Presenilin complexes with the C-terminal fragments of amyloid precursor protein at the sites of amyloid beta-protein generation.
An unusual intramembranous cleavage of the beta-amyloid precursor protein (APP) by gamma-secretase is the final step in the generation of amyloid beta-peptide (Abeta). Two conserved aspartates in transmembrane (TM) domains 6 and 7 of presenilin (PS) 1 are required for Abeta production by gamma-secretase. Here we report that the APP C-terminal fragments, C83 and C99, which are the direct substrates of gamma-secretase, can be coimmunoprecipitated with both PS1 and PS2. PS/C83 complexes were detected in cells expressing endogenous levels of PS. The complexes accumulate when gamma-secretase is inactivated either pharmacologically or by mutating the PS aspartates. PS1/C83 and PS1/C99 complexes were detected in Golgi-rich and trans-Golgi network-rich vesicle fractions. In contrast, complexes of PS1 with APP holoprotein, which is not the immediate substrate of gamma-secretase, occurred earlier in endoplasmic reticulum-rich vesicles. The major portion of intracellular Abeta at steady state was found in the same Golgi/trans-Golgi network-rich vesicles, and Abeta levels in these fractions were markedly reduced when either PS1 TM aspartate was mutated to alanine. Furthermore, de novo generation of Abeta in a cell-free microsomal reaction occurred specifically in these same vesicle fractions and was markedly inhibited by mutating either TM aspartate. Thus, PSs are complexed with the gamma-secretase substrates C83 and C99 in the subcellular locations where Abeta is generated, indicating that PSs are directly involved in the pathogenically critical intramembranous proteolysis of APP.
Xia
W
W
Department of Neurology and Program in Neuroscience, Harvard Medical School and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, MA 02115, USA. xia@cnd.bwh.harvard.edu
Ray
W J
WJ
Ostaszewski
B L
BL
Rahmati
T
T
Kimberly
W T
WT
Wolfe
M S
MS
Zhang
J
J
Goate
A M
AM
Selkoe
D J
DJ
D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D010450:Endopeptidases / Q000187:drug effects; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008565:Membrane Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D053764:Presenilin-1
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D008565:Membrane Proteins; C508853:PSEN1 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human