Publications by authors named "Birgitta Wiehager"

15 Publications

  • Page 1 of 1

The Bri2 and Bri3 BRICHOS Domains Interact Differently with Aβ and Alzheimer Amyloid Plaques.

J Alzheimers Dis Rep 2018 Feb 16;2(1):27-39. Epub 2018 Feb 16.

Department of Neurobiology, Care Sciences and Society (NVS), Center for Alzheimer Research, Division of Neurogeriatrics, Karolinska Institutet, Huddinge, Sweden.

Alzheimer's disease (AD) is the most common form of dementia and there is no successful treatment available. Evidence suggests that fibril formation of the amyloid β-peptide (Aβ) is a major underlying cause of AD, and treatment strategies that reduce the toxic effects of Aβ amyloid are sought for. The BRICHOS domain is found in several proteins, including Bri2 (also called integral membrane protein 2B (ITM2B)), mutants of which are associated with amyloid and neurodegeneration, and Bri3 (ITM2C). We have used mouse hippocampal neurons and brain tissues from mice and humans and show Bri3 deposits dispersed on AD plaques. In contrast to what has been shown for Bri2, Bri3 immunoreactivity is decreased in AD brain homogenates compared to controls. Both Bri2 and Bri3 BRICHOS domains interact with Aβ and Aβ present in neurons and reduce Aβ amyloid fibril formation , but Bri3 BRICHOS is less efficient. These results indicate that Bri2 and Bri3 BRICHOS have different roles in relation to Aβ aggregation.
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http://dx.doi.org/10.3233/ADR-170051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6159705PMC
February 2018

TOM70 Sustains Cell Bioenergetics by Promoting IP3R3-Mediated ER to Mitochondria Ca Transfer.

Curr Biol 2018 02 27;28(3):369-382.e6. Epub 2018 Jan 27.

Center for Alzheimer Research, Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society, Novum 5(th) Floor, Karolinska Institutet, 141 57 Huddinge, Sweden. Electronic address:

The mitochondrial translocase of the outer membrane (TOM) is a protein complex that is essential for the post-translational import of nuclear-encoded mitochondrial proteins. Among its subunits, TOM70 and TOM20 are only transiently associated with the core complex, suggesting their possible additional roles within the outer mitochondrial membrane (OMM). Here, by using different mammalian cell lines, we demonstrate that TOM70, but not TOM20, clusters in distinct OMM foci, frequently overlapping with sites in which the endoplasmic reticulum (ER) contacts mitochondria. Functionally, TOM70 depletion specifically impairs inositol trisphosphates (IP3)-linked ER to mitochondria Ca transfer. This phenomenon is dependent on the capacity of TOM70 to interact with IP3-receptors and favor their functional recruitment close to mitochondria. Importantly, the reduced constitutive Ca transfer to mitochondria, observed in TOM70-depleted cells, dampens mitochondrial respiration, affects cell bioenergetics, induces autophagy, and inhibits proliferation. Our data reveal a hitherto unexpected role for TOM70 in pro-survival ER-mitochondria communication, reinforcing the view that the ER-mitochondria signaling platform is a key regulator of cell fate.
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http://dx.doi.org/10.1016/j.cub.2017.12.047DOI Listing
February 2018

Monoamine oxidase B is elevated in Alzheimer disease neurons, is associated with γ-secretase and regulates neuronal amyloid β-peptide levels.

Alzheimers Res Ther 2017 Aug 1;9(1):57. Epub 2017 Aug 1.

Karolinska Institutet, Department NVS, Center for Alzheimer Research, Division of Neurogeriatrics, Huddinge, Sweden.

Background: Increased levels of the pathogenic amyloid β-peptide (Aβ), released from its precursor by the transmembrane protease γ-secretase, are found in Alzheimer disease (AD) brains. Interestingly, monoamine oxidase B (MAO-B) activity is also increased in AD brain, but its role in AD pathogenesis is not known. Recent neuroimaging studies have shown that the increased MAO-B expression in AD brain starts several years before the onset of the disease. Here, we show a potential connection between MAO-B, γ-secretase and Aβ in neurons.

Methods: MAO-B immunohistochemistry was performed on postmortem human brain. Affinity purification of γ-secretase followed by mass spectrometry was used for unbiased identification of γ-secretase-associated proteins. The association of MAO-B with γ-secretase was studied by coimmunoprecipitation from brain homogenate, and by in-situ proximity ligation assay (PLA) in neurons as well as mouse and human brain sections. The effect of MAO-B on Aβ production and Notch processing in cell cultures was analyzed by siRNA silencing or overexpression experiments followed by ELISA, western blot or FRET analysis. Methodology for measuring relative intraneuronal MAO-B and Aβ42 levels in single cells was developed by combining immunocytochemistry and confocal microscopy with quantitative image analysis.

Results: Immunohistochemistry revealed MAO-B staining in neurons in the frontal cortex, hippocampus CA1 and entorhinal cortex in postmortem human brain. Interestingly, the neuronal staining intensity was higher in AD brain than in control brain in these regions. Mass spectrometric data from affinity purified γ-secretase suggested that MAO-B is a γ-secretase-associated protein, which was confirmed by immunoprecipitation and PLA, and a neuronal location of the interaction was shown. Strikingly, intraneuronal Aβ42 levels correlated with MAO-B levels, and siRNA silencing of MAO-B resulted in significantly reduced levels of intraneuronal Aβ42. Furthermore, overexpression of MAO-B enhanced Aβ production.

Conclusions: This study shows that MAO-B levels are increased not only in astrocytes but also in pyramidal neurons in AD brain. The study also suggests that MAO-B regulates Aβ production in neurons via γ-secretase and thereby provides a key to understanding the relationship between MAO-B and AD pathogenesis. Potentially, the γ-secretase/MAO-B association may be a target for reducing Aβ levels using protein-protein interaction breakers.
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http://dx.doi.org/10.1186/s13195-017-0279-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5540560PMC
August 2017

Mitofusin-2 knockdown increases ER-mitochondria contact and decreases amyloid β-peptide production.

J Cell Mol Med 2016 09 20;20(9):1686-95. Epub 2016 May 20.

Center for Alzheimer Research, Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden.

Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum (ER). Such contacts are formed between mitochondria-associated ER membranes (MAM), specialized subregions of ER, and the outer mitochondrial membrane (OMM). We have previously shown increased expression of MAM-associated proteins and enhanced ER to mitochondria Ca(2+) transfer from ER to mitochondria in Alzheimer's disease (AD) and amyloid β-peptide (Aβ)-related neuronal models. Here, we report that siRNA knockdown of mitofusin-2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca(2+) transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra- and extracellular Aβ40 and Aβ42 . Analysis of γ-secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ-secretase complex function. Amyloid-β precursor protein (APP), β-site APP-cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 siRNA treatment. In summary, our data shows that modulation of ER-mitochondria contact affects γ-secretase activity and Aβ generation. Increased ER-mitochondria contact results in lower γ-secretase activity suggesting a new mechanism by which Aβ generation can be controlled.
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http://dx.doi.org/10.1111/jcmm.12863DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988279PMC
September 2016

Proton myo-inositol cotransporter is a novel γ-secretase associated protein that regulates Aβ production without affecting Notch cleavage.

FEBS J 2015 Sep 14;282(17):3438-51. Epub 2015 Jul 14.

Division for Neurogeriatrics, Department of NVS, Center for Alzheimer Research, Karolinska Institutet, Huddinge, Sweden.

γ-Secretase is a transmembrane protease complex that is responsible for the processing of a multitude of type 1 transmembrane proteins, including the amyloid precursor protein and Notch. γ-Secretase processing of amyloid precursor protein results in the release of the amyloid β-peptide (Aβ), which is involved in the pathogenesis in Alzheimer's disease. Processing of Notch leads to the release of its intracellular domain, which is important for cell development. γ-Secretase associated proteins (GSAPs) could be of importance for substrate selection, and we have previously shown that affinity purification of γ-secretase in combination with mass spectrometry can be used for finding such proteins. In the present study, we used this methodology to screen for novel GSAPs from human brain, and studied their effect on Aβ production in a comprehensive gene knockdown approach. Silencing of probable phospholipid-transporting ATPase IIA, brain-derived neurotrophic factor/neurotrophin-3 growth factor receptor precursor and proton myo-inositol cotransporter (SLC2A13) showed a clear reduction of Aβ and these proteins were selected for further studies on Aβ production and Notch cleavage using small interfering RNA-mediated gene silencing, as well as an overexpression approach. Silencing of these reduced Aβ secretion in a small interfering RNA dose-dependent manner. Interestingly, SLC2A13 had a lower effect on Notch processing. Furthermore, overexpression of SLC2A13 increased Aβ40 generation. Finally, the interaction between γ-secretase and SLC2A13 was confirmed using immunoprecipitation and a proximity ligation assay. In summary, SLC2A13 was identified as a novel GSAP that regulates Aβ production without affecting Notch cleavage. We suggest that SLC2A13 could be a target for Aβ lowering therapy aimed at treating Alzheimer's disease.
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http://dx.doi.org/10.1111/febs.13353DOI Listing
September 2015

Human brain proteins showing neuron-specific interactions with γ-secretase.

FEBS J 2015 Jul 2;282(14):2587-99. Epub 2015 Jul 2.

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division for Neurogeriatrics, Huddinge, Sweden.

The transmembrane protease complex γ-secretase is a key enzyme in Alzheimer disease pathogenesis as it liberates the neurotoxic amyloid β-peptide (Aβ); however, the mechanism of regulation of its activity in various cell types and subcellular compartments is largely unknown. Several γ-secretase inhibitors have been developed, but none have been released due to side-effects that appear to arise from reduced processing of Notch, one of many γ-secretase substrates. Hence, it is desirable to specifically inhibit Aβ production. In our previous studies, we have identified several γ-secretase-associated proteins (GSAPs) from brain, which affect Aβ production without having any major effects on Notch processing. In the present study using detergent-resistant membranes prepared from brain, we have identified four GSAPs that affect Aβ production to a greater extent than Notch processing. We evaluated the interaction between GSAPs and γ-secretase in various cell types and their mRNA expression in various human organs. Using an in situ proximity ligation assay, we demonstrated that many GSAPs showed considerably greater interaction with γ-secretase in neurons than in human embryonic kidney cells stably over-expressing APP, and showed that several GSAPs are highly expressed in human brain. This study underscores the importance of studying protein-protein interactions in relevant cell types, and suggests that reducing Aβ production by interfering with brain- or neuron-specific γ-secretase/GSAP interactions may reduce the risk of unwanted side-effects associated with treatment of Alzheimer disease.
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http://dx.doi.org/10.1111/febs.13303DOI Listing
July 2015

Stress Conditions Increase Vimentin Cleavage by Omi/HtrA2 Protease in Human Primary Neurons and Differentiated Neuroblastoma Cells.

Mol Neurobiol 2015 Dec 8;52(3):1077-1092. Epub 2014 Oct 8.

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society (NVS), Center for Alzheimer Research, Division for Neurogeriatrics, Novum 5th floor, SE-141 57, Huddinge, Sweden.

Dysfunctional Omi/HtrA2, a mitochondrial serine protease, has been implicated in various neurodegenerative disorders. Despite the wealth of evidence on the roles of Omi/HtrA2 in apoptosis, little is known about its cytosolic targets, the cleavage of which could account for the observed morphological changes such as cytoskeletal reorganizations in axons. By proteomic analysis, vimentin was identified as a substrate for Omi/HtrA2 and we have reported increased Omi/HtrA2 protease activity in Alzheimer disease (AD) brain. Here, we investigated a possible link between Omi/HtrA2 and vimentin cleavage, and consequence of this cleavage on mitochondrial distribution in neurons. In vitro protease assays showed vimentin to be cleaved by Omi/HtrA2 protease, and proximity ligation assay demonstrated an increased interaction between Omi/HtrA2 and vimentin in human primary neurons upon stress stimuli. Using differentiated neuroblastoma SH-SY5Y cells, we showed that Omi/HtrA2 under several different stress conditions induces cleavage of vimentin in wild-type as well as SH-SY5Y cells transfected with amyloid precursor protein with the Alzheimer disease-associated Swedish mutation. After stress treatment, inhibition of Omi/HtrA2 protease activity by the Omi/HtrA2 specific inhibitor, Ucf-101, reduced the cleavage of vimentin in wild-type cells. Following altered vimentin filaments integrity by stress stimuli, mitochondria was redistributed in differentiated SH-SY5Y cells and human primary neurons. In summary, the findings outlined in this paper suggest a role of Omi/HtrA2 in modulation of vimentin filamentous structure in neurons. Our results provide important findings for understanding the biological role of Omi/HtrA2 activity during stress conditions, and give knowledge of interplay between Omi/HtrA2 and vimentin which might affect mitochondrial distribution in neurons.
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http://dx.doi.org/10.1007/s12035-014-8906-3DOI Listing
December 2015

Amyloid-β peptides are generated in mitochondria-associated endoplasmic reticulum membranes.

J Alzheimers Dis 2015 ;43(2):369-74

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division for Neurogeriatrics, Stockholm, Sweden.

Extracellular aggregates of amyloid-β peptides (Aβ) are a hallmark in Alzheimer's disease (AD) brains. Recent findings suggest that Aβ is generated intracellularly and potential production sites include endosomes and trans-Golgi network. We determined the production of Aβ in subcellular fractions isolated from mouse brain. We found that a considerable amount of Aβ is produced at mitochondria-endoplasmic reticulum (ER) contact sites including outer mitochondrial membrane and mitochondria-associated ER membranes. Enhanced Aβ production at this site may disturb ER, mitochondrial and mitochondria-ER contact site function. This may be one key step in the cascade of events eventually leading to neurodegeneration in AD.
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http://dx.doi.org/10.3233/JAD-132543DOI Listing
July 2015

Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

Proc Natl Acad Sci U S A 2013 May 25;110(19):7916-21. Epub 2013 Apr 25.

Department of Neurobiology, Care Sciences and Society, Karolinska Institutet-Alzheimer's Disease Research Center, Karolinska Institutet, 141 86 Stockholm, Sweden.

It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER-mitochondria interplay in the brain has so far remained unknown. Here, we studied ER-mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and σ1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP)Swe/Lon mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER-mitochondria bridging complex, inositol-1,4,5-triphosphate receptor-voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid β-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER-mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER-mitochondria contacts and cross-talk in AD pathology.
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http://dx.doi.org/10.1073/pnas.1300677110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651455PMC
May 2013

Biochemical studies of poly-T variants in the Alzheimer's disease associated TOMM40 gene.

J Alzheimers Dis 2012 ;31(3):527-36

KI-Alzheimer's Disease Research Center, Karolinska Institutet, Department of Neurobiology, Care Sciences and Society (NVS), Stockholm, Sweden.

The apolipoprotein E (APOE) gene remains the most strongly established risk factor for late onset Alzheimer's disease (LOAD). Recently the gene, TOMM40, which is in linkage disequilibrium with APOE, was identified to be associated with LOAD in genome-wide association studies. One of the identified polymorphisms in TOMM40 is rs10524523, which is located in intron 6 and composed of thymidine repeats varying between 14 to 36 base-pairs in length. Reported results are contradictory in regard to the very long poly-T variant that has been associated with both increased and decreased risk of LOAD. Our study aimed to elucidate the functional implication of rs10524523 in an in vitro model of human fibroblast cells obtained from cognitively healthy APOE ε3/ε4 carriers harboring very long or short poly-T variants coupled to their APOE ε3 allele. We have studied (i) expression levels of TOM40 protein and mRNA, (ii) TOM40 mRNA splicing, and (iii) mitochondrial function and morphology; and we have found no significant differences in regards to very long or short poly-T variant.
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http://dx.doi.org/10.3233/JAD-2012-120580DOI Listing
May 2013

Mitochondrial γ-secretase participates in the metabolism of mitochondria-associated amyloid precursor protein.

FASEB J 2011 Jan 10;25(1):78-88. Epub 2010 Sep 10.

Karolinska Institutet and Dainippon Sumitomo Pharma Alzheimer Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge, Sweden.

Intracellular amyloid-β peptide (Aβ) has been implicated in the pathogenesis of Alzheimer's disease (AD). Mitochondria were found to be the target both for amyloid precursor protein (APP) that accumulates in the mitochondrial import channels and for Aβ that interacts with several proteins inside mitochondria and leads to mitochondrial dysfunction. Here, we have studied the role of mitochondrial γ-secretase in processing different substrates. We found that a significant proportion of APP is associated with mitochondria in cultured cells and that γ-secretase cleaves the shedded C-terminal part of APP identified as C83 associated with the outer membrane of mitochondria (OMM). Moreover, we have established the topology of the C83 in the OMM and found the APP intracellular domain (AICD) to be located inside mitochondria. Our data show for the first time that APP is a substrate for the mitochondrial γ-secretase and that AICD is produced inside mitochondria. Thus, we provide a mechanistic view of the mitochondria-associated APP metabolism where AICD, P3 peptide and potentially Aβ are produced locally and may contribute to mitochondrial dysfunction in AD.
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http://dx.doi.org/10.1096/fj.10-157230DOI Listing
January 2011

Association of Omi/HtrA2 with γ-secretase in mitochondria.

Neurochem Int 2010 Nov 10;57(6):668-75. Epub 2010 Aug 10.

Karolinska Institutet and Dainippon Sumitomo Pharma Alzheimer Center (KASPAC), Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet, Huddinge, Sweden.

Omi/HtrA2, a mitochondrial serine protease with chaperone activity, is involved in varied intracellular processes. Dysfunctional Omi/HtrA2 has thus been implicated in various neurodegenerative disorders. Previously, we have shown that γ-secretase complexes are present and active in mitochondria. Here, we demonstrate that peptide corresponding to C-terminus of presenilin-1, as previously reported to activate Omi/HtrA2, interacts with Omi/HtrA2 in isolated mitochondria. Moreover, we show that Omi/HtrA2 interacts with presenilin in active γ-secretase complexes located to mitochondria. Using a biotinylated γ-secretase inhibitor and confocal microscopy, we could further confirm the association of γ-secretase complexes with mitochondrial Omi/HtrA2. Furthermore, determination of γ-secretase complex topology in isolated mitochondria revealed an association of γ-secretase complexes with the outer membrane of mitochondria with the extreme PS1 C-terminus facing the inter-membrane space. We have also studied the impact of Omi/HtrA2 on γ-secretase activity, measuring APP intracellular domain (AICD) production. We found reduced AICD production in mitochondria isolated from Omi/HtrA2 knockout mouse embryonic fibroblasts, indicating a significant role of Omi/HtrA2 on γ-secretase activity. Thus, our results provide information for understanding the interplay between mitochondrial Omi/HtrA2 and γ-secretase complexes in AD.
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http://dx.doi.org/10.1016/j.neuint.2010.08.004DOI Listing
November 2010

The amyloid beta-peptide is imported into mitochondria via the TOM import machinery and localized to mitochondrial cristae.

Proc Natl Acad Sci U S A 2008 Sep 29;105(35):13145-50. Epub 2008 Aug 29.

Karolinska Institutet Dainippon Sumitomo Pharma Alzheimer Center, NVS, Novum, 141 57 Huddinge, Sweden.

The amyloid beta-peptide (Abeta) has been suggested to exert its toxicity intracellularly. Mitochondrial functions can be negatively affected by Abeta and accumulation of Abeta has been detected in mitochondria. Because Abeta is not likely to be produced locally in mitochondria, we decided to investigate the mechanisms for mitochondrial Abeta uptake. Our results from rat mitochondria show that Abeta is transported into mitochondria via the translocase of the outer membrane (TOM) machinery. The import was insensitive to valinomycin, indicating that it is independent of the mitochondrial membrane potential. Subfractionation studies following the import experiments revealed Abeta association with the inner membrane fraction, and immunoelectron microscopy after import showed localization of Abeta to mitochondrial cristae. A similar distribution pattern of Abeta in mitochondria was shown by immunoelectron microscopy in human cortical brain biopsies obtained from living subjects with normal pressure hydrocephalus. Thus, we present a unique import mechanism for Abeta in mitochondria and demonstrate both in vitro and in vivo that Abeta is located to the mitochondrial cristae. Importantly, we also show that extracellulary applied Abeta can be internalized by human neuroblastoma cells and can colocalize with mitochondrial markers. Together, these results provide further insight into the mitochondrial uptake of Abeta, a peptide considered to be of major significance in Alzheimer's disease.
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http://dx.doi.org/10.1073/pnas.0806192105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2527349PMC
September 2008

Differential role of Presenilin-1 and -2 on mitochondrial membrane potential and oxygen consumption in mouse embryonic fibroblasts.

J Neurosci Res 2006 Sep;84(4):891-902

Department of Neurobiology, Karolinska Institutet Dainippon Sumitomo Pharmaceuticals Alzheimer Center, Caring Sciences and Society, Novum, Huddinge, Sweden.

Increasing evidence indicates that mitochondrial alterations contribute to the neuronal death in Alzheimer's disease (AD). Presenilin 1 (PS1) and Presenilin 2 (PS2) mutations have been shown to sensitize cells to apoptosis by mechanisms suggested to involve impaired mitochondrial function. We have previously detected active gamma-secretase complexes in mitochondria. We investigated the impact of PS/gamma-secretase on mitochondrial function using mouse embryonal fibroblasts derived from wild-type, PS1-/-, PS2-/- and PS double knock-out (PSKO) embryos. Measurements of mitochondrial membrane potential (DeltaPsim) showed a higher percentage of fully functional mitochondria in PS1-/- and PSwt as compared to PS2-/- and PSKO cells. This result was evident both in whole cell preparations and in isolated mitochondria. Interestingly, pre-treatment of isolated mitochondria with the gamma-secretase inhibitor L-685,458 resulted in a decreased population of mitochondria with high DeltaPsim in PSwt and PS1-/- cells, indicating that PS2/gamma-secretase activity can modify DeltaPsim. PS2-/- cells showed a significantly lower basal respiratory rate as compared to other cell lines. However, all cell lines demonstrated competent bioenergetic function. These data point toward a specific role of PS2/gamma-secretase activity for proper mitochondrial function and indicate interplay between PS1 and PS2 in mitochondrial functionality.
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http://dx.doi.org/10.1002/jnr.20990DOI Listing
September 2006

Presenilin expression during induced differentiation of the human neuroblastoma SH-SY5Y cell line.

Neurochem Int 2004 Jun;44(7):487-96

Neurotec Department, Division of Experimental Geriatrics, Karolinska Institutet, KASPAC, Novum pl 5, S-141 86 Huddinge, Sweden.

Human neuroblastoma SH-SY5Y cells stably transfected with both wild-type and exon-9 deleted (deltaE9) presenilin constructs were used to study the role of the presenilin proteins during differentiation. Cells transfected with either wild-type or deltaE9 PS1, of which the latter abolishes normal endoproteolytic cleavage of the protein, showed no obvious differences in their ability to differentiate to a neuronal-like phenotype upon treatment with retinoic acid (RA). A defined pattern of PS1 expression was observed during differentiation with both RA and the phorbol ester TPA. Full-length PS1 was shown to increase dramatically within 5-24 h of RA treatment. TPA gave an earlier and longer lasting increase in full-length PS1 levels. The intracellular distribution pattern of PS1 was markedly altered following RA treatment. Within 24h PS1 was highly up-regulated throughout the cell body around the nucleus. Between 2 and 4 weeks PS1 staining appeared punctate and also localised to the nucleus. Increases in PS1 expression upon treatment with RA and TPA were blocked by treatment with cycloheximide, indicating a role of de-novo protein synthesis in this effect. PS2 expression remained unchanged during differentiation. Levels of full-length PS1 were also seen to increase during neurogenesis and neuronal differentiation in the forebrain of first trimester human foetuses between 6.5 and 11 weeks. These combined observations support the idea that PS1 is involved in neuronal differentiation by a mechanism likely independent of endoproteolysis of the protein.
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http://dx.doi.org/10.1016/j.neuint.2003.09.002DOI Listing
June 2004