title: Intramembrane proteolysis of β-amyloid precursor protein by γ-secretase is an unusually slow process.
abstract: Intramembrane proteolysis has emerged as a key mechanism required for membrane proteostasis and cellular signaling. One of the intramembrane-cleaving proteases (I-CLiPs), γ-secretase, is also intimately implicated in Alzheimer's disease, a major neurodegenerative disease and leading cause of dementia. High-resolution crystal structural analyses have revealed that I-CLiPs harbor their active sites buried deeply in the membrane bilayer. Surprisingly, however, the key kinetic constants of these proteases, turnover number kcat and catalytic efficiency kcat/KM, are largely unknown. By investigating the kinetics of intramembrane cleavage of the Alzheimer's disease-associated β-amyloid precursor protein in vitro and in human embryonic kidney cells, we show that γ-secretase is a very slow protease with a kcat value similar to those determined recently for rhomboid-type I-CLiPs. Our results indicate that low turnover numbers may be a general feature of I-CLiPs.
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany.
authors.forename: Frits
authors.initials: F
authors.lastname: Kamp
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Winkler
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Trambauer
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany.
authors.forename: Amelie
authors.initials: A
authors.lastname: Ebke
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany; DZNE-German Center for Neurodegenerative Diseases, Munich, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Fluhrer
authors.affiliation: Metabolic Biochemistry, Ludwig-Maximilians-University, München, Germany; DZNE-German Center for Neurodegenerative Diseases, Munich, Germany. Electronic address: harald.steiner@med.uni-muenchen.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Steiner
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry*; D057809:HEK293 Cells; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry; D007700:Kinetics; D059748:Proteolysis
chemical_list: D016564:Amyloid beta-Protein Precursor; D053829:Amyloid Precursor Protein Secretases