Evidence That Tumor Necrosis Factor α Converting Enzyme Is Involved in Regulated α-Secretase Cleavage of the Alzheimer Amyloid Protein Precursor

Joseph D Buxbaum,Kang-Nian Liu,Yuxia Luo,Jennifer L Slack,Kim L Stocking,Jacques J Peschon,Richard S Johnson,Beverly J Castner,Douglas Pat Cerretti,Roy A Black

doi:10.1074/jbc.273.43.27765

Abstract

The amyloid protein, Abeta, which accumulates in the brains of Alzheimer patients, is derived by proteolysis of the amyloid protein precursor (APP). APP can undergo endoproteolytic processing at three sites, one at the amino terminus of the Abeta domain (beta-cleavage), one within the Abeta domain (alpha-cleavage), and one at the carboxyl terminus of the Abeta domain (gamma-cleavage). The enzymes responsible for these activities have not been unambiguously identified. By the use of gene disruption (knockout), we now demonstrate that TACE (tumor necrosis factor alpha converting enzyme), a member of the ADAM family (a disintegrin and metalloprotease-family) of proteases, plays a central role in regulated alpha-cleavage of APP. Our data suggest that TACE may be the alpha-secretase responsible for the majority of regulated alpha-cleavage in cultured cells. Furthermore, we show that inhibiting this enzyme affects both APP secretion and Abeta formation in cultured cells.

Highlights

In most cells in culture, a fraction (10 –30%) of all amyloid protein precursor (APP) undergoes ␣-cleavage (4 –7)
In cells derived from control mice, regulated secretion was stimulated 300 –500% by activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA)
In cells derived from knockout mice, there was no increase in the formation and secretion of APPs caused by the addition of PMA (Fig. 1) or okadaic acid

Summary

Introduction

In most cells in culture, a fraction (10 –30%) of all APP undergoes ␣-cleavage (4 –7) This results in the secretion of the large extracellular domain of APP into the medium. The generation of soluble TNF-␣ from membrane-bound TNF-␣ involves an enzyme activity denoted TNF-␣ converting enzyme (TACE) [28, 29], which is a member of the ADAM family (a disintegrin and metalloprotease family) of proteases [30, 31] Members of this family of proteases contain an autoinhibitory domain that must be removed for activity, a proteolytic domain, a disintegrin domain, a cysteine-rich domain, and most importantly for APP, a transmembrane domain. We determined whether TACE might play a role in the regulated ␣-cleavage of APP

Methods

Results

Conclusion