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Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling
Poster Abstracts
34-POS
Board 34
Insights into HER2 Biology Through Structure-based Protein Engineering
Jakob C. Stüber
, Christian Jost, Iwo König, Yann Waltenspühl, Annemarie Honegger,
Benjamin Schuler, Andreas Plückthun.
University of Zurich, Zürich, Switzerland.
Biparatopic Designed Ankyrin Repeat Proteins (DARPins) binding the oncoprotein HER2
outperform clinically approved antibody drugs in tissue culture experiments by a novel,
apoptosis-inducing mechanism of cytotoxicity. X-ray structures of the DARPin moieties in
complex with single extracellular subdomains require us to postulate previously unreported
HER2 orientations to be induced by DARPin binding.
Our work aims at elucidation of the molecular mechanism of biparatopic DARPins by three
approaches: (1) Specific receptor labeling on live cells for fluorescence-based methods such as
superresolution microscopy and fluorescence cross-correlation spectroscopy for dynamic and
structural information; (2) overexpression and purification of HER2 from insect cells for
structural investigations by electron microscopy; and (3) protein engineering to deliberately alter
the DARPin properties and limit degrees of freedom within the DARPin-receptor complexes.
Our current data are indeed in agreement with the adoption of non-native HER2 conformations
upon DARPin binding, and furthermore suggest the formation of higher-order HER2 oligomers.
These results might contribute to the formulation of a new therapeutic principle in receptor
tyrosine kinase targeting.