TY - JOUR
T1 - Apolipoprotein E4 has extensive conformational heterogeneity in lipid-free and lipid-bound forms
AU - Stuchell-Brereton, Melissa D.
AU - Zimmerman, Maxwell I.
AU - Miller, Justin J.
AU - Mallimadugula, Upasana L.
AU - Incicco, J. Jeremías
AU - Roy, Debjit
AU - Smith, Louis G.
AU - Cubuk, Jasmine
AU - Baban, Berevan
AU - DeKoster, Gregory T.
AU - Frieden, Carl
AU - Bowman, Gregory R.
AU - Soranno, Andrea
N1 - Publisher Copyright:
Copyright © 2023 the Author(s).
PY - 2023/2/14
Y1 - 2023/2/14
N2 - The ϵ4-allele variant of apolipoprotein E (ApoE4) is the strongest genetic risk factor for Alzheimer's disease, although it only differs from its neutral counterpart ApoE3 by a single amino acid substitution. While ApoE4 influences the formation of plaques and neurofibrillary tangles, the structural determinants of pathogenicity remain undetermined due to limited structural information. Previous studies have led to conflicting models of the C-terminal region positioning with respect to the N-terminal domain across isoforms largely because the data are potentially confounded by the presence of heterogeneous oligomers. Here, we apply a combination of single-molecule spectroscopy and molecular dynamics simulations to construct an atomically detailed model of monomeric ApoE4 and probe the effect of lipid association. Importantly, our approach overcomes previous limitations by allowing us to work at picomolar concentrations where only the monomer is present. Our data reveal that ApoE4 is far more disordered and extended than previously thought and retains significant conformational heterogeneity after binding lipids. Comparing the proximity of the N- and C-terminal domains across the three major isoforms (ApoE4, ApoE3, and ApoE2) suggests that all maintain heterogeneous conformations in their monomeric form, with ApoE2 adopting a slightly more compact ensemble. Overall, these data provide a foundation for understanding how ApoE4 differs from nonpathogenic and protective variants of the protein.
AB - The ϵ4-allele variant of apolipoprotein E (ApoE4) is the strongest genetic risk factor for Alzheimer's disease, although it only differs from its neutral counterpart ApoE3 by a single amino acid substitution. While ApoE4 influences the formation of plaques and neurofibrillary tangles, the structural determinants of pathogenicity remain undetermined due to limited structural information. Previous studies have led to conflicting models of the C-terminal region positioning with respect to the N-terminal domain across isoforms largely because the data are potentially confounded by the presence of heterogeneous oligomers. Here, we apply a combination of single-molecule spectroscopy and molecular dynamics simulations to construct an atomically detailed model of monomeric ApoE4 and probe the effect of lipid association. Importantly, our approach overcomes previous limitations by allowing us to work at picomolar concentrations where only the monomer is present. Our data reveal that ApoE4 is far more disordered and extended than previously thought and retains significant conformational heterogeneity after binding lipids. Comparing the proximity of the N- and C-terminal domains across the three major isoforms (ApoE4, ApoE3, and ApoE2) suggests that all maintain heterogeneous conformations in their monomeric form, with ApoE2 adopting a slightly more compact ensemble. Overall, these data provide a foundation for understanding how ApoE4 differs from nonpathogenic and protective variants of the protein.
KW - Alzheimer's disease
KW - apolipoprotein E
KW - protein folding
KW - single-molecule FRET
UR - http://www.scopus.com/inward/record.url?scp=85147720777&partnerID=8YFLogxK
U2 - 10.1073/pnas.2215371120
DO - 10.1073/pnas.2215371120
M3 - Article
C2 - 36749730
AN - SCOPUS:85147720777
SN - 0027-8424
VL - 120
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 7
M1 - e2215371120
ER -