Endocytosis plays a critical role in proteolytic processing of the Hendra virus fusion protein.
The Hendra virus fusion (F) protein is synthesized as a precursor protein, F(0), which is proteolytically processed to the mature form, F(1) + F(2). Unlike the case for the majority of paramyxovirus F proteins, the processing event is furin independent, does not require the addition of exogenous proteases, is not affected by reductions in intracellular Ca(2+), and is strongly affected by conditions that raise the intracellular pH (C. T. Pager, M. A. Wurth, and R. E. Dutch, J. Virol. 78:9154-9163, 2004). The Hendra virus F protein cytoplasmic tail contains a consensus motif for endocytosis, YXXPhi. To analyze the potential role of endocytosis in the processing and membrane fusion promotion of the Hendra virus F protein, mutation of tyrosine 525 to alanine (Hendra virus F Y525A) or phenylalanine (Hendra virus F Y525F) was performed. The rate of endocytosis of Hendra virus F Y525A was significantly reduced compared to that of the wild-type (wt) F protein, confirming the functional importance of the endocytosis motif. An intermediate level of endocytosis was observed for Hendra virus F Y525F. Surprisingly, dramatic reductions in the rate of proteolytic processing were observed for Hendra virus F Y525A, although initial transport to the cell surface was not affected. The levels of surface expression for both Hendra virus F Y525A and Hendra virus F Y525F were higher than that of the wt protein, and these mutants displayed enhanced syncytium formation. These results suggest that endocytosis is critically important for Hendra virus F protein cleavage, representing a new paradigm for proteolytic processing of paramyxovirus F proteins.
Meulendyke
Kelly Ann
KA
Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, 40536-0509, USA.
Wurth
Mark Allen
MA
McCann
Richard O
RO
Dutch
Rebecca Ellis
RE
D000595:Amino Acid Sequence; D000818:Animals; D002468:Cell Physiological Phenomena; D002522:Chlorocebus aethiops; D004705:Endocytosis / Q000502:physiology*; D045404:Hendra Virus / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D014709:Vero Cells / Q000821:virology; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D014760:Viral Fusion Proteins