Amyloid β-Protein Precursor Juxtamembrane Domain Regulates Specificity of γ-Secretase-dependent Cleavages

• Published in: The Journal of biological chemistry Vol. 282; no. 48; pp. 35350 - 35360
• Main Authors: Ren, Zhao, Schenk, Dale, Basi, Guriqbal S., Shapiro, I. Paul
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.11.2007; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Amyloid beta-Peptides - chemistry; Amyloid beta-Peptides - metabolism; Amyloid Precursor Protein Secretases - metabolism; Cell Line; Cell Membrane - metabolism; Enzyme-Linked Immunosorbent Assay; Humans; Lysine - chemistry; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Structure, Secondary; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Serine - chemistry; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M702739200

Amyloid β-protein (Aβ), the major component of cerebral plaques associated with Alzheimer disease, is derived from amyloid β-protein precursor (APP) through sequential proteolytic cleavage involving β- and γ-secretase. The intramembrane cleavage of APP by γ-secretase occurs at two major sites, γ and ϵ, although the temporal and/or mechanistic relationships between these cleavages remain unknown. In our attempt to address this issue, we uncovered an important regulatory role for the APP luminal juxtamembrane domain. We demonstrated in cell-based assays that domain replacements in this region can greatly reduce secreted Aβ resulting from γ-cleavage without affecting the ϵ-cleavage product. This Aβ reduction is likely due to impaired proteolysis at the γ-cleavage site. Further analyses with site-directed mutagenesis identified two juxtamembrane residues, Lys-28 and Ser-26 (Aβ numbering), as the critical determinants for efficient intramembrane proteolysis at the γ-site. Consistent with the growing evidence that ϵ-cleavage of APP precedes γ-processing, longer Aβ species derived from the γ-cleavage-deficient substrates were detected intracellularly. These results indicate that the luminal juxtamembrane region of APP is an important regulatory domain that modulates γ-secretase-dependent intramembrane proteolysis, particularly in differentiating γ- and ϵ-cleavages.