title: Overexpression of nicastrin increases Abeta production.
abstract: Gamma-secretase cleavage is the final proteolytic step that releases the amyloid beta-peptide (Abeta) from the amyloid beta-protein precursor (APP). Significant evidence indicates that the presenilins (PS) are catalytic components of a high molecular weight gamma-secretase complex. The glycoprotein nicastrin was recently identified as a functional unit of this complex based on 1) binding to PS and 2) the ability to modulate Abeta production following mutation of a conserved DYIGS region. In contrast to the initial report, we find that overexpression of wild-type (WT) nicastrin increases Abeta production, whereas DYIGS mutations (MT) have little or no effect. The increase in Abeta production is associated with an increase in gamma-secretase activity but not with a detectable increase in PS1 levels. Subcellular fractionation studies show that WT but not MT nicastrin matures into buoyant membrane fractions enriched in gamma-secretase activity. These data support the hypothesis that nicastrin is an essential component of the gamma-secretase complex. The finding that WT nicastrin overexpression can increase gamma-secretase activity without altering levels of the presumed catalytic component (PS) of the enzyme may point to a role for nicastrin in facilitating cleavage by regulating substrate interactions with the gamma-secretase complex.
authors.affiliation: Mayo Clinic Jacksonville, Laboratory of Molecular Neurobiology, Department of Neuroscience, 4500 San Pablo Rd, Jacksonville, Florida 32224, USA.
authors.forename: M Paul
authors.initials: MP
authors.lastname: Murphy
authors.forename: Pritam
authors.initials: P
authors.lastname: Das
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Nyborg
authors.forename: Marjorie J
authors.initials: MJ
authors.lastname: Rochette
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dodson
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Loosbrock
authors.forename: Terrance M
authors.initials: TM
authors.lastname: Souder
authors.forename: Chris
authors.initials: C
authors.lastname: McLendon
authors.forename: Sami L
authors.initials: SL
authors.lastname: Merit
authors.forename: Siân C
authors.initials: SC
authors.lastname: Piper
authors.forename: Karen R
authors.initials: KR
authors.lastname: Jansen
authors.forename: Todd E
authors.initials: TE
authors.lastname: Golde
mesh_terms: D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis*; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D010455:Peptides / Q000378:metabolism; D021122:Protein Subunits; D014162:Transfection
chemical_list: D016229:Amyloid beta-Peptides; D008562:Membrane Glycoproteins; D010455:Peptides; D021122:Protein Subunits; C413604:nicastrin protein; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human