The effects of dimer and oligomer separation on cell signaling in the EGFR family

The EGFR family of receptor tyrosine kinases (RTKs) includes EGFR, HER2/ErbB2, HER3/ErbB3, and HER4/ErbB. The EGFR family members play crucial roles in development and in regulating normal cellular processes. However, these receptors are found to be overexpressed or mutated in various cancers. The complete mechanism by which the EGFR family is autoregulated is still unknown. This work focuses on the role of the extracellular domain of EGFR family members on receptor activation, dimerization/oligomerization, and downstream signaling. We generated a system using designed ankyrin repeat proteins (DARPins) to study EGFR extracellular domain dimers of varying separation distances. We biochemically, cellularly, and structurally characterize interactions between HER3 and A30, an RNA that binds to the extracellular domain of HER3 and reduces HER2 phosphorylation. This work also includes preliminary efforts to characterize HER2-HER3 oligomers using single molecule photobleaching experiments. This work lays the groundwork for future studies involving EGFR family receptor regulation