PT  - JOURNAL ARTICLE
AU  - Alexander Götz
AU  - Philipp Högel
AU  - Mara Silber
AU  - Iro Chaitoglou
AU  - Burkhard Luy
AU  - Claudia Muhle-Goll
AU  - Christina Scharnagl
AU  - Dieter Langosch
TI  - Increased γ-Site H-Bond Stability Relates to Altered ε-Efficiency and Aβ Levels in the I45T Familial Alzheimer’s Disease Mutant of APP
AID  - 10.1101/372698
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 372698
4099  - http://biorxiv.org/content/early/2018/07/19/372698.short
4100  - http://biorxiv.org/content/early/2018/07/19/372698.full
AB  - Cleavage of the amyloid precursor protein’s (APP) transmembrane domain (TMD) by γ-secretase is a crucial step in the etiology of Alzheimer’s Disease (AD). Mutations in the APP TMD alter cleavage and lead to familial forms of AD (FAD). The majority of FAD mutations shifts the preference of initial cleavage from ε49 to ε48, thus raising the AD-related Aβ42/Aβ40 ratio. The I45T mutation is among the few FAD mutations that do not alter ε-site preference, while it dramatically reduces the efficiency of ε-cleavage. Here we investigate the impact of the I45T mutation on the backbone dynamics of the substrate TMD. Amide exchange experiments and molecular dynamics simulations in solvent and a lipid bilayer reveal an increased stability of amide hydrogen bonds at the ζ-and γ-cleavage sites. Stiffening of the H-bond network is caused by an additional H-bond between the T45 side chain and the TMD backbone, which alters dynamics within the cleavage domain. In particular, the increased H-bond stability inhibits an upward movement of the ε-sites in the I45T mutant. Thus, an altered presentation of ε-sites to the active site of γ-secretase as a consequence of restricted local flexibility provides a rationale for reduced ε-efficiency of the I45T FAD mutant.AβAmyloid β fragmentADAlzheimer’s diseaseAICDAmyloid intracellular domainAPPAmyloid Precursor ProteinCDcircular dichroismC9999 amino acid long fragment of the Amyloid Precursor ProteinDHXdeuterium hydrogen exchangeETDelectron transfer dissociationewMCMensemble weighed maximally correlated motionFADfamilial Alzheimer’s diseaseFMfunctional modeFMAfunctional mode analysisH-bondhydrogen bondHDXhydrogen deuterium exchangeI45TI45T FAD mutation of C99LMPGlyso-myristoylphosphatidylglycerolMDmolecular dynamicsMSmass-spectrometryMSFmean-squared fluctuationNMRNuclear magnetic resonance spectroscopyPLSpartial least squaresPOPC1-palmitoyl-2-oleoylphosphatidylcholineTFE2,2,2-trifluorethanolTMtransmembraneTMDtransmembrane domainTM-CC-terminal part of the amyloid precursor protein transmembrane domainTM-NN-terminal part of the amyloid precursor protein transmembrane domainWTwild-type