AUTHOR=Feilen Lukas P. , Haubrich Kevin , Strecker Paul , Probst Sabine , Eggert Simone , Stier Gunter , Sinning Irmgard , Konietzko Uwe , Kins Stefan , Simon Bernd , Wild Klemens TITLE=Fe65-PTB2 Dimerization Mimics Fe65-APP Interaction JOURNAL=Frontiers in Molecular Neuroscience VOLUME=10 YEAR=2017 URL=https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2017.00140 DOI=10.3389/fnmol.2017.00140 ISSN=1662-5099 ABSTRACT=

Physiological function and pathology of the Alzheimer’s disease causing amyloid precursor protein (APP) are correlated with its cytosolic adaptor Fe65 encompassing a WW and two phosphotyrosine-binding domains (PTBs). The C-terminal Fe65-PTB2 binds a large portion of the APP intracellular domain (AICD) including the GYENPTY internalization sequence fingerprint. AICD binding to Fe65-PTB2 opens an intra-molecular interaction causing a structural change and altering Fe65 activity. Here we show that in the absence of the AICD, Fe65-PTB2 forms a homodimer in solution and determine its crystal structure at 2.6 Å resolution. Dimerization involves the unwinding of a C-terminal α-helix that mimics binding of the AICD internalization sequence, thus shielding the hydrophobic binding pocket. Specific dimer formation is validated by nuclear magnetic resonance (NMR) techniques and cell-based analyses reveal that Fe65-PTB2 together with the WW domain are necessary and sufficient for dimerization. Together, our data demonstrate that Fe65 dimerizes via its APP interaction site, suggesting that besides intra- also intermolecular interactions between Fe65 molecules contribute to homeostatic regulation of APP mediated signaling.