Ludwig-Maximilians-Universität, Chair of Metabolic Biochemistry
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Presenilin-dependent intramembrane proteolysis of CD44 leads to the liberation of its intracellular domain and the secretion of an Abeta-like peptide

J Biol Chem 277(47): 44754-9

Authors/Editors: Lammich S
Okochi M
Takeda M
Kaether C
Capell A
Zimmer AK
Edbauer D
Walter J
Steiner H
Haass C
Publication Date: 2002
Type of Publication: Journal Article
Alzheimer's disease (AD)-associated gamma-secretase is a presenilin (PS)- dependent proteolytic activity involved in the intramembraneous cleavage of the beta-amyloid precursor protein, Notch, LDL receptor-related protein, E-cadherin, and ErbB-4. This cut produces the corresponding intracellular domains (ICD), which are required for nuclear signaling of Notch and probably ErbB-4, the beta-amyloid precursor protein, E-cadherin, and the LDL receptor-related protein as well. We have now investigated CD44, a cell surface adhesion molecule, which also undergoes an intramembraneous cleavage to liberate its ICD. We demonstrate that this cleavage requires a PS-dependent gamma-secretase activity. A loss-of-function PS1 mutation, a PS1/PS2 knockout, as well as two independent and highly specific gamma-secretase inhibitors, abolish this cleavage. Surprisingly, small peptides similar to the amyloid beta-peptide (Abeta) are generated by an additional cut in the middle of the transmembrane region of CD44. Like Abeta, these CD44 beta-peptides are generated in a PS-dependent manner. These findings therefore suggest a dual intramembraneous cleavage mechanism mediated by PS proteins. The dual cleavage mechanism is required for nuclear signaling as well as removal of remaining transmembrane domains, a general function of PS in membrane protein metabolism.

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