Functional Analysis of the Transmembrane Domains of Presenilin 1

Abstract

␥-Secretase is a multimeric membrane protein complex composed of presenilin (PS), nicastrin, Aph-1, and Pen-2, which mediates intramembrane proteolysis of a range of type I transmembrane proteins. We previously analyzed the functional roles of the N-terminal transmembrane domains (TMDs) 1-6 of PS1 in the assembly and proteolytic activity of the ␥-secretase using a series of TMD-swap PS1 mutants. Here we applied the TMD-swap method to all the TMDs of PS1 for the structurefunction analysis of the proteolytic mechanism of ␥-secretase. We found that TMD2-or -6-swapped mutant PS1 failed to bind the helical peptide-based, substrate-mimic ␥-secretase inhibitor. Cross-linking experiments revealed that both TMD2 and TMD6 of PS1 locate in proximity to the TMD9, the latter being implicated in the initial substrate binding. Taken together, our data suggest that TMD2 and the luminal side of TMD6 are involved in the formation of the initial substrate-binding site of the ␥-secretase complex.

Competition Between Homodimerization and Cholesterol Binding to the C99 Domain of the Amyloid Precursor Protein

“…It therefore seems possible that the enzyme may be able to bind one C99 molecule at its active site and a second at the docking site. (71–74) Whether the Gly zipper-associated homodimerization interface of C99 could be maintained with one subunit at the active site and the other at the docking site is not yet clear. It is important to note that γ-secretase has many other single span membrane protein substrates and many do not have a Gly zipper, GXXXG-class motifs, or a known propensity to homodimerize.…”

The matricellular protein thrombospondin-1 globally regulates cardiovascular function and responses to stress via CD47

“…CD47 is an integral membrane protein containing an extracellular IgV domain, a domain that spans the membrane 5 times that is probably derived from a presenilin transmembrane domain (Watanabe et al, 2010), and a short variably spliced C-terminal cytoplasmic tail (Frazier et al, 2010) (Fig. 1).…”

Cutting in on a secretase pas de deux

“…Addition of peptides representing the various TMDs of presenilin gave results consistent with TMD 6 as the binding site for 3AA and XYT472B. Presenilin's TMD 6 contributes to the γ-secretase active site and is likely involved in gating of substrates into the active site [8,9]. Thus, the new compounds would have to bind TMD 6 in a manner that does not interfere with these important functions, which would otherwise inhibit γ-secretase activity directly.…”