Embedded in the Membrane: How Lipids Confer Activity and Specificity to Intramembrane Proteases

Abstract

Proteases, sharp yet unforgivable tools of every cell, require tight regulation to ensure specific non-aberrant cleavages. The relatively recent discovered class of intramembrane proteases has gained increasing interest due to their involvement in important signaling pathways linking them to diseases including Alzheimer's disease and cancer. Despite tremendous efforts, their regulatory mechanisms have only started to unravel. There is evidence that the membrane composition itself can regulate intramembrane protease activity and specificity. In this review, we highlight the work on γ-secretase and rhomboid proteases and summarize several studies as to how different lipids impact on enzymatic activity.

A combination of solid-state NMR and MD simulations reveals the binding mode of a rhomboid protease inhibitor

“…[21][22][23][24][25][26] This is of particular importance since rhomboid proteases are highly dependent on their lipid environment, which can alter their cleavage activity and specicity. 4,27,28 Previously, we have shown that we can achieve high quality, 1 H-detected solid-state NMR spectra of GlpG in liposomes, enabling a residue-specic structural and dynamic investigation. 9 1 H-detected solid-state NMR has become a valuable approach to study membrane proteins due to the higher sensitivity compared to 13 C detection and the additional information available on H/D exchange and water accessibility.…”

Active site geometry stabilization of a presenilin homolog by the lipid bilayer promotes intramembrane proteolysis

“…Polyclonal antibody 6687 against APP-CTF was described previously 8 (immunoprecipitation (IP): 1:100-1:200). Polyclonal antibody Anti-β-Amyloid (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) to Aβ22-35 (Sigma-Aldrich, A3356, IB: 1:1000) and monoclonal antibodies 4G8 to Aβ17-24 (BioLegend, 800702, IP: 1:500-1:2,500), Penta-His Antibody (Qiagen, 34660, IB: 1:1000) and Y188 to APP C-terminus (Abcam, ab32136, IB: 1:5000) were purchased from the indicated suppliers.…”

“…To gain basic insights into the enzymatic workings of presenilin proteases, we thus set out to characterize the influence of two fundamentally different hydrophobic environments on the activity of PSH and asked if cleavage of C99 by the solubilized enzyme in detergent micelles would differ from a lipid-reconstituted state and if so, whether such differences could be correlated with the structural dynamics of this prototype presenilin protease or its E-S. Although the influence of lipids on the activity of presenilin and other intramembrane proteases is well documented 30 , there are so far no studies in which biochemically determined activities of these proteases were linked with structural information that could explain how lipids, in particular a membrane bilayer environment, affect intramembrane protease structural dynamics and enzyme function. Since presenilins are not active in detergent micelles without lipids 31 this critical question can however not be addressed for γ-secretase directly and requires a suitable model protease such as PSH.…”

Lipid class composition of membrane and raft fractions from brains of individuals with Alzheimer's disease

“…The local membrane lipid microenvironment has a potent effect on γ-secretase activity and cleavage sites. Increased cholesterol in membrane lipids augments Aβ production and shows a positive correlation with AD development [5]. In vitro assays for the γ-secretase cleavage of APP revealed that subtle changes in phospholipid composition greatly modify the activity of γ-secretase.…”