Mutagenesis Mapping of the Presenilin 1 Calcium Leak Conductance Pore

Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 06/2011; 286(25):22339-47. DOI: 10.1074/jbc.M111.243063
Source: PubMed


Missense mutations in presenilin 1 (PS1) and presenilin 2 (PS2) proteins are a major cause of familial Alzheimer disease. Presenilins are proteins with nine transmembrane (TM) domains that function as catalytic subunits of the γ-secretase complex responsible for the cleavage of the amyloid precursor protein and other type I transmembrane proteins. The water-filled cavity within presenilin is necessary to mediate the intramembrane proteolysis reaction. Consistent with this idea, cysteine-scanning mutagenesis and NMR studies revealed a number of water-accessible residues within TM7 and TM9 of mouse PS1. In addition to γ-secretase function, presenilins also demonstrate a low conductance endoplasmic reticulum Ca(2+) leak function, and many familial Alzheimer disease presenilin mutations impair this function. To map the potential Ca(2+) conductance pore in PS1, we systematically evaluated endoplasmic reticulum Ca(2+) leak activity supported by a series of cysteine point mutants in TM6, TM7, and TM9 of mouse PS1. The results indicate that TM7 and TM9, but not TM6, could play an important role in forming the conductance pore of PS1. These results are consistent with previous cysteine-scanning mutagenesis and NMR analyses of PS1 and provide further support for our hypothesis that the hydrophilic catalytic cavity of presenilins may also constitute a Ca(2+) conductance pore.

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    • "It was next proposed that presenilin holoproteins act as passive Ca 2+ channels in the ER and those PS FAD mutations alter channel conductance [93]. In an elegant mutagenesis study it was subsequently demonstrated that the hydrophilic catalytic cavity of PS1 facilitates the formation of a calcium leak conductance pore [107]. In parallel, the presenilins have been shown to regulate Ca 2+ levels through interactions with and activation of Ca 2+ channels such the sarco/ER Ca 2+ -ATPase (SERCA) pump [108], the inositol triphosphate receptor (InsP 3 R) [109], and the Ryanodine receptor (RyR) [110] [111]. "
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    ABSTRACT: The presenilins are the catalytic subunit of the membrane-embedded tetrameric γ-secretase protease complexes. More that 90 transmembrane proteins have been reported to be γ-secretase substrates, including the widely studied amyloid precursor protein (APP) and the Notch receptor, which are precursors for the generation of amyloid-β peptides and biologically active APP intracellular domain (AICD) and Notch intracellular domain (NICD). The diversity of γ-secretase substrates highlights the importance of presenilin-dependent γ-secretase protease activities as a regulatory mechanism in a range of biological systems. However, there is also a growing body of evidence that supports the existence of γ-secretase-independent functions for the presenilins in the regulation and progression of an array of cell signalling pathways. In this review, we will present an overview of current literature that proposes evolutionarily conserved presenilin functions outside of the γ-secretase complex, with a focus on the suggested role of the presenilins in the regulation of Wnt/β-catenin signalling, protein trafficking and degradation, calcium homeostasis and apoptosis.
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    • "ther potential source of variability in the patho - logical consequences of different PSEN1 mutations is their role in calcium homeostasis , which could have implications for vascular , immune , and neuronal function . The function of presenilins as calcium leak channels in the endoplasmic reticulum appears to be impaired by most PSEN1 mutations ( Nelson et al . , 2011 ) . However , calcium leak function is preserved with certain mutations , partic - ularly those in a cluster located beyond codon 200 in exons 8e9 ( Nelson et al . , 2010 ) , which tend to be associated with cotton wool plaque pathology . Further work investigating functionally relevant differences between mutations at different sites w"
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    • "Such molecular alterations include increased oxidative stress, mitochondrial dysfunction , cell cycle alterations and elevated apoptosis (reviewed in [25] [26] [27] [28] [29] [30]). Well-documented impairments observed in AD lymphocytes also include changes in calcium homeostasis, particularly related to endoplasmic reticulum (ER) stress and the impaired leak channel function of mutated presenilins in ER membranes [31] [32]. Ca 2+ dyshomeostasis in AD lymphocytes also involved the effects of mutated presenilins on the IP3 receptor in the ER [33] and capacitative Ca 2+ entry mediated by Orai/Stim interactions [34]. "
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