Enhanced ER proteostasis and temperature differentially impact the mutational tolerance of influenza hemagglutinin

• Published in: eLife Vol. 7
• Main Authors: Phillips, Angela M, Doud, Michael B, Gonzalez, Luna O, Butty, Vincent L, Lin, Yu-Shan, Bloom, Jesse D, Shoulders, Matthew D
• Format: Journal Article
• Language: English
• Published: England eLife Science Publications, Ltd 06.09.2018; eLife Sciences Publications Ltd; eLife Sciences Publications, Ltd
• Subjects: Amino Acid Sequence; Amino acids; Antibodies; Biochemistry and Chemical Biology; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum Stress - genetics; Evolution; Evolutionary Biology; Fever; Gene Expression Profiling; Genetic aspects; Haplotypes; HEK293 Cells; Hemagglutinin Glycoproteins, Influenza Virus - genetics; Hemagglutinin Glycoproteins, Influenza Virus - metabolism; Hemagglutinins; Humans; Immunological tolerance; Influenza; Lectins; membrane protein; Membrane proteins; Mutation; Protein folding; Proteins; Proteostasis; Quality control; Regression analysis; Secretory Pathway - genetics; Temperature; Temperature tolerance; Tetracyclines; unfolded protein response; Unfolded Protein Response - genetics; United States > US; Massachusetts; influenza; unfolded protein response; evolutionary biology; chemical biology; biochemistry; membrane protein; protein folding; evolution; proteostasis; human; virus
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.38795

We systematically and quantitatively evaluate whether endoplasmic reticulum (ER) proteostasis factors impact the mutational tolerance of secretory pathway proteins. We focus on influenza hemaggluttinin (HA), a viral membrane protein that folds in the host's ER via a complex pathway. By integrating chemical methods to modulate ER proteostasis with deep mutational scanning to assess mutational tolerance, we discover that upregulation of ER proteostasis factors broadly enhances HA mutational tolerance across diverse structural elements. Remarkably, this proteostasis network-enhanced mutational tolerance occurs at the same sites where mutational tolerance is most reduced by propagation at fever-like temperature. These findings have important implications for influenza evolution, because influenza immune escape is contingent on HA possessing sufficient mutational tolerance to evade antibodies while maintaining the capacity to fold and function. More broadly, this work provides the first experimental evidence that ER proteostasis mechanisms define the mutational tolerance and, therefore, the evolution of secretory pathway proteins.