A translation-independent function of PheRS activates growth and proliferation in Drosophila

Effects of unstable β-PheRS on food avoidance, growth, and development are suppressed by the appetite hormone CCHa2

Amino acyl-tRNA synthetases perform diverse non-canonical functions aside from their essential role in charging tRNAs with their cognate amino acid. The phenylalanyl-tRNA synthetase (PheRS/FARS) is an α2β2 tetramer that is needed for charging the tRNAPhe for its translation activity. Fragments of the α-subunit have been shown to display an additional, translation-independent, function that activates growth and proliferation and counteracts Notch signalling. Here we show in Drosophila that overexpressing the β-subunit in the context of the complete PheRS leads to larval roaming, food avoidance, slow growth, and a developmental delay that can last several days and even prevents pupation. These behavioural and developmental phenotypes are induced by PheRS expression in CCHa2+ and Pros+ cells. Simultaneous expression of β-PheRS, α-PheRS, and the appetite-inducing CCHa2 peptide rescued these phenotypes, linking this β-PheRS activity to the appetite-controlling pathway. The fragmentation dynamic of the excessive β-PheRS points to β-PheRS fragments as possible candidate inducers of these phenotypes. Because fragmentation of human FARS has also been observed in human cells and mutations in human β-PheRS (FARSB) can lead to problems in gaining weight, Drosophila β-PheRS can also serve as a model for the human phenotype and possibly also for obesity.

Mechanistic insights into the antitumoral potential and in vivo antiproliferative efficacy of a silver-based core@shell nanosystem

This study delves into the biomolecular mechanisms underlying the antitumoral efficacy of a hybrid nanosystem, comprised of a silver core@shell (Ag@MSNs) functionalized with transferrin (Tf). Employing a SILAC proteomics strategy, we identified over 150 de-regulated proteins following exposure to the nanosystem. These proteins play pivotal roles in diverse cellular processes, including mitochondrial fission, calcium homeostasis, endoplasmic reticulum (ER) stress, oxidative stress response, migration, invasion, protein synthesis, RNA maturation, chemoresistance, and cellular proliferation. Rigorous validation of key findings substantiates that the nanosystem elicits its antitumoral effects by activating mitochondrial fission, leading to disruptions in calcium homeostasis, as corroborated by RT-qPCR and flow cytometry analyses. Additionally, induction of ER stress was validated through western blotting of ER stress markers. The cytotoxic action of the nanosystem was further affirmed through the generation of cytosolic and mitochondrial reactive oxygen species (ROS). Finally, in vivo experiments using a chicken embryo model not only confirmed the antitumoral capacity of the nanosystem, but also demonstrated its efficacy in reducing cellular proliferation. These comprehensive findings endorse the potential of the designed Ag@MSNs-Tf nanosystem as a groundbreaking chemotherapeutic agent, shedding light on its multifaceted mechanisms and in vivo applicability.

FARSB Facilitates Hepatocellular Carcinoma Progression by Activating the mTORC1 Signaling Pathway

Hepatocellular carcinoma (HCC) is a common malignant tumor with high mortality. Human phenylalanine tRNA synthetase (PheRS) comprises two α catalytic subunits encoded by the FARSA gene and two β regulatory subunits encoded by the FARSB gene. FARSB is a potential oncogene, but no experimental data show the relationship between FARSB and HCC progression. We found that the high expression of FARSB in liver cancer is closely related to patients' low survival and poor prognosis. In liver cancer cells, the mRNA and protein expression levels of FARSB are increased and promote cell proliferation and migration. Mechanistically, FARSB activates the mTOR complex 1 (mTORC1) signaling pathway by binding to the component Raptor of the mTORC1 complex to play a role in promoting cancer. In addition, we found that FARSB can inhibit erastin-induced ferroptosis by regulating the mTOR signaling pathway, which may be another mechanism by which FARSB promotes HCC progression. In summary, FARSB promotes HCC progression and is associated with the poor prognosis of patients. FARSB is expected to be a biomarker for early screening and treatment of HCC.

Recessive aminoacyl-tRNA synthetase disorders: lessons learned from in vivo disease models

Protein synthesis is a fundamental process that underpins almost every aspect of cellular functioning. Intriguingly, despite their common function, recessive mutations in aminoacyl-tRNA synthetases (ARSs), the family of enzymes that pair tRNA molecules with amino acids prior to translation on the ribosome, cause a diverse range of multi-system disorders that affect specific groups of tissues. Neurological development is impaired in most ARS-associated disorders. In addition to central nervous system defects, diseases caused by recessive mutations in cytosolic ARSs commonly affect the liver and lungs. Patients with biallelic mutations in mitochondrial ARSs often present with encephalopathies, with variable involvement of peripheral systems. Many of these disorders cause severe disability, and as understanding of their pathogenesis is currently limited, there are no effective treatments available. To address this, accurate in vivo models for most of the recessive ARS diseases are urgently needed. Here, we discuss approaches that have been taken to model recessive ARS diseases in vivo, highlighting some of the challenges that have arisen in this process, as well as key results obtained from these models. Further development and refinement of animal models is essential to facilitate a better understanding of the pathophysiology underlying recessive ARS diseases, and ultimately to enable development and testing of effective therapies.

First Report of FARSA in the Regulation of Cell Cycle and Survival in Mantle Cell Lymphoma Cells via PI3K-AKT and FOXO1-RAG1 Axes

Cancer-associated factors have been largely identified in the understanding of tumorigenesis and progression. However, aminoacyl-transfer RNA (tRNA) synthetases (aaRSs) have so far been neglected in cancer research due to their canonical activities in protein translation and synthesis. FARSA, the alpha subunit of the phenylalanyl-tRNA synthetase is elevated across many cancer types, but its function in mantle cell lymphoma (MCL) remains undetermined. Herein, we found the lowest levels of FARSA in patients with MCL compared with other subtypes of lymphomas, and the same lower levels of FARSA were observed in chemoresistant MCL cell lines. Unexpectedly, despite the essential catalytic roles of FARSA, knockdown of FARSA in MCL cells did not lead to cell death but resulted in accelerated cell proliferation and cell cycle, whereas overexpression of FARSA induced remarkable cell-cycle arrest and overwhelming apoptosis. Further RNA sequencing (RNA-seq) analysis and validation experiments confirmed a strong connection between FARSA and cell cycle in MCL cells. Importantly, FARSA leads to the alteration of cell cycle and survival via both PI3K-AKT and FOXO1-RAG1 axes, highlighting a FARSA-mediated regulatory network in MCL cells. Our findings, for the first time, reveal the noncanonical roles of FARSA in MCL cells, and provide novel insights into understanding the pathogenesis and progression of B-cell malignancies.

Aminoacyl-tRNA Synthetases: On Anti-Synthetase Syndrome and Beyond

Anti-synthetase syndrome (ASSD) is an autoimmune disease characterized by the presence of autoantibodies targeting one of several aminoacyl t-RNA synthetases (aaRSs) along with clinical features including interstitial lung disease, myositis, Raynaud’s phenomenon, arthritis, mechanic’s hands, and fever. The family of aaRSs consists of highly conserved cytoplasmic and mitochondrial enzymes, one for each amino acid, which are essential for the RNA translation machinery and protein synthesis. Along with their main functions, aaRSs are involved in the development of immune responses, regulation of transcription, and gene-specific silencing of translation. During the last decade, these proteins have been associated with cancer, neurological disorders, infectious responses, and autoimmune diseases including ASSD. To date, several aaRSs have been described to be possible autoantigens in different diseases. The most commonly described are histidyl (HisRS), threonyl (ThrRS), alanyl (AlaRS), glycyl (GlyRS), isoleucyl (IleRS), asparaginyl (AsnRS), phenylalanyl (PheRS), tyrosyl (TyrRS), lysyl (LysRS), glutaminyl (GlnRS), tryptophanyl (TrpRS), and seryl (SerRS) tRNA synthetases. Autoantibodies against the first eight autoantigens listed above have been associated with ASSD while the rest have been associated with other diseases. This review will address what is known about the function of the aaRSs with a focus on their autoantigenic properties. We will also describe the anti-aaRSs autoantibodies and their association to specific clinical manifestations, and discuss their potential contribution to the pathogenesis of ASSD.

First person – Manh Tin Ho and Jiongming Lu

First Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms, helping early-career researchers promote themselves alongside their papers. Manh Tin Ho and Jiongming Lu are co-first authors on ‘A translation-independent activity of PheRS activates growth and proliferation in Drosophila’, published in DMM. Manh Tin conducted the research described in this article while a PhD student in the lab of Beat Suter at the University of Bern, Bern, Switzerland, and is now a postdoctoral researcher in the lab of Daniel Fuster at the University of Bern, investigating kidney disease and sodium/proton exchange membrane proteins. Jiongming conducted the research described in this article while a PhD student in the lab of Beat Suter at the University of Bern, and is now a postdoctoral researcher in the lab of Linda Partridge at the Max Planck Institute for Biology of Ageing, Köln, Germany, investigating molecular mechanisms and new strategies of healthy ageing.