Unlike the well-established picture for the entry of enveloped viruses, the mechanism of cellular entry of non-enveloped eukaryotic viruses remains largely mysterious. Picornaviruses are representative models for such...Unlike the well-established picture for the entry of enveloped viruses, the mechanism of cellular entry of non-enveloped eukaryotic viruses remains largely mysterious. Picornaviruses are representative models for such viruses, and initiate this entry process by their functional receptors. Here we present the structural and functional studies of SCARB2, a functional receptor of the important human enterovirus 71 （EV71）. SCARB2 is responsible for attachment as well as uncoating of EV71. Differences in the structures of SCARB2 under neutral and acidic conditions reveal that SCARB2 undergoes a pivotal pH-dependent conformational change which opens a lipid-transfer tunnel to mediate the expulsion of a hydrophobic pocket factor from the virion, a pre-requisite for uncoating. We have also identified the key residues essential for attachment to SCARB2, identifying the canyon region of EV71 as mediating the receptor interaction. Together these results provide a clear understanding of cellular attachment and initiation of uncoating for enteroviruses.展开更多
Ebolavirus can cause hemorrhagic fever in humans with a mortality rate of 50%-90%. Currently, no approved vaccines and antiviral therapies are available. Human TIM1 is considered as an attachment factor for EBOV, enha...Ebolavirus can cause hemorrhagic fever in humans with a mortality rate of 50%-90%. Currently, no approved vaccines and antiviral therapies are available. Human TIM1 is considered as an attachment factor for EBOV, enhancing viral infection through interaction with PS located on the viral envelope. However, reasons under- lying the preferable usage of hTIM-1, but not other PS binding receptors by filovirus, remain unknown. We firstly demonstrated a direct interaction between hTIM-1 and EBOV GP in vitro and determined the crystal structures of the Ig V domains of hTIM-1 and hTIM-4. The binding region in hTIM-1 to EBOV GP was mapped by chimeras and mutation assays, which were designed based on structural analysis. Pseudovirion infection assays performed using hTIM-1 and its homologs as well as point mutants verified the location of the GP binding site and the importance of EBOV GP-hTIM-1 interaction in EBOV cellular entry.展开更多
Coxsackievirus A16 belongs to the family Picornaviridae,and is a major agent of hand-foot-and-mouth disease that infects mostly children,and to date no vaccines or antivi-ral therapies are available.2A protease of ent...Coxsackievirus A16 belongs to the family Picornaviridae,and is a major agent of hand-foot-and-mouth disease that infects mostly children,and to date no vaccines or antivi-ral therapies are available.2A protease of enterovirus is a nonstructural protein and possesses both self-cleavage activity and the ability to cleave the eukaryotic translation initiation factor 4G.Here we present the crystal structure of coxsackievirus A162A protease,which interestingly forms hexamers in crystal as well as in solution.This structure shows an open conformation,with its active site accessible,ready for substrate binding and cleav-age activity.In conjunction with a previously reported“closed”state structure of human rhinovirus 2,we were able to develop a detailed hypothesis for the conforma-tional conversion triggered by two“switcher”residues Glu88 and Tyr89 located within the bll2-cII loop.Substrate recognition assays revealed that amino acid residues P1′,P2 and P4 are essential for substrate specificity,which was verifi ed by our substrate binding model.In addition,we compared the in vitro cleavage effi ciency of 2A pro-teases from coxsackievirus A16 and enterovirus 71 upon the same substrates by fl uorescence resonance energy transfer(FRET),and observed higher protease activity of enterovirus 71 compared to that of coxsackievirus A16.In conclusion,our study shows an open conformation of coxsackievirus A162A protease and the underlying mechanisms for conformational conversion and substrate specifi city.These new insights should facilitate the future rational design of effi cient 2A protease inhibitors.展开更多
基金ACKNOWLEDGEMENTS We thank Neil Shaw, Haitao Yang, Fei Sun, Yuguang Zhao, Jingshan Ren, David I. Stuart and Elizabeth E. Fry for assistance with the manuscript and advice, Wei Peng, Pi Liu, Jialong Zhang provided expert assistance. We gratefully acknowledge the assistance of the staff of the beamline BL5A and BL17A at the Photon Factory （PF） in Japan with the X-ray diffraction data col- lection. We also thank Core Facility in the Institute of Biophysics, Chinese Academy of Sciences （CAS）. Work was supported by the National Basic Research Program （973 Program） （No. 2014CB542800）, National Natural Science Foundation of China （Grant No. 81330036） and the Strategic Priority Research Program of the Chinese Academy of Sciences, （Grant No. XDB08020200）.
文摘Unlike the well-established picture for the entry of enveloped viruses, the mechanism of cellular entry of non-enveloped eukaryotic viruses remains largely mysterious. Picornaviruses are representative models for such viruses, and initiate this entry process by their functional receptors. Here we present the structural and functional studies of SCARB2, a functional receptor of the important human enterovirus 71 （EV71）. SCARB2 is responsible for attachment as well as uncoating of EV71. Differences in the structures of SCARB2 under neutral and acidic conditions reveal that SCARB2 undergoes a pivotal pH-dependent conformational change which opens a lipid-transfer tunnel to mediate the expulsion of a hydrophobic pocket factor from the virion, a pre-requisite for uncoating. We have also identified the key residues essential for attachment to SCARB2, identifying the canyon region of EV71 as mediating the receptor interaction. Together these results provide a clear understanding of cellular attachment and initiation of uncoating for enteroviruses.
文摘Ebolavirus can cause hemorrhagic fever in humans with a mortality rate of 50%-90%. Currently, no approved vaccines and antiviral therapies are available. Human TIM1 is considered as an attachment factor for EBOV, enhancing viral infection through interaction with PS located on the viral envelope. However, reasons under- lying the preferable usage of hTIM-1, but not other PS binding receptors by filovirus, remain unknown. We firstly demonstrated a direct interaction between hTIM-1 and EBOV GP in vitro and determined the crystal structures of the Ig V domains of hTIM-1 and hTIM-4. The binding region in hTIM-1 to EBOV GP was mapped by chimeras and mutation assays, which were designed based on structural analysis. Pseudovirion infection assays performed using hTIM-1 and its homologs as well as point mutants verified the location of the GP binding site and the importance of EBOV GP-hTIM-1 interaction in EBOV cellular entry.
基金the National Basic Research Program(973 Program)(Nos.2014CB542800 and 2011CB915501)the National Natural Science Foundation of China(Grant No.31170702).
文摘Coxsackievirus A16 belongs to the family Picornaviridae,and is a major agent of hand-foot-and-mouth disease that infects mostly children,and to date no vaccines or antivi-ral therapies are available.2A protease of enterovirus is a nonstructural protein and possesses both self-cleavage activity and the ability to cleave the eukaryotic translation initiation factor 4G.Here we present the crystal structure of coxsackievirus A162A protease,which interestingly forms hexamers in crystal as well as in solution.This structure shows an open conformation,with its active site accessible,ready for substrate binding and cleav-age activity.In conjunction with a previously reported“closed”state structure of human rhinovirus 2,we were able to develop a detailed hypothesis for the conforma-tional conversion triggered by two“switcher”residues Glu88 and Tyr89 located within the bll2-cII loop.Substrate recognition assays revealed that amino acid residues P1′,P2 and P4 are essential for substrate specificity,which was verifi ed by our substrate binding model.In addition,we compared the in vitro cleavage effi ciency of 2A pro-teases from coxsackievirus A16 and enterovirus 71 upon the same substrates by fl uorescence resonance energy transfer(FRET),and observed higher protease activity of enterovirus 71 compared to that of coxsackievirus A16.In conclusion,our study shows an open conformation of coxsackievirus A162A protease and the underlying mechanisms for conformational conversion and substrate specifi city.These new insights should facilitate the future rational design of effi cient 2A protease inhibitors.
