Year: 2023
Type: preprint
Abstract: Alzheimer’s disease is characterized pathologically by cerebral deposition of 42-residue amyloid β-peptide (Aβ42), proteolytically produced from amyloid precursor protein (APP) by β- and γ-secretases. 1 Although mutations in APP and presenilin, the catalytic component of γ-secretase, cause familial Alzheimer’s disease (FAD), a role for Aβ42 as the primary disease driver has not been clearly established and remains controversial. 2,3 Here we show through comprehensive analysis of the multi-step proteolysis of APP substrate C99 by γ-secretase that FAD mutations are consistently deficient in early proteolytic events, not later events that produce secreted Aβ peptides. Cryo-electron microscopy revealed that a substrate mimetic traps γ-secretase at the transition state for intramembrane proteolysis, and this structure closely aligns with activated enzyme-substrate complex captured by molecular dynamics simulations. In silico simulations and fluorescence lifetime imaging microscopy in cultured cells support stabilization by FAD mutations of enzyme-substrate and/or enzyme-intermediate complexes. Neuronal expression of C99 and/or presenilin-1 in Caenorabditis elegans led to age-dependent synaptic loss only when one of the transgenes carried an FAD mutation. Designed mutations that stabilize the enzyme-substrate complex and block proteolysis likewise led to synaptic loss. Collectively, these findings implicate the stalled process—not the released products—of γ-secretase cleavage of substrates in FAD pathogenesis.
Authors: Sujan Devkota, Rui Zhou, Vaishnavi Nagarajan, Masato Maesako, Hung Do, Arshad Noorani, Caitlin Overmeyer, Sanjay Bhattarai, Justin T. Douglas, Anita Saraf, Yinglong Miao, Brian D. Ackley, Yigong Shi, Michael S. Wolfe
Language: English
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W4386579685