title: Molecular determinants defining the triggering range of prefusion F complexes of canine distemper virus.
abstract: The morbillivirus cell entry machinery consists of a fusion (F) protein trimer that refolds to mediate membrane fusion following receptor-induced conformational changes in its binding partner, the tetrameric attachment (H) protein. To identify molecular determinants that control F refolding, we generated F chimeras between measles virus (MeV) and canine distemper virus (CDV). We located a central pocket in the globular head domain of CDV F that regulates the stability of the metastable, prefusion conformational state of the F trimer. Most mutations introduced into this "pocket'" appeared to mediate a destabilizing effect, a phenotype associated with enhanced membrane fusion activity. Strikingly, under specific triggering conditions (i.e., variation of receptor type and H protein origin), some F mutants also exhibited resistance to a potent morbillivirus entry inhibitor, which is known to block F triggering by enhancing the stability of prefusion F trimers. Our data reveal that the molecular nature of the F stimulus and the intrinsic stability of metastable prefusion F both regulate the efficiency of F refolding and escape from small-molecule refolding blockers.
  
  
  OBJECTIVE
  With the aim to better characterize the thermodynamic basis of morbillivirus membrane fusion for cell entry and spread, we report here that the activation energy barrier of prefusion F trimers together with the molecular nature of the triggering "stimulus" (attachment protein and receptor types) define a "triggering range," which governs the initiation of the membrane fusion process. A central "pocket" microdomain in the globular F head contributes substantially to the regulation of the conformational stability of the prefusion complexes. The triggering range also defines the mechanism of viral escape from entry inhibitors and describes how the cellular environment can affect membrane fusion efficiency.
authors.affiliation: Division of Neurological Sciences, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: Mislay
authors.initials: M
authors.lastname: Avila
authors.forename: Lisa
authors.initials: L
authors.lastname: Alves
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Khosravi
authors.forename: Nadine
authors.initials: N
authors.lastname: Ader-Ebert
authors.forename: Francesco
authors.initials: F
authors.lastname: Origgi
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schneider-Schaulies
authors.forename: Andreas
authors.initials: A
authors.lastname: Zurbriggen
authors.forename: Richard K
authors.initials: RK
authors.lastname: Plemper
authors.forename: Philippe
authors.initials: P
authors.lastname: Plattet
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D002459:Cell Fusion; D002522:Chlorocebus aethiops; D003412:Cricetulus; D004217:Distemper Virus, Canine / Q000502:physiology*; D004285:Dogs; D008561:Membrane Fusion; D008958:Models, Molecular; D009154:Mutation; D000075983:Nectins; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D011991:Receptors, Virus / Q000378:metabolism; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053586:Virus Internalization
chemical_list: D015815:Cell Adhesion Molecules; D000075983:Nectins; D011991:Receptors, Virus; D014760:Viral Fusion Proteins; D014764:Viral Proteins