Perturbing dimer interactions and allosteric communication modulates the immunosuppressive activity of human galectin-7.

The design of allosteric modulators to control protein function is a key objective in drug discovery programs. Altering functionally essential allosteric residue networks provides unique protein family subtype specificity, minimizes unwanted off-target effects, and helps avert resistance acquisition typically plaguing drugs that target orthosteric sites. In this work, we used protein engineering and dimer interface mutations to positively and negatively modulate the immunosuppressive activity of the proapoptotic human galectin-7 (GAL-7). Using the PoPMuSiC and BeAtMuSiC algorithms, mutational sites and residue identity were computationally probed and predicted to either alter or stabilize the GAL-7 dimer interface. By designing a covalent disulfide bridge between protomers to control homodimer strength and stability, we demonstrate the importance of dimer interface perturbations on the allosteric network bridging the two opposite glycan-binding sites on GAL-7, resulting in control of induced apoptosis in Jurkat T cells. Molecular investigation of G16X GAL-7 variants using X-ray crystallography, biophysical, and computational characterization illuminates residues involved in dimer stability and allosteric communication, along with discrete long-range dynamic behaviors involving loops 1, 3, and 5. We show that perturbing the protein-protein interface between GAL-7 protomers can modulate its biological function, even when the overall structure and ligand-binding affinity remains unaltered. This study highlights new avenues for the design of galectin-specific modulators influencing both glycan-dependent and glycan-independent interactions.

The Val430Ile neuraminidase (NA) substitution, identified in influenza B virus isolates, impacts the catalytic 116Arg residue causing reduced susceptibility to NA inhibitors.

As part of a 2015-2018 clinical trial of peramivir treatment for acute influenza infections in the elderly, an influenza B/Yamagata/16/1988-like isolate harbouring a Val430Ile neuraminidase (NA) substitution was recovered from a single patient. This substitution was detected in respiratory samples collected before and during peramivir treatment. In NA inhibition assays, oseltamivir, zanamivir and peramivir IC50s of the Val430Ile isolate were 4-, 15- and 16-fold higher compared to a wild-type (WT) strain. In reverse genetics experiments, the Ile430Val reversion restored the drug susceptible phenotype. The Val430Ile mutant and the WT strain had comparable replication kinetics in ST6GalI-MDCK cells and the NA mutation was stable after four passages in that cell line. Molecular dynamics simulations suggested that Val430Ile impacts the NA binding through a mechanism involving the catalytic Arg116 residue. The potential of some NA mutations not part of the active site to alter the susceptibility to NA inhibitors highlights the need to develop novel antiviral strategies against influenza B infections.