IMPDH2 filaments protect from neurodegeneration in AMPD2 deficiency.

Metabolic dysregulation is one of the most common causes of pediatric neurodegenerative disorders. However, how the disruption of ubiquitous and essential metabolic pathways predominantly affect neural tissue remains unclear. Here we use mouse models of a childhood neurodegenerative disorder caused by AMPD2 deficiency to study cellular and molecular mechanisms that lead to selective neuronal vulnerability to purine metabolism imbalance. We show that mouse models of AMPD2 deficiency exhibit predominant degeneration of the hippocampal dentate gyrus, despite a general reduction of brain GTP levels. Neurodegeneration-resistant regions accumulate micron-sized filaments of IMPDH2, the rate limiting enzyme in GTP synthesis, while these filaments are barely detectable in the hippocampal dentate gyrus. Furthermore, we show that IMPDH2 filament disassembly reduces GTP levels and impairs growth of neural progenitor cells derived from individuals with human AMPD2 deficiency. Together, our findings suggest that IMPDH2 polymerization prevents detrimental GTP deprivation, opening the possibility of exploring the induction of IMPDH2 assembly as a therapy for neurodegeneration.

IMPDH2 suppression impedes cell proliferation by instigating cell cycle arrest and stimulates apoptosis in pediatric hepatoblastoma.

BACKGROUND: Hepatoblastoma (HB) is the most common pediatric liver tumor, presenting significant therapeutic challenges due to its high rates of recurrence and metastasis. While Inosine Monophosphate Dehydrogenase 2(IMPDH2) has been associated with cancer progression, its specific role and clinical implications in HB have not been fully elucidated. METHODS: This study utilized Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) and Tissue Microarray (TMA) for validation. Following this, IMPDH2 was suppressed, and a series of in vitro assays were conducted. Flow cytometry was employed to assess apoptosis and cell cycle arrest. Additionally, the study explored the synergistic therapeutic effects of mycophenolate mofetil (MMF) and doxorubicin (DOX) on HB cell lines. RESULTS: The study identified a marked overexpression of IMPDH2 in HB tissues, which was strongly correlated with reduced Overall Survival (OS) and Event-Free Survival (EFS). IMPDH2 upregulation was also found to be associated with key clinical-pathological features, including pre-chemotherapy alpha-fetoprotein (AFP) levels, presence of preoperative metastasis, and the pre-treatment extent of tumor (PRETEXT) staging system. Knockdown of IMPDH2 significantly inhibited HB cell proliferation and tumorigenicity, inducing cell cycle arrest at the G0/G1 phase. Notably, the combination of MMF, identified as a specific IMPDH2 inhibitor, with DOX, substantially enhanced the therapeutic response. CONCLUSION: The overexpression of IMPDH2 was closely linked to adverse outcomes in HB patients and appeared to accelerate cell cycle progression. These findings suggest that IMPDH2 may serve as a valuable prognostic indicator and a potential therapeutic target for HB. IMPACT: The present study unveiled a significant overexpression of inosine monophosphate dehydrogenase 2 (IMPDH2) in hepatoblastoma (HB) tissues, particularly in association with metastasis and recurrence of the disease. The pronounced upregulation of IMPDH2 was found to be intimately correlated with adverse outcomes in HB patients. This overexpression appears to accelerate the progression of the cell cycle, suggesting that IMPDH2 may serve as a promising candidate for both a prognostic marker and a therapeutic target in the context of HB.

Impdh2 deficiency suppresses osteoclastogenesis through mitochondrial oxidative phosphorylation and alleviates ovariectomy-induced osteoporosis.

Abnormalities in osteoclastic generation or activity disrupt bone homeostasis and are highly involved in many pathologic bone-related diseases, including rheumatoid arthritis, osteopetrosis, and osteoporosis. Control of osteoclast-mediated bone resorption is crucial for treating these bone diseases. However, the mechanisms of control of osteoclastogenesis are incompletely understood. In this study, we identified that inosine 5'-monophosphate dehydrogenase type II (Impdh2) positively regulates bone resorption. By histomorphometric analysis, Impdh2 deletion in mouse myeloid lineage cells (Impdh2LysM-/- mice) showed a high bone mass due to the reduced osteoclast number. qPCR and western blotting results demonstrated that the expression of osteoclast marker genes, including Nfatc1, Ctsk, Calcr, Acp5, Dcstamp, and Atp6v0d2, was significantly decreased in the Impdh2LysM-/- mice. Furthermore, the Impdh inhibitor MPA treatment inhibited osteoclast differentiation and induced Impdh2-cytoophidia formation. The ability of osteoclast differentiation was recovered after MPA deprivation. Interestingly, genome-wide analysis revealed that the osteoclastic mitochondrial biogenesis and functions, such as oxidative phosphorylation, were impaired in the Impdh2LysM-/- mice. Moreover, the deletion of Impdh2 alleviated ovariectomy-induced bone loss. In conclusion, our findings revealed a previously unrecognized function of Impdh2, suggesting that Impdh2-mediated mechanisms represent therapeutic targets for osteolytic diseases.

Vitexicarpin suppresses malignant progression of colorectal cancer through affecting c-Myc ubiquitination by targeting IMPDH2.

BACKGROUND: Colorectal cancer (CRC) is the second most common cause of cancer-related mortality and is characterised by extensive invasive and metastatic potential. Previous studies have shown that vitexicarpin extracted from the fruits of Vitex rotundifolia can impede tumour progression. However, the molecular mechanisms involved in CRC treatment are still not fully established. PURPOSE: Our study aimed to investigate the anticancer activity, targets, and molecular mechanisms of vitexicarpin in CRC hoping to provide novel therapies for patients with CRC. STUDY DESIGN/METHODS: The impact of vitexicarpin on CRC was assessed through various experiments including MTT, clone formation, EDU, cell cycle, and apoptosis assays, as well as a tumour xenograft model. CETSA, label-free quantitative proteomics, and Biacore were used to identify the vitexicarpin targets. WB, Co-IP, Ubiquitination assay, IF, molecular docking, MST, and cell transfection were used to investigate the mechanism of action of vitexicarpin in CRC cells. Furthermore, we analysed the expression patterns and correlation of target proteins in TCGA and GEPIA datasets and clinical samples. Finally, wound healing, Transwell, tail vein injection model, and tissue section staining were used to demonstrate the antimetastatic effect of vitexicarpin on CRC in vitro and in vivo. RESULTS: Our findings demonstrated that vitexicarpin exhibits anticancer activity by directly binding to inosine monophosphate dehydrogenase 2 (IMPDH2) and that it promotes c-Myc ubiquitination by disrupting the interaction between IMPDH2 and c-Myc, leading to epithelial-mesenchymal transition (EMT) inhibition. Vitexicarpin hinders the migration and invasion of CRC cells by reversing EMT both in vitro and in vivo. Additionally, these results were validated by the overexpression and knockdown of IMPDH2 in CRC cells. CONCLUSION: These results demonstrated that vitexicarpin regulates the interaction between IMPDH2 and c-Myc to inhibit CRC proliferation and metastasis both in vitro and in vivo. These discoveries introduce potential molecular targets for CRC treatment and shed light on new mechanisms for c-Myc regulation in tumours.

Deletion of Impdh2 in adipocyte precursors limits the expansion of white adipose tissue and enhances metabolic health with overnutrition.

The equilibrium between the hypertrophic growth of existing adipocytes and adipogenesis is vital in managing metabolic stability in white adipocytes when faced with overnutrition. Adipogenesis has been established as a key player in combating metabolic irregularities caused by various factors. However, the benefits of increasing adipogenesis-mediated white adipose tissue (WAT) expansion for metabolic health regulation remain uncertain. Our findings reveal an increase in Impdh2 expression during the adipogenesis phase, both in vivo and in vitro. Xmp enhances adipogenic potential by fostering mitotic clonal expansion (MCE). The conditional knockout of Impdh2 in adipocyte progenitor cells(APCs) in adult and aged mice effectively curbs white adipose tissue expansion, ameliorates glucose tolerance, and augments energy expenditure under high-fat diet (HFD). However, no significant difference is observed under normal chow diet (NCD). Concurrently, the knockout of Impdh2 in APCs significantly reduces the count of new adipocytes induced by HFD, without affecting adipocyte size. Mechanistically, Impdh2 regulates the proliferation of APCs during the MCE phase via Xmp. Exogenous Xmp can significantly offset the reduction in adipogenic abilities of APCs due to Impdh2 deficiency. In summary, we discovered that adipogenesis-mediated WAT expansion, induced by overnutrition, also contributes to metabolic abnormalities. Moreover, the pivotal role of Impdh2 in regulating adipogenesis in APCs offers a novel therapeutic approach to combat obesity.

IMPDH2 Positively Impacts the Proliferation Potential of Hepatoblastoma Cells by Activating JunB Signaling Pathway.

BACKGROUND: Amplification of inosine monophosphate dehydrogenase II, EC 1,1,1,205 (IMPDH2) has been reported in various cancers, which results in transformation and tumorigenicity. In our current work, we have explored the oncogenic properties and the underlying pathophysiology of IMPDH2 in hepatoblastoma (HB). METHODS: To investigate IMPDH2 expression in HB tissues and prognostic significance in HB patients, gene expression profiling interactive analysis (GEPIA) has been adopted. Immunohistochemistry has also helped to validate the protein expression of IMPDH2 in HB tissues. The effect of IMPDH2 overexpression or depletion on the proliferation of Hepatoblastoma cells in vitro has been evaluated by CCK8 assays and colony formation assays. Xenograft tumor growth of mice has been detected. Luciferase reporter assays have been conducted to determine the interaction of IMPDH2 and JunB, which was further asserted by pharmacological inhibition of JunB. RESULTS: IMPDH2 was highly expressed in HB tissues. Experimentally, the proliferation and colony formation of HuH6 cells were increased by IMPDH2 overexpression. Conversely, genetic inactivation of IMPDH2 impaired the proliferative efficiency and colony-forming rate of HepG2 cells. Besides, the luciferase reporter assay validated IMPDH2 overexpression to be associated with enhanced JunB transcriptional activity, while its activity was diminished in the case of IMPDH2 depletion. JunB inhibitor neutralized the IMPDH2-mediated increased phosphorylation of JunB. CONCLUSION: Our findings, thus, suggest that IMPDH2 exhibits its oncogenic role in HB partially via JunB-dependent proliferation.

Targeting human inosine 5' monophosphate dehydrogenase type 2 for anti-dengue lead identification - a computational approach.

Dengue is a rapidly evolving arboviral disease that mainly affects tropical and subtropical regions of the world. The lack of therapeutic drugs and effective vaccines suggests that further resources need to be investigated. The effectiveness of the existing dengue vaccine is improbable as its efficacy depends on prior exposure to the dengue virus(DENV). Although the mechanism underlying the action of bioactive compounds to limit viral replication is less studied and still needs to be further explored, medicinal plants are excellent alternatives to combat DENV infection. In the current study, an in silico screening of phytochemicals from Annona reticulata Linn. against human Impdh2 was performed using Autodock Vina. Daucosterol (-9.0 kcal/mol) and Kaurenoic acid (-8.5 kcal/mol) were chosen as the top hits based on molecular interaction analysis. The hits were further exposed to pharmacokinetics and toxicity properties to determine their drug-like parameters. Molecular dynamics simulation studies of the Impdh2-top hits were carried out to investigate their kinetic behaviour and structural stabilities. The binding free energies of the Impdh2-hit complexes were determined using MM-PBSA analysis. According to the overall conclusions of the study, Daucosterol showed good binding affinity and high structural stability to the binding site residues of the target, therefore it is recommended as a lead compound against dengue.Communicated by Ramaswamy H. Sarma.

Wnt/ß-catenin signalling activates IMPDH2-mediated purine metabolism to facilitate oxaliplatin resistance by inhibiting caspase-dependent apoptosis in colorectal cancer.

BACKGROUND: Oxaliplatin resistance usually leads to therapeutic failure and poor prognosis in colorectal cancer (CRC), while the underlying mechanisms are not yet fully understood. Metabolic reprogramming is strongly linked to drug resistance, however, the role and mechanism of metabolic reprogramming in oxaliplatin resistance remain unclear. Here, we aim to explore the functions and mechanisms of purine metabolism on the oxaliplatin-induced apoptosis of CRC. METHODS: An oxaliplatin-resistant CRC cell line was generated, and untargeted metabolomics analysis was conducted. The inosine 5'-monophosphate dehydrogenase type II (IMPDH2) expression in CRC cell lines was determined by quantitative real-time polymerase chain reaction (qPCR) and western blotting analysis. The effects of IMPDH2 overexpression, knockdown and pharmacological inhibition on oxaliplatin resistance in CRC were assessed by flow cytometry analysis of cell apoptosis in vivo and in vitro. RESULTS: Metabolic analysis revealed that the levels of purine metabolites, especially guanosine monophosphate (GMP), were markedly elevated in oxaliplatin-resistant CRC cells. The accumulation of purine metabolites mainly arose from the upregulation of IMPDH2 expression. Gene set enrichment analysis (GSEA) indicated high IMPDH2 expression in CRC correlates with PURINE_METABOLISM and MULTIPLE-DRUG-RESISTANCE pathways. CRC cells with higher IMPDH2 expression were more resistant to oxaliplatin-induced apoptosis. Overexpression of IMPDH2 in CRC cells resulted in reduced cell death upon treatment with oxaliplatin, whereas knockdown of IMPDH2 led to increased sensitivity to oxaliplatin through influencing the activation of the Caspase 7/8/9 and PARP1 proteins on cell apoptosis. Targeted inhibition of IMPDH2 by mycophenolic acid (MPA) or mycophenolate mofetil (MMF) enhanced cell apoptosis in vitro and decreased in vivo tumour burden when combined with oxaliplatin treatment. Mechanistically, the Wnt/ß-catenin signalling was hyperactivated in oxaliplatin-resistant CRC cells, and a reciprocal positive regulatory mechanism existed between Wnt/ß-catenin and IMPDH2. Blocking the Wnt/ß-catenin pathway could resensitize resistant cells to oxaliplatin, which could be restored by the addition of GMP. CONCLUSIONS: IMPDH2 is a predictive biomarker and therapeutic target for oxaliplatin resistance in CRC.

IMPDH2 forms spots at branching sites and distal ends of astrocyte stem processes.

Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme in the de novo GTP biosynthesis pathway. Recent studies suggest that IMPDH2, an isoform of IMPDH, can localize to specific subcellular compartments under certain conditions and regulate site-specific GTP availability and small GTPase activity in invasive cancer cells. However, it is unclear whether IMPDH2 plays a site-specific regulatory role in subcellular functions in healthy cells. In this study, we focused on brain cells and examined the localization pattern of IMPDH2. We discovered that IMPDH2 forms localized spots in the astrocytes of the adult mouse hippocampus. Further analysis of spot distribution in primary astrocyte cultures revealed that IMPDH2 spots are predominantly localized on branching sites and distal ends of astrocyte stem processes. Our findings suggest a potential unidentified role for IMPDH2 and GTP synthesis specifically at specialized nodes of astrocyte branches.

Single-cell RNA sequencing in double-hit lymphoma: IMPDH2 induces the progression of lymphoma by activating the PI3K/AKT/mTOR signaling pathway.

BACKGROUND: IMPDH2 is the rate-limiting enzyme of the de novo GTP synthesis pathway and has a key role in tumors; however, the specific mechanism underlying IMPDH2 activity in diffuse large B cell lymphoma (DLBCL) is still undetermined. This study aims to explore the potential mechanism of IMPDH2 in DLBCL, and its possible involvement in double-hit lymphoma (DHL), i.e., cases with translocations involving MYC and BCL2 and/or BCL6. METHODS: Using single-cell sequencing and bioinformatics analysis to screen for IMPDH2. Exploring the differential expression of IMPDH2 and its correlation with prognosis through multiplexed immunofluorescence analysis. Using CCK8, EdU, clone formation assay, and animal model to analyze biological behavior changes after inhibiting IMPDH2. Explaining the potential mechanism of IMPDH2 in DLBCL by Western blot and multiplexed immunofluorescence. RESULTS: Prognostic risk model was constructed by single-cell sequencing, which identified IMPDH2 as a DHL-related gene. IMPDH2 was highly expressed in cell lines and tissues, associated with poor patient prognosis and an independent prognostic factor. In vitro and in vivo experiments showed that IMPDH2 inhibition significantly inhibited DHL cell proliferation. Flow cytometry showed apoptosis and cycle arrest. Western blot results suggested that c-Myc regulated the activation of PI3K/AKT/mTOR signaling pathway by IMPDH2 to promote tumor development in DHL. Moreover, multiplex immunofluorescence revealed decreased T-cell infiltration within the tumor microenvironment exhibiting concurrent high expression of IMPDH2 and PD-L1. CONCLUSIONS: Our results suggest that IMPDH2 functions as a tumor-promoting factor in DHL. This finding is expected to generate novel insights into the pathogenesis of these patients, thereby identifying potential therapeutic targets.

Berberrubine is a novel and selective IMPDH2 inhibitor that impairs the growth of colorectal cancer.

Inosine monophosphate dehydrogenase (IMPDH) catalyzes the rate-limiting reaction in the de novo synthesis pathway of guanine nucleotides that is highly required for cancer cell outgrowth. Herein, we found that IMPDH isoform 2 (IMPDH2) is highly expressed in colorectal cancer (CRC) and is correlated with poor patient prognosis. Via structure-based virtual screening, we identified berberrubine, a critical ingredient of the medical plant Coptis chinensis, as a novel, selective, and competitive inhibitor of IMPDH2, which demonstrated over 15-fold selectivity to IMPDH2 than IMPDH1. Besides, we also confirmed the interaction between berberrubine and IMPDH2. Of note, berberrubine treatment significantly impairs the growth of human CRC cells in a dose-dependent manner, which can be rescued by supplementing with guanosine. Furthermore, oral administration of berberrubine remarkably reduced tumor volume and weight in a human cell line-derived xenograft model. Importantly, the anti-cancer activity of berberrubine was also confirmed by using the azoxymethane (AOM) / dextran sulfate sodium (DSS)-induced spontaneous CRC mouse model. Taken together, our study highlights that berberrubine acts as a novel IMPDH2 inhibitor, suppressing the growth of CRC in vitro and in vivo, providing a fresh perspective for its potential application in the treatment of CRC.

Hypoxia-induced TMTC3 expression in esophageal squamous cell carcinoma potentiates tumor angiogenesis through Rho GTPase/STAT3/VEGFA pathway.

BACKGROUND: Hypoxia is one of most typical features in the tumor microenvironment of solid tumor and an inducer of endoplasmic reticulum (ER) stress, and HIF-1α functions as a key transcription factor regulator to promote tumor angiogenesis in the adaptive response to hypoxia. Increasing evidence has suggested that hypoxia plays an important regulatory role of ER homeostasis. We previously identified TMTC3 as an ER stress mediator under nutrient-deficiency condition in esophageal squamous cell carcinoma (ESCC), but the molecular mechanism in hypoxia is still unclear. METHODS: RNA sequencing data of TMTC3 knockdown cells and TCGA database were analyzed to determine the association of TMTC3 and hypoxia. Moreover, ChIP assay and dual-luciferase reporter assay were performed to detect the interaction of HIF-1α and TMTC3 promoter. In vitro and in vivo assays were used to investigate the function of TMTC3 in tumor angiogenesis. The molecular mechanism was determined using co-immunoprecipitation assays, immunofluorescence assays and western blot. The TMTC3 inhibitor was identified by high-throughput screening of FDA-approved drugs. The combination of TMTC3 inhibitor and cisplatin was conducted to confirm the efficiency in vitro and in vivo. RESULTS: The expression of TMTC3 was remarkably increased under hypoxia and regulated by HIF-1α. Knockdown of TMTC3 inhibited the capability of tumor angiogenesis and ROS production in ESCC. Mechanistically, TMTC3 promoted the production of GTP through interacting with IMPDH2 Bateman domain. The activity of Rho GTPase/STAT3, regulated by cellular GTP levels, decreased in TMTC3 knockdown cells, whereas reversed by IMPDH2 overexpression. Additionally, TMTC3 regulated the expression of VEGFA through Rho GTPase/STAT3 pathway. Allopurinol inhibited the expression of TMTC3 and further reduced the phosphorylation and activation of STAT3 signaling pathway in a dose-dependent manner in ESCC. Additionally, the combination of allopurinol and cisplatin significantly inhibited the cell viability in vitro and tumor growth in vivo, comparing with single drug treatment, respectively. CONCLUSIONS: Collectively, our study clarified the molecular mechanism of TMTC3 in regulating tumor angiogenesis and highlighted the potential therapeutic combination of TMTC3 inhibitor and cisplatin, which proposed a promising strategy for the treatment of ESCC.

B7-H3 Associates with IMPDH2 and Regulates Cancer Cell Survival.

Lung cancer is one of the most common cancers worldwide, and despite improvements in treatment regimens, patient prognosis remains poor. Lung adenocarcinomas develop from the lung epithelia and understanding how specific genetic and environmental factors lead to oncogenic transformation in these cells is of great importance to define the pathways that contribute to tumorigenesis. The recent rise in the use of immunotherapy to treat different cancers has prompted the exploration of immune modulators in tumour cells that may provide new targets to manipulate this process. Of these, the B7 family of cell surface receptors, which includes PD-1, is of particular interest due to its role in modulating immune cell responses within the tumour microenvironment. B7-H3 (CD276) is one family member that is upregulated in many cancer types and suggested to contribute to tumour-immune interactions. However, the function and ligand(s) for this receptor in normal lung epithelia and the mechanisms through which the overexpression of B7-H3 regulate cancer progression in the absence of immune cell interactions remain unclear. Here, we present evidence that B7-H3 is associated with one of the key rate-limiting metabolic enzymes IMPDH2, and the localisation of this complex is altered in human lung cancer cells that express high levels of B7-H3. Mechanistically, the IMPDH2:B7-H3 complex provides a protective role in cancer cells to escape oxidative stress triggered by chemotherapy, thus leading to cell survival. We further demonstrate that the loss of B7-H3 in cancer cells has no effect on growth or migration in 2D but promotes the expansion of 3D spheroids in an IMPDH2-dependent manner. These findings provide new insights into the B7-H3 function in the metabolic homeostasis of normal and transformed lung cancer cells, and whilst this molecule remains an interesting target for immunotherapy, these findings caution against the use of anti-B7-H3 therapies in certain clinical settings.

Growth Transformation of B Cells by Epstein-Barr Virus Requires IMPDH2 Induction and Nucleolar Hypertrophy.

The in vitro growth transformation of primary B cells by Epstein-Barr virus (EBV) is the initial step in the development of posttransplant lymphoproliferative disorder (PTLD). We performed electron microscopic analysis and immunostaining of primary B cells infected with wild-type EBV. Interestingly, the nucleolar size was increased by two days after infection. A recent study found that nucleolar hypertrophy, which is caused by the induction of the IMPDH2 gene, is required for the efficient promotion of growth in cancers. In the present study, RNA-seq revealed that the IMPDH2 gene was significantly induced by EBV and that its level peaked at day 2. Even without EBV infection, the activation of primary B cells by the CD40 ligand and interleukin-4 increased IMPDH2 expression and nucleolar hypertrophy. Using EBNA2 or LMP1 knockout viruses, we found that EBNA2 and MYC, but not LMP1, induced the IMPDH2 gene during primary infections. IMPDH2 inhibition by mycophenolic acid (MPA) blocked the growth transformation of primary B cells by EBV, leading to smaller nucleoli, nuclei, and cells. Mycophenolate mofetil (MMF), which is a prodrug of MPA that is approved for use as an immunosuppressant, was tested in a mouse xenograft model. Oral MMF significantly improved the survival of mice and reduced splenomegaly. Taken together, these results indicate that EBV induces IMPDH2 expression through EBNA2-dependent and MYC-dependent mechanisms, leading to the hypertrophy of the nucleoli, nuclei, and cells as well as efficient cell proliferation. Our results provide basic evidence that IMPDH2 induction and nucleolar enlargement are crucial for B cell transformation by EBV. In addition, the use of MMF suppresses PTLD. IMPORTANCE EBV infections cause nucleolar enlargement via the induction of IMPDH2, which are essential for B cell growth transformation by EBV. Although the significance of IMPDH2 induction and nuclear hypertrophy in the tumorigenesis of glioblastoma has been reported, EBV infection brings about the change quickly by using its transcriptional cofactor, EBNA2, and MYC. Moreover, we present here, for the novel, basic evidence that an IMPDH2 inhibitor, namely, MPA or MMF, can be used for EBV-positive posttransplant lymphoproliferative disorder (PTLD).

Rare variants in IMPDH2 cause autosomal dominant dystonia in Chinese population.

STUDY OBJECTIVES: Recently, IMPDH2 has been linked to dystonia. However, no replication study from other cohorts has been conducted to confirm the association. We aimed to systematically evaluate the genetic associations of IMPDH2 with dystonia in a large dystonia cohort. METHODS: We analyzed rare variants (minor allele frequency < 0.01) of IMPDH2 in 688 Chinese dystonia patients with whole exome sequencing. The over-representation of rare variants in patients was examined with Fisher's exact test at allele and gene levels. RESULTS: Four rare variants were detected in IMPDH2 in four patients with dystonia in our cohort, including three missense variants (p.Ser508Leu, p.Ala396Thr, and p.Phe24Val) and one splice acceptor variant (c.1296-1G>T). Two of them (c.1296-1G>T and p.Ser508Leu) were co-segregated in the family co-segregation analysis and were classified as pathogenic and likely pathogenic variant according to the American College of Medical Genetics and Genomics (ACMG) guidelines, respectively. Gene burden analysis revealed enrichment of rare variants in IMPDH2 in dystonia. CONCLUSIONS: Our work supplemented the evidence on the role of IMPDH2 in autosomal dominant dystonia in Chinese population, and expanded the genetic and phenotypic spectrum of IMPDH2, paving way for future studies.

Genetic analysis of IMPDH2 gene in Taiwanese patients with isolated or combined dystonia.

The inosine monophosphate dehydrogenase gene (IMPDH2) was recently reported as a novel gene associated with autosomal dominantly inherited dystonia. We investigated 245 Taiwanese patients with molecularly unassigned isolated or combined dystonia without features of neurodevelopmental disorders and found none had pathogenic variants. Our findings suggest that IMPDH2 may not play a major role in dystonia.

c-Myc-IMPDH1/2 axis promotes tumourigenesis by regulating GTP metabolic reprogramming.

BACKGROUND: Metabolic reprogramming is a hallmark of cancer. Metabolic rate-limiting enzymes and oncogenic c-Myc (Myc) play critical roles in metabolic reprogramming to affect tumourigenesis. However, a systematic assessment of metabolic rate-limiting enzymes and their relationship with Myc in human cancers is lacking. METHODS: Multiple Pan-cancer datasets were used to develop the transcriptome, genomic alterations, clinical outcomes and Myc correlation landscapes of 168 metabolic rate-limiting enzymes across 20 cancers. Real-time quantitative PCR and immunoblotting were, respectively, used to examine the mRNA and protein of inosine monophosphate dehydrogenase 1 (IMPDH1) in human colorectal cancer (CRC), azoxymethane/dextran sulphate sodium-induced mouse CRC and spontaneous intestinal tumours from APCMin/+ mice. Clone formation, CCK-8 and subcutaneous xenograft model were applied to investigate the possible mechanisms connecting IMPDH1 to CRC growth. Co-immunoprecipitation and protein half-life assay were used to explore the mechanisms underlying the regulation of IMPDH1. RESULTS: We explored the global expression patterns, dysregulation profiles, genomic alterations and clinical relevance of 168 metabolic rate-limiting enzymes across human cancers. Importantly, a series of enzymes were associated with Myc, especially top three upregulated enzymes (TK1, RRM2 and IMPDH1) were positively correlated with Myc in multiple cancers. As a proof-of-concept exemplification, we demonstrated that IMPDH1, a rate-limiting enzyme in GTP biosynthesis, is highly upregulated in CRC and promotes CRC growth in vitro and in vivo. Mechanistically, IMPDH2 stabilizes IMPDH1 by decreasing the polyubiquitination levels of IMPDH1, and Myc promotes the de novo GTP biosynthesis by the transcriptional activation of IMPDH1/2. Finally, we confirmed that the Myc-IMPDH1/2 axis is dysregulated across human cancers. CONCLUSIONS: Our study highlights the essential roles of metabolic rate-limiting enzymes in tumourigenesis and their crosstalk with Myc, and the Myc-IMPDH1/2 axis promotes tumourigenesis by altering GTP metabolic reprogramming. Our results propose the inhibition of IMPDH1 as a viable option for cancer treatment.

Genistein promotes apoptosis of lung cancer cells through the IMPDH2/AKT1 pathway.

OBJECTIVE: Lung cancer (LC) is a clinically challenging cancer. Genistein is a natural isoflavone product with anti-tumor effects. This study aims to investigate the effect of genistein on A549 cell apoptosis, to provide more experimental evidence for clinical treatment. METHODS: Real-time quantitative polymerase chain reaction, western blotting, molecular docking, and target prediction methods were performed to detect the effect of genistein on LC cells. Cell viability of A549 treated by genistein was measured by a CCK-8 assay. The A549 cell apoptosis after genistein treatment was detected by flow cytometry. RESULTS: Genistein promoted the apoptosis of LC cells in a time- and concentration-dependent manner. In addition, the low expression of inosine monophosphate dehydrogenase-2 (IMPDH2) inhibited the effect of genistein on LC cells. By predicting IMPDH2 LC-related apoptosis genes and finding the closely related gene protein kinase B (AKT1), it was found that the highly expressed AKT1 inhibited the effect of genistein on LC cell apoptosis and viability. CONCLUSION: Genistein may be a promising treatment for LC.

SARS-CoV-2 Nsp14 protein associates with IMPDH2 and activates NF-κB signaling.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to NF-κB activation and induction of pro-inflammatory cytokines, though the underlying mechanism for this activation is not fully understood. Our results reveal that the SARS-CoV-2 Nsp14 protein contributes to the viral activation of NF-κB signaling. Nsp14 caused the nuclear translocation of NF-κB p65. Nsp14 induced the upregulation of IL-6 and IL-8, which also occurred in SARS-CoV-2 infected cells. IL-8 upregulation was further confirmed in lung tissue samples from COVID-19 patients. A previous proteomic screen identified the putative interaction of Nsp14 with host Inosine-5'-monophosphate dehydrogenase 2 (IMPDH2), which is known to regulate NF-κB signaling. We confirmed the Nsp14-IMPDH2 protein interaction and identified that IMPDH2 knockdown or chemical inhibition using ribavirin (RIB) and mycophenolic acid (MPA) abolishes Nsp14- mediated NF-κB activation and cytokine induction. Furthermore, IMPDH2 inhibitors (RIB, MPA) or NF-κB inhibitors (bortezomib, BAY 11-7082) restricted SARS-CoV-2 infection, indicating that IMPDH2-mediated activation of NF-κB signaling is beneficial to viral replication. Overall, our results identify a novel role of SARS-CoV-2 Nsp14 in inducing NF-κB activation through IMPDH2 to promote viral infection.

Microglia-Dependent and Independent Brain Cytoprotective Effects of Mycophenolate Mofetil During Neuronal Damage.

Acute lesions of the central nervous system often lead to permanent limiting deficits. In addition to the initial primary damage, accompanying neuroinflammation is responsible for progression of damage. Mycophenolate mofetil (MMF) as a selective inhibitor of inosine 5-monophosphate dehydrogenase (IMPDH) was shown to modulate the inflammatory response and promote neuronal survival when applied in specific time windows after neuronal injury. The application of brain cytoprotective therapeutics early after neuronal damage is a fundamental requirement for a successful immunomodulation approach. This study was designed to evaluate whether MMF can still mediate brain cytoprotection when applied in predefined short time intervals following CNS injury. Furthermore, the role of microglia and changes in IMPDH2 protein expression were assessed. Organotypic hippocampal slice cultures (OHSC) were used as an in vitro model and excitotoxically lesioned with N-methyl-aspartate (NMDA). Clodronate (Clo) was used to deplete microglia and analyze MMF mediated microglia independent effects. The temporal expression of IMPDH2 was studied in primary glial cell cultures treated with lipopolysaccharide (LPS). In excitotoxically lesioned OHSC a significant brain cytoprotective effect was observed between 8 and 36 h but not within 8 and 24 h after the NMDA damage. MMF mediated effects were mainly microglia dependent at 24, 36, 48 h after injury. However, further targets like astrocytes seem to be involved in protective effects 72 h post-injury. IMPDH2 expression was detected in primary microglia and astrocyte cell cultures. Our data indicate that MMF treatment in OHSC should still be started no later than 8-12 h after injury and should continue at least until 36 h post-injury. Microglia seem to be an essential mediator of the observed brain cytoprotective effects. However, a microglia-independent effect was also found, indicating involvement of astrocytes.