Anchoring the Spring: The Role of Transmembrane Domain Interactions in Viral Fusion Protein Function

Dr. Rebecca Dutch, University of Kentucky

Host: Dr. Jinwoo Lee

Abstract: Enveloped viruses utilize surface glycoproteins to bind and fuse with a target cell membrane. The zoonotic Hendra virus (HeV), a member of the Paramyxoviridae family, utilizes the HeV attachment protein (G) and fusion protein (F) to perform these critical functions. Upon triggering, the trimeric F protein undergoes a set of large, irreversible conformation changes to drive membrane fusion. We have shown that the transmembrane domain (TM) of the F protein, separate from the rest of the protein, is present in a monomer-trimer equilibrium, and that specific sequences drive this association. Importantly, we have demonstrated similar TM-TM interactions in the TM regions from multiple viral fusion proteins. Our work with Hendra virus F shown that this TM-TM association contributes to the stability of the pre-fusion form of the protein, supporting a role for TM-TM interactions in control of F protein conformational changes. To determine the impact of disrupting TM-TM interactions, constructs expressing the HeV F TM with limited flanking sequences were synthesized. Co-expression of these constructs with HeV F resulted in dramatically reductions in the stability of F protein expression and ablation of fusion activity. In contrast, no effects were observed when the HeV F TM constructs were co-expressed with the non-homologous parainfluenza virus 5 (PIV5) fusion protein, indicating a requirement for specific interactions. To further examine this, a TM peptide homologous to the PIV5 F TM domain was synthesized. Addition of the peptide prior to infection inhibited viral infection with PIV5, but did not significantly affect infection of human metapneumovirus, a related virus. These findings indicate that TM-TM interactions are a critical stabilizer for the pre-fusion form of viral fusion proteins, and suggest that disruption of these interactions inactivates F protein function, likely by prematurely triggering F protein conformational changes.

Biochemistry Seminar