Rationally engineered IR-783 octanoate as an enzyme-activatable fluorogenic tool for functional imaging of h Notum in living systems

As a vital negative regulator of Wnt signaling pathway,human Notum(hNotum)plays a crucial regulatory role in the progression of many human diseases.Deciphering the relevance of h Notum to human diseases requires practical and reliable tools for visualizing h Notum activity in living systems.Herein,an enzyme-activatable fluorogenic tool(IR-783 octanoate)was rationally engineered for sensing and imaging h Notum activity in living systems by integrating computer-aided molecular design and biochemical assays.IR-783 octanoate showed good optical properties,excellent specificity and high binding-affinity towards h Notum(K_(m)=0.98μmol/L).IR-783 octanoate could be well up-taken into the cancerous cells or tumors that over-expressed organic anion transporting polypeptides(OATPs),and then hydrolyzed by cellular h Notum to release free IR-783 ketone,which created brightly fluorescent signals around 646 nm.Further investigations showed that IR-783 octanoate achieved a good performance for in-situ functional imaging of h Notum in both living cells,cancerous tissues and organs.It was also found that some SW620cells with multipolar spindles could be stained by IR-783 octanoate to emit extremely bright signals,suggesting that this agent could be used as a novel visualizing tool for tracing the cells undergoing abnormal cell mitoses.Collectively,this study devises a highly specific fluorogenic tool for in-situ functional imaging of hNotum in living systems,which offers a practical and reliable tool to dynamically track the changes in h Notum activity under various conditions.