Bunyamwera orthobunyavirus glycoprotein precursor is processed by cellular signal peptidase and signal peptide peptidase

Proc Natl Acad Sci U S A. 2016 Aug 2;113(31):8825-30. doi: 10.1073/pnas.1603364113. Epub 2016 Jul 20.


The M genome segment of Bunyamwera virus (BUNV)-the prototype of both the Bunyaviridae family and the Orthobunyavirus genus-encodes the glycoprotein precursor (GPC) that is proteolytically cleaved to yield two viral structural glycoproteins, Gn and Gc, and a nonstructural protein, NSm. The cleavage mechanism of orthobunyavirus GPCs and the host proteases involved have not been clarified. In this study, we investigated the processing of BUNV GPC and found that both NSm and Gc proteins were cleaved at their own internal signal peptides (SPs), in which NSm domain I functions as SP(NSm) and NSm domain V as SP(Gc) Moreover, the domain I was further processed by a host intramembrane-cleaving protease, signal peptide peptidase, and is required for cell fusion activities. Meanwhile, the NSm domain V (SP(Gc)) remains integral to NSm, rendering the NSm topology as a two-membrane-spanning integral membrane protein. We defined the cleavage sites and boundaries between the processed proteins as follows: Gn, from residue 17-312 or nearby residues; NSm, 332-477; and Gc, 478-1433. Our data clarified the mechanism of the precursor cleavage process, which is important for our understanding of viral glycoprotein biogenesis in the genus Orthobunyavirus and thus presents a useful target for intervention strategies.

Keywords: Bunyamwera virus; Bunyavirus; glycoprotein precursor processing; signal peptidase; signal peptide peptidase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Animals
  • Aspartic Acid Endopeptidases / metabolism*
  • Binding Sites / genetics
  • Bunyamwera virus / genetics
  • Bunyamwera virus / metabolism*
  • Bunyamwera virus / physiology
  • Cell Line
  • Cell Line, Tumor
  • Chlorocebus aethiops
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • HEK293 Cells
  • Host-Pathogen Interactions
  • Humans
  • Membrane Proteins / metabolism*
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Proteolysis
  • Serine Endopeptidases / metabolism*
  • Vero Cells
  • Viral Nonstructural Proteins / genetics
  • Viral Nonstructural Proteins / metabolism


  • Glycoproteins
  • Membrane Proteins
  • Protein Precursors
  • Viral Nonstructural Proteins
  • Serine Endopeptidases
  • type I signal peptidase
  • Aspartic Acid Endopeptidases
  • signal peptide peptidase