Generating and validating renewable affimer protein binding reagents targeting SH2 domains

Despite SH2 domains, being pivotal in protein interactions linked to various diseases like cancer, we lack specific research tools for intracellular assays. Understanding SH2-mediated interactions and creating effective inhibitors requires tools which target individual protein domains. Affimer reagents exhibit promise, yet their potential against the extensive SH2 domain family remains largely unexplored. Our study aimed to bridge this gap by identifying Affimer reagents that selectively bind to 22 out of 41 SH2 domains. These reagents enabled a medium-throughput screening approach resembling siRNA studies, shedding light on their functionality. Notably, select Affimers demonstrated the ability to curtail the nuclear translocation of pERK, with Grb2 being a prominent target. Further analyses revealed that these Grb2-specific Affimer reagents displayed competitive inhibition with impressive metrics: IC50s ranging from 270.9 nM to 1.22 µM, together with low nanomolar binding affinities. Moreover, they exhibited the ability to pull down endogenous Grb2 from cell lysates, illustrating their efficacy in binding the Grb2 SH2 domain. This comprehensive assessment underscores the potential of Affimer reagents as domain-specific inhibitors. Their viability for medium/high-throughput phenotypic screening presents a promising avenue via which to identify and characterize potential drug targets within the SH2 domain family.