Since the incident of Severe Acute Respiratory Syndrome Corona Virus (SARS-CoV), animal coronaviruses have been thrust into the limelight as important pathogens to study in relation to human disease. An important step in coronavirus entry is the fusion of the viral membrane with the target cell. Fusion is mediated by viral fusion (spike) proteins (In coronaviruses, the crucial spike glycoprotein is comprised of two glycopolypeptides SI and S2) and is dependent on the exposure of a fusion peptide. The fusion peptide inserts into the target membrane following conformational rearrangements in the spike protein that are triggered by receptor binding or low pH. For many viruses, a proteolytic cleavage site within the spike protein, the use of which acts as a priming event, precedes the fusion peptide. We are studying the Beaudette strain of the avian coronavirus Infectious Bronchitis Virus (IBV Bdtte). This is a lab-adapted strain that displays a wide species tropism in comparison to the prototypical clinical strain Massachusetts 41 which only infects primary chicken cells. To date, no bona fide fusion peptides have been characterized for IBV, or any other coronavirus. We use IBV as a model for studying coronavirus entry since the fundamental mechanism of entry is conserved within the Coronaviridae and thus, applicable to highly pathogenic viruses like SARS-CoV. A bioinformatics analysis of the IBV Bdtte spike protein revealed a unique consensus Furin cleavage site within the S2 domain of the spike protein. We are investigating the possibility that the 20-30 amino acids directly C-terminal to the furin cleavage site in S2 constitutes the coronavirus fusion peptide (FP). This proposed work will utilize a combination of techniques encompassing virology, molecular cell biology and biochemistry. Studies on elucidating the general mechanism of coronavirus entry and coronavirus fusion peptides are relevant to public health as potential applications in the form of antiviral pretreatment for both livestock and human populations are yet to be developed. ? ? ?
| Belouzard, Sandrine; Madu, Ikenna; Whittaker, Gary R (2010) Elastase-mediated activation of the severe acute respiratory syndrome coronavirus spike protein at discrete sites within the S2 domain. J Biol Chem 285:22758-63 |
| Madu, Ikenna G; Belouzard, Sandrine; Whittaker, Gary R (2009) SARS-coronavirus spike S2 domain flanked by cysteine residues C822 and C833 is important for activation of membrane fusion. Virology 393:265-71 |
| Madu, Ikenna G; Roth, Shoshannah L; Belouzard, Sandrine et al. (2009) Characterization of a highly conserved domain within the severe acute respiratory syndrome coronavirus spike protein S2 domain with characteristics of a viral fusion peptide. J Virol 83:7411-21 |
