Overexpression of nicastrin increases Abeta production.
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.
Murphy
M Paul
MP
Mayo Clinic Jacksonville, Laboratory of Molecular Neurobiology, Department of Neuroscience, 4500 San Pablo Rd, Jacksonville, Florida 32224, USA.
Das
Pritam
P
Nyborg
Andrew C
AC
Rochette
Marjorie J
MJ
Dodson
Mark W
MW
Loosbrock
Nicole M
NM
Souder
Terrance M
TM
McLendon
Chris
C
Merit
Sami L
SL
Piper
Siân C
SC
Jansen
Karen R
KR
Golde
Todd E
TE
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
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