Biology subjects

Ryback, B.

Publications and source records attributed to Ryback, B..

4 recordsLinked to original sources

bioRxiv2024

Renalase inhibition regulates β cell metabolism to defend against acute and chronic stress

Renalase (Rnls), annotated as an oxidase enzyme, is a GWAS gene associated with Type 1 Diabetes (T1D) risk. We previously discovered that Rnls inhibition delays diabetes onset in mouse models of T1D in vivo, and protects pancreatic {beta} cells against autoimmune killing, ER and oxidative stress in vitro. The molecular biochemistry and functions of Rnls are entirely uncharted. Here we find that Rnls inhibition defends against loss of {beta} cell mass and islet dysfunction in chronically stressed Akita mice in vivo. We used RNA sequencing, untargeted and targeted metabolomics and metabolic function experiments in mouse and human {beta} cells and discovered a robust and conserved metabolic shift towards glycolysis, amino acid abundance and GSH synthesis to counter protein misfolding stress, in vitro. Our work illustrates a function for Rnls in mammalian cells, and suggests an axis by which manipulating intrinsic properties of {beta} cells can rewire metabolism to protect against diabetogenic stress.

physiology↗

bioRxiv2024

Ergothioneine boosts mitochondrial respiration and exercise performance via direct activation of MPST

Ergothioneine (EGT) is a diet-derived, atypical amino acid that accumulates to high levels in human tissues. Reduced EGT levels have been linked to age-related disorders, including neurodegenerative and cardiovascular diseases, while EGT supplementation is protective in a broad range of disease and aging models in mice. Despite these promising data, the direct and physiologically relevant molecular target of EGT has remained elusive. Here we use a systematic approach to identify how mitochondria remodel their metabolome in response to exercise training. From this data, we find that EGT accumulates in muscle mitochondria upon exercise training. Proteome-wide thermal stability studies identify 3-mercaptopyruvate sulfurtransferase (MPST) as a direct molecular target of EGT; EGT binds to and activates MPST, thereby boosting mitochondrial respiration and exercise training performance in mice. Together, these data identify the first physiologically relevant EGT target and establish the EGT-MPST axis as a molecular mechanism for regulating mitochondrial function and exercise performance.

molecular biology↗

bioRxiv2024

Mitochondrial membrane potential regulates nuclear DNA methylation and gene expression through phospholipid remodeling

Maintenance of the mitochondrial inner membrane potential ({Delta}{Psi}M) is critical for many aspects of mitochondrial function, including mitochondrial protein import and ion homeostasis. While {Delta}{Psi}M loss and its consequences are well studied, little is known about the effects of increased {Delta}{Psi}M. In this study, we used cells deleted of ATPIF1, a natural inhibitor of the hydrolytic activity of the ATP synthase, as a genetic model of mitochondrial hyperpolarization. Our data show that chronic {Delta}{Psi}M increase leads to nuclear DNA hypermethylation, regulating transcription of mitochondria, carbohydrate and lipid metabolism genes. Surprisingly, remodeling of phospholipids, but not metabolites or redox changes, mechanistically links the {Delta}{Psi}M to the epigenome. These changes were also observed upon chemical exposures and reversed by decreasing the {Delta}{Psi}M, highlighting them as hallmark adaptations to chronic mitochondrial hyperpolarization. Our results reveal the {Delta}{Psi}M as the upstream signal conveying the mitochondrial status to the epigenome to regulate cellular biology, providing a new framework for how mitochondria can influence health outcomes in the absence of canonical dysfunction. HighlightsO_LIMitochondria hyperpolarization leads to nuclear DNA hypermethylation C_LIO_LIDNA methylation regulates expression of mitochondrial and lipid metabolism genes C_LIO_LIPhospholipid remodeling mediates the epigenetic effects of mitochondrial hyperpolarization C_LI

genomics↗

bioRxiv2022

Elevated arginine levels in liver tumors promote metabolic reprogramming and tumor growth

Arginine auxotropy, due to reduced expression of urea cycle genes, is common in cancer. However, little is known about the levels of arginine in these cancers. Here, we report that arginine levels are elevated in hepatocellular carcinoma (HCC) despite reduced expression of urea cycle enzymes. Liver tumors accumulate high levels specifically of arginine via increased uptake and, more importantly, via suppression of arginine-to-polyamine conversion due to reduced arginase 1 (ARG1) and agmatinase (AGMAT) expression. Furthermore, the high levels of arginine are required for tumor growth. Mechanistically, high levels of arginine promote tumorigenesis via transcriptional regulation of metabolic genes, including upregulation of asparagine synthetase (ASNS). ASNS-derived asparagine further enhances arginine uptake, creating a positive feedback loop to sustain high arginine levels and oncogenic metabolism. Thus, arginine is a novel second messenger-like molecule that reprograms metabolism to promote tumor growth.

cancer biology↗