Abstract
γ-Secretase plays a pivotal role in the production of neurotoxic amyloid β-peptides (Aβ) in Alzheimer disease (AD) and consists of a heterotetrameric core complex that includes the aspartyl intramembrane protease presenilin (PS). The human genome codes for two presenilin paralogs. To understand the causes for distinct phenotypes of PS paralog-deficient mice and elucidate whether PS mutations associated with early-onset AD affect the molecular environment of mature γ-secretase complexes, quantitative interactome comparisons were undertaken. Brains of mice engineered to express wild-type or mutant PS1, or HEK293 cells stably expressing PS paralogs with N-terminal tandem-affinity purification tags served as biological source materials. The analyses revealed novel interactions of the γ-secretase core complex with a molecular machinery that targets and fuses synaptic vesicles to cellular membranes and with the H(+)-transporting lysosomal ATPase macrocomplex but uncovered no differences in the interactomes of wild-type and mutant PS1. The catenin/cadherin network was almost exclusively found associated with PS1. Another intramembrane protease, signal peptide peptidase, predominantly co-purified with PS2-containing γ-secretase complexes and was observed to influence Aβ production.
Highlights
IntroductionResults: PS paralogs are embedded in overlapping but distinct molecular environments, with signal peptide peptidase (SPP) primarily binding to PS2
The human genome codes for two presenilin (PS) paralogs, PS1 and PS2
We further report on the gentle purification of active PS-containing ␥-secretase complexes from HEK293 parental cells that express PS1 or PS2 variants equipped with an N-terminal tandem affinity purification (TAP) tag in the context of endogenous nicastrin, Aph-1, and Pen-2
Summary
Results: PS paralogs are embedded in overlapping but distinct molecular environments, with signal peptide peptidase (SPP) primarily binding to PS2. Conclusion: Study paves the way for understanding functional divergence of PS paralogs. Significance: Example of an interaction between a Type I- and Type II-directed intramembrane protease. ␥-Secretase plays a pivotal role in the production of neurotoxic amyloid -peptides (A) in Alzheimer disease (AD) and consists of a heterotetrameric core complex that includes the aspartyl intramembrane protease presenilin (PS). The human genome codes for two presenilin paralogs. To understand the causes for distinct phenotypes of PS paralog-deficient mice and elucidate whether PS mutations associated with early-onset AD affect the molecular environment of mature ␥-secretase complexes, quantitative interactome comparisons were undertaken
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