Spinal cord injury-induced motor dysfunction is associated with neuroinflammation.Studies have shown that the triterpenoid lupenone,a natural product found in various plants,has a remarkable anti-inflammatory effect i...Spinal cord injury-induced motor dysfunction is associated with neuroinflammation.Studies have shown that the triterpenoid lupenone,a natural product found in various plants,has a remarkable anti-inflammatory effect in the context of chronic inflammation.However,the effects of lupenone on acute inflammation induced by spinal cord injury remain unknown.In this study,we established an impact-induced mouse model of spinal cord injury,and then treated the injured mice with lupenone(8 mg/kg,twice a day)by intrape ritoneal injection.We also treated BV2 cells with lipopolysaccharide and adenosine5’-triphosphate to simulate the inflammatory response after spinal cord injury.Our res ults showed that lupenone reduced IKBa activation and p65 nuclear translocation,inhibited NLRP3 inflammasome function by modulating nuclear factor kappa B,and enhanced the conve rsion of proinflammatory M1 mic roglial cells into anti-inflammatory M2 microglial cells.Furthermore,lupenone decreased NLRP3 inflammasome activation,NLRP3-induced mic roglial cell polarization,and microglia pyroptosis by inhibiting the nuclear factor kappa B pathway.These findings suggest that lupenone protects against spinal cord injury by inhibiting inflammasomes.展开更多
Glycosylation is an important post-modification reaction in plant secondary metabolism,and contributes to structural diversity of bioactive natural products.In plants,glycosylation is usually catalyzed by UDP-glycosyl...Glycosylation is an important post-modification reaction in plant secondary metabolism,and contributes to structural diversity of bioactive natural products.In plants,glycosylation is usually catalyzed by UDP-glycosyltransferases.Flavonoid 2′-O-glycosides are rare glycosides.However,no UGTs have been reported,thus far,to specifically catalyze 2′-O-glycosylation of flavonoids.In this work,UGT71AP2 was identified from the medicinal plant Scutellaria baicalensis as the first flavonoid 2′-O-glycosyltransferase.It could preferentially transfer a glycosyl moiety to 2′-hydroxy of at least nine flavonoids to yield six new compounds.Some of the 2′-O-glycosides showed noticeable inhibitory activities against cyclooxygenase 2.The crystal structure of UGT71AP2(2.15Å)was solved,and mechanisms of its regio-selectivity was interpreted by pKa calculations,molecular docking,MD simulation,MM/GBSA binding free energy,QM/MM,and hydrogen‒deuterium exchange mass spectrometry analysis.Through structure-guided rational design,we obtained the L138T/V179D/M180T mutant with remarkably enhanced regio-selectivity(the ratio of 7-O-glycosylation byproducts decreased from 48%to 4%)and catalytic efficiency of 2′-O-glycosylation(kcat/Km,0.23 L/(s·μmol),12-fold higher than the native).Moreover,UGT71AP2 also possesses moderate UDP-dependent de-glycosylation activity,and is a dual function glycosyltransferase.This work provides an efficient biocatalyst and sets a good example for protein engineering to optimize enzyme catalytic features through rational design.展开更多
Mitophagy is an essential intracellular process that eliminates dysfunctional mitochondria and maintains cellular homeostasis. Mitophagy is regulated by the post-translational modification of mitophagy receptors. Fun1...Mitophagy is an essential intracellular process that eliminates dysfunctional mitochondria and maintains cellular homeostasis. Mitophagy is regulated by the post-translational modification of mitophagy receptors. Fun14 domain-containing protein 1 （FUNDC1） was reported to be a new receptor for hypoxia-induced mitophagy in mammalian cells and interact with micro-tubule-associated protein light chain 3 beta （LC3B） through its LC3 interaction region （LIR）. Moreover, the phosphorylation modification of FUNDC1 affects its binding affinity for LC3B and regulates selective mitophagy. However, the structural basis of this regulation mechanism remains unclear. Here, we present the crystal structure of LC3B in complex with a FUNDCI LIR peptide phosphorylated at Ser17 （pS17）, demonstrating the key residues of LC3B for the specific recognition of the phosphorylated or dephosphorylated FUNDC1. Intriguingly, the side chain of LC3B Lys49 shifts remarkably and forms a hydrogen bond and electrostatic interaction with the phosphate group of FUNDC1 pS17. Alternatively, phosphorylated Tyr18 （PY18） and Ser13 （PS13） in FUNDC1 significantly obstruct their interaction with the hydrophobic pocket and Arg10 of LC3B, respectively. Structural observations are further validated by mutation and isothermal titration calorimetry （ITC） assays. Therefore, our structural and biochemical results reveal a working model for thespecific recognition of FUNDCI by LC3B and imply that the reversible phosphorylation modification of mitophagy receptors may be a switch for selective mitophagy.展开更多
In the fission yeast Schizosaccharomyces pombe,Mei2,an RNA-binding protein essential for entry into meiosis,regulates meiosis initiation.Mei2 binds to a specific non-coding RNA species,meiRNA,and accumulates at the sm...In the fission yeast Schizosaccharomyces pombe,Mei2,an RNA-binding protein essential for entry into meiosis,regulates meiosis initiation.Mei2 binds to a specific non-coding RNA species,meiRNA,and accumulates at the sme2 gene locus,which encodes meiRNA.Previous research has shown that the Mei2 C-terminal RNA recognition motif(RRM3)physically interacts with the meiRNA 5'region in vitro and stimulates meiosis in vivo.However,the underlying mechanisms still remain elusive.We first employed an in vitro crosslinking and immunoprecipitation sequencing(CLIP-seq)assay and demonstrated a preference for U-rich motifs of meiRNA by Mei2 RRM3.We then solved the crystal structures of Mei2 RRM3 in the apo form and complex with an 8 mer RNA fragment,derived from meiRNA,as detected by in vitro CLIP-seq.These results provide structural insights into the Mei2 RRM3-meiRNA complex and reveal that Mei2 RRM3 binds specifically to the Uuc(U)sequence.Furthermore,a structure-based Mei2 mutation,Mei2F644A causes defective karyogamy,suggesting an essential role of the RNA-binding ability of Mei2 in regulating meiosis.展开更多
Dear Editor,Polycomb repressive complex 2 （PRC2） plays a critical role in organ development, adult homeostasis, and tumorigene- sis via enzymatic activities to di- or td-methylate lysine 27 of H3 （H3K27me2/me3）, w...Dear Editor,Polycomb repressive complex 2 （PRC2） plays a critical role in organ development, adult homeostasis, and tumorigene- sis via enzymatic activities to di- or td-methylate lysine 27 of H3 （H3K27me2/me3）, which is a hallmark of transcriptional repression and gene silencing （Margueron and Reinberg, 2011）.展开更多
基金supported by the National Natural Science Foundation of China,Nos.81801226(to QK and XS)and 82101445(to XJ)。
文摘Spinal cord injury-induced motor dysfunction is associated with neuroinflammation.Studies have shown that the triterpenoid lupenone,a natural product found in various plants,has a remarkable anti-inflammatory effect in the context of chronic inflammation.However,the effects of lupenone on acute inflammation induced by spinal cord injury remain unknown.In this study,we established an impact-induced mouse model of spinal cord injury,and then treated the injured mice with lupenone(8 mg/kg,twice a day)by intrape ritoneal injection.We also treated BV2 cells with lipopolysaccharide and adenosine5’-triphosphate to simulate the inflammatory response after spinal cord injury.Our res ults showed that lupenone reduced IKBa activation and p65 nuclear translocation,inhibited NLRP3 inflammasome function by modulating nuclear factor kappa B,and enhanced the conve rsion of proinflammatory M1 mic roglial cells into anti-inflammatory M2 microglial cells.Furthermore,lupenone decreased NLRP3 inflammasome activation,NLRP3-induced mic roglial cell polarization,and microglia pyroptosis by inhibiting the nuclear factor kappa B pathway.These findings suggest that lupenone protects against spinal cord injury by inhibiting inflammasomes.
基金supported by the National Key Research and Development Program of China(No.2023YFA0914100)China National Postdoctoral Program for Innovation Talents(No.BX20220022)+2 种基金National Natural Science Foundation of China(No.82304326)Natural Science Foundation of Anhui Province(No.2008085MC92,China)the National Supercomputer Center(SNIC2022-3-34)at Linköping University(Sweden).
文摘Glycosylation is an important post-modification reaction in plant secondary metabolism,and contributes to structural diversity of bioactive natural products.In plants,glycosylation is usually catalyzed by UDP-glycosyltransferases.Flavonoid 2′-O-glycosides are rare glycosides.However,no UGTs have been reported,thus far,to specifically catalyze 2′-O-glycosylation of flavonoids.In this work,UGT71AP2 was identified from the medicinal plant Scutellaria baicalensis as the first flavonoid 2′-O-glycosyltransferase.It could preferentially transfer a glycosyl moiety to 2′-hydroxy of at least nine flavonoids to yield six new compounds.Some of the 2′-O-glycosides showed noticeable inhibitory activities against cyclooxygenase 2.The crystal structure of UGT71AP2(2.15Å)was solved,and mechanisms of its regio-selectivity was interpreted by pKa calculations,molecular docking,MD simulation,MM/GBSA binding free energy,QM/MM,and hydrogen‒deuterium exchange mass spectrometry analysis.Through structure-guided rational design,we obtained the L138T/V179D/M180T mutant with remarkably enhanced regio-selectivity(the ratio of 7-O-glycosylation byproducts decreased from 48%to 4%)and catalytic efficiency of 2′-O-glycosylation(kcat/Km,0.23 L/(s·μmol),12-fold higher than the native).Moreover,UGT71AP2 also possesses moderate UDP-dependent de-glycosylation activity,and is a dual function glycosyltransferase.This work provides an efficient biocatalyst and sets a good example for protein engineering to optimize enzyme catalytic features through rational design.
基金This work was supported by National Natural Science Founda- tion （Grant No. 31400629） the Strategic Priority Research Program of the Chinese Academy of Science （No. XDB08010101）+1 种基金 Ministry Of Science And Technology of China （No. 2016YFA0500700） China Postdoctoral Science Foundation （No. 2015M582009 and 2016T90579） and National Natural Science Foundation （Grant No. 31330018）.
文摘Mitophagy is an essential intracellular process that eliminates dysfunctional mitochondria and maintains cellular homeostasis. Mitophagy is regulated by the post-translational modification of mitophagy receptors. Fun14 domain-containing protein 1 （FUNDC1） was reported to be a new receptor for hypoxia-induced mitophagy in mammalian cells and interact with micro-tubule-associated protein light chain 3 beta （LC3B） through its LC3 interaction region （LIR）. Moreover, the phosphorylation modification of FUNDC1 affects its binding affinity for LC3B and regulates selective mitophagy. However, the structural basis of this regulation mechanism remains unclear. Here, we present the crystal structure of LC3B in complex with a FUNDCI LIR peptide phosphorylated at Ser17 （pS17）, demonstrating the key residues of LC3B for the specific recognition of the phosphorylated or dephosphorylated FUNDC1. Intriguingly, the side chain of LC3B Lys49 shifts remarkably and forms a hydrogen bond and electrostatic interaction with the phosphate group of FUNDC1 pS17. Alternatively, phosphorylated Tyr18 （PY18） and Ser13 （PS13） in FUNDC1 significantly obstruct their interaction with the hydrophobic pocket and Arg10 of LC3B, respectively. Structural observations are further validated by mutation and isothermal titration calorimetry （ITC） assays. Therefore, our structural and biochemical results reveal a working model for thespecific recognition of FUNDCI by LC3B and imply that the reversible phosphorylation modification of mitophagy receptors may be a switch for selective mitophagy.
基金This work was financially supported by grants from the Ministry of Science and Technology of China(2019YFA0508403)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB39010300)+2 种基金the National Natural Science Foundation of China(32090040,31870760,32171222,92149302,U1932122,and 32100958)the China Postdoctoral Science Foundation(2019M662182)the Fundamental Research Funds for the Central Universities(WK2340000097).
文摘In the fission yeast Schizosaccharomyces pombe,Mei2,an RNA-binding protein essential for entry into meiosis,regulates meiosis initiation.Mei2 binds to a specific non-coding RNA species,meiRNA,and accumulates at the sme2 gene locus,which encodes meiRNA.Previous research has shown that the Mei2 C-terminal RNA recognition motif(RRM3)physically interacts with the meiRNA 5'region in vitro and stimulates meiosis in vivo.However,the underlying mechanisms still remain elusive.We first employed an in vitro crosslinking and immunoprecipitation sequencing(CLIP-seq)assay and demonstrated a preference for U-rich motifs of meiRNA by Mei2 RRM3.We then solved the crystal structures of Mei2 RRM3 in the apo form and complex with an 8 mer RNA fragment,derived from meiRNA,as detected by in vitro CLIP-seq.These results provide structural insights into the Mei2 RRM3-meiRNA complex and reveal that Mei2 RRM3 binds specifically to the Uuc(U)sequence.Furthermore,a structure-based Mei2 mutation,Mei2F644A causes defective karyogamy,suggesting an essential role of the RNA-binding ability of Mei2 in regulating meiosis.
基金We thank Prof. Rolf Boelens, Dr Hens Weik in Utrecht University for the help of NMR structure calculation. We thank the staff of the BeamLine BL17U1 at SSRF for assistance with data collection. We thank Yaqing Zhao in our lab for providing tzap zinc finger protein as a gift. We thank Ministry of Science and Technology of China （2016YFA0500700） Strategic Pdority Research Program of the Chinese Academy of Sciences （XDB08010100 and XDB08030302） and Chinese National Natural Science Foundation （31330018） for supporting this work.
文摘Dear Editor,Polycomb repressive complex 2 （PRC2） plays a critical role in organ development, adult homeostasis, and tumorigene- sis via enzymatic activities to di- or td-methylate lysine 27 of H3 （H3K27me2/me3）, which is a hallmark of transcriptional repression and gene silencing （Margueron and Reinberg, 2011）.
