Endoproteolytic Cleavage and Proteasomal Degradation of Presenilin 2 in Transfected Cells

doi:10.1074/jbc.272.17.11006

Endoproteolytic Cleavage and Proteasomal Degradation of Presenilin 2 in Transfected Cells*

From the Genetics and Aging Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129

^§Pew Scholar. To whom correspondence should be addressed:
Genetics and Aging Unit, Massachusetts General Hospital, 149 13th St., Charlestown, MA 02129
. Tel.: 617-726-6845; Fax: 617-726-5677; E-mail: tanzi{at}helix.mgh.harvard.edu.

Abstract

Mutations in the presenilin genes, PS1 and PS2, cause a major portion of early onset familial Alzheimer's disease (FAD). The biological roles of the presenilins and how their pathological mutations confer FAD are unknown. In this study, we set out to examine the processing and degradation pathways of PS2. For regulated expression of PS2, we have established inducible cell lines expressing PS2 under the tight control of the tetracycline-responsive transactivator. Western blot analysis revealed that PS2 was detected as an ∼53-55-kDa polypeptide (54-kDa PS2) as well as a high molecular mass form (HMW-PS2). Using a stably transfected, inducible cell system, we have found that PS2 is proteolytically cleaved into two stable cellular polypeptides including an ∼20-kDa C-terminal fragment and an ∼34-kDa N-terminal fragment. PS2 is polyubiquitinated in vivo, and the degradation of PS2 is inhibited by proteasome inhibitors, N-acetyl-L-leucinal-L-norleucinal and lactacystin. Our studies suggest that PS2 normally undergoes endoproteolytic cleavage and is degraded via the proteasome pathway.

Footnotes

↵^‡ Recipient of a National Research Service Award.
↵* This work was supported by grants from NIA and NINDS, National Institutes of Health, and the Metropolitan Life Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

AD

Alzheimer's disease

FAD

familial Alzheimer's disease

ER

endoplasmic reticulum

ALLN

N-acetyl-L-leucinal-L-norleucinal

PS1

presenilin 1

PS2

presenilin 2

BFA

brefeldin A

Aβ

amyloid β-peptide

HMW-PS2

high molecular mass forms of PS2

PS2-CTF

presenilin 2 C-terminal endoproteolytic fragment

PS2-NTF

presenilin 2 N-terminal endoproteolytic fragment

PAGE

polyacrylamide gel electrophoresis

PIPES

1,4-piperazinediethanesulfonic acid

APP

amyloid β-protein precursor.
- Received January 21, 1997.
- Revision received February 24, 1997.