Protein arginine methyltransferase 1, a major regulator of biological processes.

Protein arginine methyltransferase 1 (PRMT1) is a major type I arginine methyltransferase that catalyzes the formation of monomethyl and asymmetric dimethylarginine in protein substrates. It was first identified to asymmetrically methylate histone H4 at the third arginine residue forming the H4R3me2a active histone mark. However, several protein substrates are now identified as being methylated by PRMT1. As a result of its association with diverse classes of substrates, PRMT1 regulates several biological processes like chromatin dynamics, transcription, RNA processing, and signal transduction. The review provides an overview of PRMT1 structure, biochemical features, specificity, regulation, and role in cellular functions. We discuss the genomic distribution of PRMT1 and its association with tRNA genes. Further, we explore the different substrates of PRMT1 involved in splicing. In the end, we discuss the proteins that interact with PRMT1 and their downstream effects in diseased states.

Attenuation of protein arginine dimethylation via S-nitrosylation of protein arginine methyltransferase 1.

Upregulation of nitric oxide (NO) production contributes to the pathogenesis of numerous diseases via S-nitrosylation, a post-translational modification of proteins. This process occurs due to the oxidative reaction between NO and a cysteine thiol group; however, the extent of this reaction remains unknown. S-Nitrosylation of PRMT1, a major asymmetric arginine methyltransferase of histones and numerous RNA metabolic proteins, was induced by NO donor treatment. We found that nitrosative stress leads to S-nitrosylation of cysteine 119, located near the active site, and attenuates the enzymatic activity of PRMT1. Interestingly, RNA sequencing analysis revealed similarities in the changes in expression elicited by NO and PRMT1 inhibitors or knockdown. A comprehensive search for PRMT1 substrates using the proximity-dependent biotin identification method highlighted many known and new substrates, including RNA-metabolizing enzymes. To validate this result, we selected the RNA helicase DDX3 and demonstrated that arginine methylation of DDX3 is induced by PRMT1 and attenuated by NO treatment. Our results suggest the existence of a novel regulatory system associated with transcription and RNA metabolism via protein S-nitrosylation.

Inhibition of PRMT1 Suppresses the Growth of U87MG-Derived Glioblastoma Stem Cells by Blocking the STAT3 Signaling Pathway.

Glioblastoma stem cells (GSCs) play a pivotal role in the initiation, progression, resistance to treatment, and relapse of glioblastoma multiforme (GBM). Thus, identifying potential therapeutic targets and drugs that interfere with the growth of GSCs may contribute to improved treatment outcomes for GBM. In this study, we first demonstrated the functional role of protein arginine methyltransferase 1 (PRMT1) in GSC growth. Furamidine, a PRMT1 inhibitor, effectively inhibited the proliferation and tumorsphere formation of U87MG-derived GSCs by inducing cell cycle arrest at the G0/G1 phase and promoting the intrinsic apoptotic pathway. Moreover, furamidine potently suppressed the in vivo tumor growth of U87MG GSCs in a chick embryo chorioallantoic membrane model. In particular, the inhibitory effect of furamidine on U87MG GSC growth was associated with the downregulation of signal transducer and activator of transcription 3 (STAT3) and key GSC markers, including CD133, Sox2, Oct4, Nanog, aldehyde dehydrogenase 1, and integrin α6. Our results also showed that the knockdown of PRMT1 by small interfering RNA significantly inhibited the proliferation of U87MG GSCs in vitro and in vivo through a molecular mechanism similar to furamidine. In addition, combined treatment with furamidine and berbamine, a calcium/calmodulin-dependent protein kinase II gamma (CaMKIIγ) inhibitor, inhibited the growth of U87MG GSCs more strongly than single-compound treatment. The increased antiproliferative effect of combining the two compounds resulted from a stronger downregulation of STAT3-mediated downstream GBM stemness regulators through dual PRMT1 and CaMKIIγ function blockade. In conclusion, these findings suggest that PRMT1 and its inhibitor, furamidine, are potential novel therapeutic targets and drug candidates for effectively suppressing GSC growth.

Protein arginine methyltransferase 1 in the generation of immune megakaryocytes: A perspective review.

Megakaryocytes (Mks) in bone marrow are heterogeneous in terms of polyploidy. They not only produce platelets but also support the self-renewal of hematopoietic stem cells and regulate immune responses. Yet, how the diverse functions are generated from the heterogeneous Mks is not clear at the molecular level. Advances in single-cell RNA seq analysis from several studies have revealed that bone marrow Mks are heterogeneous and can be clustered into 3 to 4 subpopulations: a subgroup that is adjacent to the hematopoietic stem cells, a subgroup expressing genes for platelet biogenesis, and a subgroup expressing immune-responsive genes, the so-called immune Mks that exist in both humans and mice. Immune Mks are predominantly in the low-polyploid (≤8 N nuclei) fraction and also exist in the lung. Protein arginine methyltransferase 1 (PRMT1) expression is positively correlated with the expression of genes involved in immune response pathways and is highly expressed in immune Mks. In addition, we reported that PRMT1 promotes the generation of low-polyploid Mks. From this perspective, we highlighted the data suggesting that PRMT1 is essential for the generation of immune Mks via its substrates RUNX1, RBM15, and DUSP4 that we reported previously. Thus, we suggest that protein arginine methylation may play a critical role in the generation of proinflammatory platelet progeny from immune Mks, which may affect many immune, thrombotic, and inflammatory disorders.

Inhibition of protein arginine methyltransferase 1 alleviates liver fibrosis by attenuating the activation of hepatic stellate cells in mice.

Protein arginine methyltransferase 1 (PRMT1) has been reported to be involved in various diseases. The expression of PRMT1 was increased in cirrhotic livers from human patients. However, the role of PRMT1 in hepatic fibrogenesis remains largely unexplored. In this study, we investigated the effect of PRMT1 on hepatic fibrogenesis and its underlying mechanism. We found that PRMT1 expression was significantly higher in fibrotic livers of the mice treated with thioacetamide (TAA) or 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet. Immunofluorescence staining revealed that PRMT1 expression was augmented in both hepatocytes and hepatic stellate cells (HSCs) in the fibrotic livers. Applying a selective inhibitor of PRMT1, PT1001B, significantly suppressed PRMT1 activity and mitigated liver fibrosis in mice. Hepatocyte-specific Prmt1 knockout did not affect liver fibrosis in mice. PRMT1 overexpression promoted the expression of fibrotic genes in the LX-2 cells, whereas knockdown of PRMT1 or treatment with PT1001B exhibited reversal effects, suggesting that PRMT1 plays an important role in HSC activation. Additionally, HSC-specific Prmt1 knockout attenuated HSC activation and liver fibrosis in TAA-induced fibrotic model. RNA-seq analysis revealed that Prmt1 knockout in HSCs significantly suppressed pro-inflammatory NF-κB and pro-fibrotic TGF-ß signals, and also downregulated the expression of pro-fibrotic mediators in mouse livers. Moreover, treatment with PT1001B consistently inhibited hepatic inflammatory response in fibrotic model. In conclusion, PRMT1 plays a vital role in HSC activation. Inhibition of PRMT1 mitigates hepatic fibrosis by attenuating HSC activation in mice. Therefore, targeting PRMT1 could be a feasible therapeutic strategy for liver fibrosis.

The methyltransferase PRMT1 regulates γ-globin translation.

Induction of fetal hemoglobin to overcome adult ß-globin gene deficiency is an effective therapeutic strategy to ameliorate human ß-hemoglobinopathies. Previous work has revealed that fetal γ-globin can be translationally induced via integrated stress signaling, but other studies have indicated that activating stress may eventually suppress γ-globin expression transcriptionally. The mechanism by which γ-globin expression is regulated at the translational level remains largely unknown, limiting our ability to determine whether activating stress is a realistic therapeutic option for these disorders. In this study, we performed a functional CRISPR screen targeting protein arginine methyltransferases (PRMTs) to look for changes in γ-globin expression in K562 cells. We not only discovered that several specific PRMTs may block γ-globin transcription, but also revealed PRMT1 as a unique family member that is able to suppress γ-globin synthesis specifically at the translational level. We further identified that a non-AUG uORF within the 5' untranslated region of γ-globin serves as a barrier for translation, which is bypassed upon PRMT1 deficiency. Finally, we found that this novel mechanism of γ-globin suppression could be pharmacologically targeted by the PRMT1 inhibitor, furamidine dihydrochloride. These data raise new questions regarding methyltransferase function and may offer a new therapeutic direction for ß-hemoglobinopathies.

The polymorphism rs975484 in the protein arginine methyltransferase 1 gene modulates expression of immune checkpoint genes in hepatocellular carcinoma.

Protein arginine methyltransferase 1 (PRMT1) is a key regulator of hepatic immune responses. Recently, we reported that PRMT1 regulates the tumor immune response in hepatocellular carcinoma (HCC). Here we found that PRMT1 expression in human HCC correlates with that of programmed cell death 1 ligand 1 (PD-L1), PD-L2, and other checkpoint genes. PRMT1 deletion in mice reduced PD-L1 and PD-L2 expression in tumors and reduced the efficiency of PD-1 antibody treatment in a diethylnitrosamine-induced HCC mouse model, suggesting that PRMT1 regulates the hepatic immune checkpoint. Mice had reduced PD-L1 and PD-L2 expression when PRMT1 was specifically deleted in tumor cells or macrophages, but PRMT1 deletion in dendritic cells did not alter PD-L1 and PD-L2 expression. rs975484 is a common polymorphism in the human PRMT1 gene promoter, and we found that it alters PRMT1 expression in blood monocytes and tumor-associated macrophages in human HCC. PRMT1 expression was higher in individuals with a GG genotype than in individuals with a CC genotype, and heterozygous carriers had intermediate expression. Luciferase reporter assays indicated that this differential expression is due to an extra C/EBPß-binding site in the PRMT1 promoter of individuals carrying the minor G allele. The rs975484 genotype also correlated with PRMT1 target expression in HCC. Individuals with the GG genotype had significantly higher levels of the PRMT1 targets PD-L1, PD-L2, and VISTA than those with the CC genotype. We conclude that PRMT1 critically controls immune checkpoints in mice and humans and that the PRMT1 polymorphism rs975484 affects checkpoint gene expression in HCC.

Protein arginine methyltransferase 1 mediates renal fibroblast activation and fibrogenesis through activation of Smad3 signaling.

Protein arginine methyltransferase 1 (PRMT1), which primarily causes asymmetric arginine methylation of histone and nonhistone proteins, has been found to activate gene expression and mediate multiple pathological processes. Its role in renal fibrosis, however, remains unclear. In the present study, we observed that PRMT1 and its specific epigenetic marker, asymmetric di-methylated histone 4 arginine 3 (H4R3Me2a), were highly expressed in cultured renal interstitial fibroblasts. Treatment of PRMT1 with AMI-1, a selective inhibitor of PRMT1, or silencing PRMT1 with siRNA inhibited serum-induced and transforming growth factor (TGF)-ß1-induced expression of α-smooth muscle actin (α-SMA) and collagen type I, two hallmarks of renal fibroblast activation, in a dose-dependent and time-dependent manner. In a murine model of renal fibrosis induced by unilateral ureteral obstruction, PRMT1 expression and H4R3Me2a were also upregulated, which was coincident with increased expression of α-SMA, collagen type I, and fibronectin. Administration of AMI-1 reduced PRMT1 and H4R3Me2a expression, attenuated extracellular matrix protein deposition, and inhibited renal fibroblast activation and proliferation. Moreover, AMI-1 treatment inhibited Smad3 phosphorylation and TGF-ß receptor I expression but prevented Smad7 downregulation both in the kidney after unilateral ureteral obstruction injury and in cultured renal interstitial fibroblasts exposed to TGF-ß1. Collectively, these results demonstrate that PRMT1 may mediate renal fibroblast activation and renal fibrosis development through activation of the TGF-ß/Smad3 signaling pathway. They also suggest that PRMT1 inhibition may be a potential therapeutic approach for the treatment of fibrotic kidney disease.

Protein Arginine Methyltransferase 1 (PRMT1) Selective Inhibitor, TC-E 5003, Has Anti-Inflammatory Properties in TLR4 Signaling.

Protein arginine methyltransferase 1 (PRMT1) is the most predominant PRMT and is type I, meaning it generates monomethylarginine and asymmetric dimethylarginine. PRMT1 has functions in oxidative stress, inflammation and cancers, and modulates diverse diseases; consequently, numerous trials to develop PRMT1 inhibitors have been attempted. One selective PRMT1 inhibitor is N,N'-(Sulfonyldi-4,1-phenylene)bis(2-chloroacetamide), also named TC-E 5003 (TC-E). In this study, we investigated whether TC-E regulated inflammatory responses. Nitric oxide (NO) production was evaluated by the Griess assay and the inflammatory gene expression was determined by conducting RT-PCR. Western blot analyzing was carried out for inflammatory signaling exploration. TC-E dramatically reduced lipopolysaccharide (LPS)-induced NO production and the expression of inflammatory genes (inducible NO synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α and interleukin (IL)-6) as determined using RT-PCR. TC-E downregulated the nuclear translocation of the nuclear factor (NF)-κB subunits p65 and p50 and the activator protein (AP)-1 transcriptional factor c-Jun. Additionally, TC-E directly regulated c-Jun gene expression following LPS treatment. In NF-κB signaling, the activation of IκBα and Src was attenuated by TC-E. Taken together, these data show that TC-E modulates the lipopolysaccharide (LPS)-induced AP-1 and NF-κB signaling pathways and could possibly be further developed as an anti-inflammatory compound.

PRMT1 Promoted HCC Growth and Metastasis In Vitro and In Vivo via Activating the STAT3 Signalling Pathway.

BACKGROUND/AIMS: Although it has been widely accepted that protein arginine methyltransferase 1 (PRMT1) is a cancer-promoting gene in various cancers, the mechanism of PRMT1 in hepatocellular carcinoma (HCC) requires more exploration. This study aimed to investigate the role of PRMT1 in HCC growth and metastasis. METHODS: We compared PRMT1 expression and clinicopathological characteristics using paired HCC and adjacent noncancerous liver tissues from 210 patients and immunohistochemistry analyses. Cell proliferation, colony formation and migration were determined in HCC cell lines with PRMT1 overexpression or downregulation through MTT, crystal violet and Boyden chamber assays. Tumour growth was monitored in a xenograft model, and intrahepatic metastasis models were established. RESULTS: PRMT1 expression was greatly increased in clinical HCC samples and strongly associated with poor prognosis and recurrence; PRMT1 expression was also positively correlated with microvascular invasion (P = 0.024), tumour differentiation (P = 0.014), tumour size (P = 0.002), and portal vein tumour thrombus (PVTT) (P = 0.028). Cell proliferation, colony formation and migration in vitro were enhanced by PRMT1 upregulation and decreased by PRMT1 downregulation in HCC cell lines. Moreover, low PRMT1 expression resulted in slow tumour growth and decreased tumour weight in vivo, as well as tumour metastasis. These phenotypes were associated with STAT3 signalling pathway activation. Cryptotanshinone, a STAT3 inhibitor, inhibited STAT3 phosphorylation and reversed the HCC phenotype of PRMT1 expression. CONCLUSIONS: We revealed a significant role for PRMT1 in HCC progression and metastasis in vitro and in vivo via STAT3 signalling pathway activation. PRMT1 may be a potential novel prognostic biomarker and new therapeutic target for HCC.

Constitutive high expression of protein arginine methyltransferase 1 in asthmatic airway smooth muscle cells is caused by reduced microRNA-19a expression and leads to enhanced remodeling.

BACKGROUND: In asthma remodeling airway smooth muscle cells (ASMCs) contribute to airway wall thickness through increased proliferation, migration, and extracellular matrix deposition. Previously, we described that protein arginine methyltransferase 1 (PRMT1) participates in airway remodeling in pulmonary inflammation in E3 rats. OBJECTIVE: We sought to define the asthma-specific regulatory mechanism of PRMT1 in human ASMCs. METHODS: ASMCs from healthy subjects and asthmatic patients were activated with platelet-derived growth factor (PDGF)-BB. PRMT1 was localized by means of immunohistochemistry in human lung tissue sections and by means of immunofluorescence in isolated ASMCs. PRMT1 activity was suppressed by the pan-PRMT inhibitor AMI-1, signal transducer and activator of transcription 1 (STAT1) was suppressed by small interfering RNA, and extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK) was suppressed by PD98059. MicroRNAs (miRs) were assessed by using real-time quantitative PCR and regulated by miR mimics or inhibitors. RESULTS: PRMT1 expression was significantly increased in lung tissue sections and in isolated ASMCs of patients with severe asthma. PDGF-BB significantly increased PRMT1 expression through ERK1/2 MAPK and STAT1 signaling in control ASMCs, whereas in ASMCs from asthmatic patients, these proteins were constitutively expressed. ASMCs from asthmatic patients had reduced miR-19a expression, causing upregulation of ERK1/2 MAPK, STAT1, and PRMT1. Inhibition of PRMT1 abrogated collagen type I and fibronectin deposition, cell proliferation, and migration of ASMCs from asthmatic patients. CONCLUSIONS: PRMT1 is a central regulator of tissue remodeling in ASMCs from asthmatic patients through the pathway: PDGF-BB-miR-19a-ERK1/2 MAPK and STAT1. Low miR-19a expression in ASMCs from asthmatic patients is the key event that results in constitutive increased PRMT1 expression and remodeling. Therefore PRMT1 is an attractive target to limit airway wall remodeling in asthmatic patients.

Caveolin1/protein arginine methyltransferase1/sirtuin1 axis as a potential target against endothelial dysfunction.

Endothelial dysfunction (ED), an established response to cardiovascular risk factors, is characterized by increased levels of soluble molecules secreted by endothelial cells (EC). Evidence suggest that ED is an independent predictor of cardiac events and that it is associated with a deficiency in production or bioavailability of nitric oxide (NO) and/or an imbalance in the relative contribution of endothelium-derived relaxing and contracting factors. ED can be reversed by treating cardiovascular risk factors, hence, beyond ambiguity, ED contributes to initiation and progression of atherosclerotic disease. Majority of cardiovascular risk factors act by a common pathway, oxidative stress (OS), characterized by an imbalance in bioavailability of NO and reactive oxygen species (ROS). Enhanced ROS, through several mechanisms, alters competence of EC that leads to ED, reducing its potential to maintain homeostasis and resulting in development of cardiovascular disease (CVD). Influential mechanisms that have been implicated in the development of ED include (i) presence of elevated levels of NOS inhibitor, asymmetric dimethylarginine (ADMA) due to augmented enzyme activity of protein arginine methyl transferase-1 (PRMT1); (ii) decrease in NO generation by endothelial nitric oxide synthase (eNOS) uncoupling, or by reaction of NO with free radicals and (iii) impaired post translational modification of protein (PTM) such as eNOS, caveolin-1 (cav1) and sirtuin-1 (SIRT1). However, the inter-related mechanisms that concur to developing ED is yet to be understood. The events that possibly overlay include OS-induced sequestration of SIRT1 to caveolae facilitating cav1-SIRT1 association; potential increase in lysine acetylation of enzymes such as eNOS and PRMT1 leading to enhanced ADMA formation; imbalance in acetylation-methylation ratio (AMR); diminished NO generation and ED. Here we review current literature from research showing interdependent association between cav1-PRMT1-SIRT1 to the outcomes of experimental and clinical research aiming to preserve endothelial function with gene- or pharmaco-therapy.

Identification and Characterization of Protein Arginine Methyltransferase 1 in Acanthamoeba castellanii.

Protein arginine methyltransferase (PRMT) is an important epigenetic regulator in eukaryotic cells. During encystation, an essential process for Acanthamoeba survival, the expression of a lot of genes involved in the encystation process has to be regulated in order to be induced or inhibited. However, the regulation mechanism of these genes is yet unknown. In this study, the full-length 1,059 bp cDNA sequence of Acanthamoeba castellanii PRMT1 (AcPRMT1) was cloned for the first time. The AcPRMT1 protein comprised of 352 amino acids with a SAM-dependent methyltransferase PRMT-type domain. The expression level of AcPRMT1 was highly increased during encystation of A. castellanii. The EGFP-AcPRMT1 fusion protein was distributed over the cytoplasm, but it was mainly localized in the nucleus of Acanthamoeba. Knock down of AcPRMT1 by synthetic siRNA with a complementary sequence failed to form mature cysts. These findings suggested that AcPRMT1 plays a critical role in the regulation of encystation of A. castellanii. The target gene of AcPRMT1 regulation and the detailed mechanisms need to be investigated by further studies.

Monomethylated and unmethylated FUS exhibit increased binding to Transportin and distinguish FTLD-FUS from ALS-FUS.

Deposition of the nuclear DNA/RNA-binding protein Fused in sarcoma (FUS) in cytosolic inclusions is a common hallmark of some cases of frontotemporal lobar degeneration (FTLD-FUS) and amyotrophic lateral sclerosis (ALS-FUS). Whether both diseases also share common pathological mechanisms is currently unclear. Based on our previous finding that FUS deposits are hypomethylated in FTLD-FUS but not in ALS-FUS, we have now investigated whether genetic or pharmacological inactivation of Protein arginine methyltransferase 1 (PRMT1) activity results in unmethylated FUS or in alternatively methylated forms of FUS. To do so, we generated FUS-specific monoclonal antibodies that specifically recognize unmethylated arginine (UMA), monomethylated arginine (MMA) or asymmetrically dimethylated arginine (ADMA). Loss of PRMT1 indeed not only results in an increase of UMA FUS and a decrease of ADMA FUS, but also in a significant increase of MMA FUS. Compared to ADMA FUS, UMA and MMA FUS exhibit much higher binding affinities to Transportin-1, the nuclear import receptor of FUS, as measured by pull-down assays and isothermal titration calorimetry. Moreover, we show that MMA FUS occurs exclusively in FTLD-FUS, but not in ALS-FUS. Our findings therefore provide additional evidence that FTLD-FUS and ALS-FUS are caused by distinct disease mechanisms although both share FUS deposits as a common denominator.

SERBP1 Is a Component of the Liver Receptor Homologue-1 Transcriptional Complex.

Liver receptor homologue-1 (LRH1) is an orphan nuclear receptor that has been shown to play a role in the transcriptional regulation of pathways involved in cancer. Elucidating the components of the LRH1 transcriptional complex to better understand endogenous regulation of the receptor as well as its role in cancer remains a high priority. A sub-cellular enrichment strategy coupled with proteomic approaches was employed to identify putative LRH1 co-regulators. Nuclear fractionation protocol was essential for detection of LRH1 peptides by mass spectrometry (MS), with most peptides being observed in the insoluble fraction (receptor bound to DNA). SERBP1 and ILF3 were identified as LRH1 interacting partners by both Western blot and MS/MS analysis. Receptor knockdown by siRNA showed an increase in SERBP1 expression, while ILF3 expression was unchanged. In contrast, receptor overexpression decreased only SERBP1 mRNA levels. Consistent with these data, in a promoter:reporter assay, binding of LRH1 to the promoter region of SERBP1 resulted in a decrease in the expression level of the reporter gene, subsequently inhibiting transcription. Given the receptor's role in cancer progression, the study here elucidates additional transcriptional machinery involved in LRH1 signaling and potentially provides new targets for therapeutics development.

Serelaxin reduces oxidative stress and asymmetric dimethylarginine in angiotensin II-induced hypertension.

Recent findings suggest the therapeutic action of relaxin during hypertension is dependent on nitric oxide synthase (NOS) activation; however, the mechanisms underlying the beneficial effects of relaxin on the NOS system have not been fully elucidated. We hypothesized that the protective effects of relaxin include reducing both oxidative stress and the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA). We examined the effect of Serelaxin [human recombinant relaxin-2 (RLX)] in male Sprague-Dawley rats given high-dose angiotensin (ANG) II (400 ng·kg(-1)·min(-1) sc) for 6 wk or shams. RLX was administered (4 µg/h sc) to half of the rats in each group after 2 wk of ANG II for the remaining 4 wk. ANG II induced hypertension and proteinuria, reduced NO oxidation products (NOx), and increased oxidative stress (NADPH oxidase activity, thiobarbituric acid-reactive substances, and 8-isoprostane excretion) and plasma ADMA. While RLX had no effect on sham rats, RLX attenuated the ANG II-dependent hypertension (165 ± 5 vs. 135 ± 13 mmHg, P < 0.05) and proteinuria at 6 wk (62 ± 6 vs. 41 ± 4 mg·day(-1)·100 g(-1), P < 0.05) and normalized oxidative stress and circulating ADMA, in association with restored NOx excretion and kidney cortex NOx. We found that RLX had no impact on the ADMA-regulatory enzymes protein arginine methyltransferase and dimethylarginine-dimethylaminohydrolase (DDAH). Furthermore, RLX treatment did not increase DDAH activity in kidney cortex or liver. These data suggest that benefits of RLX treatment include reduced ADMA levels and increased NO bioavailability, possibly due to its antioxidant effects.

Overview of PRMT1 modulators: Inhibitors and degraders.

Protein arginine methyltransferase 1 (PRMT1) is pivotal in executing normal cellular functions through its catalytic action on the methylation of arginine side chains on protein substrates. Emerging research has revealed a correlation between the dysregulation of PRMT1 expression and the initiation and progression of tumors, significantly influence on patient prognostication, attributed to the essential role played by PRMT1 in a number of biological processes, including transcriptional regulation, signal transduction or DNA repair. Therefore, PRMT1 emerged as a promising therapeutic target for anticancer drug discovery in the past decade. In this review, we first summarize the structure and biological functions of PRMT1 and its association with cancer. Next, we focus on the recent advances in the design and development of PRMT1 modulators, including isoform-selective PRMT1 inhibitors, pan type I PRMT inhibitors, PRMT1-based dual-target inhibitors, and PRMT1-targeting PROTAC degraders, from the perspectives of rational design, pharmacodynamics, pharmacokinetics, and clinical status. Finally, we discuss the challenges and future directions for PRMT1-based drug discovery for cancer therapy.

PRMT1 accelerates cell proliferation, migration, and tumor growth by upregulating ZEB1/H4R3me2as in thyroid carcinoma.

Thyroid carcinoma (TC) represents the most prevalent malignancy of the endocrine system. Protein arginine methyltransferase 1 (PRMT1) is a critical member of the protein arginine methyltransferase family in mammals and is involved in multiple biological processes. This study aimed to investigate the function of PRMT1 in TC. In the present study, human TC cell lines (8505C, CAL62, and BCPAP) and a normal human thyroid cell line Nthy­ori 3­1 were employed. Small interfering RNA targeting PRMT1 was used to knock down PRMT1 expression in 8505C cells, and PRMT1 overexpression plasmids were transfected into BCPAP cells. Cell viability was assessed using a CCK­8 and colony formation assays. Apoptosis was measured using flow cytometry and TUNEL assays. Cell migration was assessed using wound healing and Transwell assays. Reverse transcription­quantitative PCR was used to determine the mRNA expression levels of PRMT1. Western blotting was used to detect the protein expression levels of PRMT1, E­cadherin, vimentin, H4R3me2as, and zinc­finger E homeobox­binding 1 (ZEB1). Notably, PRMT1 expression was elevated in TC (P<0.01). PRMT1 knockdown inhibited TC cell proliferation and migration and concurrently enhanced migration. Furthermore, PRMT1 knockdown suppressed tumor growth and metastasis in a mouse model of TC. PRMT1 downregulation increased E­cadherin expression and decreased the expression of vimentin, H4R3me2as, and ZEB1 in the TC cells and the mouse model of TC. Conversely, PRMT1 overexpression had the opposite effect on TC malignant characteristics (P<0.05). These findings suggest that PRMT1 knockdown inhibited TC malignancy by downregulating H4R3me2as/ZEB1, thereby highlighting novel therapeutic targets and diagnostic markers for the management of TC.

Inhibition of PRMT1 alleviates sepsis-induced acute kidney injury in mice by blocking the TGF-ß1 and IL-6 trans-signaling pathways.

Sepsis-induced acute kidney injury (SI-AKI) causes renal dysfunction and has a high mortality rate. Protein arginine methyltransferase-1 (PRMT1) is a key regulator of renal insufficiency. In the present study, we explored the potential involvement of PRMT1 in SI-AKI. A murine model of SI-AKI was induced by cecal ligation and perforation. The expression and localization of PRMT1 and molecules involved in the transforming growth factor (TGF)-ß1/Smad3 and interleukin (IL)-6/signal transducer and activator of transcription 3 (STAT3) signaling pathways were detected in mouse kidney tissues by western blot analysis, immunofluorescence, and immunohistochemistry. The association of PRMT1 with downstream molecules of the TGF-ß1/Smad3 and IL-6/STAT3 signaling pathways was further verified in vitro in mouse renal tubular epithelial cells. Cecal ligation and perforation caused epithelial-mesenchymal transition, apoptosis, and inflammation in renal tissues, and this was alleviated by inhibition of PRMT1. Inhibition of PRMT1 in SI-AKI mice decreased the expression of TGF-ß1 and phosphorylation of Smad3 in the renal cortex, and downregulated the expression of soluble IL-6R and phosphorylation of STAT3 in the medulla. Knockdown of PRMT1 in mouse renal tubular epithelial cells restricted the expression of Cox-2, E-cadherin, Pro-caspase3, and phosphorylated Smad3 (involved in the TGF-ß1-mediated signaling pathway), and also blocked IL-6/soluble IL-6R, inducing the expression of Cox-2 and phosphorylated-STAT3. In conclusion, our findings suggest that inhibition of PRMT1 mitigates SI-AKI by inactivating the TGF-ß1/Smad3 pathway in the cortex and the IL-6/STAT3 pathway in the medulla. Our findings may aid in the identification of potential therapeutic target molecules for SI-AKI.

Protein arginine methyltransferase 1 upregulates matrix metalloproteinase-2/9 expression via Zeste Homolog 2 to promote human rheumatoid arthritis fibroblast-like synovial cell survival and metastasis.

OBJECTIVE: To explore the role of protein arginine methyltransferase 1 (PRMT1) in the development of rheumatoid arthritis (RA). METHODS: Fibroblast-like synoviocytes (FLS) were isolated from synovial tissues, cultured and transfected with plasmid vector or short hairpin RNA (shRNA). The morphology and surface markers of FLS were investigated by light microscopy and flow cytometry. The expression levels of PRMT1, Zeste Homolog 2 (EZH2), matrix metalloproteinase-2 (MMP-2) and MMP-9 were detected by real-time polymerase chain reaction and Western blotting. Cell viability was tested by MTT assay, cell proliferation was assessed by EdU assay, cell invasion was evaluated by Transwell invasion test, cell migration was detected by wound healing assay, and cell apoptosis was detected by flow cytometry. RESULTS: The expression of PRMT1 was elevated in RA synovial tissues compared with control tissues. FLS from control tissues showed a lower level of PRMT1 than FLS from RA tissues, and FLS from RA tissues had a stronger ability of cell survival and metastasis than those from control tissues. When silencing PRMT1 expression, FLS from RA tissues showed a decreased ability of cell survival and metastasis. Additionally, FLS from RA tissues expressed a higher level of MMP-2 and MMP-9. When silencing PRMT1 expression, the expression of MMP-2 and MMP-9 of FLS was suppressed. Furthermore, the effect of PRMT1 on FLS was mediated by EZH2. CONCLUSION: We found that PRMT1 had an overall effect on FLS via EZH2, which contributed to the development of RA. Hence, PRMT1 and EZH2 provide potential targets for RA treatment.