Oral Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Structures of the active HER2/HER3 receptor complex reveal dynamics at the dimerization interface induced by binding of a single ligand (#8)

Raphael Trenker 1 , Devan Diwanji 1 2 , Tarjani M Thaker 1 3 , Feng Wang 4 , David A Agard 4 , Kliment A Verba 5 6 , Natalia Jura 1 7
  1. Cardiovascular Research Institute , University of California San Francisco, San Francisco, CA, USA
  2. Medical Scientist Training Program , University of California San Francisco, San Francisco, CA, USA
  3. Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ, United. States
  4. Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
  5. Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, CA, USA
  6. Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA
  7. Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA

The Human Epidermal Growth Factor Receptor 3 (HER3) and the orphan receptor HER2 assemble into a singly liganded, pro-oncogenic heterocomplex upon binding to the HER3 ligand neuregulin-1β (NRG1β). In the absence of structures of the HER2/HER3 heterodimer, the mechanism by which HER2 and HER3 interact upon ligand binding remains unknown. We isolated the near full-length HER2/HER3/NRG1β heterocomplex and obtained a 2.9Å cryo-electron microscopy (cryo-EM) reconstruction of the extracellular domain module. Surprisingly, the structure reveals unexpected dynamics at the HER2/HER3 dimerization interface with an unresolved dimerization arm of NRG1β-bound HER3. This is likely because the apo HER2 monomer fails to undergo a ligand-induced conformational change required to establish a HER3 dimerization arm binding pocket. In a second heterodimer structure of HER3 bound to the most frequent oncogenic extracellular domain mutant of HER2, S310F, we observe that this mutation is perfectly positioned to stabilize the HER3 dimerization arm and thus increases the dimerization interface of the oncogenic heterocomplex.  We show that both HER2/HER3/NRG1b and HER2-S310F/HER3/NRG1β retain the capacity to bind to the HER2-directed therapeutic antibody trastuzumab, but the mutant complex does not bind to pertuzumab. Our 3.5Å structure of the HER2-S310F/HER3/NRG1β complex bound to the trastuzumab Fragment antigen binding (Fab) fragment shows that the receptor dimer undergoes a conformational change to accommodate trastuzumab. Thus, oncogenic mutations and therapeutics appear to exploit the intrinsic dynamics of the HER2/HER3 heterodimer. The unique features of the singly liganded HER2/HER3 heterodimer underscore an allosteric connection between the ligand-binding pocket and the dimerization interface and explain why extracellular domains of unliganded HER2 do not homo-associate via canonical active dimer interfaces.

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  4. Diwanji, D*. & Trenker, R*. et al. Structures of the active HER2/HER3 receptor complex reveal dynamics at the dimerization interface induced by binding of a single ligand. BioRxiv doi: https://doi.org/10.1101/2021.05.03.442258 (2021). Accepted for publication in Nature. *Contributed equally