title: Presenilin-1 maintains a nine-transmembrane topology throughout the secretory pathway.
abstract: Presenilin-1 is a polytopic membrane protein that assembles with nicastrin, PEN-2, and APH-1 into an active gamma-secretase complex required for intramembrane proteolysis of type I transmembrane proteins. Although essential for a correct understanding of structure-function relationships, its exact topology remains an issue of strong controversy. We revisited presenilin-1 topology by inserting glycosylation consensus sequences in human PS1 and expressing the obtained mutants in a presenilin-1 and 2 knock-out background. Based on the glycosylation status of these variants we provide evidence that presenilin-1 traffics through the Golgi after a conformational change induced by complex assembly. Based on our glycosylation variants of presenilin-1 we hypothesize that complex assembly occurs during transport between the endoplasmic reticulum and the Golgi apparatus. Furthermore, our data indicate that presenilin-1 has a nine-transmembrane domain topology with the COOH terminus exposed to the lumen/extracellular surface. This topology is independently underscored by lysine mutagenesis, cell surface biotinylation, and cysteine derivation strategies and is compatible with the different physiological functions assigned to presenilin-1.
authors.affiliation: Laboratory of Membrane Trafficking, Department of Human Genetics, Gasthuisberg, Katholieke Universiteit Leuven/VIB11, B-3000 Leuven, Belgium.
authors.forename: Dragana
authors.initials: D
authors.lastname: Spasic
authors.forename: Alexandra
authors.initials: A
authors.lastname: Tolia
authors.forename: Katleen
authors.initials: K
authors.lastname: Dillen
authors.forename: Veerle
authors.initials: V
authors.lastname: Baert
authors.forename: Bart
authors.initials: B
authors.lastname: De Strooper
authors.forename: Stefan
authors.initials: S
authors.lastname: Vrijens
authors.forename: Wim
authors.initials: W
authors.lastname: Annaert
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000818:Animals; D006031:Glycosylation; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D053764:Presenilin-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D053764:Presenilin-1; D053829:Amyloid Precursor Protein Secretases