A mutant fusion (F) protein of simian virus 5 induces hemagglutinin-neuraminidase-independent syncytium formation despite the internalization of the F protein.
The fusion (F) protein of simian virus 5 strain W3A induces syncytium formation independently of coexpression of the hemagglutinin-neuraminidase protein. This property can be transferred to the F protein of strain WR by replacing the leucine at position 22 with the W3A F counterpart, proline. The resulting mutant L22P has a conformation that is distinct from that of the WR F protein. Se-L22P is a cleavage site mutant of L22P that is cleavable only by addition of exogenous trypsin. We showed here that the cell surface-localized L22P was internalized with a t1/2 of 25 min and degraded in the cell, while the WR F protein was not. The cell surface-localized Se-L22P underwent a significant conformational change upon cleavage. Intriguingly, it disappeared from the cell surface due to its internalization, while inducing extensive syncytium formation. These results indicate that L22P may display an internalization signal during the course of fusion induction.
Tsurudome
Masato
M
Department of Microbiology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan. turudome@doc.medic.mie-u.ac.jp
Ito
Morihiro
M
Nishio
Machiko
M
Kawano
Mitsuo
M
Komada
Hiroshi
H
Ito
Yasuhiko
Y
D019943:Amino Acid Substitution; D001693:Biological Transport, Active; D015726:Giant Cells / Q000821:virology; D006367:HeLa Cells; D006389:Hemagglutinins, Viral / Q000502:physiology; D006801:Humans; D008970:Molecular Weight; D009439:Neuraminidase / Q000502:physiology; D045402:Parainfluenza Virus 5 / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D017354:Point Mutation; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*
D006389:Hemagglutinins, Viral; D021382:Protein Sorting Signals; D014760:Viral Fusion Proteins; D009439:Neuraminidase