The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Paola Pizzo - One of the best experts on this subject based on the ideXlab platform.
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PSEN2 (Presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca2+ homeostasis
2019Co-Authors: Chiara Fedeli, Riccardo Filadi, Alice Rossi, Cristina Mammucari, Paola PizzoAbstract:PSEN2 (Presenilin 2) is one of the 3 proteins that, when mutated, causes early onset familial Alzheimer disease (FAD) cases. In addition to its well-known role within the γ-secretase complex (the enzyme ultimately responsible for Aβ peptides formation), PSEN2 is endowed with some γ-secretase-independent functions in distinct cell signaling pathways, such as the modulation of intracellular Ca2+ homeostasis. Here, by using different FAD-PSEN2 cell models, we demonstrate that mutated PSEN2 impairs autophagy by causing a block in the degradative flux at the level of the autophagosome-lysosome fusion step. The defect does not depend on an altered lysosomal functionality but rather on a decreased recruitment of the small GTPase RAB7 to autophagosomes, a key event for normal autophagy progression. Importantly, FAD-PSEN2 action on autophagy is unrelated to its γ-secretase activity but depends on its previously reported ability to partially deplete ER Ca2+ content, thus reducing cytosolic Ca2+ response upon IP3-linked cell stimulations. Our data sustain the pivotal role for Ca2+ signaling in autophagy and reveal a novel mechanism by which FAD-linked Presenilins alter the degradative process, reinforcing the view of a causative role for a dysfunctional quality control pathway in AD neurodegeneration. Abbreviations: Aβ: amyloid β; AD: Alzheimer disease; ACTB: actin beta; AMPK: AMP-activated protein kinase; APP: amyloid-beta precursor protein; BafA: bafilomycin A1; BAPTA-AM: 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester; CFP: cyan fluorescent protein; EGTA-AM: ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid acetoxymethyl ester; ER: endoplasmic reticulum; EGFP-HDQ74: enhanced GFP-huntingtin exon 1 containing 74 polyglutamine repeats; FAD: familial Alzheimer disease; FCS: fetal calf serum; FRET: fluorescence/Förster resonance energy transfer; GFP: green fluorescent protein; IP3: inositol trisphosphate; KD: knockdown; LAMP1: lysosomal associated membrane protein 1; MAP1LC3-II/LC3-II: lipidated microtubule-associated protein 1 light chain 3; MCU: mitochondrial calcium uniporter; MICU1: mitochondrial calcium uptake 1; MEFs: mouse embryonic fibroblasts; MFN2: mitofusin 2; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; SQSTM1/p62: sequestosome 1; PSEN1: Presenilin 1; PSEN2: Presenilin 2; RAB7: RAB7A: member RAS oncogene family; RFP: red fluorescent protein; ATP2A/SERCA: ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting; siRNA: small interference RNA; V-ATPase: vacuolar-type H+-ATPase; WT: wild type
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Presenilin 2 modulates endoplasmic reticulum mitochondria coupling by tuning the antagonistic effect of mitofusin 2
Cell Reports, 2016Co-Authors: Riccardo Filadi, Tullio Pozzan, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Paola PizzoAbstract:Summary Communication between organelles plays key roles in cell biology. In particular, physical and functional coupling of the endoplasmic reticulum (ER) and mitochondria is crucial for regulation of various physiological and pathophysiological processes. Here, we demonstrate that Presenilin 2 (PS2), mutations in which underlie familial Alzheimer's disease (FAD), promotes ER-mitochondria coupling only in the presence of mitofusin 2 (Mfn2). PS2 is not necessary for the antagonistic effect of Mfn2 on organelle coupling, although its abundance can tune it. The two proteins physically interact, whereas their homologues Mfn1 and PS1 are dispensable for this interplay. Moreover, PS2 mutants associated with FAD are more effective than the wild-type form in modulating ER-mitochondria tethering because their binding to Mfn2 in mitochondria-associated membranes is favored. We propose a revised model for ER-mitochondria interaction to account for these findings and discuss possible implications for FAD pathogenesis.
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ca2 dysregulation in neurons from transgenic mice expressing mutant Presenilin 2
Aging Cell, 2012Co-Authors: M J Kipanyula, Enrico Zampese, Cristina Fasolato, Paola Pizzo, Laura Contreras, Cristian Lazzari, Andrea Wong, Tullio PozzanAbstract:Mutations in amyloid precursor protein (APP), and Presenilin-1 and Presenilin-2 (PS1 and PS2) have causally been implicated in Familial Alzheimer's Disease (FAD), but the mechanistic link between the mutations and the early onset of neurodegeneration is still debated. Although no consensus has yet been reached, most data suggest that both FAD-linked PS mutants and endogenous PSs are involved in cellular Ca2+ homeostasis. We here investigated subcellular Ca2+ handling in primary neuronal cultures and acute brain slices from wild type and transgenic mice carrying the FAD-linked PS2-N141I mutation, either alone or in the presence of the APP Swedish mutation. Compared with wild type, both types of transgenic neurons show a similar reduction in endoplasmic reticulum (ER) Ca2+ content and decreased response to metabotropic agonists, albeit increased Ca2+ release induced by caffeine. In both transgenic neurons, we also observed a higher ER-mitochondria juxtaposition that favors increased mitochondrial Ca2+ uptake upon ER Ca2+ release. A model is described that integrates into a unifying hypothesis the contradictory effects on Ca2+ homeostasis of different PS mutations and points to the relevance of these findings in neurodegeneration and aging.
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Presenilin 2 modulates endoplasmic reticulum er mitochondria interactions and ca2 cross talk
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Enrico Zampese, Cristina Fasolato, M J Kipanyula, Mario Bortolozzi, Tullio Pozzan, Paola PizzoAbstract:Presenilin mutations are the main cause of familial Alzheimer's disease (FAD). Presenilins also play a key role in Ca2+ homeostasis, and their FAD-linked mutants affect cellular Ca2+ handling in several ways. We previously have demonstrated that FAD-linked Presenilin 2 (PS2) mutants decrease the Ca2+ content of the endoplasmic reticulum (ER) by inhibiting sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) activity and increasing ER Ca2+ leak. Here we focus on the effect of Presenilins on mitochondrial Ca2+ dynamics. By using genetically encoded Ca2+ indicators specifically targeted to mitochondria (aequorin- and GFP-based probes) in SH-SY5Y cells and primary neuronal cultures, we show that overexpression or down-regulation of PS2, but not of Presenilin 1 (PS1), modulates the Ca2+ shuttling between ER and mitochondria, with its FAD mutants strongly favoring Ca2+ transfer between the two organelles. This effect is not caused by a direct PS2 action on mitochondrial Ca2+-uptake machinery but rather by an increased physical interaction between ER and mitochondria that augments the frequency of Ca2+ hot spots generated at the cytoplasmic surface of the outer mitochondrial membrane upon stimulation. This PS2 function adds further complexity to the multifaceted nature of Presenilins and to their physiological role within the cell. We also discuss the importance of this additional effect of FAD-linked PS2 mutants for the understanding of FAD pathogenesis.
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Presenilin 2 dampens intracellular ca2 stores by increasing ca2 leakage and reducing ca2 uptake
Journal of Cellular and Molecular Medicine, 2009Co-Authors: Lucia Brunello, Enrico Zampese, Tullio Pozzan, Paola Pizzo, Cristina Florean, Cristina FasolatoAbstract:We have previously shown that familial Alzheimer’s disease mutants of Presenilin-2 (PS2) and, to a lesser extent, of Presenilin-1 (PS1) lower the Ca2+ concentration of intracellular stores. We here examined the mechanism by which wild-type and mutant PS2 affect store Ca2+ handling. By using HeLa, SH-SY5Y and MEFs as model cells, and recombinant aequorins as Ca2+ probes, we show evidence that transient expression of either wild-type or mutant PS2 increases the passive Ca2+ leakage: both ryanodine- and IP3-receptors contribute to Ca2+ exit out of the ER, whereas the ribosome translocon complex is not involved. In SH-SY5Y cells and MEFs, wild-type and mutant PS2 potently reduce the uptake of Ca2+ inside the stores, an effect that can be counteracted by over-expression of SERCA-2B. On this line, in wild-type MEFs, lowering the endogenous level of PS2 by RNA interference, increases the Ca2+-loading capability of intracellular stores. Furthermore, we show that in PS double knockout MEFs, reduction of Ca2+ stores is mimicked by the expression of PS2-D366A, a loss-of-function mutant, uncleaved because also devoid of Presenilinase activity but not by co-expression of the two catalytic active fragments of PS2. In summary, both physiological and increased levels of wild-type and mutant PS2 reduce the Ca2+ uptake by intracellular stores. To exert this newly described function, PS2 needs to be in its full-length form, even if it can subsequently be cleaved.
Tullio Pozzan - One of the best experts on this subject based on the ideXlab platform.
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Presenilin 2 modulates endoplasmic reticulum mitochondria coupling by tuning the antagonistic effect of mitofusin 2
Cell Reports, 2016Co-Authors: Riccardo Filadi, Tullio Pozzan, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Paola PizzoAbstract:Summary Communication between organelles plays key roles in cell biology. In particular, physical and functional coupling of the endoplasmic reticulum (ER) and mitochondria is crucial for regulation of various physiological and pathophysiological processes. Here, we demonstrate that Presenilin 2 (PS2), mutations in which underlie familial Alzheimer's disease (FAD), promotes ER-mitochondria coupling only in the presence of mitofusin 2 (Mfn2). PS2 is not necessary for the antagonistic effect of Mfn2 on organelle coupling, although its abundance can tune it. The two proteins physically interact, whereas their homologues Mfn1 and PS1 are dispensable for this interplay. Moreover, PS2 mutants associated with FAD are more effective than the wild-type form in modulating ER-mitochondria tethering because their binding to Mfn2 in mitochondria-associated membranes is favored. We propose a revised model for ER-mitochondria interaction to account for these findings and discuss possible implications for FAD pathogenesis.
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ca2 dysregulation in neurons from transgenic mice expressing mutant Presenilin 2
Aging Cell, 2012Co-Authors: M J Kipanyula, Enrico Zampese, Cristina Fasolato, Paola Pizzo, Laura Contreras, Cristian Lazzari, Andrea Wong, Tullio PozzanAbstract:Mutations in amyloid precursor protein (APP), and Presenilin-1 and Presenilin-2 (PS1 and PS2) have causally been implicated in Familial Alzheimer's Disease (FAD), but the mechanistic link between the mutations and the early onset of neurodegeneration is still debated. Although no consensus has yet been reached, most data suggest that both FAD-linked PS mutants and endogenous PSs are involved in cellular Ca2+ homeostasis. We here investigated subcellular Ca2+ handling in primary neuronal cultures and acute brain slices from wild type and transgenic mice carrying the FAD-linked PS2-N141I mutation, either alone or in the presence of the APP Swedish mutation. Compared with wild type, both types of transgenic neurons show a similar reduction in endoplasmic reticulum (ER) Ca2+ content and decreased response to metabotropic agonists, albeit increased Ca2+ release induced by caffeine. In both transgenic neurons, we also observed a higher ER-mitochondria juxtaposition that favors increased mitochondrial Ca2+ uptake upon ER Ca2+ release. A model is described that integrates into a unifying hypothesis the contradictory effects on Ca2+ homeostasis of different PS mutations and points to the relevance of these findings in neurodegeneration and aging.
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Presenilin 2 modulates endoplasmic reticulum er mitochondria interactions and ca2 cross talk
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Enrico Zampese, Cristina Fasolato, M J Kipanyula, Mario Bortolozzi, Tullio Pozzan, Paola PizzoAbstract:Presenilin mutations are the main cause of familial Alzheimer's disease (FAD). Presenilins also play a key role in Ca2+ homeostasis, and their FAD-linked mutants affect cellular Ca2+ handling in several ways. We previously have demonstrated that FAD-linked Presenilin 2 (PS2) mutants decrease the Ca2+ content of the endoplasmic reticulum (ER) by inhibiting sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) activity and increasing ER Ca2+ leak. Here we focus on the effect of Presenilins on mitochondrial Ca2+ dynamics. By using genetically encoded Ca2+ indicators specifically targeted to mitochondria (aequorin- and GFP-based probes) in SH-SY5Y cells and primary neuronal cultures, we show that overexpression or down-regulation of PS2, but not of Presenilin 1 (PS1), modulates the Ca2+ shuttling between ER and mitochondria, with its FAD mutants strongly favoring Ca2+ transfer between the two organelles. This effect is not caused by a direct PS2 action on mitochondrial Ca2+-uptake machinery but rather by an increased physical interaction between ER and mitochondria that augments the frequency of Ca2+ hot spots generated at the cytoplasmic surface of the outer mitochondrial membrane upon stimulation. This PS2 function adds further complexity to the multifaceted nature of Presenilins and to their physiological role within the cell. We also discuss the importance of this additional effect of FAD-linked PS2 mutants for the understanding of FAD pathogenesis.
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Presenilin 2 dampens intracellular ca2 stores by increasing ca2 leakage and reducing ca2 uptake
Journal of Cellular and Molecular Medicine, 2009Co-Authors: Lucia Brunello, Enrico Zampese, Tullio Pozzan, Paola Pizzo, Cristina Florean, Cristina FasolatoAbstract:We have previously shown that familial Alzheimer’s disease mutants of Presenilin-2 (PS2) and, to a lesser extent, of Presenilin-1 (PS1) lower the Ca2+ concentration of intracellular stores. We here examined the mechanism by which wild-type and mutant PS2 affect store Ca2+ handling. By using HeLa, SH-SY5Y and MEFs as model cells, and recombinant aequorins as Ca2+ probes, we show evidence that transient expression of either wild-type or mutant PS2 increases the passive Ca2+ leakage: both ryanodine- and IP3-receptors contribute to Ca2+ exit out of the ER, whereas the ribosome translocon complex is not involved. In SH-SY5Y cells and MEFs, wild-type and mutant PS2 potently reduce the uptake of Ca2+ inside the stores, an effect that can be counteracted by over-expression of SERCA-2B. On this line, in wild-type MEFs, lowering the endogenous level of PS2 by RNA interference, increases the Ca2+-loading capability of intracellular stores. Furthermore, we show that in PS double knockout MEFs, reduction of Ca2+ stores is mimicked by the expression of PS2-D366A, a loss-of-function mutant, uncleaved because also devoid of Presenilinase activity but not by co-expression of the two catalytic active fragments of PS2. In summary, both physiological and increased levels of wild-type and mutant PS2 reduce the Ca2+ uptake by intracellular stores. To exert this newly described function, PS2 needs to be in its full-length form, even if it can subsequently be cleaved.
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reduction of ca2 stores and capacitative ca2 entry is associated with the familial alzheimer s disease Presenilin 2 t122r mutation and anticipates the onset of dementia
Neurobiology of Disease, 2005Co-Authors: Marta Giacomello, Cristina Fasolato, Tullio Pozzan, Giuliano Binetti, Rosanna Squitti, Laura Barbiero, Roberta Ghidoni, Giancarlo Zatti, Paola PizzoAbstract:Abstract Mutations in the Presenilin genes PS1 and PS2, the major cause of familial Alzheimer's disease (FAD), are associated with alterations in Ca2+ signalling. In contrast to the majority of FAD-linked PS1 mutations, which cause an overload of intracellular Ca2+ pools, the FAD-linked PS2 mutation M239I reduces Ca2+ release from intracellular stores [Zatti, G., Ghidoni, R., Barbiero, L., Binetti, G., Pozzan, T., Fasolato, C., Pizzo, P., 2004. The Presenilin 2 M239I mutation associated with Familial Alzheimer's Disease reduces Ca2+ release from intracellular stores. Neurobiol. Dis. 15/2, 269–278]. We here show that in human FAD fibroblasts another PS2 mutation (T122R) reduces both Ca2+ release and capacitative Ca2+ entry. The observation, done in two monozygotic twins, is of note since only one of the subjects showed overt signs of disease at the time of biopsy whereas the other one developed the disease 3 years later. This finding indicates that Ca2+ dysregulation anticipates the onset of dementia. A similar Ca2+ alteration occurred in HeLa and HEK293 cells transiently expressing PS2-T122R. Based on these data, the “Ca2+ overload” hypothesis in AD pathogenesis is here discussed and reformulated.
Michael Lardelli - One of the best experts on this subject based on the ideXlab platform.
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in frame and frameshift mutations in zebrafish Presenilin 2 affect different cellular functions in young adult brains
Journal of Alzheimer's Disease Reports, 2021Co-Authors: Karissa Barthelson, Morgan Newman, Haowei Jiang, Stephen Pederson, Michael LardelliAbstract:Background Mutations in Presenilin 2 (PSEN2) cause early onset familial Alzheimer's disease (EOfAD) but their mode of action remains elusive. One consistent observation for all Presenilin gene mutations causing EOfAD is that a transcript is produced with a reading frame terminated by the normal stop codon-the "reading frame preservation rule". Mutations that do not obey this rule do not cause the disease. The reasons for this are debated. Objective To predict cellular functions affected by heterozygosity for a frameshift, or a reading frame-preserving mutation in zebrafish psen2 using bioinformatic techniques. Methods A frameshift mutation (psen2 N140fs ) and a reading frame-preserving (in-frame) mutation (psen2 T141 _ L142delinsMISLISV ) were previously isolated during genome editing directed at the N140 codon of zebrafish psen2 (equivalent to N141 of human PSEN2). We mated a pair of fish heterozygous for each mutation to generate a family of siblings including wild type and heterozygous mutant genotypes. Transcriptomes from young adult (6 months) brains of these genotypes were analyzed. Results The in-frame mutation uniquely caused subtle, but statistically significant, changes to expression of genes involved in oxidative phosphorylation, long-term potentiation and the cell cycle. The frameshift mutation uniquely affected genes involved in Notch and MAPK signaling, extracellular matrix receptor interactions and focal adhesion. Both mutations affected ribosomal protein gene expression but in opposite directions. Conclusion A frameshift and an in-frame mutation at the same position in zebrafish psen2 cause discrete effects. Changes in oxidative phosphorylation, long-term potentiation and the cell cycle may promote EOfAD pathogenesis in humans.
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A Review of the Familial Alzheimer's Disease Locus Presenilin 2 and Its Relationship to Presenilin 1.
Journal of Alzheimer's disease : JAD, 2018Co-Authors: Haowei Jiang, Michael Lardelli, Suman Jayadev, Morgan NewmanAbstract:Presenilin 1 (PSEN1) and Presenilin 2 (PSEN2) genes are loci for mutations causing familial Alzheimer's disease (fAD). However, the function of these genes and how they contribute to fAD pathogenesis has not been fully determined. This review provides a summary of the overlapping and independent functions of the PresenilinS with a focus on the lesser studied PSEN2. As a core component of the γ-secretase complex, the PSEN2 protein is involved in many γ-secretase-related physiological activities, including innate immunity, Notch signaling, autophagy, and mitochondrial function. These physiological activities have all been associated with AD progression, indicating that PSEN2 plays a particular role in AD pathogenesis.
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the zebrafish orthologue of familial alzheimer s disease gene Presenilin 2 is required for normal adult melanotic skin pigmentation
PLOS ONE, 2018Co-Authors: Haowei Jiang, Morgan Newman, Michael LardelliAbstract:Alzheimer’s disease is the most common form of age-related dementia. At least 15 mutations in the human gene Presenilin 2 (PSEN2) have been found to cause familial Alzheimer’s disease (fAD). Zebrafish possess an orthologous gene, psen2, and present opportunities for investigation of Presenilin function related to Alzheimer’s disease. The most prevalent and best characterized fAD mutation in PSEN2 is N141I. The equivalent codon in zebrafish psen2 is N140. We used genome editing technology in zebrafish to target generation of mutations to the N140 codon. We isolated two mutations: psen2N140fs, (hereafter “N140fs”), causing truncation of the coding sequence, and psen2T141_L142delinsMISLISV, (hereafter “T141_L142delinsMISLISV”), that deletes the two codons immediately downstream of N140 and replaces them with seven codons coding for amino acid residues MISLISV. Thus, like almost every fAD mutation in the Presenilin genes, this latter mutation does not truncate the gene’s open reading frame. Both mutations are homozygous viable although N140fs transcripts are subject to nonsense-mediated decay and lack any possibility of coding for an active γ-secretase enzyme. N140fs homozygous larvae initially show grossly normal melanotic skin pigmentation but subsequently lose this as they grow while retaining pigmentation in the retinal pigmented epithelium. T141_L142delinsMISLISV homozygotes retain faint skin melanotic pigmentation as adults, most likely indicating that the protein encoded by this allele retains weak γ-secretase activity. Null mutations in the human Presenilin genes do not cause Alzheimer’s disease so these two mutations may be useful for future investigation of the differential effects of null and fAD-like Presenilin mutations on brain aging.
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the zebrafish orthologue of familial alzheimer s disease gene Presenilin 2 is required for normal adult melanotic skin pigmentation
bioRxiv, 2018Co-Authors: Haowei Jiang, Morgan Newman, Michael LardelliAbstract:Abstract Alzheimer’s disease is the most common form of age-related dementia. At least 15 mutations in the human gene Presenilin 2 (PSEN2) have been found to cause familial Alzheimer’s disease (fAD). Zebrafish possess an orthologous gene, psen2, and present opportunities for investigation of Presenilin function related to Alzheimer’s disease. The most prevalent and best characterized fAD mutation in PSEN2 is N141I. The equivalent codon in zebrafish psen2 is N140. We used genome editing technology in zebrafish to target generation of mutations to the N140 codon. We isolated two mutations: psen2N140fs, (hereafter “N140fs”), causing truncation of the coding sequence, and psen2T141_L142delinsMISLISV, (hereafter “T141_L142delinsMISLISV”), that deletes the two codons immediately downstream of N140 and replaces them with seven codons coding for amino acid residues MISLISV. Thus, like almost every fAD mutation in the Presenilin genes, this latter mutation does not truncate the gene’s open reading frame. Both mutations are homozygous viable although N140fs transcripts are subject to nonsense-mediated decay and lack any possibility of coding for an active γ-secretase enzyme. N140fs homozygous larvae initially show grossly normal melanotic skin pigmentation but subsequently lose this as they grow while retaining pigmentation in the retinal pigmented epithelium. T141_L142delinsMISLISV homozygotes retain faint skin melanotic pigmentation as adults, most likely indicating that the protein encoded by this allele retains weak γ-secretase activity. Null mutations in the human Presenilin genes do not cause Alzheimer’s disease so these two mutations may be useful for future investigation of the differential effects of null and fAD-like Presenilin mutations on brain aging. Financial Disclosure Statement This research was supported by grants from the National Health and Medical Research Council of Australia, GNT1061006 and GNT1126422, and by funds from the School of Biological Sciences of the University of Adelaide. HJ is supported by an Adelaide Scholarship International from the University of Adelaide. Conflict of Interest Statement The authors declare no conflict of interest.
Frederic Checler - One of the best experts on this subject based on the ideXlab platform.
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Presenilin 1 and Presenilin 2 target γ secretase complexes to distinct cellular compartments
Journal of Biological Chemistry, 2016Co-Authors: Xavier Meckler, Frederic CheclerAbstract:γ-Secretase complexes achieve the production of amyloid peptides playing a key role in Alzheimer disease. These proteases have many substrates involved in important physiological functions. They are composed of two constant subunits, nicastrin and PEN2, and two variable ones, Presenilin (PS1 or PS2) and APH1 (APH1aL, APH1aS, or APH1b). Whether the composition of a given γ-secretase complex determines a specific cellular targeting remains unsolved. Here we combined a bidirectional inducible promoter and 2A peptide technology to generate constructs for the temporary, stoichiometric co-expression of six different combinations of the four γ-secretase subunits including EGFP-tagged nicastrin. These plasmids allow for the formation of functional γ-secretase complexes displaying specific activities and maturations. We show that PS1-containing γ-secretase complexes were targeted to the plasma membrane, whereas PS2-containing ones were addressed to the trans-Golgi network, to recycling endosomes, and, depending on the APH1-variant, to late endocytic compartments. Overall, these novel constructs unravel a Presenilin-dependent subcellular targeting of γ-secretase complexes. These tools should prove useful to determine whether the cellular distribution of γ-secretase complexes contributes to substrate selectivity and to delineate regulations of their trafficking.
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the c terminal fragment of Presenilin 2 triggers p53 mediated staurosporine induced apoptosis a function independent of the Presenilinase derived n terminal counterpart
Journal of Biological Chemistry, 2003Co-Authors: Cristine Alves Da Costa, Mark P Mattson, Karine Ancolio, Frederic CheclerAbstract:Abstract Mutations on Presenilins are responsible for most of familial forms of Alzheimer's disease. These holoproteins undergo rapid maturation by Presenilinase mainly in the endoplasmic reticulum, leading to the production of N- and C-terminal fragments. We show first that overexpression of the Presenilinase-derived maturation product of Presenilin 2 (CTF-PS2) increases Aβ recovery, the production of which is almost abolished by a caspase 3 inhibitor and increased by staurosporine. This and the observation that the apoptotic inducer staurosporine enhances CTF-PS2 degradation clearly link CTF-PS2 to apoptotic cascade effectors. This prompted us to analyze the putative ability of CTF-PS2 to modulate cell death. CTF-PS2 overexpression decreases cell viability and augments both caspase 3 activity and immunoreactivity. This is accompanied by loweredbcl2-like immunoreactivity and increased poly(ADP-ribose) polymerase cleavage and cytochromec translocation into the cytosol. Interestingly, CTF-PS2-induced caspase 3 activation is prevented by pifithrin-α, a selective blocker of p53 transcriptional activity. On line with the latter data, CTF-PS2 drastically increases p53 immunoreactivity and transcriptional activity. Of most interest is our observation that CTF-PS2 expression also triggers increased caspase 3 activity and immunoreactivity in fibroblasts in which Presenilins had been deleted. Therefore, CTF-PS2 could modulate cell death out of the NTF/CTF heterodimeric complex thought to correspond to the biologically functional entity. This is the first direct demonstration that CTF-PS2 could exhibit some of its functions in the absence of the Presenilin 2 N-terminal fragment (NTF-PS2) counterpart derived from the Presenilinase cleavage.
Toshitaka Kawarai - One of the best experts on this subject based on the ideXlab platform.
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both the sequence and length of the c terminus of pen 2 are critical for intermolecular interactions and function of Presenilin complexes
Journal of Biological Chemistry, 2004Co-Authors: Hiroshi Hasegawa, Toshitaka Kawarai, Fusheng Chen, Nobuo Sanjo, Taiichi Katayama, Cortney Shier, Agnes Petit, Stephen D Schmidt, Paul M Mathews, Gerold SchmittulmsAbstract:Presenilin 1 or Presenilin 2, nicastrin, APH-1, and PEN-2 form high molecular weight complexes that play a pivotal role in the cleavage of various Type I transmembrane proteins, including the β-amyloid precursor protein. The specific function of PEN-2 is unclear. To explore its function and intermolecular interactions, we conducted deletion and mutagenesis studies on a series of conserved residues at the C terminus of PEN-2. These studies suggest that: 1) both the presence and amino acid sequence of the conserved DYLSF domain at the C terminus of PEN-2 (residues 90–94) is critical for binding PEN-2 to other components in the Presenilin complex and 2) the overall length of the exposed C terminus is critical for functional γ-secretase activity.
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mutation of conserved aspartates affect maturation of Presenilin 1 and Presenilin 2 complexes
Acta Neurologica Scandinavica, 2000Co-Authors: Gang Yu, Anurag Tandon, Masaki Nishimura, Toshitaka Kawarai, Harald Steiner, Fusheng ChenAbstract:Presenilin (PS1 and PS2) holoproteins are transiently incorporated into low molecular weight (MW) complexes. During subsequent incorporation into a higher MW complex, they undergo endoproteolysis to generate stable N- and C-terminal fragments (NTF/CTF). Mutation of either of two conserved aspartate residues in transmembrane domains inhibits both Presenilin-endoproteolysis and the proteolytic processing of APP and Notch. We show that aspartate-mutant holoprotein Presenilins are not incorporated into the high molecular weight, NTF/CTF-containing complexes. Aspartate-mutant Presenilin holoproteins also preclude entry of endogenous wild-type PS1/PS2 into the high molecular weight complexes, but do not affect the incorporation of wild-type holoproteins into lower molecular weight holoprotein complexes. These data suggest that the loss-of-function aspartate-mutants cause altered PS complex maturation, and argue that the functional Presenilin moieties are contained in the high molecular weight Presenilin NTF/CTF-containing complexes.
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nicastrin modulates Presenilin mediated notch glp 1 signal transduction and βapp processing
Nature, 2000Co-Authors: Masaki Nishimura, Anurag Tandon, Toshitaka Kawarai, Fusheng Chen, Diane Levitan, Shigeki Arawaka, Ekaterina Rogaeva, Lili Zhang, Youqiang Song, Agnes SupalaAbstract:Nicastrin, a transmembrane glycoprotein, forms high molecular weight complexes with Presenilin 1 and Presenilin 2. Suppression of nicastrin expression in Caenorhabditis elegans embryos induces a subset of notch/glp-1 phenotypes similar to those induced by simultaneous null mutations in both Presenilin homologues of C. elegans (sel-12 and hop-1). Nicastrin also binds carboxy-terminal derivatives of β-amyloid precursor protein (βAPP), and modulates the production of the amyloid β-peptide (Aβ) from these derivatives. Missense mutations in a conserved hydrophilic domain of nicastrin increase Aβ42 and Aβ40 peptide secretion. Deletions in this domain inhibit Aβ production. Nicastrin and Presenilins are therefore likely to be functional components of a multimeric complex necessary for the intramembranous proteolysis of proteins such as Notch/GLP-1 and βAPP.
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mutation of conserved aspartates affects maturation of both aspartate mutant and endogenous Presenilin 1 and Presenilin 2 complexes
Journal of Biological Chemistry, 2000Co-Authors: Gang Yu, Anurag Tandon, Masaki Nishimura, Toshitaka Kawarai, Harald Steiner, Fusheng ChenAbstract:Abstract Presenilin (PS1 and PS2) holoproteins are transiently incorporated into low molecular weight (MW) complexes. During subsequent incorporation into a higher MW complex, they undergo endoproteolysis to generate stable N- and C-terminal fragments. Mutation of either of two conserved aspartate residues in transmembrane domains inhibits both Presenilin-endoproteolysis and the proteolytic processing of β-amyloid precursor protein and Notch. We show that although PS1/PS2 endoproteolysis is not required for inclusion into the higher MW N- and C-terminal fragment-containing complex, aspartate mutant holoprotein Presenilins are not incorporated into the high MW complexes. Aspartate mutant Presenilin holoproteins also preclude entry of endogenous wild type PS1/PS2 into the high MW complexes but do not affect the incorporation of wild type holoproteins into lower MW holoprotein complexes. These data suggest that the loss of function effects of the aspartate mutants result in altered PS complex maturation and argue that the functional Presenilin moieties are contained in the high molecular weight complexes.