A temperature-regulated bioorthogonal reaction to target lysine:Hemiacetal pharmacophore in genipin irreversibly binds with UCP2,inhibiting mitochondrial thermogenesis

Mitochondria are essential for eukaryotic life as powerhouses for energy metabolism. Excessive mitochondrial hyperthermia and reactive oxygen species(ROS) production have been associated with aging, cancer,neurodegenerative diseases, and other disorders. Uncoupling protein 2(UCP2) is the effector responsible for regulating cellular thermogenesis and ROS production via dissipating protons in an electrochemical gradient. A UCP2 inhibitor named genipin(GNP) is being researched for its effect on mitochondrial temperature, but little is known about its mechanisms. This study developed several molecular probes to explore the interactions between GNP and UCP2. The result indicated that the hemiacetal structure in GNP could selectively react with the ?-amine of lysine on the UCP2 proton leakage channel through ringopening condensation at the mitochondrial, cellular, and animal levels. A notable feature of the reaction is its temperature sensitivity and ability to conjugate with UCP2 at high fever as lysine-specific covalent inhibitors that prevent mitochondrial thermogenesis. The result not only clarifies the existence of an antipyretic properties of GNP via its irreversible coupling to UCP2, but also reveals a bioorthogonal reaction of hemiacetal iridoid aglycone for selectively binding with the ?-amine of lysine on proteins.

Chemical proteomics reveals ligustilide targets SMAD3,inhibiting collagen synthesis in aortic endothelial cells

Atherosclerosis is a persistent inflammatory state,while vascular endothelial fibrosis is one of the primary causes of atherosclerosis development.Although ligustilide(Lig) was shown to exert obvious antiatherogenic effects in previous studies,its precise mechanism has not been deeply discussed.In this paper,we designed a Lig-derived photoaffinity labelling(PAL) probe to identify potential therapeutic targets of Lig via chemical proteomics approach.Mothers against decapentaplegic homologue 3(SMAD3),a signal transmitter of transforming growth factor-β(TGF-β) which promotes the development of vascular fibrosis,was identified as a potential target of Lig.Lig suppressed the phosphorylation and nuclear translocation of SMAD3 by blocking the interaction between SMAD3 and TGF-β receptor 1,thereby inhibiting the collagen synthesis process.Hence,developing a novel SMAD3 inhibitor may present a promising therapeutic option for preventing vascular fibrosis.