| Title | gamma-Secretase: successive tripeptide and tetrapeptide release from the transmembrane domain of beta-carboxyl terminal fragment. | | Author(s) | Takami M, Nagashima Y, Sano Y, Ishihara S, Morishima-Kawashima M, Funamoto S, Ihara Y | | Institution | Department of Neuropathology, Faculty of Life and Medical Sciences, Doshisha University, Kizugawa 619-0225, Japan. | | Source | J Neurosci 2009 Oct 14; 29(41):13042-52. | | MeSH | Amyloid Precursor Protein Secretases
Amyloid beta-Protein
Amyloid beta-Protein Precursor
Analysis of Variance
Animals
CHO Cells
Cell Membrane
Cholic Acids
Chromatography, Liquid
Cricetinae
Cricetulus
Detergents
Immunoprecipitation
Models, Biological
Oligopeptides
Peptide Fragments
Protein Structure, Tertiary
Substrate Specificity
Tandem Mass Spectrometry
Time Factors
| | Abstract | Amyloid beta protein (Abeta), a pathogenic molecule associated with Alzheimer's disease, is produced by gamma-secretase, which cleaves the beta-carboxyl terminal fragment (betaCTF) of beta-amyloid precursor protein in the middle of its transmembrane domain. How the cleavage proceeds within the membrane has long been enigmatic. We hypothesized previously that betaCTF is cleaved first at the membrane-cytoplasm boundary, producing two long Abetas, Abeta(48) and Abeta(49), which are processed further by releasing three residues at each step to produce Abeta(42) and Abeta(40), respectively. To test this hypothesis, we used liquid chromatography tandem mass spectrometry (LC-MS/MS) to quantify the specific tripeptides that are postulated to be released. Using CHAPSO (3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxyl-1-propanesulfonate)-reconstituted gamma-secretase system, we confirmed that Abeta(49) is converted to Abeta(43/40) by successively releasing two or three tripeptides and that Abeta(48) is converted to Abeta(42/38) by successively releasing two tripeptides or these plus an additional tetrapeptide. Most unexpectedly, LC-MS/MS quantification revealed an induction period, 3-4 min, in the generation of peptides. When extrapolated, each time line for each tripeptide appears to intercept the same point on the x-axis. According to numerical simulation based on the successive reaction kinetics, the induction period exists. These results strongly suggest that Abeta is generated through the stepwise processing of betaCTF by gamma-secretase. | | Language | eng | | Pub Type(s) | Journal Article
Research Support, Non-U.S. Gov't
| | PubMed ID | 19828817 |
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