A conserved GXXXG motif in APH-1 is critical for assembly and activity of the gamma-secretase complex.
The multipass membrane protein APH-1, found in the gamma-secretase complex together with presenilin, nicastrin, and PEN-2, is essential for Notch signaling in Caenorhabditis elegans embryos and is required for intramembrane proteolysis of Notch and beta-amyloid precursor protein in mammalian and Drosophila cells. In C. elegans, a mutation of the conserved transmembrane Gly123 in APH-1 (mutant or28) leads to a notch/glp-1 loss-of-function phenotype. In this study, we show that the corresponding mutation in mammalian APH-1aL (G122D) disrupts the physical interaction of APH-1aL with hypoglycosylated immature nicastrin and the presenilin holoprotein as well as with mature nicastrin, presenilin, and PEN-2. The G122D mutation also reduced gamma-secretase activity in intramembrane proteolysis of membrane-tethered Notch. Moreover, we found that the conserved transmembrane Gly122, Gly126, and Gly130 in the fourth transmembrane region of mammalian APH-1aL are part of the membrane helix-helix interaction GXXXG motif and are essential for the stable association of APH-1aL with presenilin, nicastrin, and PEN-2. These findings suggest that APH-1 plays a GXXXG-dependent scaffolding role in both the initial assembly and subsequent maturation and maintenance of the active gamma-secretase complex.
Lee
Sheu-Fen
SF
Center for Basic Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9111, USA.
Shah
Sanjiv
S
Yu
Cong
C
Wigley
W Christian
WC
Li
Harry
H
Lim
Myungsil
M
Pedersen
Kia
K
Han
Weiping
W
Thomas
Philip
P
Lundkvist
Johan
J
Hao
Yi-Heng
YH
Yu
Gang
G
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010447:Peptide Hydrolases; D053764:Presenilin-1; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C469349:PSENEN protein, human; D053764:Presenilin-1; D011994:Recombinant Proteins; C413604:nicastrin protein; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human