Nicastrin is critical for stability and trafficking but not association of other presenilin/gamma-secretase components

J Biol Chem. 2005 Apr 29;280(17):17020-6. doi: 10.1074/jbc.M409467200. Epub 2005 Feb 11.


gamma-Secretase, which is responsible for the intramembranous cleavage of Alzheimer beta-amyloid precursor protein and the signaling receptor Notch, is a multiprotein complex consisting of at least four components: presenilin (PS); nicastrin (Nct); APH-1 (anterior pharynx-defective-1); and presenilin enhancer-2 (PEN-2). Presenilin 1 (PS1) is known to be essential for the stability, interaction, and trafficking of the other PS1/gamma-secretase components. However, the precise functions of the other components remain elusive. Here, we investigated the functions of Nct within the PS1/gamma-secretase complex. We demonstrated that the loss of Nct expression in the embryonic fibroblast cells (Nct KO cells) results in dramatically decreased levels of APH-1, PEN-2, and PS1 fragments accompanied by a significant accumulation of full-length PS1. In the absence of Nct, PEN-2 and full-length PS1 are subjected to proteasome-mediated degradation, whereas the degradation of APH-1 is mediated by both proteasomal and lysosomal pathways. Unlike the case of wild type cells in which the gamma-secretase complex mainly locates in the trans-Golgi network, the majority of residual PEN-2, APH-1, and the uncleaved full-length PS1 in Nct KO cells reside in the endoplasmic reticulum, which remain associated with each other in the absence of Nct. Interestingly, significant amounts of full-length PS1 and PEN-2, but not APH-1, are detected on the plasma membrane in Nct KO cells, suggesting the Nct-independent cell surface delivery of the PEN-2.PS1. Finally, the diminished PEN-2 protein level in Nct-deficient cells can be partially restored by overexpression of exogenous PS1, APH-1, or PEN-2 individually or collectively, indicating a dispensable role for Nct in controlling PEN-2 level. Taken together, our study demonstrates a critical role of Nct in the stability and proper intracellular trafficking of other components of the PS1/ gamma-secretase complex but not in maintaining the association of PEN-2, APH-1, and full-length PS1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amyloid Precursor Protein Secretases
  • Animals
  • Aspartic Acid Endopeptidases
  • Biotinylation
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Endopeptidases / metabolism*
  • Fibroblasts / metabolism
  • Immunoprecipitation
  • Kinetics
  • Lysosomes / metabolism
  • Membrane Glycoproteins / metabolism
  • Membrane Glycoproteins / physiology*
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism
  • Membrane Proteins / physiology*
  • Mice
  • Mice, Knockout
  • Microscopy, Fluorescence
  • Models, Biological
  • Presenilin-1
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Binding
  • Protein Transport
  • RNA Interference
  • Receptors, Notch
  • trans-Golgi Network / metabolism


  • Membrane Glycoproteins
  • Membrane Proteins
  • PSEN1 protein, human
  • PSENEN protein, human
  • Presenilin-1
  • Receptors, Notch
  • nicastrin protein
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Aspartic Acid Endopeptidases
  • BACE1 protein, human
  • Bace1 protein, mouse
  • Proteasome Endopeptidase Complex