Inhibiting Amyloid Precursor Protein C-terminal Cleavage Promotes an Interaction with Presenilin 1

Giuseppe Verdile,Ralph N Martins,Monika Duthie,Erin Holmes,Peter H St George-Hyslop,Paul E Fraser

doi:10.1074/jbc.c000208200

Giuseppe Verdile, Ralph N Martins + Show 4 more

Open Access

https://doi.org/10.1074/jbc.c000208200

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Abstract

Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-beta protein, which is central to the pathogenesis of Alzheimer's disease. It has been demonstrated that PS1 regulates the gamma-secretase proteolysis of the amyloid precursor protein (APP) C-terminal fragment (APP-C100), which is the final step in amyloid-beta protein production. The mechanism and detailed pathway of this PS1 activity has yet to be fully resolved, but it may be due to a presenilin-controlled trafficking of the APP fragment or possibly an inherent PS1 proteolytic activity. We have investigated the possibility of a direct interaction of PS1 and the APP-C100 within the high molecular mass presenilin complex. However, the APP-C100 is rapidly degraded, and if it forms, then any PS1.APP complex is likely to be very transitory. To circumvent this problem, we have utilized the protease inhibitor N-acetyl-leucyl-norleucinal (LLnL) and the lysosomotropic agent NH(4)Cl, which inhibits the turnover of the APP-C100. Under these conditions, levels of the fragment increased appreciably, and as shown by glycerol gradient analysis, the APP-C100 shifted to a higher molecular mass complex that overlapped with PS1. Immunoprecipitation studies demonstrated that a significant population of the APP-C100 co-precipitated with PS1. These findings suggest that PS1 may mediate the shuttling of APP fragments and/or facilitate their presentation for gamma-secretase cleavage through a direct interaction.

Highlights

Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-␤ protein, which is central to the pathogenesis of Alzheimer’s disease
It has been demonstrated that PS1 regulates the ␥-secretase proteolysis of the amyloid precursor protein (APP) C-terminal fragment (APP-C100), which is the final step in amyloid-␤ protein production
We have investigated the possibility of a direct interaction of PS1 and the APP-C100 within the high molecular mass presenilin complex

Summary

Introduction

Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-␤ protein, which is central to the pathogenesis of Alzheimer’s disease. Levels of the fragment increased appreciably, and as shown by glycerol gradient analysis, the APP-C100 shifted to a higher molecular mass complex that overlapped with PS1. This has yet to be substantiated, it is perhaps more plausible that PS1 is involved in the trafficking of the APP C-terminal fragment or may present substrates to a complex containing ␥-secretase and possibly other components [17].

Results

Conclusion