Leucine-rich Pentatricopeptide Repeat-containing Research Articles

METTL3-mediated SMPDL3A promotes cell growth, metastasis and immune process of hepatocellular carcinoma by regulating LRPPRC

BackgroundMethyltransferase-like protein 3 (METTL3) has been confirmed to act as a tumor promoter to regulate hepatocellular carcinoma (HCC) progression. Therefore, more roles and mechanisms of METTL3 in HCC progression deserve to be further revealed. MethodsThe mRNA and protein levels of METTL3, sphingomyelin phodiesterase acid-like 3 A (SMPDL3A), and leucine rich pentatricopeptide repeat containing (LRPPRC) were determined by qRT-PCR and western blot. Cell proliferation, apoptosis, invasion and migration were detected by CCK8 assay, EdU assay, flow cytometry, transwell assay and wound healing assay. HCC cells were co-cultured with phytohemagglutinin-stimulated peripheral blood mononuclear cells, cytokine-induced killer cells, or CD8 + T-cells. IFN-γ, TNF-α levels, HCC cell survival rate and CD8 + T-cell apoptosis were determined to assess cell immune process. The interaction between METTL3, SMPDL3A and LRPPRC was assessed by MeRIP assay, RIP assay, dual-luciferase reporter assay or Co-IP assay. Animal experiments were performed to evaluate the effect of METTL3 knockdown on HCC tumorigenesis and lung metastasis. ResultsMETTL3 was upregulated in HCC tissues and cells, and its knockdown repressed HCC cell proliferation, invasion, migration, immune process and promoted apoptosis. METTL3 increased SMPDL3A mRNA stability by m6A methylation modification, and this modification could be recognized by IGF2BP1. SMPDL3A overexpression reversed the inhibitory effect of METTL3 knockdown on HCC cell growth, metastasis and immune process. SMPDL3A interacted with LRPPRC to positively regulate its expression, and LRPPRC overexpression also eliminated the regulation of SMPDL3A silencing on HCC progression. In addition, downregulation of METTL3 repressed HCC tumorigenesis and lung metastasis via mediating SMPDL3A/LRPPRC axis. ConclusionMETTL3 accelerated HCC cell growth, metastasis and immune process by regulating SMPDL3A/LRPPRC axis, providing a potential target for HCC treatment.

Transcriptome-Wide N6-Methyladenosine Alternations in Pulmonary Arteries of Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats and Novel Therapeutic Targets.

N6-methyladenosine (m6A) is a post-transcriptional epigenetic change with transcriptional stability and functionality regulated by specific m6A-modifying enzymes. However, the significance of genes modified by m6A and enzymes specific to m6A regulation in the context of pulmonary arterial hypertension (PAH) remains largely unexplored. MeRIP-seq and RNA-seq were applied to explore variances in m6A and RNA expression within the pulmonary artery tissues of control and monocrotaline-induced PAH rats. Functional enrichments were analyzed using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. To screen candidate m6A-related genes, the STRING and Metascape databases were used to construct a protein-protein interaction network followed by a real-time PCR validation of their expression. The expression level of an m6A regulator was further investigated using immunohistochemical staining, immunofluorescence, and Western blot techniques. Additionally, proliferation assays were conducted on primary rat pulmonary artery smooth muscle cells (PASMCs). We identified forty-two differentially expressed genes that exhibited either hypermethylated or hypomethylated m6A. These genes are predominantly related to the extracellular matrix structure, MAPK, and PI3K/AKT pathways. A candidate gene, centromere protein F (CENPF), was detected with increased expression in the PAH group. Additionally, we first identified an m6A reader, leucine rich pentatricopeptide repeat containing (LRPPRC), which was downregulated in the PAH rat model. The in vitro downregulation of Lrpprc mediated by siRNA resulted in the enhanced proliferation and elevated expression of Cenpf mRNA in primary rat PASMCs. Our study revealed a modified transcriptome-wide m6A landscape and associated regulatory mechanisms in the pulmonary arteries of PAH rats, potentially offering a novel target for therapeutic strategies in the future.

ChemRAP uncovers specific mRNA translation regulation via RNA 5′ phospho-methylation

5′-end modifications play key roles in determining RNA fates. Phospho-methylation is a noncanonical cap occurring on either 5′-PPP or 5′-P ends. We used ChemRAP, in which affinity purification of cellular proteins with chemically synthesized modified RNAs is coupled to quantitative proteomics, to identify 5′-Pme “readers”. We show that 5′-Pme is directly recognized by EPRS, the central subunit of the multisynthetase complex (MSC), through its linker domain, which has previously been involved in key noncanonical EPRS and MSC functions. We further determine that the 5′-Pme writer BCDIN3D regulates the binding of EPRS to specific mRNAs, either at coding regions rich in MSC codons, or around start codons. In the case of LRPPRC (leucine-rich pentatricopeptide repeat containing), a nuclear-encoded mitochondrial protein associated with the French Canadian Leigh syndrome, BCDIN3D deficiency abolishes binding of EPRS around its mRNA start codon, increases its translation but ultimately results in LRPPRC mislocalization. Overall, our results suggest that BCDIN3D may regulate the translation of specific mRNA via RNA-5′-Pme.

Prognostic significance of LRPPRC and its association with immune infiltration in liver hepatocellular carcinoma.

Leucine rich pentatricopeptide repeat containing (LRPPRC) protein is a multifunctional protein involved in cell cycle progression and tumor development. However, its prognostic significance and association with immune infiltration in Liver hepatocellular carcinoma (LIHC) remain unclear. We utilized transcriptomic and clinical data from The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression (GTEx) databases of LIHC patients to investigate the potential pro-cancer role of LRPPRC, including differential expression of LRPPRC in LIHC, prognostic value, clinicopathological features, immune cell infiltration relevance and function enrichment analysis. Our findings suggest that LRPPRC is upregulated in LIHC and exhibits correlations with survival, clinical stage, and tumor grade in LIHC patients. Additionally, immune infiltration analysis revealed significant negative correlations between LRPPRC expression and multiple tumor-infiltrating immune cells, including CTLs, DCs, pDCs, B cells, Th17 cells, neutrophils, T cells, Mast cells, Th1 cells, Tregs, and NK cells, whereas a significant positive correlation was observed with infiltration of Th2 cells, T helper cells and Tcms. Furthermore, functional enrichment analysis indicated that LRPPRC may be involved in G2m checkpoint, mitotic spindle, E2f targets, Wnt Beta catenin signaling, spermatogenesis and other processes.

Alternations of N6-methyladenosine RNA methylation landscape in pulmonary arterial hypertension

Abstract Background N6-methyladenosine (m6A) methylation is the most prevalent and abundant RNA modifications in eukaryotes. Deregulation of m6A changes by m6A-specific enzymes can affect the stability and function of transcripts. However, the relevance of m6A mRNA and m6A-specific enzymes in pulmonary arterial hypertension (PAH) have not been extensively explored. Objectives This study aimed to analyze m6A methylation transcriptomic profiling in the pulmonary arteries of PAH rats, and to find potential m6A regulators corelated with PAH epi-transcriptomic changes. Methods MeRIP-seq and RNA-seq were applied to identify differences in m6A methylation and gene expression in pulmonary artery tissues from control and monocrotaline PAH rats. The expression of a m6A regulator in pulmonary arteries was further analyzed by western blot, flow cytometry, immunohistochemical staining and immunofluorescence. The proliferation and apoptosis assays were further performed in primary rat pulmonary artery smooth muscle cells (PASMCs). Results Twenty-seven differentially expressed genes with hypermethylated or hypomethylated m6A modifications were identified. These differentially expressed genes were mainly linked to the extracellular matrix and structure, MAPK and PI3K-Akt signaling pathways. Furthermore, we firstly detected a m6A reader leucine rich pentatricopeptide repeat containing (LRPPRC) with downregulated expression in PAH rats. PASMCs with a siRNA knockdown of the LRPPRC promoted proliferation and apoptotic resistance. Conclusion This study showed that altered m6A transcriptome-wide landscape and relevant regulatory mechanisms of the PAH pulmonary artery tissues in rats, which might provide a new and potential target for therapeutic interventions in PAH.LRPPRC functional studies in PASMCs

A STAT3 protein complex required for mitochondrial mRNA stability and cancer

Signal transducer and activator of transcription 3 (STAT3) is a potent transcription factor necessary for life whose activity is corrupted in diverse diseases, including cancer. STAT3 biology was presumed to be entirely dependent on its activity as a transcription factor until the discovery of a mitochondrial pool of STAT3, which is necessary for normal tissue function and tumorigenesis. However, the mechanism of this mitochondrial activity remained elusive. This study uses immunoprecipitation and mass spectrometry to identify a complex containing STAT3, leucine-rich pentatricopeptide repeat containing (LRPPRC), and SRA stem-loop-interacting RNA-binding protein (SLIRP) that is required for the stability of mature mitochondrially encoded mRNAs and transport to the mitochondrial ribosome. Moreover, we show that this complex is enriched in patients with lung adenocarcinoma and that its deletion inhibits the growth of lung cancer invivo, providing therapeutic opportunities through the specific targeting of the mitochondrial activity of STAT3.

A traditional gynecological medicine inhibits ovarian cancer progression and eliminates cancer stem cells via the LRPPRC–OXPHOS axis

BackgroundOvarian cancer (OC) is the most lethal malignant gynecological tumor type for which limited therapeutic targets and drugs are available. Enhanced mitochondrial oxidative phosphorylation (OXPHOS), which enables cell growth, migration, and cancer stem cell maintenance, is a critical driver of disease progression and a potential intervention target of OC. However, the current OXPHOS intervention strategy mainly suppresses the activity of the electron transport chain directly and cannot effectively distinguish normal tissues from cancer tissues, resulting in serious side effects and limited efficacy.MethodsWe screened natural product libraries to investigate potential anti-OC drugs that target OXPHOS. Additionally, LC-MS, qRT-PCR, western-blot, clonogenic assay, Immunohistochemistry, wound scratch assay, and xenograft model was applied to evaluate the anti-tumor mechanism of small molecules obtained by screening in OC.ResultsGossypol acetic acid (GAA), a widely used gynecological medicine, was screened out from the drug library with the function of suppressing OXPHOS and OC progression by targeting the leucine-rich pentatricopeptide repeat containing (LRPPRC) protein. Mechanically, LRPPRC promotes the synthesis of OXPHOS subunits by binding to RNAs encoded by mitochondrial DNA. GAA binds to LRPPRC directly and induces LRPPRC rapid degradation in a ubiquitin-independent manner. LRPPRC was overexpressed in OC, which is highly correlated with the poor outcomes of OC and could promote the malignant phenotype of OC cells in vitro and in vivo. GAA management inhibits cell growth, clonal formation, and cancer stem cell maintenance in vitro, and suppresses subcutaneous graft tumor growth in vivo.ConclusionsOur study identified a therapeutic target and provided a corresponding inhibitor for OXPHOS-based OC therapy. GAA inhibits OC progression by suppressing OXPHOS complex synthesis via targeting LRPPRC protein, supporting its potential utility as a natural therapeutic agent for ovarian cancer.

The RNA-binding protein LRPPRC promotes resistance to CDK4/6 inhibition in lung cancer

Kinase inhibitors against Cyclin Dependent Kinase 4 and 6 (CDK4/6i) are promising cancer therapeutic drugs. However, their effects are limited by primary or acquired resistance in virtually all tumor types. Here, we demonstrate that Leucine Rich Pentatricopeptide Repeat Containing (LRPPRC) controls CDK4/6i response in lung cancer by forming a feedback loop with CDK6. LRPPRC binds to CDK6-mRNA, increasing the stability and expression of CDK6. CDK6 and its downstream E2F Transcription Factor 1 (E2F1), bind to the LRPPRC promoter and elevate LRPPRC transcription. The activation of the LRPPRC-CDK6 loop facilitates cell cycle G1/S transition, oxidative phosphorylation, and cancer stem cell generation. Gossypol acetate (GAA), a gynecological medicine that has been repurposed as a degrader of LRPPRC, enhances the CDK4/6i sensitivity in vitro and in vivo. Our study reveals a mechanism responsible for CDK4/6i resistance and provides an enlightening approach to investigating the combinations of CDK4/6 and LRPPRC inhibitors in cancer therapy.

The Role of RNA Methylation Modification Related Genes in Prognosis and Immunotherapy of Colorectal Cancer.

Researches showed RNA methylation genes can affect the prognosis of tumors. Thus, the study aimed to comprehensively analyze the effects of RNA methylation regulatory genes in prognosis and treatment of colorectal cancer (CRC). Prognostic signature associated with CRCs were constructed by differential expression analysis, Cox and Least Absolute Shrinkage and Selection Operator (LASSO) analyses. Receiver operating characteristic (ROC) and Kaplan-Meier survival analyses were used to validate the reliability of the developed model. Gene Ontology (GO), Gene set variation analysis (GSVA), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed for functional annotation. Finally, normal and cancerous tissue were collected to validate gene by quantitative real-time PCR (qRT-PCR). A prognostic risk model based on leucine rich pentatricopeptide repeat containing (LRPPRC) and ubiquitin-like with PHD and ring finger domains 2 (UHRF2) was constructed and relevant to the overall survival (OS) of CRC. Functional enrichment analysis revealed that collagen fibrous tissue, ion channel complex and other pathways were significantly enriched, which might help explain the underlying molecular mechanisms. There were significant differences in ImmuneScore, StromalScore, ESTIMATEScore between high- and low-risk groups (p < 0.05). Ultimately, qRT-PCR validation showed that a significant upregulation in the expression of LRPPRC and UHRF2 in cancerous tissue, which verified the effectiveness of our signature. In conclusion, 2 prognostic genes (LRPPRC and UHRF2) related to RNA methylation were identified by bioinformatics analysis, which might supply a new insight into the treatment and evaluation of CRC.

Mitochondrial-Associated Protein LRPPRC is Related With Poor Prognosis Potentially and Exerts as an Oncogene Via Maintaining Mitochondrial Function in Pancreatic Cancer.

Background: The mitochondrial-associated protein leucine-rich pentatricopeptide repeat-containing (LRPPRC) exerts multiple functions involved in physiological processes, including mitochondrial gene translation, cell cycle progression, and tumorigenesis. Previously, LRPPRC was reported to regulate mitophagy by interacting with Bcl-2 and Beclin-1 and thus modifying the activation of PI3KCIII and autophagy. Considering that LRPPRC was found to be negatively associated with survival rate, we hypothesize that LRPPRC may be involved in pancreatic cancer progression via its regulation of autophagy. Methods: Real-time quantitative polymerase chain reaction was performed to detect the expression of LRPPRC in 90 paired pancreatic cancer and adjacent tissues and five pancreatic cancer cell lines. Mitochondrial reactive oxidative species level and function were measured. Mitophagy was measured by performing to detect LC3 levels. Results: By performing a real-time quantitative polymerase chain reaction, the association of LRPPRC with the prognosis of pancreatic cancer was established, and pancreatic cancer tissues had significantly higher LRPPRC expression than adjacent tissues. LRPPRC was negatively associated with the overall survival rate. LRPPRC was also upregulated in pancreatic cancer cell lines. Knockdown of LRPPRC promoted reactive oxidative species accumulation, decreased mitochondrial membrane potential, promoted autophagy/mitophagy, and induced mitochondrial dysfunction. Subsequently, knockdown of LRPPRC inhibited malignant behaviors in PANC-1 cells, including proliferation, migration, invasion, tumor formation, and chemoresistance to gemcitabine. Finally, by inhibiting autophagy/mitophagy using 3-MA, the inhibitory effect of LRPPRC knockdown on proliferation was reversed. Conclusion: Taken together, our results indicate that LRPPRC may act as an oncogene via maintaining mitochondrial homeostasis and could be used as a predictive marker for patient prognosis in pancreatic cancer.

Expression signature of the Leigh syndrome French-Canadian type

As a result of a founder effect, a Leigh syndrome variant called Leigh syndrome, French-Canadian type (LSFC, MIM / 220,111) is more frequent in Saguenay–Lac-Saint-Jean (SLSJ), a geographically isolated region on northeastern Quebec, Canada. LSFC is a rare autosomal recessive mitochondrial neurodegenerative disorder due to damage in mitochondrial energy production. LSFC is caused by pathogenic variants in the nuclear gene leucine-rich pentatricopeptide repeat-containing (LRPPRC). Despite progress understanding the molecular mode of action of LRPPRC gene, there is no treatment for this disease.The present study aims to identify the biological pathways altered in the LSFC disorder through microarray-based transcriptomic profile analysis of twelve LSFC cell lines compared to twelve healthy ones, followed by gene ontology (GO) and pathway analyses.A set of 84 significantly differentially expressed genes were obtained (p ≥ 0.05; Fold change (Flc) ≥ 1.5). 45 genes were more expressed (53.57%) in LSFC cell lines compared to controls and 39 (46.43%) had lower expression levels. Gene ontology analysis highlighted altered expression of genes involved in the mitochondrial respiratory chain and energy production, glucose and lipids metabolism, oncogenesis, inflammation and immune response, cell growth and apoptosis, transcription, and signal transduction. Considering the metabolic nature of LSFC disease, genes included in the mitochondrial respiratory chain and energy production cluster stood out as the most important ones to be involved in LSFC mitochondrial disorder. In addition, the protein-protein interaction network indicated a strong interaction between the genes included in this cluster. The mitochondrial gene NDUFA4L2 (NADH dehydrogenase [ubiquinone] 1 alpha subcomplex, 4-like 2), with higher expression in LSFC cells, represents a target for functional studies to explain the role of this gene in LSFC disease.This work provides, for the first time, the LSFC gene expression profile in fibroblasts isolated from affected individuals. This represents a valuable resource to understand the pathogenic basis and consequences of LRPPRC dysfunction.

LRPPRC regulates redox homeostasis via the circANKHD1/FOXM1 axis to enhance bladder urothelial carcinoma tumorigenesis

Reactive oxygen species (ROS) which are continuously generated mainly by mitochondria, have been proved to play an important role in the stress signaling of cancer cells. Moreover, pentatricopeptide repeat (PPR) proteins have been suggested to take part in mitochondrial metabolism. However, the mechanisms integrating the actions of these distinct networks in urothelial carcinoma of the bladder (UCB) pathogenesis are elusive. In this study, we found that leucine rich pentatricopeptide repeat containing (LRPPRC) was frequently upregulated in UCB and that it was an independent prognostic factor in UCB. We further revealed that LRPPRC promoted UCB tumorigenesis by regulating the intracellular ROS homeostasis. Mechanistically, LRPPRC modulates ROS balance and protects UCB cells from oxidative stress via mt-mRNA metabolism and the circANKHD1/FOXM1 axis. In addition, the SRA stem-loop interacting RNA binding protein (SLIRP) directly interacted with LRPPRC to protect it from ubiquitination and proteasomal degradation. Notably, we showed that LRPPRC modulated the tumorigenesis of UCB cells in a circANKHD1-FOXM1-dependent manner. In conclusion, LRPPRC exerts critical roles in regulating UCB redox homeostasis and tumorigenesis, and is a prognostic factor for UCB; suggesting that LRPPRC may serve as an exploitable therapeutic target in UCB.

LncRNA SNHG17 interacts with LRPPRC to stabilize c-Myc protein and promote G1/S transition and cell proliferation

Oncogenic c-Myc is a master regulator of G1/S transition. Long non-coding RNAs (lncRNAs) emerge as new regulators of various cell activities. Here, we found that lncRNA SnoRNA Host Gene 17 (SNHG17) was elevated at the early G1-phase of cell cycle. Both gain- and loss-of function studies disclosed that SNHG17 increased c-Myc protein level, accelerated G1/S transition and cell proliferation, and consequently promoted tumor cell growth in vitro and in vivo. Mechanistically, the 1-150-nt of SNHG17 physically interacted with the 1035-1369-aa of leucine rich pentatricopeptide repeat containing (LRPPRC) protein, and disrupting this interaction abrogated the promoting role of SNHG17 in c-Myc expression, G1/S transition, and cell proliferation. The effect of SNHG17 in stimulating cell proliferation was attenuated by silencing c-Myc or LRPPRC. Furthermore, silencing SNHG17 or LRPPRC increased the level of ubiquitylated c-Myc and reduced the stability of c-Myc protein. Analysis of human hepatocellular carcinoma (HCC) tissues revealed that SNHG17, LRPPRC, and c-Myc were significantly upregulated in HCC, and they showed a positive correlation with each other. High level of SNHG17 or LRPPRC was associated with worse survival of HCC patients. These data suggest that SNHG17 may inhibit c-Myc ubiquitination and thus enhance c-Myc level and facilitate proliferation by interacting with LRPPRC. Our findings identify a novel SNHG17-LRPPRC-c-Myc regulatory axis and elucidate its roles in G1/S transition and tumor growth, which may provide potential targets for cancer therapy.

Humoral responses to the measles, mumps and rubella vaccine are impaired in Leigh Syndrome French Canadian patients.

Leigh Syndrome French Canadian (LSFC) is a rare autosomal recessive metabolic disorder characterized by severe lactic acidosis crises and early mortality. LSFC patients carry mutations in the Leucine Rich Pentatricopeptide Repeat Containing (LRPPRC) gene, which lead to defects in the respiratory chain complexes and mitochondrial dysfunction. Mitochondrial respiration modulates cellular metabolic activity, which impacts many cell types including the differentiation and function of immune cells. Hence, we postulated that, in addition to neurological and metabolic disorders, LSFC patients may show impaired immune activity. To gain insight into the quality of the immune response in LSFC patients, we examined the response to the measles, mumps and rubella (MMR) vaccine by measuring antibody titers to MMR in the plasma. In a cohort of eight LSFC patients, the response to the MMR vaccine was variable, with some individuals showing antibodies to all three viruses, while others had antibodies to two or fewer viruses. These results suggest that the mutations in the LRPPRC gene present in LSFC patients may affect the immune response to vaccines. Monitoring vaccine response in this fragile population should be considered to ensure full protection against pathogens.

Novel LRPPRC compound heterozygous mutation in a child with early-onset Leigh syndrome French-Canadian type: case report of an Italian patient

BackgroundMitochondrial diseases, also known as oxidative phosphorylation (OXPHOS) disorders, with a prevalence rate of 1:5000, are the most frequent inherited metabolic diseases. Leigh Syndrome French Canadian type (LSFC), is caused by mutations in the nuclear gene (2p16) leucine-rich pentatricopeptide repeat-containing (LRPPRC). It is an autosomal recessive neurogenetic OXPHOS disorder, phenotypically distinct from other types of Leigh syndrome, with a carrier frequency up to 1:23 and an incidence of 1:2063 in the Saguenay-Lac-St Jean region of Quebec. Recently, LSFC has also been reported outside the French-Canadian population.Patient presentationWe report a male Italian (Sicilian) child, born preterm at 28 + 6/7 weeks gestation, carrying a novel LRPPRC compound heterozygous mutation, with facial dysmorphisms, neonatal hypotonia, non-epileptic paroxysmal motor phenomena, and absent sucking-swallowing-breathing coordination requiring, at 4.5 months, a percutaneous endoscopic gastrostomy tube placement. At 5 months brain Magnetic Resonance Imaging showed diffuse cortical atrophy, hypoplasia of corpus callosum, cerebellar vermis hypoplasia, and unfolded hippocampi. Both auditory and visual evoked potentials were pathological. In the following months Video EEG confirmed the persistence of sporadic non epileptic motor phenomena. No episode of metabolic decompensation, acidosis or ketosis, frequently observed in LSFC has been reported. Actually, aged 14 months corrected age for prematurity, the child shows a severe global developmental delay. Metabolic investigations and array Comparative Genomic Hybridization (aCGH) results were normal. Whole-genome sequencing (WGS) found a compound heterozygous mutation in the LRPPRC gene, c.1921–7A > G and c.2056A > G (p.Ile686Val), splicing-site and missense variants, inherited from the mother and the father, respectively.ConclusionsWe first characterized the clinical and molecular features of a novel LRPPRC variant in a male Sicilian child with early onset encephalopathy and psychomotor impairment. Our patient showed a phenotype characterized by a severe neurodevelopmental delay and absence of metabolic decompensation attributable to a probable residual enzymatic activity. LRPPRC is a rare cause of metabolic encephalopathy outside of Québec. Our patient adds to and broaden the spectrum of LSFC phenotypes. WGS analysis is a pivotal genetic test and should be performed in infants and children with hypotonia and developmental delay in whom metabolic investigations and aCGH are normal.

Mitochondria-associated protein LRPPRC exerts cardioprotective effects against doxorubicin-induced toxicity, potentially via inhibition of ROS accumulation.

Doxorubicin (DOX) has been widely employed to treat cancer, particularly solid tumors and hematological malignancies, owing to its high efficacy; however, chemotherapy has been indicated to be cardiotoxic and induce adverse effects, including mitochondrial dysfunction and DNA damage, which limits its application. The mitochondria-associated protein leucine-rich pentatricopeptide repeat-containing (LRPPRC) has been reported to serve critical regulatory roles in physiological processes via regulating mitochondrial function. The aim of the present study was to investigate the possible protective effects of LRPPRC against DOX-induced cardiac injury. In a DOX-induced cardiotoxicity model in H9C2 cells, LRPPRC was indicated to be transcriptionally upregulated and stabilize Bcl-2 and Bax. LRPPRC overexpression exhibited protective effects against proliferation and both apoptotic and non-apoptotic cell death following DOX treatment, but not under normal conditions. It was additionally observed that overexpressed LRPPRC reversed the decreases in ATP synthesis, mitochondrial mass and transcriptional activity, which were induced by DOX exposure. Overexpressed LRPPRC also decreased the accumulation of reactive oxygen species (ROS) under DOX treatment and inhibited cell death to a similar extent as N-acetyl-L-cysteine, which is a known ROS scavenger, indicating that LRPPRC potentially exerts protective effects via inhibiting ROS accumulation. Moreover, LRPPRC overexpression protected H9C2 cells against oxidative stress induced by H2O2, which also indicated its ROS-scavenging function. The present study demonstrated for the first time, to the best of our knowledge, that DOX-induced LRPPRC may exert cardioprotective effects via inhibiting ROS accumulation, thereby maintaining mitochondrial function.

MTORC1 is required for expression of LRPPRC and cytochrome-c oxidase but not HIF-1α in Leigh syndrome French Canadian type patient fibroblasts.

Leigh syndrome French Canadian type (LSFC) is a mitochondrial disease caused by mutations in the leucine-rich pentatricopeptide repeat-containing (LRPPRC) gene leading to a reduction of cytochrome-c oxidase (COX) expression reaching 50% in skin fibroblasts. We have shown that under basal conditions, LSFC and control cells display similar ATP levels. We hypothesized that this occurs through upregulation of mechanistic target of rapamycin (mTOR)-mediated metabolic reprogramming. Our results showed that compared with controls, LSFC cells exhibited an upregulation of the mTOR complex 1 (mTORC1)/p70 ribosomal S6 kinase pathway and higher levels of hypoxia-inducible factor 1α (HIF-1α) and its downstream target pyruvate dehydrogenase kinase 1 (PDHK1), a regulator of mitochondrial pyruvate dehydrogenase 1 (PDH1). Consistent with these signaling alterations, LSFC cells displayed a 40-61% increase in [U-13C6]glucose contribution to pyruvate, lactate, and alanine formation, as well as higher levels of the phosphorylated and inactive form of PDH1-α. Interestingly, inhibition of mTOR with rapamycin did not alter HIF-1α or PDHK1 protein levels in LSFC fibroblasts. However, this treatment increased PDH1-α phosphorylation in control and LSFC cells and reduced ATP levels in control cells. Rapamycin also decreased LRPPRC expression by 41 and 11% in LSFC and control cells, respectively, and selectively reduced COX subunit IV expression in LSFC fibroblasts. Taken together, our data demonstrate the importance of mTORC1, independent of the HIF-1α/PDHK1 axis, in maintaining LRPPRC and COX expression in LSFC cells.

DANCR Promotes Metastasis and Proliferation in Bladder Cancer Cells by Enhancing IL-11-STAT3 Signaling and CCND1 Expression.

The prognosis for patients with bladder cancer (BCa) with lymph node (LN) metastasis is poor, and it is not improved by current treatments. Long noncoding RNAs (lncRNAs) are involved in the pathology of various tumors, including BCa. However, the role of Differentiation antagonizing non-protein coding RNA (DANCR) in BCa LN metastasis remains unclear. In this study, we discover that DANCR was significantly upregulated in BCa tissues and cases with LN metastasis. DANCR expression was positively correlated with LN metastasis status, tumor stage, histological grade, and poor patient prognosis. Functional assays demonstrated that DANCR promoted BCa cell migration, invasion, and proliferation invitro and enhanced tumor LN metastasis and growth invivo. Mechanistic investigations revealed that DANCR activated IL-11-STAT3 signaling and increased cyclin D1 and PLAU expression via guiding leucine-rich pentatricopeptide repeat containing (LRPPRC) to stabilize mRNA. Moreover, oncogenesis facilitated by DANCR was attenuated by anti-IL-11 antibody or a STAT3 inhibitor (BP-1-102). In conclusion, our findings indicate that DANCR induces BCa LN metastasis and proliferation via an LRPPRC-mediated mRNA stabilization mechanism. DANCR may serve as a multi-potency target for clinical intervention in LN-metastatic BCa.

Mitochondrial Proteomics Approach Reveals Voltage-Dependent Anion Channel 1 (VDAC1) as a Potential Biomarker of Gastric Cancer

Background/Aims: Gastric cancer (GC) remains the second leading cause of cancer-related deaths in the world. Successful early cancer detection is hampered by lack of highly sensitive and specific biomarkers. Mitochondrial dysfunction contributes to an aggressive carcinogenic phenotype of many cancers. We hypothesized that changes in the mitochondrial proteome are required to support development of GC. Methods: TMT method followed by mass spectrometry analysis was utilized to quantify alterations in protein abundance in mitochondria enriched between noncancer and gastric cancer tissues. Results: Of a total data set that included 738 identified proteins, about 40.1% were found to be mitochondrial and associated proteins. Among them, 234 proteins were at least 1.5-fold up- or down-regulated in the gastric cancer compared with the adherent normal tissues. A number of markers (e.g. HSP70, HSP60, HSP90, leucine-rich pentatricopeptide repeat containing (LRPPRC), SOD2 and cathepsin B) were previously reported as biomarkers of GC. Additionally, several potential biomarkers participated in mitochondrial oxidative phosphorylation and active fatty acid oxidation were firstly identified differentially expressed in GC samples. Our findings also suggest that VDAC1 may be a novel biomarker for GC. Conclusion: The results show that subcellular proteomics of tumor tissue is feasible and a promising avenue for exploring oncogenesis.

Mitochondrion-associated protein LRPPRC suppresses the initiation of basal levels of autophagy via enhancing Bcl-2 stability

The mitochondrion-associated protein LRPPRC (leucine-rich pentatricopeptide repeat-containing) interacts with one of the microtubule-associated protein family members MAP1S (microtubule-associated protein 1 small form), originally named C19ORF5 (chromosome 19 open reading frame 5), to form a complex. MAP1S interacts with LC3 (light chain 3), the mammalian homologue of yeast autophagy marker ATG8 and one of the most important autophagy markers in mammalian cells, and helps the attachment of autophagosomes with microtubules for trafficking and recruitment of substrate mitochondria into autophagosomes for degradation. MAP1S activates autophagosomal biogenesis and degradation to remove misfolded/aggregated proteins and dysfunctional organelles such as mitochondria and suppress oxidative stress-induced genomic instability and tumorigenesis. Previously, various studies have attributed LRPPRC nucleic acid-associated functions. Instead, in the present study, we show that LRPPRC associates with mitochondria, interacts with Beclin 1 and Bcl-2 and forms a ternary complex to maintain the stability of Bcl-2. Suppression of LRPPRC leads to reduction in mitochondrial potential and reduction in Bcl-2. Lower levels of Bcl-2 lead to release of more Beclin 1 to form the Beclin 1–PI3KCIII (class III phosphoinositide 3-kinase) complex to activate autophagy and accelerate the turnover of dysfunctional mitochondria through the PI3K (phosphoinositide 3-kinase)/Akt/mTOR (mammalian target of rapamycin) pathway. The activation of autophagy induced by LRPPRC suppression occurs upstream of the ATG5–ATG12 conjugate-mediated conversion of LC3-I into LC3-II and has been confirmed in multiple mammalian cell lines with multiple autophagy markers including the size of GFP–LC3 punctate foci, the intensity of LC3-II and p62 protein and the size of the vacuolar structure. The activated autophagy enhances the removal of mitochondria through lysosomes. LRPPRC therefore acts to suppress the initiation of basal levels of autophagy to clean up dysfunctional mitochondria and other cellular debris during the normal cell cycle.