title: Effects of RNAi-mediated silencing of PEN-2, APH-1a, and nicastrin on wild-type vs FAD mutant forms of presenilin 1.
abstract: The gamma-secretase complex consists of PS1/PS2, nicastrin, APH-1a, and PEN-2. PS1 undergoes endoproteolytic processing to yield two fragments: PS1-NTF and PS1-CTF. Changes in PEN-2 levels have been shown previously to affect the endoproteolytic processing of wild-type (wt)-PS1. However, the effects of PEN-2 on the proteolytic processing of familial Alzheimer's disease (FAD) mutant forms of PS1 have not yet been reported. To determine whether PEN-2 affects the proteolytic processing of mutant PS1 in the same manner as that of wt-PS1, we established RNA interference (RNAi) for PEN-2 in H4 human neuroglioma cells stably transfected to express wt or FAD mutant forms of PS1 including L286V, A246E, and that lacking exon 9 (Delta9). As expected, in H4 cells expressing wt-PS1, RNAi for PEN-2 increased levels of PS1-FL and attenuated PS1 endoproteolysis. Likewise, in cells expressing PS1 with the FAD missense mutations, L286V and A246E, RNAi for PEN-2 increased PS1-FL and reduced PS1 endoproteolysis. However, in H4 cells stably transfected to express the FAD-linked Delta9 mutation (PS1 lacking exon 9), RNAi for PEN-2 did not increase but, instead, decreased PS1-FL. In contrast, RNAi for nicastrin and APH-1a decreased PS1-FL in H4 cells expressing either wt-PS1 or Delta9-PS1. In summary, the metabolism of wt-PS1 and FAD-linked Delta9-PS1 is specifically and differentially affected by loss of function of PEN-2.
authors.affiliation: MassGeneral Institute for Neurodegenerative Disease, Department of NeurologyMassachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129-2060, USA.
authors.forename: Zhongcong
authors.initials: Z
authors.lastname: Xie
authors.forename: Donna M
authors.initials: DM
authors.lastname: Romano
authors.forename: Rudolph E
authors.initials: RE
authors.lastname: Tanzi
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases; D045744:Cell Line, Tumor; D010450:Endopeptidases; D020868:Gene Silencing; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010447:Peptide Hydrolases; D053764:Presenilin-1; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
chemical_list: D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C469349:PSENEN protein, human; D053764:Presenilin-1; D034741:RNA, Small Interfering; C413604:nicastrin protein; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases