Abstract
The insulin receptor entrains tissue growth and metabolism to nutritional conditions. Complete loss of function in humans leads to extreme insulin resistance and infantile mortality, while loss of 80-90% function permits longevity of decades. Even low-level activation of severely compromised receptors, for example by anti-receptor monoclonal antibodies, thus offers the potential for decisive clinical benefit. A barrier to genetic diagnosis and translational research is the increasing identification of variants of uncertain significance in the INSR gene, encoding the insulin receptor. By coupling saturation mutagenesis to flow-based assays, we stratified approximately 14,000 INSR extracellular missense variants by cell surface expression, insulin binding, and insulin- or monoclonal antibody-stimulated signalling. Resulting function scores correlate strongly with clinical syndromes, offer insights into dynamics of insulin binding, and reveal novel potential gain-of-function variants. This INSR sequence-function map has biochemical, diagnostic and translational utility, aiding rapid identification of variants amenable to activation by non-canonical INSR agonists.