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.
    Full-text · Article · Oct 2015 · Cellular Signalling
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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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    ABSTRACT: In Alzheimer's disease (AD), molecular changes are observed not only in patients' neurons but also in peripheral cells, such as blood lymphocytes. These include changes in the level of oxidative stress markers, mitochondria impairment, and aberrant cell cycle regulation in AD blood lymphocytes. While the concepts of early causes of AD are currently highly controversial, these findings provide support for the cell cycle hypothesis of AD pathomechanism and emphasize the systemic nature of the disease. Moreover, because of difficulties in studying dynamic processes in the human brain, lymphocytes seem to be useful for readout of AD molecular mechanisms. In addition, lymphocytes as easily accessible human cells have potential diagnostic value. We summarize current perspectives for the development of new therapeutic strategies based on oxidative stress and cell cycle dysregulation in AD, and for diagnostic methodologies involving new markers in AD lymphocytes.
    Full-text · Article · Mar 2015 · Journal of Alzheimer's disease: JAD
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    • "This has been documented in fibroblasts isolated from FAD patients, in cellular systems expressing wild type and mutated PS and in hippocampal and cortical neurons of AD mice [67,68,70-72]. PS were also shown to support ER Ca2+ leakage [74,75], likely through their function as low conductance, passive ER Ca2+ leak channels, independently of their γ-secretase activity [74,76-79]. Even if PS-mediated ER Ca2+ leak was recently debated [80,81], recent data obtained by other laboratories and using different systems tend now to confirm the leak function of PS [82,83]. "
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    ABSTRACT: Perturbed Endoplasmic Reticulum (ER) calcium (Ca2+) homeostasis emerges as a central player in Alzheimer disease (AD). Accordingly, different studies have reported alterations of the expression and the function of Ryanodine Receptors (RyR) in human AD-affected brains, in cells expressing familial AD-linked mutations on the beta amyloid precursor protein (betaAPP) and presenilins (the catalytic core in gamma-secretase complexes cleaving the betaAPP, thereby generating amyloid beta (Abeta) peptides), as well as in the brain of various transgenic AD mice models. Data converge to suggest that RyR expression and function alteration are associated to AD pathogenesis through the control of: i) betaAPP processing and Abeta peptide production, ii) neuronal death; iii) synaptic function; and iv) memory and learning abilities. In this review, we document the network of evidences suggesting that RyR could play a complex dual "compensatory/protective versus pathogenic" role contributing to the setting of histopathological lesions and synaptic deficits that are associated with the disease stages. We also discuss the possible mechanisms underlying RyR expression and function alterations in AD. Finally, we review recent publications showing that drug-targeting blockade of RyR and genetic manipulation of RyR reduces Abeta production, stabilizes synaptic transmission, and prevents learning and memory deficits in various AD mouse models. Chemically-designed RyR "modulators" could therefore be envisioned as new therapeutic compounds able to delay or block the progression of AD.
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