Presenilin Transmembrane Domain 8 Conserved AXXXAXXXG Motifs Are Required for the Activity of the γ-Secretase Complex

• Published in: The Journal of biological chemistry 2015-03, Vol.290 (11), p.7169-7184
• Main Authors: Marinangeli, Claudia, Tasiaux, Bernadette, Opsomer, Rémi, Hage, Salim, Sodero, Alejandro O., Dewachter, Ilse, Octave, Jean Noël, Smith, Steven O., Constantinescu, Stefan N., Kienlen-Campard, Pascal
• Format: Article
• Language: English
• Subjects: Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Peptides - metabolism; Amyloid Precursor Protein (APP); Amyloid Precursor Protein Secretases - chemistry; Amyloid Precursor Protein Secretases - metabolism; Animals; Cell Line; CHO Cells; Conserved Sequence; Cricetulus; gamma-Secretase; HEK293 Cells; Humans; Mice; Molecular Sequence Data; Mutation; Neurobiology; Notch Receptor; Presenilin; Presenilin-1 - chemistry; Presenilin-1 - metabolism; Presenilin-2 - chemistry; Presenilin-2 - metabolism; Protein Structure, Tertiary; Transmembrane Domain
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.601286

Understanding the molecular mechanisms controlling the physiological and pathological activity of γ-secretase represents a challenging task in Alzheimer disease research. The assembly and proteolytic activity of this enzyme require the correct interaction of the 19 transmembrane domains (TMDs) present in its four subunits, including presenilin (PS1 or PS2), the γ-secretase catalytic core. GXXXG and GXXXG-like motifs are critical for TMDs interactions as well as for protein folding and assembly. The GXXXG motifs on γ-secretase subunits (e.g. APH-1) or on γ-secretase substrates (e.g. APP) are known to be involved in γ-secretase assembly and in Aβ peptide production, respectively. We identified on PS1 and PS2 TMD8 two highly conserved AXXXAXXXG motifs. The presence of a mutation causing an inherited form of Alzheimer disease (familial Alzheimer disease) in the PS1 motif suggested their involvement in the physiopathological configuration of the γ-secretase complex. In this study, we targeted the role of these motifs on TMD8 of PSs, focusing on their role in PS assembly and catalytic activity. Each motif was mutated, and the impact on complex assembly, activity, and substrate docking was monitored. Different amino acid substitutions on the same motif resulted in opposite effects on γ-secretase activity, without affecting the assembly or significantly impairing the maturation of the complex. Our data suggest that AXXXAXXXG motifs in PS TMD8 are key determinants for the conformation of the mature γ-secretase complex, participating in the switch between the physiological and pathological functional conformations of the γ-secretase. Background: Presenilin TMD8 contains a conserved AXXXAXXXG motif, involved in transmembrane protein interactions. Results: Mutation of PS AXXXAXXXG motifs strongly impacts γ-secretase activity. Conclusion: The geometry and activity of γ-secretase depend on the integrity of the conserved AXXXAXXXG motifs in TMD8. Significance: The PS AXXXAXXXG motif is a key determinant for understanding the structure, assembly, and function of the γ-secretase complex.