The presenilin C-terminus is required for ER-retention, nicastrin-binding and gamma-secretase activity.
gamma-Secretase is an intramembrane cleaving protease involved in Alzheimer's disease. gamma-Secretase occurs as a high molecular weight complex composed of presenilin (PS1/2), nicastrin (NCT), anterior pharynx-defective phenotype 1 and PS enhancer 2. Little is known about the cellular mechanisms of gamma-secretase assembly. Here we demonstrate that the cytoplasmic tail of PS1 fulfills several functions required for complex formation, retention of unincorporated PS1 and gamma-secretase activity. The very C-terminus interacts with the transmembrane domain of NCT and may penetrate into the membrane. Deletion of the last amino acid is sufficient to completely block gamma-secretase assembly and release of PS1 from the endoplasmic reticulum (ER). This suggests that unincorporated PS1 is actively retained within the ER. We identified a hydrophobic stretch of amino acids within the cytoplasmic tail of PS1 distinct from the NCT-binding site, which is required to retain unincorporated PS1 within the ER. Deletion of the retention signal results in the release of PS1 from the ER and the assembly of a nonfunctional gamma-secretase complex, suggesting that at least a part of the retention motif may also be required for the function of PS1.
Kaether
Christoph
C
Laboratory for Alzheimer's and Parkinson's Disease Research, Department of Biochemistry, Adolf-Butenandt-Institute, Ludwig-Maximilians-Universität, München, Germany. ckaether@med.uni-muenchen.de
Capell
Anja
A
Edbauer
Dieter
D
Winkler
Edith
E
Novak
Bozidar
B
Steiner
Harald
H
Haass
Christian
C
D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D010450:Endopeptidases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D053764:Presenilin-1; D011485:Protein Binding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D053764:Presenilin-1; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C413604:nicastrin protein; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases