Meng Xin Sun's research while affiliated with Nanjing Medical University and other places

Many efforts have been made to understand excitotoxicity and develop neuroprotectants for the therapy of ischemic stroke. The narrow treatment time window is still to be solved. Given that the ischemic core expanded over days, treatment with an extended time window is anticipated. Bestrophin 1 (BEST1) belongs to a bestrophin family of calcium-activated chloride channels. We revealed an increase in neuronal BEST1 expression and function within the peri-infarct from 8 to 48 h after ischemic stroke in mice. Interfering the protein expression or inhibiting the channel function of BEST1 by genetic manipulation displayed neuroprotective effects and improved motor functional deficits. Using electrophysiological recordings, we demonstrated that extrasynaptic glutamate release through BEST1 channel resulted in delayed excitotoxicity. Finally, we confirmed the therapeutic efficacy of pharmacological inhibition of BEST1 during 6–72 h post-ischemia in rodents. This delayed treatment prevented the expansion of infarct volume and the exacerbation of neurological functions. Our study identifies the glutamate-releasing BEST1 channel as a potential therapeutic target against ischemic stroke with a wide time window.

The vicinal oxygen chelate (VOC) metalloenzyme superfamily catalyzes a highly diverse set of reactions with the mechanism characterized by the bidentate coordination of vicinal oxygen atoms to metal ion centers, but there remains a lack of a platform to steer the reaction trajectories, especially for o‐quinone metabolizing pathways. Herein, we present the directed‐evolution‐enabled bifunctional turnover of ChaP, which is a homotetramer and represents an unprecedented VOC enzyme class. Unlike the ChaP catalysis of extradiol‐like o‐quinone cleavage and concomitant α‐keto acid decarboxylation, a group of ChaP variants (CVs) catalyze intradiol‐like o‐quinone deconstruction and CO2 liberation from the resulting o‐hydroxybenzoic acid scaffolds with high regioselectivity. Enzyme crystal structures, labeling experiments and computational simulations corroborated that the D49L mutation allows the metal ion to change its coordination with the tyrosine phenoxy atoms in different monomers, thereby altering the reaction trajectory with the regiospecificity further improved by the follow‐up replacement of the Y92 residue with any of alanine, glycine, threonine, and serine. The study highlights the unpredicted catalytic versatility and enzymatic plasticity of VOC enzymes with biotechnological significance.

The vicinal oxygen chelate (VOC) metalloenzyme superfamily catalyzes a highly diverse set of reactions with the mechanism characterized by the bidentate coordination of vicinal oxygen atoms to metal ion centers, but there remains a lack of a platform to steer the reaction trajectories, especially for o ‐quinone metabolizing pathways. Herein, we present the directed‐evolution‐enabled bifunctional turnover of ChaP, which is a homotetramer and represents an unprecedented VOC enzyme class. Unlike the ChaP catalysis of extradiol‐like o ‐quinone cleavage and concomitant α‐keto acid decarboxylation, a group of ChaP variants (CVs) catalyze intradiol‐like o ‐quinone deconstruction and CO2 liberation from the resulting o‐hydroxybenzoic acid scaffolds with high regioselectivity. Enzyme crystal structures, labeling experiments and computational simulations corroborated that the D49L mutation allows the metal ion to change its coordination with the tyrosine phenoxy atoms in different monomers, thereby altering the reaction trajectory with the regiospecifity further improved by the follow‐up replacement of the Y92 residue with any of alanine, glycine, threonine, and serine. The study highlights the unpredicted catalytic versatility and enzymatic plasticity of VOC enzymes with biotechnological significance.