Revealing Mitochondrion-Lysosome Dynamic Interactions and pH Variations in Live Cells with a pH-Sensitive Fluorescent Probe.

Mitochondrion-lysosome interactions have garnered significant attention in recent research. Numerous studies have shown that mitochondrion-lysosome interactions, including mitochondrion-lysosome contact (MLC) and mitophagy, are involved in various biological processes and pathological conditions. Single fluorescent probes are termed a pivotal chemical tool in unraveling the intricate spatiotemporal interorganelle interplay in live cells. However, current chemical tools are insufficient to deeply understand mitochondrion-lysosome dynamic interactions and related diseases, Moreover, the rational design of mitochondrion-lysosome dual-targeting fluorescent probes is intractable. Herein, we designed and synthesized a pH-sensitive fluorescent probe called INSA, which could simultaneously light up mitochondria (red emission) and lysosomes (green emission) for their internal pH differences. Employing INSA, we successfully recorded long-term dynamic interactions between lysosomes and mitochondria. More importantly, the increasing mitochondrion-lysosome interactions in ferroptotic cells were also revealed by INSA. Further, we observed pH variations in mitochondria and lysosomes during ferroptosis for the first time. In brief, this work not only introduced a pH-sensitive fluorescent probe INSA for the disclosure of the mitochondrion-lysosome dynamic interplays but also pioneered the visualization of the organellar pH alternation in a specific disease model.

Development of a Highly Selective and Sensitive Fluorescent Probe for Imaging RNA Dynamics in Live Cells.

RNA imaging is of great importance for understanding its complex spatiotemporal dynamics and cellular functions. Considerable effort has been devoted to the development of small-molecule fluorescent probes for RNA imaging. However, most of the reported studies have mainly focused on improving the photostability, permeability, long emission wavelength, and compatibility with live-cell imaging of RNA probes. Less attention has been paid to the selectivity and detection limit of this class of probes. Highly selective and sensitive RNA probes are still rarely available. In this study, a new set of styryl probes were designed and synthesized, with the aim of upgrading the detection limit and maintaining the selectivity of a lead probe QUID-1 for RNA. Among these newly synthesized compounds, QUID-2 was the most promising candidate. The limit of detection (LOD) value of QUID-2 for the RNA was up to 1.8 ng/mL in solution. This property was significantly improved in comparison with that of QUID-1. Further spectroscopy and cell imaging studies demonstrated the advantages of QUID-2 over a commercially available RNA staining probe, SYTO RNASelect, for highly selective and sensitive RNA imaging. In addition, QUID-2 exhibited excellent photostability and low cytotoxicity. Using QUID-2, the global dynamics of RNA were revealed in live cells. More importantly, QUID-2 was found to be potentially applicable for detecting RNA granules in live cells. Collectively, our work provides an ideal probe for RNA imaging. We anticipate that this powerful tool may create new opportunities to investigate the underlying roles of RNA and RNA granules in live cells.

Discovery of Novel Coumarin-quinolinium Derivatives as Pan-KRAS Translation Inhibitors by Targeting 5'-UTR RNA G-Quadruplexes.

Hyperactivated KRAS mutations fuel tumorigenesis and represent attractive targets for cancer treatment. While covalent inhibitors have shown clinical benefits against the KRASG12C mutant, advancements for non-G12C mutants remain limited, highlighting the urgent demand for pan-KRAS inhibitors. RNA G-quadruplexes (rG4s) in the 5'-untranslated region of KRAS mRNA can regulate KRAS translation, making them promising targets for pan-KRAS inhibitor development. Herein, we designed and synthesized 50 novel coumarin-quinolinium derivatives, leveraging our previously developed rG4-specific ligand, QUMA-1. Notably, several compounds exhibited potent antiproliferative activity against cancer cells as pan-KRAS translation inhibitors. Among them, 15a displayed exceptional capability in stabilizing KRAS rG4s, suppressing KRAS translation, and consequently modulating MAPK and PI3K-AKT pathways. 15a induced cell cycle arrest, prompted apoptosis in KRAS-driven cancer cells, and effectively inhibited tumor growth in a KRAS mutant xenograft model. These findings underscore the potential of 15a as a pan-KRAS translation inhibitor, offering a novel and promising approach to target various KRAS-driven cancers.