Many small‑molecule drugs are known to accumulate within both host cells and the cells of the gut microbiome. However, the molecular consequences of such intracellular bioaccumulation remain largely unexplored. The authors of the source study investigated whether intracellular accumulation of a clinically used small molecule could perturb RNA–protein interactions broadly across cellular networks. The motivation stems from a need to understand off‑target molecular effects that could contribute to variation in drug efficacy or toxicity and to perturbations of host–microbiome interactions.
Using the antidepressant duloxetine as a test compound, the investigators report a widespread reduction in RNA‑binding capacity across phylogenetically diverse bacteria and human intestinal cell models. In the bacterial strain Escherichia coli IAI1 and in human Caco‑2 intestinal epithelial cells, approximately 80% of detected RNA‑binding proteins responded to duloxetine treatment. This response pattern indicates a network‑scale disruption of RNA–protein interactions rather than a limited effect on a small subset of RBPs.
The reported effect was consistent across the bacterial and human cell contexts included in the study, supporting the concept that intracellular accumulation of certain small molecules can have broad and conserved impacts on post‑transcriptional regulation.
As a mechanistic example illustrating how drug accumulation can alter RNA–protein interactions, the study describes effects on the enzyme PyrB (a pyrimidine biosynthesis enzyme). Duloxetine disrupted PyrB’s interactions with specific transcripts that encode metabolically linked functions. In the native state, PyrB binds to transcripts via 3′ UTR localized stem‑loop structures; duloxetine exposure weakened these interactions, altering PyrB’s RNA‑binding behavior.
This example links a metabolic enzyme’s ligand binding to its RNA‑binding capability, demonstrating that small molecules can modulate RNA–protein associations by interfering with substrate or ligand interactions at the protein’s active or binding sites.
The authors provide biochemical and structural analyses supporting a competitive interaction between duloxetine and the natural substrate of PyrB, aspartate. According to the reported data, duloxetine competes with aspartate for interaction with PyrB, and this competition correlates with weakened binding of PyrB to RNA stem‑loop structures in its partner transcripts.
These biochemical and structural observations are presented as a mechanistic basis for duloxetine’s disruption of PyrB–RNA interactions, linking small‑molecule binding at a metabolic enzyme’s substrate site to altered RNA‑binding function.
The study’s findings introduce a previously unrecognized off‑target mode of drug action: network‑scale disruption of RNA–protein interactions due to intracellular drug accumulation. Several implications follow from this observation:
Intracellular accumulation of therapeutics may perturb large sets of RNA‑protein interactions, with potential downstream effects on post‑transcriptional regulation and metabolic coordination.
Off‑target effects on RNA‑binding proteins might contribute to interindividual variation in drug responses, including efficacy and adverse effects, especially for drugs that accumulate in host or microbial cells.
Alterations in RNA–protein interaction networks in gut microbes or intestinal cells could affect host–microbiome interactions and drug metabolism in ways not previously accounted for.
Overall, the results expand the conceptual framework for assessing drug off‑target activity beyond canonical protein targets to include effects on RNA–protein interaction networks.
The provided source text is an article abstract and summary from a preprint. It reports the major findings and a mechanistic example but does not include many experimental specifics in the excerpt provided here. The following details were not reported in the supplied text and therefore are not available for summary:
Readers should consult the full preprint for experimental detail, data figures, and supplementary information. The authors declared no competing interests, and funding sources were noted in the source article.