Ferroptosis is an iron-dependent form of oxidative cell death, and the inhibition of ferroptosis is a promising strategy with which to prevent and treat neurological diseases. Herein we report a new ferroptosis inhibitor 9a with a novel mechanism of action. It is demonstrated that nuclear receptor coactivator 4 (NCOA4), a cargo receptor for ferritinophagy, is the target of 9a . Compound 9a blocks ferroptosis by reducing the amount of bioavailable intracellular ferrous iron through disrupting the NCOA4–FTH1 protein–protein interaction. Further studies indicate that 9a directly binds to recombinant protein NCOA4 383–522 and effectively blocks the NCOA4 383–522 –FTH1 interaction. In a rat model of ischemic stroke, 9a significantly ameliorates the ischemic-refusion injury. With the first ligand 9a , this work reveals that NCOA4 is a promising drug target. Additionally, 9a is the first NCOA4–FTH1 interaction inhibitor. This work paves a new road to the development of ferroptosis inhibitors against neurological diseases.
Because of the absence of methods for tracking RNA G-quadruplex dynamics, especially the folding and unfolding of this attractive structure in live cells, understanding of the biological roles of RNA G-quadruplexes is so far limited. Herein, we report a new red-emitting fluorescent probe, QUMA-1, for the selective, continuous, and real-time visualization of RNA G-quadruplexes in live cells. The applications of QUMA-1 in several previously intractable applications, including live-cell imaging of the dynamic folding, unfolding, and movement of RNA G-quadruplexes and the visualization of the unwinding of RNA G-quadruplexes by RNA helicase have been demonstrated. Notably, our real-time results revealed the complexity of the dynamics of RNA G-quadruplexes in live cells. We anticipate that the further application of QUMA-1 in combination with appropriate biological and imaging methods to explore the dynamics of RNA G-quadruplexes will uncover more information about the biological roles of RNA G-quadruplexes.
Because of the absence of methods for tracking RNA G-quadruplex dynamics,e specially the folding and unfolding of this attractive structure in live cells,u nderstanding of the biological roles of RNAG -quadruplexes is so far limited. Herein, we report an ew red-emitting fluorescent probe, QUMA-1,f or the selective,c ontinuous,a nd real-time visualization of RNAG-quadruplexes in live cells.The applications of QUMA-1 in several previously intractable applications, including live-cell imaging of the dynamic folding,u nfolding, and movement of RNAG-quadruplexes and the visualization of the unwinding of RNAG -quadruplexes by RNAh elicase have been demonstrated. Notably,o ur real-time results revealed the complexity of the dynamics of RNAG -quadruplexes in live cells.W eanticipate that the further application of QUMA-1 in combination with appropriate biological and imaging methods to explore the dynamics of RNAGquadruplexesw ill uncover more information about the biological roles of RNAG-quadruplexes.
The mitochondrial DNA G-quadruplex (mtDNA G4) is a potential regulatory element for the regulation of mitochondrial functions; however, its relevance and specific roles in diseases remain largely unknown. Here, we engineered a set of chemical probes, including MitoISCH, an mtDNA G4-specific fluorescent probe, together with MitoPDS, a mitochondria-targeted G4-stabilizing agent, to thoroughly investigate mtDNA G4s. Using MitoISCH to monitor previously intractable dynamics of mtDNA G4s, we surprisingly found that their formation was prevalent only in endothelial and cancer cells that rely on glycolysis for energy production. Consistent with this, promotion of mtDNA G4 folding by MitoPDS in turn caused glycolysis-related gene activation and glycolysis enhancement. Remarkably, this close relationship among mtDNA G4s, glycolysis, and cancer cells further allowed MitoISCH to accumulate in tumors and label them in vivo. Our work reveals an unprecedented link between mtDNA G4s and cell glycolysis, suggesting that mtDNA G4s may be a novel cancer biomarker and therapeutic target deserving further exploration.
Inter-organelle interactions play a vital role in diverse biological processes. Thus, chemical tools are highly desirable for understanding the spatiotemporal dynamic interplay among organelles in live cells and in vivo. However, designing such tools is still a great challenge due to the lack of universal design strategies. To break this bottleneck, herein, a novel unimolecular platform integrating the twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) dual mechanisms was proposed. As a proof of concept, two organelles, lipid droplets (LDs) and mitochondria, were selected as models. Also, the first TICT-AIE integration molecule, BETA-1, was designed for simultaneous and dual-color imaging of LDs and mitochondria. BETA-1 can simultaneously target LDs and mitochondria due to its lipophilicity and cationic structure and emit cyan fluorescence in LDs and red fluorescence in mitochondria. Using BETA-1, for the first time, we obtained long-term tracking of dynamic LD–mitochondrion interactions and identified several impressive types of dynamic interactions between these two organelles. More importantly, the increase in LD–mitochondrion interactions during ferroptosis was revealed with BETA-1, suggesting that intervening in the LD–mitochondrion interactions may modulate this cell death. BETA-1 was also successfully applied for in vivo imaging of LD–mitochondrion interactions in C. elegans. This study not only provides an effective tool for uncovering LD–mitochondrion interactions and deciphering related biological processes but also sheds light on the design of new probes with an integrated TICT-AIE mechanism for imaging of inter-organelle interactions.
Ligand-Induced duplex-quadruplex transition within the c-MYC promoter region is one of the most studied and advanced ideas for c-MYC regulation. Despite its importance, there is a lack of methods for monitoring such process in cells, hindering a better understanding of the essence of c-MYC G-quadruplex as a drug target. Here we developed a new fluorescent probe ISCH-MYC for specific c-MYC G-quadruplex recognition based on GTFH (G-quadruplex-Triggered Fluorogenic Hybridization) strategy. We validated that ISCH-MYC displayed distinct fluorescence enhancement upon binding to c-MYC G-quadruplex, which allowed the duplex-quadruplex transition detection of c-MYC G-rich DNA in cells. Using ISCH-MYC, we successfully characterized the induction of duplex to G-quadruplex transition in the presence of G-quadruplex stabilizing ligand PDS and further monitored and evaluated the altered interactions of relevant transcription factors Sp1 and CNBP with c-MYC G-rich DNA. Thus, our study provides a visualization strategy to explore the mechanism of G-quadruplex stabilizing ligand action on c-MYC G-rich DNA and relevant proteins, thereby empowering future drug discovery efforts targeting G-quadruplexes.
Developing c-MYC transcription inhibitors that target the G-quadruplex has generated significant interest; however, few compounds have demonstrated specificity for c-MYC G-quadruplex and cancer cells. In this study, we designed and synthesized a series of benzoazole derivatives as potential G-quadruplex ligand-based c-MYC transcription inhibitors. Surprisingly, benzoselenazole derivatives, which are rarely reported as G-quadruplex ligands, demonstrated greater c-MYC G-quadruplex selectivity and cancer cell specificity compared to their benzothiazole and benzoxazole analogues. The most promising compound, benzoselenazole m-Se3, selectively inhibited c-MYC transcription by specifically stabilizing the c-MYC G-quadruplex. This led to selective inhibition of hepatoma cell growth and proliferation by affecting the MYC target gene network, as well as effective tumor growth inhibition in hepatoma xenografts. Collectively, our study demonstrates that m-Se3 holds significant promise as a potent and selective inhibitor of c-MYC transcription for cancer treatment. Furthermore, our findings inspire the development of novel selenium-containing heterocyclic compounds as c-MYC G-quadruplex-specific ligands and transcription inhibitors.
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