Amyloid precursor protein (APP) cleavage by the β-secretase produces the C99 transmembrane (TM) protein, which contains three dimerization-inducing Gly-x-x-x-Gly motifs. We demonstrate that dimeric C99 TM orientations regulate the precise cleavage lines by γ-secretase. Of all possible dimeric orientations imposed by a coiled-coil to the C99 TM domain, the dimer containing the Gly-x-x-x-Gly motif in the interface promoted the Aβ processing line and APP intracellular domain-dependent gene transcription, including the induction of BACE1 mRNA, enhancing amyloidogenic processing and signaling. Another orientation exhibiting the Gly-x-x-x-Gly motif in the interface favored processing to Aβ. It induced significantly less gene transcription, while promoting formation of SDS-resistant "Aβ-like" oligomers, reminiscent of Aβ peptide oligomers. These required both Val24 of a pro-β motif and the Gly-x-x-x-Gly interface. Thus, crossing angles imposed by precise dimeric orientations control γ-secretase initial cleavage at Aβ or Aβ linking the former to enhanced signaling and Aβ production.
Perrin, F., Papadopoulos, N., Suelves Caballol, N., Opsomer, R., Vadukul, D. M., Vrancx, C., Smith, S. O., Vertommen, D., Kienlen-Campard, P., & Constantinescu, S. (2020). Dimeric Transmembrane Orientations of APP/C99 Regulate γ-Secretase Processing Line Impacting Signaling and Oligomerization. iScience, 23(12), 101887. https://doi.org/10.1016/j.isci.2020.101887 (Original work published 2020)