Genetic analysis of the SARS-coronavirus spike glycoprotein functional domains involved in cell-surface expression and cell-to-cell fusion.

Academic Article

Abstract

  • The SARS-coronavirus (SARS-CoV) is the etiological agent of severe acute respiratory syndrome (SARS). The SARS-CoV spike (S) glycoprotein mediates membrane fusion events during virus entry and virus-induced cell-to-cell fusion. To delineate functional domains of the SARS-CoV S glycoprotein, single point mutations, cluster-to-lysine and cluster-to-alanine mutations, as well as carboxyl-terminal truncations were investigated in transient expression experiments. Mutagenesis of either the coiled-coil domain of the S glycoprotein amino terminal heptad repeat, the predicted fusion peptide, or an adjacent but distinct region, severely compromised S-mediated cell-to-cell fusion, while intracellular transport and cell-surface expression were not adversely affected. Surprisingly, a carboxyl-terminal truncation of 17 amino acids substantially increased S glycoprotein-mediated cell-to-cell fusion suggesting that the terminal 17 amino acids regulated the S fusogenic properties. In contrast, truncation of 26 or 39 amino acids eliminating either one or both of the two endodomain cysteine-rich motifs, respectively, inhibited cell fusion in comparison to the wild-type S. The 17 and 26 amino-acid deletions did not adversely affect S cell-surface expression, while the 39 amino-acid truncation inhibited S cell-surface expression suggesting that the membrane proximal cysteine-rich motif plays an essential role in S cell-surface expression. Mutagenesis of the acidic amino-acid cluster in the carboxyl terminus of the S glycoprotein as well as modification of a predicted phosphorylation site within the acidic cluster revealed that this amino-acid motif may play a functional role in the retention of S at cell surfaces. This genetic analysis reveals that the SARS-CoV S glycoprotein contains extracellular domains that regulate cell fusion as well as distinct endodomains that function in intracellular transport, cell-surface expression, and cell fusion.
  • Published In

  • Virology  Journal
  • Keywords

  • Amino Acid Sequence, Amino Acid Substitution, Animals, Cell Fusion, Cell Membrane, Cercopithecus aethiops, Immunohistochemistry, Membrane Fusion, Membrane Glycoproteins, Molecular Sequence Data, Point Mutation, Protein Structure, Tertiary, Protein Transport, SARS Virus, Sequence Deletion, Spike Glycoprotein, Coronavirus, Vero Cells, Viral Envelope Proteins, Viral Fusion Proteins
  • Digital Object Identifier (doi)

    Author List

  • Petit CM; Melancon JM; Chouljenko VN; Colgrove R; Farzan M; Knipe DM; Kousoulas KG
  • Start Page

  • 215
  • End Page

  • 230
  • Volume

  • 341
  • Issue

  • 2