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-secretase complex assembly in the early secretory pathway
Correspondence to Wim Annaert: Willem.Annaert{at}med.kuleuven.be
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-secretase complex, consisting of presenilin, nicastrin, presenilin enhancer-2 (PEN-2), and anterior pharynx defective-1 (APH-1) cleaves type I integral membrane proteins like amyloid precursor protein and Notch in a process of regulated intramembrane proteolysis. The regulatory mechanisms governing the multistep assembly of this "proteasome of the membrane" are unknown. We characterize a new interaction partner of nicastrin, the retrieval receptor Rer1p. Rer1p binds preferentially immature nicastrin via polar residues within its transmembrane domain that are also critical for interaction with APH-1. Absence of APH-1 substantially increased binding of nicastrin to Rer1p, demonstrating the competitive nature of these interactions. Moreover, Rer1p expression levels control the formation of
-secretase subcomplexes and, concomitantly, total cellular
-secretase activity. We identify Rer1p as a novel limiting factor that negatively regulates
-secretase complex assembly by competing with APH-1 during active recycling between the endoplasmic reticulum (ER) and Golgi. We conclude that total cellular
-secretase activity is restrained by a secondary ER control system that provides a potential therapeutic value. ![]()
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J. Cell Biol. 2007 176: 549a.
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