Details

Autor(en) / Beteiligte

• Nyborg, Andrew C.
• Kornilova, Anna Y.
• Jansen, Karen
• Ladd, Thomas B.
• Wolfe, Michael S.
• Golde, Todd E.

Titel

Signal Peptide Peptidase Forms a Homodimer That Is Labeled by an Active Site-directed γ-Secretase Inhibitor

Ist Teil von

• The Journal of biological chemistry, 2004-04, Vol.279 (15), p.15153-15160

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2004

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Presenilin (PS) is the presumptive catalytic component of the intramembrane aspartyl protease γ-secretase complex. Recently a family of presenilin homologs was identified. One member of this family, signal peptide peptidase (SPP), has been shown to be a protease, which supports the hypothesis that PS and presenilin homologs are related intramembrane-cleaving aspartyl proteases. SPP has been reported as a glycoprotein of ∼45 kDa. Our initial characterization of SPP isolated from human brain and cell lines demonstrated that SPP is primarily present as an SDS-stable ∼95-kDa protein on Western blots. Upon heating or treatment of this ∼95-kDa SPP band with acid, a ∼45-kDa band could be resolved. Co-purification of two different epitope-tagged forms of SPP from a stably transfected cell line expressing both tagged versions demonstrated that the ∼95-kDa band is a homodimer of SPP. Pulse-chase metabolic labeling studies demonstrated that the SPP homodimer assembles rapidly and is metabolically stable. In a glycerol velocity gradient, SPP sedimented from ∼100–200 kDa. Significantly the SPP homodimer was specifically labeled by an active site-directed photoaffinity probe (III-63) for PS, indicating that the active sites of SPP and PS/γ-secretase are similar and providing strong evidence that the homodimer is functionally active. Collectively these data suggest that SPP exists in vivo as a functional dimer.