Mechanism for active membrane fusion triggering by morbillivirus attachment protein.
The paramyxovirus entry machinery consists of two glycoproteins that tightly cooperate to achieve membrane fusion for cell entry: the tetrameric attachment protein (HN, H, or G, depending on the paramyxovirus genus) and the trimeric fusion protein (F). Here, we explore whether receptor-induced conformational changes within morbillivirus H proteins promote membrane fusion by a mechanism requiring the active destabilization of prefusion F or by the dissociation of prefusion F from intracellularly preformed glycoprotein complexes. To properly probe F conformations, we identified anti-F monoclonal antibodies (MAbs) that recognize conformation-dependent epitopes. Through heat treatment as a surrogate for H-mediated F triggering, we demonstrate with these MAbs that the morbillivirus F trimer contains a sufficiently high inherent activation energy barrier to maintain the metastable prefusion state even in the absence of H. This notion was further validated by exploring the conformational states of destabilized F mutants and stabilized soluble F variants combined with the use of a membrane fusion inhibitor (3g). Taken together, our findings reveal that the morbillivirus H protein must lower the activation energy barrier of metastable prefusion F for fusion triggering.
Division of Experimental Clinical Research, Neurovirology Unit, DCR-VPH, University of Bern, Bern, Switzerland.
Nadine
N
Ader
Melinda
M
Brindley
Mislay
M
Avila
Claes
C
Örvell
Branka
B
Horvat
Georg
G
Hiltensperger
Jürgen
J
Schneider-Schaulies
Marc
M
Vandevelde
Andreas
A
Zurbriggen
Richard K
RK
Plemper
Philippe
P
Plattet
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D002460:Cell Line; D000939:Epitopes / Q000276:immunology; D006389:Hemagglutinins, Viral / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D018103:Morbillivirus / Q000502:physiology*; D011485:Protein Binding; D011487:Protein Conformation; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000378:metabolism*; D053586:Virus Internalization
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000939:Epitopes; C104413:H protein, Dolphin morbillivirus; D006389:Hemagglutinins, Viral; D014760:Viral Fusion Proteins