Sonmez, A. | bioRxiv Science

bioRxiv2026

pH-dependent trapping of cationic amphiphilic drugs perturbs insulin granule homeostasis

Pancreatic {beta}-cells store insulin in acidic secretory granules (SGs), specialized organelles that also contain monoamine neurotransmitters such as serotonin. Many neuroactive drugs with monoaminergic activity are cationic amphiphilic drugs (CADs) that accumulate in acidic compartments by pH-dependent trapping. Yet, whether insulin SGs represent a site of CAD accumulation and if this affects their properties such as monoamine storage and pH remain unclear. Here, we show that Slc18a1/VMAT1 is required for vesicular monoamine uptake and maintenance of cellular serotonin levels in insulinoma INS-1 cells. In contrast, neuroactive CADs accumulate via pH-dependent trapping at luminal pH values characteristic of insulin SGs. CADs inhibit VMAT-mediated uptake of the fluorescent monoamine probe FFN206 and induce its efflux to the extracellular space without detectable changes in SG luminal pH. Conversely, natural VMAT substrates such as serotonin and dopamine increase SG pH in a VMAT-dependent manner. These findings identify insulin SGs as acidic organelles susceptible to CAD accumulation and uncover distinct mechanisms regulating secretory granule homeostasis.

cell biology↗

bioRxiv2025

AquIRE reveals multiple mechanisms of clinically induced RNA damage and the conservation and dynamics of glycoRNAs

RNA is subject to many modifications, from small chemical changes such as methylation through to conjugation of biomolecules such as glycans. As well as these endogenously written modifications, RNA is also exposed to damage induced by its environment. Certain clinical compounds are known to drive covalent modifications of RNA with a growing appreciation for how these affect function. To understand the regulation of these modifications we need a reliable, sensitive and rapid methodology for their quantification. Thus, we developed AquIRE and applied it to the analysis of drug-induced RNA damage, showing this to be widespread with intricate temporal dynamics. Using the same methodology we identify RNA:protein crosslinking and the rewriting of the epitranscriptome as a consequence of clinical RNA damage. We also demonstrate how liquid-liquid phase separation increases RNA damage and expand the horizons of the glycoRNA world across the kingdoms of life and into cell-free glycoRNA.

molecular biology↗