Protein arginine methyltransferase 4 modulates nitric oxide synthase uncoupling and cerebral blood flow in Alzheimer's disease

An Expanded Narrative Review of Neurotransmitters on Alzheimer's Disease: The Role of Therapeutic Interventions on Neurotransmission

Alzheimer's disease (AD) is a progressive neurodegenerative disease. The accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles are the key players responsible for the pathogenesis of the disease. The accumulation of Aβ plaques and tau affect the balance in chemical neurotransmitters in the brain. Thus, the current review examined the role of neurotransmitters in the pathogenesis of Alzheimer's disease and discusses the alterations in the neurochemical activity and cross talk with their receptors and transporters. In the presence of Aβ plaques and neurofibrillary tangles, changes may occur in the expression of neuronal receptors which in turn triggers excessive release of glutamate into the synaptic cleft contributing to cell death and neuronal damage. The GABAergic system may also be affected by AD pathology in a similar way. In addition, decreased receptors in the cholinergic system and dysfunction in the dopamine neurotransmission of AD pathology may also contribute to the damage to cognitive function. Moreover, the presence of deficiencies in noradrenergic neurons within the locus coeruleus in AD suggests that noradrenergic stimulation could be useful in addressing its pathophysiology. The regulation of melatonin, known for its effectiveness in enhancing cognitive function and preventing Aβ accumulation, along with the involvement of the serotonergic system and histaminergic system in cognition and memory, becomes remarkable for promoting neurotransmission in AD. Additionally, nitric oxide and adenosine-based therapeutic approaches play a protective role in AD by preventing neuroinflammation. Overall, neurotransmitter-based therapeutic strategies emerge as pivotal for addressing neurotransmitter homeostasis and neurotransmission in the context of AD. This review discussed the potential for neurotransmitter-based drugs to be effective in slowing and correcting the neurodegenerative processes in AD by targeting the neurochemical imbalance in the brain. Therefore, neurotransmitter-based drugs could serve as a future therapeutic strategy to tackle AD.

PRMT3 and CARM1: Emerging Epigenetic Targets in Cancer

The family of protein arginine methyltransferases (PRMTs) occupies an important position in biology, especially during the initiation and development of cancer. PRMT3 and CARM1(also known as PRMT4), being type I protein arginine methyltransferases, are key in controlling tumour progression by catalysing the mono-methylation and asymmetric di-methylation of both histone and non-histone substrates. This paper reviews the functions and potential therapeutic target value of PRMT3 and CARM1 in a variety of cancers. Studies have identified abnormal expressions of PRMT3 and CARM1 in several malignancies, closely linked to cancer progression, advancement, and resistance to treatment. Such as hepatocellular carcinoma, colorectal cancer, ovarian cancer, and endometrial cancer. These findings offer new strategies and directions for cancer treatment, especially in enhancing the effectiveness of conventional treatment methods.

Protein arginine methyltransferases as regulators of cellular stress

Arginine modification can be a "switch" to regulate DNA transcription and a post-translational modification via methylation of a variety of cellular targets involved in signal transduction, gene transcription, DNA repair, and mRNA alterations. This consequently can turn downstream biological effectors "on" and "off". Arginine methylation is catalyzed by protein arginine methyltransferases (PRMTs 1-9) in both the nucleus and cytoplasm, and is thought to be involved in many disease processes. However, PRMTs have not been well-documented in the brain and their function as it relates to metabolism, circulation, functional learning and memory are understudied. In this review, we provide a comprehensive overview of PRMTs relevant to cellular stress, and future directions into PRMTs as therapeutic regulators in brain pathologies.

Blockade of A2AR improved brain perfusion and cognitive function in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 6.2 million Americans aged 65 and older, particularly women. Along with AD's main hallmarks (formation of β-amyloid plaques and tau neurofibrillary tangles), there are vascular alterations that occurs in AD pathology. Adenosine A2 receptor (A2AR) is one of the key factors of brain vascular autoregulation and is overexpressed in AD patients. Our previous findings suggest that protein arginine methyltransferase 4 (PRMT4) is overexpressed in AD, which leads to decrease in cerebral blood flow in aged female 3xTg mice. We aimed to investigate the mechanism behind A2AR signaling in the regulation of brain perfusion and blood-brain barrier integrity in age and sex-dependent 3xTg mice, and if it is related to PRMT4. Istradefylline, a highly selective A2AR antagonist, was used to modulate A2AR signaling. Aged female 3xTg and C57BL/6 J mice were evaluated for brain perfusion (via laser speckle) and cognitive function (via open field, T-maze and novel object recognition). Our results suggest that modulation of A2AR signaling in aged female 3xTg increased cerebral perfusion by decreasing PRMT4 expression, restored the levels of APP and tau, maintained blood-brain barrier integrity by maintaining the expression of tight junction proteins, and preserved functional learning/memory.

Poly-GR Impairs PRMT1-Mediated Arginine Methylation of Disease-Linked RNA-Binding Proteins by Acting as a Substrate Sink

Dipeptide repeat proteins (DPRs) are aberrant protein species found in C9orf72-linked amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two neurodegenerative diseases characterized by the cytoplasmic mislocalization and aggregation of RNA-binding proteins (RBPs). In particular, arginine (R)-rich DPRs (poly-GR and poly-PR) have been suggested to promiscuously interact with multiple cellular proteins and thereby exert high cytotoxicity. Components of the protein arginine methylation machinery have been identified as modulators of DPR toxicity and/or potential cellular interactors of R-rich DPRs; however, the molecular details and consequences of such an interaction are currently not well understood. Here, we demonstrate that several members of the family of protein arginine methyltransferases (PRMTs) can directly interact with R-rich DPRs in vitro and in the cytosol. In vitro, R-rich DPRs reduce solubility and promote phase separation of PRMT1, the main enzyme responsible for asymmetric arginine-dimethylation (ADMA) in mammalian cells, in a concentration- and length-dependent manner. Moreover, we demonstrate that poly-GR interferes more efficiently than poly-PR with PRMT1-mediated arginine methylation of RBPs such as hnRNPA3. We additionally show by two alternative approaches that poly-GR itself is a substrate for PRMT1-mediated arginine dimethylation. We propose that poly-GR may act as a direct competitor for arginine methylation of cellular PRMT1 targets, such as disease-linked RBPs.

Protein Arginine Methyltransferases: Emerging Targets in Cardiovascular and Metabolic Disease

Cardiovascular diseases (CVDs) and metabolic disorders stand as formidable challenges that significantly impact the clinical outcomes and living quality for afflicted individuals. An intricate comprehension of the underlying mechanisms is paramount for the development of efficacious therapeutic strategies. Protein arginine methyltransferases (PRMTs), a class of enzymes responsible for the precise regulation of protein methylation, have ascended to pivotal roles and emerged as crucial regulators within the intrinsic pathophysiology of these diseases. Herein, we review recent advancements in research elucidating on the multifaceted involvements of PRMTs in cardiovascular system and metabolic diseases, contributing significantly to deepen our understanding of the pathogenesis and progression of these maladies. In addition, this review provides a comprehensive analysis to unveil the distinctive roles of PRMTs across diverse cell types implicated in cardiovascular and metabolic disorders, which holds great potential to reveal novel therapeutic interventions targeting PRMTs, thus presenting promising perspectives to effectively address the substantial global burden imposed by CVDs and metabolic disorders.

The role of serum/glucocorticoid-regulated kinase 1 in brain function following cerebral ischemia

Cardiopulmonary arrest (CA) is a major cause of death/disability in the U.S. with poor prognosis and survival rates. Current therapeutic challenges are physiologically complex because they involve hypoperfusion (decreased cerebral blood flow), neuroinflammation, and mitochondrial dysfunction. We previously discovered novel serum/glucocorticoid-regulated kinase 1 (SGK1) is highly expressed in brain of neurons that are susceptible to ischemia (hippocampus and cortex). We inhibited SGK1 and utilized pharmacological (specific inhibitor, GSK650394) and neuron-specific genetic approaches (shRNA) in rodent models of CA to determine if SGK1 is responsible for hypoperfusion, neuroinflammation, mitochondrial dysfunctional, and neurological deficits after CA. Inhibition of SGK1 alleviated cortical hypoperfusion and neuroinflammation (via Iba1, GFAP, and cytokine array). Treatment with GSK650394 enhanced mitochondrial function (via Seahorse respirometry) in the hippocampus 3 and 7 days after CA. Neuronal injury (via MAP2, dMBP, and Golgi staining) in the hippocampus and cortex was observed 7 days after CA but ameliorated with SGK1-shRNA. Moreover, SGK1 mediated neuronal injury by regulating the Ndrg1-SOX10 axis. Finally, animals subjected to CA exhibited learning/memory, motor, and anxiety deficits after CA, whereas SGK1 inhibition via SGK1-shRNA improved neurocognitive function. The present study suggests the fundamental roles of SGK1 in brain circulation and neuronal survival/death in cerebral ischemia-related diseases.

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.

Functional Implications of Protein Arginine Methyltransferases (PRMTs) in Neurodegenerative Diseases

During the aging of the global population, the prevalence of neurodegenerative diseases will be continuously growing. Although each disorder is characterized by disease-specific protein accumulations, several common pathophysiological mechanisms encompassing both genetic and environmental factors have been detected. Among them, protein arginine methyltransferases (PRMTs), which catalyze the methylation of arginine of various substrates, have been revealed to regulate several cellular mechanisms, including neuronal cell survival and excitability, axonal transport, synaptic maturation, and myelination. Emerging evidence highlights their critical involvement in the pathophysiology of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal dementia-amyotrophic lateral sclerosis (FTD-ALS) spectrum, Huntington's disease (HD), spinal muscular atrophy (SMA) and spinal and bulbar muscular atrophy (SBMA). Underlying mechanisms include the regulation of gene transcription and RNA splicing, as well as their implication in various signaling pathways related to oxidative stress responses, apoptosis, neuroinflammation, vacuole degeneration, abnormal protein accumulation and neurotransmission. The targeting of PRMTs is a therapeutic approach initially developed against various forms of cancer but currently presents a novel potential strategy for neurodegenerative diseases. In this review, we discuss the accumulating evidence on the role of PRMTs in the pathophysiology of neurodegenerative diseases, enlightening their pathogenesis and stimulating future research.

Amino acid metabolism in health and disease

Amino acids are the building blocks of protein synthesis. They are structural elements and energy sources of cells necessary for normal cell growth, differentiation and function. Amino acid metabolism disorders have been linked with a number of pathological conditions, including metabolic diseases, cardiovascular diseases, immune diseases, and cancer. In the case of tumors, alterations in amino acid metabolism can be used not only as clinical indicators of cancer progression but also as therapeutic strategies. Since the growth and development of tumors depend on the intake of foreign amino acids, more and more studies have targeted the metabolism of tumor-related amino acids to selectively kill tumor cells. Furthermore, immune-related studies have confirmed that amino acid metabolism regulates the function of effector T cells and regulatory T cells, affecting the function of immune cells. Therefore, studying amino acid metabolism associated with disease and identifying targets in amino acid metabolic pathways may be helpful for disease treatment. This article mainly focuses on the research of amino acid metabolism in tumor-oriented diseases, and reviews the research and clinical research progress of metabolic diseases, cardiovascular diseases and immune-related diseases related to amino acid metabolism, in order to provide theoretical basis for targeted therapy of amino acid metabolism.