Reactive sulfur species regulate tRNA methylthiolation and contribute to insulin secretion

The 2-methylthio (ms²) modification at A37 of tRNAs is critical for accurate decoding, and contributes to metabolic homeostasis in mammals. However, the regulatory mechanism of ms² modification remains largely unknown. Here, we report that cysteine hydropersulfide (CysSSH), a newly identified reactive sulfur species, is involved in ms² modification in cells. The suppression of intracellular CysSSH production rapidly reduced ms² modification, which was rescued by the application of an exogenous CysSSH donor. Using a unique and stable isotope-labeled CysSSH donor, we show that CysSSH was capable of specifically transferring its reactive sulfur atom to the cysteine residues of ms²-modifying enzymes as well as ms² modification. Furthermore, the suppression of CysSSH production impaired insulin secretion and caused glucose intolerance in both a pancreatic β-cell line and mouse model. These results demonstrate that intracellular CysSSH is a novel sulfur source for ms² modification, and that it contributes to insulin secretion.