Functional and Evolutionary Analyses of Domain V in EGFR

Poulhazan, Alexandra

Student Work

Functional and Evolutionary Analyses of Domain V in EGFR

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The Epidermal Growth Factor Receptor (EGFR/ErbBs) is a family of receptor tyrosine kinases that plays a crucial role in regulating cell growth, proliferation, and survival. This family of proto-oncogenes has also been implicated in numerous cancers and represents a primary therapeutic target. In humans, these receptors contain four extracellular domains; in Drosophila, the receptor (dEGFR) includes a fifth extracellular domain (Domain V). Previously, Kekkon1 (Kek1) was discovered as an inhibitor of dEGFR. Interestingly, Kek1 is not capable of interacting with the human EGFR/ErbB receptors. Recent work indicates that Domain V and part of Domain IV in dEGFR are necessary to confer binding to Kek1. Given the human receptors lack Domain V, this explains their lack of interaction with Kek1. To understand the sequences driving the interaction between dEGFR and Kek1 and, therefore, the inhibitory mechanism, I undertook phylogenetic, biochemical, and modeling analyses of dEGFR. First, alignments between dEGFR and the C. elegans Let-23 ortholog were performed to identify conserved regions. These alignments were then used to generate a chimeric protein in which Domain V of the dEGFR was replaced with Domain V of Let-23. This chimera, along with a series of Domain V deletions and mutations affecting dEGFR dimerization, were then tested for Kek 1 binding. Lastly, in silico structural models of the chimera and mutant dEGFR proteins in complex with Kek1 were generated to help further define the role of Domain V in Kek 1 binding. Together, the data support a central role for Domain V in dEGFR/Kek1 binding and help identify residues underlying the specificity of their interaction. An increased understanding of the basis of their interaction by defining the binding pocket could ultimately provide a novel approach to developing cancer therapeutics.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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