Regulation of neural stem cell proliferation and survival by protein arginine methyltransferase 1

Protein Arginine Methyltransferases from Regulatory Function to Clinical Implication in Central Nervous System

Arginine methylation, catalyzed by protein arginine methyltransferases (PRMTs), is a regulatory key mechanism involved in various cellular processes such as gene expression, RNA processing, DNA damage repair. Increasing evidence highlights the crucial role of PRMTs in human diseases, including cancer, cardiovascular and metabolic diseases. Here, this review focuses on the latest findings regarding PRMTs in the central nervous system (CNS), emphasizing their regulatory roles in neural stem cells, neurons, and glial cells. Additionally, we examine the connection between PRMTs dysregulation and neurological diseases affecting the CNS, including brain tumors, neurodegenerative diseases, and neurodevelopmental disorders. Therefore, this review aims to deepen our understanding of PRMTs-mediated arginine methylation in CNS and open avenues for developing novel therapeutic strategies for neurological diseases.

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.

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.

Critical Roles of Protein Arginine Methylation in the Central Nervous System

A remarkable post-transitional modification of both histones and non-histone proteins is arginine methylation. Methylation of arginine residues is crucial for a wide range of cellular process, including signal transduction, DNA repair, gene expression, mRNA splicing, and protein interaction. Arginine methylation is modulated by arginine methyltransferases and demethylases, like protein arginine methyltransferase (PRMTs) and Jumonji C (JmjC) domain containing (JMJD) proteins. Symmetric dimethylarginine and asymmetric dimethylarginine, metabolic products of the PRMTs and JMJD proteins, can be changed by abnormal expression of these proteins. Many pathologies including cancer, inflammation and immune responses have been closely linked to aberrant arginine methylation. Currently, the majority of the literature discusses the substrate specificity and function of arginine methylation in the pathogenesis and prognosis of cancers. Numerous investigations on the roles of arginine methylation in the central nervous system (CNS) have so far been conducted. In this review, we display the biochemistry of arginine methylation and provide an overview of the regulatory mechanism of arginine methyltransferases and demethylases. We also highlight physiological functions of arginine methylation in the CNS and the significance of arginine methylation in a variety of neurological diseases such as brain cancers, neurodegenerative diseases and neurodevelopmental disorders. Furthermore, we summarize PRMT inhibitors and molecular functions of arginine methylation. Finally, we pose important questions that require further research to comprehend the roles of arginine methylation in the CNS and discover more effective targets for the treatment of neurological diseases.