Presenilin 1 Is Required for Maturation and Cell Surface Accumulation of Nicastrin

Jae Yoon Leem,Shrijay Vijayan,Ping Han,Dongming Cai,Michael Machura,Kryslaine O Lopes,Margaret L Veselits,Huaxi Xu,Gopal Thinakaran

doi:10.1074/jbc.c200148200

Abstract

Proteolytic processing of amyloid precursor protein generates beta-amyloid (Abeta) peptides that are deposited in senile plaques in brains of aged individuals and patients with Alzheimer's disease. Presenilins (PS1 and PS2) facilitate the final step in Abeta production, the intramembranous gamma-secretase cleavage of amyloid precursor protein. Biochemical and pharmacological evidence support a catalytic or accessory role for PS1 in gamma-secretase cleavage, as well as a regulatory role in select membrane protein trafficking. In this report, we demonstrate that PS1 is required for maturation and cell surface accumulation of nicastrin, an integral component of the multimeric gamma-secretase complex. Using kinetic labeling studies we show that in PS1(-/-)/PS2(-/-) cells nicastrin fails to reach the medial Golgi compartment, and as a consequence, is incompletely glycosylated. Stable expression of human PS1 restores these deficiencies in PS1(-/-) fibroblasts. Moreover, membrane fractionation studies show co-localization of PS1 fragments with mature nicastrin. These results indicate a novel chaperone-type role for PS1 and PS2 in facilitating nicastrin maturation and transport in the early biosynthetic compartments. Our findings are consistent with PS1 influencing gamma-secretase processing at multiple steps, including maturation and intracellular trafficking of substrates and component(s) of the gamma-secretase complex.

Highlights

Proteolytic processing of amyloid precursor protein generates ␤-amyloid (A␤) peptides that are deposited in senile plaques in brains of aged individuals and patients with Alzheimer’s disease
To obtain insights into the role of presenilin 1 (PS1) in mediating nicastrin biogenesis and trafficking, we examined the metabolism of endogenous nicastrin in embryonic stem cells derived from wt and PS1Ϫ/Ϫ/PS2Ϫ/Ϫ embryos
While surface-biotinylated nicastrin was readily detected in wt cells, no apparent signal was detected in PS1Ϫ/Ϫ/PS2Ϫ/Ϫ cells, indicating that surface expression of nicastrin was impaired in PS1Ϫ/Ϫ/PS2Ϫ/Ϫ cells (Fig. 1A, lanes 7 and 8)

Summary

Introduction

Proteolytic processing of amyloid precursor protein generates ␤-amyloid (A␤) peptides that are deposited in senile plaques in brains of aged individuals and patients with Alzheimer’s disease. We demonstrate that PS1 is required for maturation and cell surface accumulation of nicastrin, an integral component of the multimeric ␥-secretase complex.

Results

Conclusion