A helix-to-coil transition at the epsilon-cut site in the transmembrane dimer of the amyloid precursor protein is required for proteolysis.
Processing of amyloid precursor protein (APP) by gamma-secretase is the last step in the formation of the Abeta peptides associated Alzheimer's disease. Solid-state NMR spectroscopy is used to establish the structural features of the transmembrane (TM) and juxtamembrane (JM) domains of APP that facilitate proteolysis. Using peptides corresponding to the APP TM and JM regions (residues 618-660), we show that the TM domain forms an alpha-helical homodimer mediated by consecutive GxxxG motifs. We find that the APP TM helix is disrupted at the intracellular membrane boundary near the epsilon-cleavage site. This helix-to-coil transition is required for gamma-secretase processing; mutations that extend the TM alpha-helix inhibit epsilon cleavage, leading to a low production of Abeta peptides and an accumulation of the alpha- and beta-C-terminal fragments. Our data support a progressive cleavage mechanism for APP proteolysis that depends on the helix-to-coil transition at the TM-JM boundary and unraveling of the TM alpha-helix.
Sato
Takeshi
T
Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5115, USA.
Tang
Tzu-Chun
TC
Reubins
Gabriella
G
Fei
Jeffrey Z
JZ
Fujimoto
Taiki
T
Kienlen-Campard
Pascal
P
Constantinescu
Stefan N
SN
Octave
Jean-Noel
JN
Aimoto
Saburo
S
Smith
Steven O
SO
D000595:Amino Acid Sequence; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000737:chemistry; D019281:Dimerization; D006868:Hydrolysis; D008565:Membrane Proteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017550:Spectroscopy, Fourier Transform Infrared
D016564:Amyloid beta-Protein Precursor; D008565:Membrane Proteins