title: Inhibitors of cathepsin L prevent severe acute respiratory syndrome coronavirus entry.
abstract: Severe acute respiratory syndrome (SARS) is caused by an emergent coronavirus (SARS-CoV), for which there is currently no effective treatment. SARS-CoV mediates receptor binding and entry by its spike (S) glycoprotein, and infection is sensitive to lysosomotropic agents that perturb endosomal pH. We demonstrate here that the lysosomotropic-agent-mediated block to SARS-CoV infection is overcome by protease treatment of target-cell-associated virus. In addition, SARS-CoV infection was blocked by specific inhibitors of the pH-sensitive endosomal protease cathepsin L. A cell-free membrane-fusion system demonstrates that engagement of receptor followed by proteolysis is required for SARS-CoV membrane fusion and indicates that cathepsin L is sufficient to activate membrane fusion by SARS-CoV S. These results suggest that SARS-CoV infection results from a unique, three-step process: receptor binding and induced conformational changes in S glycoprotein followed by cathepsin L proteolysis within endosomes. The requirement for cathepsin L proteolysis identifies a previously uncharacterized class of inhibitor for SARS-CoV infection.
authors.affiliation: Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. gsimmons@mail.med.upenn.edu
authors.forename: Graham
authors.initials: G
authors.lastname: Simmons
authors.forename: Dhaval N
authors.initials: DN
authors.lastname: Gosalia
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Rennekamp
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Reeves
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
authors.forename: Paul
authors.initials: P
authors.lastname: Bates
mesh_terms: D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D006801:Humans; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology; D015394:Molecular Structure; D011480:Protease Inhibitors / Q000494:pharmacology*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000187:drug effects* / Q000502:physiology*; D045169:Severe Acute Respiratory Syndrome / Q000201:enzymology / Q000517:prevention & control* / Q000821:virology*; D013696:Temperature
chemical_list: D011480:Protease Inhibitors; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L