Examination of a Fusogenic Hexameric Core from Human Metapneumovirus and Identification of a Potent Synthetic Peptide Inhibitor from the Heptad Repeat 1 Region

Abstract

Paramyxoviruses are a leading cause of childhood illness worldwide. A recently discovered paramyxovirus, human metapneumovirus (hMPV), has been studied by our group in order to determine the structural relevance of its fusion (F) protein to other well-characterized viruses utilizing type I integral membrane proteins as fusion aids. Sequence analysis and homology models suggested the presence of requisite heptad repeat (HR) regions. Synthetic peptides from HR regions 1 and 2 (HR-1 and -2, respectively) were induced to form a thermostable (melting temperature, ϳ90°C) helical structure consistent in mass with a hexameric coiled coil. Inhibitory studies of hMPV HR-1 and -2 indicated that the synthetic HR-1 peptide was a significant fusion inhibitor with a 50% inhibitory concentration and a 50% effective concentration of ϳ50 nM. Many viral fusion proteins are type I integral membrane proteins utilizing the formation of a hexameric coiled coil of HR peptides as a major driving force for fusion. Our studies provide evidence that hMPV also uses a coiled-coil structure as a major player in the fusion process. Additionally, viral HR-1 peptide sequences may need further investigation as potent fusion inhibitors.

Integrin αvβ1 promotes infection by human metapneumovirus

“…The observed sequence conservation suggests that this region serves an important biological function in hMPV infection, as F is the major antigenic target and subject to variation in other domains (7,38,39). The structure of hMPV F has not been reported to our knowledge, but the region containing the RGD sequence is predicted to be solvent-exposed (12,30). Among the human paramyxoviruses, the RGD motif is unique to hMPV.…”

“…Concordantly, ectopic expression of hMPV F is sufficient to mediate cell-cell fusion (11). Synthetic peptides that correspond to the heptad-repeat regions are potent inhibitors of hMPV infection, suggesting that hMPV F is a class I fusion protein (12). Proteinaceous cellular receptors have been identified for some paramyxoviruses, including measles virus (13,14) and Nipah virus (15,16).…”

Residues of the Human Metapneumovirus Fusion (F) Protein Critical for Its Strain-Related Fusion Phenotype: Implications for the Virus Replication Cycle

“…Subsequent conformational changes of this prehairpin involve assembly of the HRA and HRB regions into a six-helix bundle (6HB) that brings the viral and cell membranes into proximity, ending up in fusion of both membranes. Formation of the 6HB and the associated free-energy change are tightly linked to the merger of the viral and cellular membranes and the formation of the so-called fusion pore (5,22,29).…”

Identification and Evaluation of a Highly Effective Fusion Inhibitor for Human Metapneumovirus

“…Three of the latter are glycoproteins potentially exposed at the surface of the virion and infected cells: the fusion (F), attachment, and small hydrophobic proteins (12,40). The F protein, which is the major antigenic determinant (37), is a class I transmembrane protein mediating virus-cell fusion and infected cell-cell fusion as found in other paramyxoviruses (21,28,36). Membrane fusion mechanisms have been studied largely for fusogenic viruses such as human immunodeficiency virus (HIV), influenza virus, and other paramyxoviruses (17,21,23,25,29,38,44,49).…”