title: Degradation of nicastrin involves both proteasome and lysosome.
abstract: The glycoprotein nicastrin (NCT) is an essential component of the gamma-secretase complex, a high molecular weight complex which also contains the presenilin proteins, Aph-1 and Pen-2. The gamma-secretase complex is not only involved in APP processing but also in the processing of an increasing number of other type I integral membrane proteins. As the largest subunit of the gamma-secretase complex, NCT plays a crucial role in its activation. Considerable information exists on the distribution, structure and function of NCT; however, little is known of its proteolysis. The present study is aimed at exploring the molecular mechanism of NCT degradation. We found that either proteasomal or lysosomal inhibition can significantly increase the levels of both endogenous and exogenous NCT in various cell lines, and the effect of these inhibitions on NCT was time- and dose-dependent. Immunofluorescent microscopic analysis revealed that NCT accumulates in the ER and Golgi apparatus after proteasomal inhibition, while lysosomal inhibition leads to the accumulation of NCT in the lysosomal apparatus. Co-immunoprecipitation can pull down both NCT and ubiquitin. Taken together, our results demonstrate that NCT degradation involves both the proteasome and the lysosome.
authors.affiliation: Department of Psychiatry, Brain Research Center, The University of British Columbia, Vancouver, Canada.
authors.forename: Guiqiong
authors.initials: G
authors.lastname: He
authors.forename: Hong
authors.initials: H
authors.lastname: Qing
authors.forename: Yigang
authors.initials: Y
authors.lastname: Tong
authors.forename: Fang
authors.initials: F
authors.lastname: Cai
authors.forename: Shoichi
authors.initials: S
authors.lastname: Ishiura
authors.forename: Weihong
authors.initials: W
authors.lastname: Song
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000502:physiology; D009447:Neuroblastoma; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D014162:Transfection / Q000379:methods
chemical_list: D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; C413604:nicastrin protein; C067713:lactacystin; D053829:Amyloid Precursor Protein Secretases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine