hemorrhage. This review provides an overview of recent research advances in mitochondrial pathophysiological processes after subarachnoid hemorrhage, particularly mitochondrial quality control mechanisms. It also presents potential therapeutic strategies to target mitochondrial quality control in subarachnoid hemorrhage.

PQR309, a dual PI3K/mTOR inhibitor, synergizes with gemcitabine by impairing the GSK-3β and STAT3/HSP60 signaling pathways to treat nasopharyngeal carcinoma

End-stage nasopharyngeal carcinoma (NPC) has unsatisfactory survival. The limited benefit of chemotherapy and the scarcity of targeted drugs are major challenges in NPC. New approaches to treat late-stage NPC are urgently required. In this study, we explored whether the dual PI3K/mTOR inhibitor, PQR309, exerted a favorable antineoplastic effect and sensitized the response to gemcitabine in NPC. We observed that PI3K expression was positive and elevated in 14 NPC cell lines compared with that in normal nasopharygeal cell lines. Patients with NPC with higher PI3K levels displayed poorer prognosis. We subsequently showed that PQR309 alone effectively decreased the viability, invasiveness, and migratory capability of NPC cells and neoplasm development in mice xenograft models, and dose-dependently induced apoptosis. More importantly, PQR309 remarkably strengthened the anti-NPC function of gemcitabine both in vivo and in vitro. Mechanistically, PQR309 sensitized NPC to gemcitabine by increasing caspase pathway-dependent apoptosis, blocking GSK-3β and STAT3/HSP60 signaling, and ablating epithelial-mesenchyme transition. Thus, targeting PI3K/mTOR using PQR309 might represent a treatment option to promote the response to gemcitabine in NPC, and provides a theoretical foundation for the study of targeted drugs combined with chemotherapy for NPC.

Microvascular rarefaction caused by the NOTCH signaling pathway is a key cause of TKI-apatinib-induced hypertension and cardiac damage

With the advancement of tumour-targeted therapy technology, the survival of cancer patients has continued to increase, and cardiovascular events have gradually become an important cause of death in cancer patients. This phenomenon occurs due to adverse cardiovascular reactions caused by the cardiovascular toxicity of antitumour therapy. Moreover, the increase in the proportion of elderly patients with cancer and cardiovascular diseases is due to the extension of life expectancy. Hypertension is the most common cardiovascular side effect of small molecule tyrosine kinase inhibitors (TKIs). The increase in blood pressure induced by TKIs and subsequent cardiovascular complications and events affect the survival and quality of life of patients and partly offset the benefits of antitumour therapy. Many studies have confirmed that in the pathogenesis of hypertension, arterioles and capillary thinness are involved in its occurrence and development. Our previous findings showing that apatinib causes microcirculation rarefaction of the superior mesenteric artery and impaired microvascular growth may inspire new therapeutic strategies for treating hypertension. Thus, by restoring microvascular development and branching patterns, total peripheral resistance and blood pressure are reduced. Therefore, exploring the key molecular targets of TKIs that inhibit the expression of angiogenic factors and elucidating the specific molecular mechanism involved are key scientific avenues for effectively promoting endothelial cell angiogenesis and achieving accurate repair of microcirculation injury in hypertension patients.

Mitochondrial Stress and Mitokines: Therapeutic Perspectives for the Treatment of Metabolic Diseases

Mitochondrial stress and the dysregulated mitochondrial unfolded protein response (UPRmt) are linked to various diseases, including metabolic disorders, neurodegenerative diseases, and cancer. Mitokines, signaling molecules released by mitochondrial stress response and UPRmt, are crucial mediators of inter-organ communication and influence systemic metabolic and physiological processes. In this review, we provide a comprehensive overview of mitokines, including their regulation by exercise and lifestyle interventions and their implications for various diseases. The endocrine actions of mitokines related to mitochondrial stress and adaptations are highlighted, specifically the broad functions of fibroblast growth factor 21 and growth differentiation factor 15, as well as their specific actions in regulating inter-tissue communication and metabolic homeostasis. Finally, we discuss the potential of physiological and genetic interventions to reduce the hazards associated with dysregulated mitokine signaling and preserve an equilibrium in mitochondrial stress-induced responses. This review provides valuable insights into the mechanisms underlying mitochondrial regulation of health and disease by exploring mitokine interactions and their regulation, which will facilitate the development of targeted therapies and personalized interventions to improve health outcomes and quality of life.

A new insight into fluoride induces cardiotoxicity in chickens: Involving the regulation of PERK/IRE1/ATF6 pathway and heat shock proteins

Fluorosis poses a significant threat to human and animal health and is an urgent public safety concern in various countries. Subchronic exposure to fluoride has the potential to result in pathological damage to the heart, but its potential mechanism requires further investigation. This study investigated the effects of long-term exposure to sodium fluoride (0, 500, 1000, and 2000 mg/kg) on the hearts of chickens were investigated. The results showed that an elevated exposure dose of sodium fluoride led to congested cardiac tissue and disrupted myofiber organisation. Sodium fluoride exposure activated the ERS pathways of PERK, IRE1, and ATF6, increasing HSP60 and HSP70 and decreasing HSP90. The NF-κB pathway and the activation of TNF-α and iNOS elicited an inflammatory response. BAX, cytc, and cleaved-caspase3 were increased, triggering apoptosis and leading to cardiac injury. The abnormal expression of HSP90 and HSP70 affected the stability and function of RIPK1, RIPK3, and MLKL, which are crucial necroptosis markers. HSPs inhibited TNF-α-mediated necroptosis and apoptosis of the death receptor pathway. Sodium fluoride resulted in heart injury in chickens because of the ERS and variations in HSPs, inducing inflammation and apoptosis. Cardiac-adapted HSPs impeded the activation of necroptosis. This paper may provide a reference for examining the potential cardiotoxic effects of sodium fluoride.

The role of heat shock proteins in the pathogenesis of heart failure (Review)

The influence of heat shock proteins (HSPs) on protein quality control systems in cardiomyocytes is currently under investigation. The effect of HSPs on the regulated cell death of cardiomyocytes (CMCs) is of great importance, since they play a major role in the implementation of compensatory and adaptive mechanisms in the event of cardiac damage. HSPs mediate a number of mechanisms that activate the apoptotic cascade, playing both pro‑ and anti‑apoptotic roles depending on their location in the cell. Another type of cell death, autophagy, can in some cases lead to cell death, while in other situations it acts as a cell survival mechanism. The present review considered the characteristics of the expression of HSPs of different molecular weights in CMCs in myocardial damage caused by heart failure, as well as their role in the realization of certain types of regulated cell death.

Identification of the mitochondrial protein POLRMT as a potential therapeutic target of prostate cancer

RNA polymerase mitochondria (POLRMT) is essential for mitochondrial transcription machinery and other mitochondrial functions. Its expression and potential functions in prostate cancer were explored here. The Cancer Genome Atlas prostate cancer cohort (TCGA PRAD) shows that POLRMT mRNA expression is upregulated in prostate cancer tissues and POLRMT upregulation is correlated with poor patients' survival. POLRMT mRNA and protein levels were upregulated in local prostate cancer tissues and different primary/immortalized prostate cancer cells. Genetic depletion of POLRMT, using viral shRNA or CRISPR/Cas9 gene editing methods, impaired mitochondrial functions in prostate cancer cells, leading to mitochondrial depolarization, oxidative stress, mitochondria complex I inhibition, and ATP depletion. Moreover, POLRMT depletion resulted in robust inhibition of prostate cancer cell viability, proliferation, and migration, and provoked apoptosis. Conversely, prostate cancer cell proliferation, migration, and ATP contents were strengthened following ectopic POLRMT overexpression. In vivo, intratumoral injection of POLRMT shRNA adeno-associated virus impeded prostate cancer xenograft growth in nude mice. POLRMT silencing, oxidative stress, and ATP depletion were detected in POLRMT shRNA-treated prostate cancer xenograft tissues. IMT1 (inhibitor of mitochondrial transcription 1), the first-in-class POLRMT inhibitor, inhibited prostate cancer cell growth in vitro and in vivo. Together, overexpressed POLRMT is an important mitochondrial protein for prostate cancer cell growth, representing a novel and promising diagnostic and therapeutic oncotarget.

Mitochondrial oxidative stress regulates LonP1-TDP-43 pathway and rises mitochondrial damage in carbon tetrachloride-induced liver fibrosis

Carbon tetrachloride (CCl4)-mediated liver damage has been well recognized, but the sources and mechanisms of mitochondrial damage during this progress still remain poorly understood. Accumulating evidence has revealed that LonP1-TDP-43 pathway affect proper mitochondrial integrity and function in neurodegenerative diseases. The current study aims to investigate whether mitochondrial oxidative stress regulate LonP1-TDP-43 pathway and the possible roles of this pathway in CCl4-driven liver fibrosis. We found that TDP-43 interacted with LonP1 in chronic CCl4 exposure-induced hepatic fibrogenesis. Moreover, CCl4 led to deficiency of LonP1 and excessive accumulation of TDP-43 on mitochondria. Particularly, the gene correlation analysis for liver fibrosis patients RNA sequencing (RNA-seq) results (GSE159676) showed an obvious negative correlation between LonP1 and TDP-43. By contrast, MitoQ enhanced the occurrence of mitochondrial unfolded protein response (mtUPR), especially the activation of LonP1 after CCl4 treatment. Importantly, mitochondrial antioxidant also promoted the degradation of TDP-43 and alleviated mitochondrial damage. In addition, our results showed that CCl4 induced the release of mitochondrial DNA (mtDNA) and effectively elevated cGAS-STING-mediated immune response, which can be inhibited by MitoQ. Finally, MitoQ prevented CCl4-induced liver fibrosis. Together, our study revealed that LonP1-TDP-43 pathway mediated by mitochondrial oxidative stress participated in the progress of CCl4-drived liver fibrosis. Therefore, mitigating or reversing mitochondrial damage through targeting LonP1-TDP-43 pathway may serve as a promising therapeutic strategy for CCl4 exposure-induced liver diseases.

Glutamine supplementation reverses manganese neurotoxicity by eliciting the mitochondrial unfolded protein response

Excessive exposure to manganese (Mn) can cause neurological abnormalities, but the mechanism of Mn neurotoxicity remains unclear. Previous studies have shown that abnormal mitochondrial metabolism is a crucial mechanism underlying Mn neurotoxicity. Therefore, improving neurometabolic in neuronal mitochondria may be a potential therapy for Mn neurotoxicity. Here, single-cell sequencing revealed that Mn affected mitochondrial neurometabolic pathways and unfolded protein response in zebrafish dopaminergic neurons. Metabolomic analysis indicated that Mn inhibited the glutathione metabolic pathway in human neuroblastoma (SH-SY5Y) cells. Mechanistically, Mn exposure inhibited glutathione (GSH) and mitochondrial unfolded protein response (UPR^mt). Furthermore, supplementation with glutamine (Gln) can effectively increase the concentration of GSH and triggered UPR^mt which can alleviate mitochondrial dysfunction and counteract the neurotoxicity of Mn. Our findings highlight that UPR^mt is involved in Mn-induced neurotoxicity and glutathione metabolic pathway affects UPR^mt to reverse Mn neurotoxicity. In addition, Gln supplementation may have potential therapeutic benefits for Mn-related neurological disorders.

Chaperonin counteracts diet-induced non-alcoholic fatty liver disease by aiding sirtuin 3 in the control of fatty acid oxidation

AIMS/HYPOTHESIS

The mitochondrial chaperonin heat shock protein (HSP) 60 is indispensable in protein folding and the mitochondrial stress response; however, its role in nutrient metabolism remains uncertain. This study investigated the role of HSP60 in diet-induced non-alcoholic fatty liver disease (NAFLD).

METHODS

We studied human biopsies from individuals with NAFLD, murine high-fat-diet (HFD; a diet with 60% energy from fat)-induced obesity (DIO), transgenic (Tg) mice overexpressing Hsp60 (Hsp60-Tg), and human HepG2 cells transfected with HSP60 cDNA or with HSP60 siRNA. Histomorphometry was used to assess hepatic steatosis, biochemistry kits were used to measure insulin resistance and glucose tolerance, and an automated home cage phenotyping system was used to assess energy expenditure. Body fat was assessed using MRI. Macrophage infiltration, the lipid oxidation marker 4-hydroxy-2-nonenal (4-HNE) and the oxidative damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) were detected using immunohistochemistry. Intracellular lipid droplets were evaluated by Nile red staining. Expression of HSP60, and markers of lipogenesis and fatty acid oxidation were quantified using RT-PCR and immunoblotting. Investigations were analysed using the two-way ANOVA test.

RESULTS

Decreased HSP60 expression correlated with severe steatosis in human NAFLD biopsies and murine DIO. Hsp60-Tg mice developed less body fat, had reduced serum triglyceride levels, lower levels of insulin resistance and higher serum adiponectin levels than wild-type mice upon HFD feeding. Respiratory quotient profile indicated that fat in Hsp60-Tg mice may be metabolised to meet energy demands. Hsp60-Tg mice showed amelioration of HFD-mediated hepatic steatosis, M1/M2 macrophage dysregulation, and 4-HNE and 8-OHdG overproduction. Forced HSP60 expression reduced the mitochondrial unfolded protein response, while preserving mitochondrial respiratory complex activity and enhancing fatty acid oxidation. Furthermore, HSP60 knockdown enhanced intracellular lipid formation and loss of sirtuin 3 (SIRT3) signalling in HepG2 cells upon incubation with palmitic acid (PA). Forced HSP60 expression improved SIRT3 signalling and repressed PA-mediated intracellular lipid formation. SIRT3 inhibition compromised HSP60-induced promotion of AMP-activated protein kinase (AMPK) phosphorylation and peroxisome proliferator-activated receptor α (PPARα levels), while also decreasing levels of fatty acid oxidation markers.

CONCLUSION/INTERPRETATION

Mitochondrial HSP60 promotes fatty acid oxidation while repressing mitochondrial stress and inflammation to ameliorate the development of NAFLD by preserving SIRT3 signalling. This study reveals the hepatoprotective effects of HSP60 and indicates that HSP60 could play a fundamental role in the development of therapeutics for NAFLD or type 2 diabetes.

Multi-omics analyses reveal ClpP activators disrupt essential mitochondrial pathways in triple-negative breast cancer

ClpP activators ONC201 and related small molecules (TR compounds, Madera Therapeutics), have demonstrated significant anti-cancer potential in vitro and in vivo studies, including clinical trials for refractory solid tumors. Though progress has been made in identifying specific phenotypic outcomes following ClpP activation, the exact mechanism by which ClpP activation leads to broad anti-cancer activity has yet to be fully elucidated. In this study, we utilized a multi-omics approach to identify the ClpP-dependent proteomic, transcriptomic, and metabolomic changes resulting from ONC201 or the TR compound TR-57 in triple-negative breast cancer cells. Applying mass spectrometry-based methods of proteomics and metabolomics, we identified ∼8,000 proteins and 588 metabolites, respectively. From proteomics data, 113 (ONC201) and 191 (TR-57) proteins significantly increased and 572 (ONC201) and 686 (TR-57) proteins significantly decreased in this study. Gene ontological (GO) analysis revealed strong similarities between proteins up- or downregulated by ONC201 or TR-57 treatment. Notably, this included the downregulation of many mitochondrial processes and proteins, including mitochondrial translation and mitochondrial matrix proteins. We performed a large-scale transcriptomic analysis of WT SUM159 cells, identifying ∼7,700 transcripts (746 and 1,100 significantly increasing, 795 and 1,013 significantly decreasing in ONC201 and TR-57 treated cells, respectively). Less than 21% of these genes were affected by these compounds in ClpP null cells. GO analysis of these data demonstrated additional similarity of response to ONC201 and TR-57, including a decrease in transcripts related to the mitochondrial inner membrane and matrix, cell cycle, and nucleus, and increases in other nuclear transcripts and transcripts related to metal-ion binding. Comparison of response between both compounds demonstrated a highly similar response in all -omics datasets. Analysis of metabolites also revealed significant similarities between ONC201 and TR-57 with increases in α-ketoglutarate and 2-hydroxyglutaric acid and decreased ureidosuccinic acid, L-ascorbic acid, L-serine, and cytidine observed following ClpP activation in TNBC cells. Further analysis identified multiple pathways that were specifically impacted by ClpP activation, including ATF4 activation, heme biosynthesis, and the citrulline/urea cycle. In summary the results of our studies demonstrate that ONC201 and TR-57 induce highly similar and broad effects against multiple mitochondrial processes required for cell proliferation.

Mitochondrial Alterations in Prostate Cancer: Roles in Pathobiology and Racial Disparities

Prostate cancer (PCa) affects millions of men worldwide and is a major cause of cancer-related mortality. Race-associated PCa health disparities are also common and are of both social and clinical concern. Most PCa is diagnosed early due to PSA-based screening, but it fails to discern between indolent and aggressive PCa. Androgen or androgen receptor-targeted therapies are standard care of treatment for locally advanced and metastatic disease, but therapy resistance is common. Mitochondria, the powerhouse of cells, are unique subcellular organelles that have their own genome. A large majority of mitochondrial proteins are, however, nuclear-encoded and imported after cytoplasmic translation. Mitochondrial alterations are common in cancer, including PCa, leading to their altered functions. Aberrant mitochondrial function affects nuclear gene expression in retrograde signaling and promotes tumor-supportive stromal remodeling. In this article, we discuss mitochondrial alterations that have been reported in PCa and review the literature related to their roles in PCa pathobiology, therapy resistance, and racial disparities. We also discuss the translational potential of mitochondrial alterations as prognostic biomarkers and as effective targets for PCa therapy.

Heat shock protein 60 in parasitic helminths: A role in immune responses and therapeutic applications

Heat shock protein 60 (HSP60) is an unique member of the heat shock protein family, being involved in parasite infections. To cope with harsh environments where parasites live, HSP60s are indispensable and involved in a variety of biological processes. HSP60s have relative low similarity among parasites, but their ATPase /Mg²⁺ active sites are highly conserved. The interactions of HSP60s with signaling pathway regulators in immune cells suggest a crucial role in immune responses, rendering them a potential therapeutic target. This paper reviews the current understandings of HSP60s in parasitic helminths in aspects of molecular characteristics, immunoregulatory responses and HSP60-based therapeutics.

Mitochondria inter-organelle relationships in cancer protein aggregation

Mitochondria are physically associated with other organelles, such as ER and lysosomes, forming a complex network that is crucial for cell homeostasis regulation. Inter-organelle relationships are finely regulated by both tether systems, which maintain physical proximity, and by signaling cues that induce the exchange of molecular information to regulate metabolism, Ca²⁺ homeostasis, redox state, nutrient availability, and proteostasis. The coordinated action of the organelles is engaged in the cellular integrated stress response. In any case, pathological conditions alter functional communication and efficient rescue pathway activation, leading to cell distress exacerbation and eventually cell death. Among these detrimental signals, misfolded protein accumulation and aggregation cause major damage to the cells, since defects in protein clearance systems worsen cell toxicity. A cause for protein aggregation is often a defective mitochondrial redox balance, and the ER freshly translated misfolded proteins and/or a deficient lysosome-mediated clearance system. All these features aggravate mitochondrial damage and enhance proteotoxic stress. This review aims to gather the current knowledge about the complex liaison between mitochondria, ER, and lysosomes in facing proteotoxic stress and protein aggregation, highlighting both causes and consequences. Particularly, specific focus will be pointed to cancer, a pathology in which inter-organelle relations in protein aggregation have been poorly investigated.

Mitochondrial unfolded protein response in ischemia-reperfusion injury

Mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that activates the transcriptional program of mitochondrial chaperone proteins and proteases to keep protein homeostasis in mitochondria. Ischemia-reperfusion injury results in multiple severe clinical issues linked to high morbidity and mortality in various disorders. The pathophysiology and pathogenesis of ischemia-reperfusion injury are complex and multifactorial. Emerging evidence showed the roles of UPRmt signaling in ischemia-reperfusion injury. Herein, we discuss the regulatory mechanisms underlying UPRmt signaling in C. elegans and mammals. Furthermore, we review the recent studies into the roles and mechanisms of UPRmt signaling in ischemia-reperfusion injury of the heart, brain, kidney, and liver. Further research of UPRmt signaling will potentially develop novel therapeutic strategies against ischemia-reperfusion injury.

Patent Highlights April - May 2022

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

The mitochondrial unfolded protein response (UPRmt): shielding against toxicity to mitochondria in cancer

Mitochondria are essential for tumor growth and progression. However, the heavy demand for mitochondrial activity in cancer leads to increased production of mitochondrial reactive oxygen species (mtROS), accumulation of mutations in mitochondrial DNA, and development of mitochondrial dysfunction. If left unchecked, excessive mtROS can damage and unfold proteins in the mitochondria to an extent that becomes lethal to the tumor. Cellular systems have evolved to combat mtROS and alleviate mitochondrial stress through a quality control mechanism called the mitochondrial unfolded protein response (UPR^mt). The UPR^mt system is composed of chaperones and proteases, which promote protein folding or eliminate mitochondrial proteins damaged by mtROS, respectively. UPR^mt is conserved and activated in cancer in response to mitochondrial stress to maintain mitochondrial integrity and support tumor growth. In this review, we discuss how mitochondria become dysfunctional in cancer and highlight the tumor-promoting functions of key components of the UPR^mt.