Biology subjects

Stanfield, R. L.

Publications and source records attributed to Stanfield, R. L..

3 recordsLinked to original sources

bioRxiv2024

A tale of two fusion proteins: understanding the metastability of human respiratory syncytial virus and metapneumovirus and implications for rational design of uncleaved prefusion-closed trimers

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) cause human respiratory diseases and are major targets for vaccine development. In this study, we designed uncleaved prefusion-closed (UFC) trimers for the fusion (F) proteins of both viruses by examining mutations critical to F metastability. For RSV, we assessed four previous prefusion F designs, including the first and second generations of DS-Cav1, SC-TM, and 847A. We then identified key mutations that can maintain prefusion F in a native-like, closed trimeric form (up to 76%) without introducing any interprotomer disulfide bond. For hMPV, we developed a stable UFC trimer with a truncated F2-F1 linkage and an interprotomer disulfide bond. Tens of UFC constructs were characterized by negative-stain electron microscopy (nsEM), x-ray crystallography (11 RSV-F and one hMPV-F structures), and antigenic profiling. Using an optimized RSV-F UFC trimer as bait, we identified three potent RSV neutralizing antibodies (NAbs) from a phage-displayed human antibody library, with a public NAb lineage targeting sites O and V and two cross-pneumovirus NAbs recognizing site III. In mouse immunization, rationally designed RSV-F and hMPV-F UFC trimers induced robust antibody responses with high neutralizing titers. Our study provides a foundation for future prefusion F-based RSV and hMPV vaccine development. ONE-SENTENCE SUMMARYThe metastability analysis of fusion proteins has informed rational design of uncleaved prefusion-closed trimers for RSV and hMPV vaccine development.

microbiology↗

bioRxiv2024

Mispacking of the F87 sidechain drives aggregation-promoting conformational fluctuations in the subunit interfaces of the transthyretin tetramer

Aberrant formation and deposition of human transthyretin (TTR) aggregates causes transthyretin amyloidosis. To initialize aggregation, transthyretin tetramers must first dissociate into monomers that partially unfold to promote entry into the aggregation pathway. The native TTR tetramer (T) is stabilized by docking of the F87 sidechain into an interfacial cavity enclosed by several hydrophobic residues including A120. We have previously shown that an alternative tetramer (T*) with mispacked F87 sidechains is more prone to dissociation and aggregation than the native T state. However, the molecular basis for the reduced stability in T* remains unclear. Here we report characterization of the A120L mutant, where steric hindrance is introduced into the F87 binding site. The X-ray structure of A120L shows that the F87 sidechain is displaced from its docking site across the subunit interface. In A120S, a naturally occurring pathogenic mutant that is less aggregation-prone than A120L, the F87 sidechain is correctly docked, as in the native TTR tetramer. Nevertheless, 19F-NMR aggregation assays show an elevated population of a monomeric aggregation intermediate in A120S relative to a control containing the native A120, due to accelerated tetramer dissociation and slowed monomer tetramerization. The mispacking of the F87 sidechain is associated with enhanced exchange dynamics for interfacial residues. At 298 K, the T* populations of various naturally occurring mutants fall between 4-7% ({Delta}G [~] 1.5- 1.9 kcal/mol), consistent with the free energy change expected for undocking and solvent exposure of one of the four F87 sidechains in the tetramer ({Delta}G [~] 1.6 kcal/mol). Our data provide a molecular-level picture of the likely universal F87 sidechain mispacking in tetrameric TTR that promotes interfacial conformational dynamics and increases aggregation propensity.

biophysics↗

bioRxiv2023

Probing the dissociation pathway of a kinetically labile transthyretin mutant

Aggregation of transthyretin (TTR) is associated with devastating TTR amyloid disease. Amyloidosis begins with dissociation of the native tetramer to form a monomeric intermediate that assembles into pathogenic aggregates. This process is accelerated in vitro at low pH, but the dissociation and reassembly of TTR at neutral pH remains poorly understood, due to the low population of intermediates. We use NMR studies with a highly sensitive 19F probe that allows deconvolution of relative populations of a destabilized A25T mutant at concentrations as low as 2 {micro}M. The A25T mutation, located at the weak dimer interface, perturbs both the weak and strong dimer interfaces. A tetramer-dimer-monomer (TDM) equilibrium model is proposed to account for concentration- and temperature-dependent population changes. All thermodynamic and kinetic parameters and activation energetics for dissociation of the native A25T tetramer, as well as a destabilized alternative tetramer (T*) with a mispacked F87 side chain, were extracted by vant Hoff and 19F NMR line-shape analysis. The conversion from T to T*, the slowest first-order kinetic step, shows anti-Arrhenius behavior. The 19F and methyl chemical shifts of probes close to the strong dimer interface in the dimer and T* species are degenerate, implicating interfacial perturbation as a common structural feature of these intermediate species. Molecular dynamics (MD) simulations further suggest more frequent F87 ring flipping on the nanoscale timescale in the A25T dimer than in the tetramer. Our integrated approach offers quantitative insights into the energy landscape of the dissociation pathway of TTR at neutral pH.

biophysics↗