ORCID Profile
0000-0002-0498-2473
Current Organisation
Karolinska Institutet
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Publisher: EMBO
Date: 16-12-2022
Publisher: The Company of Biologists
Date: 02-2021
DOI: 10.1242/DMM.046300
Abstract: Infantile myofibromatosis (IMF) is a benign tumor form characterized by the development of nonmetastatic tumors in skin, bone, muscle and sometimes viscera. Autosomal-dominant forms of IMF are caused by mutations in the PDGFRB gene, but a family carrying a L1519P mutation in the NOTCH3 gene has also recently been identified. In this study, we address the molecular consequences of the NOTCH3L1519P mutation and the relationship between Notch and PDGFRB signaling in IMF. The NOTCH3L1519P receptor generates enhanced downstream signaling in a ligand-independent manner. Despite the enhanced signaling, the NOTCH3L1519P receptor is absent from the cell surface and instead accumulates in the endoplasmic reticulum. Furthermore, the localization of the NOTCH3L1519P receptor in the bipartite, heterodimeric state is altered, combined with avid secretion of the mutated extracellular domain from the cell. Chloroquine treatment strongly reduces the amount of secreted NOTCH3L1519P extracellular domain and decreases signaling. Finally, NOTCH3L1519P upregulates PDGFRB expression in fibroblasts, supporting a functional link between Notch and PDGF dysregulation in IMF. Collectively, our data define a NOTCH3–PDGFRB axis in IMF, in which an IMF-mutated NOTCH3 receptor elevates PDGFRB expression. The functional characterization of a ligand-independent gain-of-function NOTCH3 mutation is important for Notch therapy considerations for IMF, including strategies aimed at altering lysosome function.
Publisher: Wiley
Date: 2014
Publisher: Cold Spring Harbor Laboratory
Date: 12-07-2022
DOI: 10.1101/2022.07.11.499563
Abstract: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common monogenic form of familial small vessel disease and no preventive or curative therapy is available. CADASIL is caused by mutations in the NOTCH3 gene, resulting in a mutated NOTCH3 receptor, with aggregation of the NOTCH3 extracellular domain (ECD) around vascular smooth muscle cells. In this study we have developed a novel active immunization therapy specifically targeting CADASIL-like aggregated NOTCH3 ECD. Immunizing CADASIL TgN3R182C 150 mice with aggregates composed of CADASIL-R133C mutated and wild type EGF1-5 repeats for a total of four months resulted in a marked reduction (38-48%) in NOTCH3 deposition around brain capillaries, increased microglia activation and lowered serum levels of NOTCH3 ECD. Active immunization did not impact body weight, general behavior or the number and integrity of vascular smooth muscle cells in the retina, suggesting that the therapy is tolerable. This is the first therapeutic study reporting a successful reduction of CADASIL-like NOTCH3 accumulation in mice supporting further development towards clinical application for the benefit of CADASIL patients.
Publisher: Elsevier BV
Date: 03-2002
Publisher: Public Library of Science (PLoS)
Date: 24-05-2013
Publisher: Elsevier BV
Date: 2005
DOI: 10.1016/J.NEUROSCIENCE.2005.01.062
Abstract: In most parts of the peripheral nervous system galanin is expressed at very low levels. To further understand the functional role of galanin, a mouse overexpressing galanin under the platelet-derived growth factor-B was generated, and high levels of galanin expression were observed in several peripheral tissues and spinal cord. Thus, a large proportion of neurons in autonomic and sensory ganglia were galanin-positive, as were most spinal motor neurons. Strong galanin-like immunoreactivity was also seen in nerve terminals in the corresponding target tissues, including skin, blood vessels, sweat and salivary glands, motor end-plates and the gray matter of the spinal cord. In transgenic superior cervical ganglia around half of all neuron profiles expressed galanin mRNA but axotomy did not cause a further increase, even if mRNA levels were increased in in idual neurons. In transgenic dorsal root ganglia galanin mRNA was detected in around two thirds of all neuron profiles, including large ones, and after axotomy the percentage of galanin neuron profiles was similar in overexpressing and wild type mice. Axotomy reduced the total number of DRG neurons less in overexpressing than in wild type mice, indicating a modest rescue effect. Aging by itself increased galanin expression in the superior cervical ganglion in wild type and transgenic mice, and in the latter also in preganglionic cholinergic neurons projecting to the superior cervical ganglion. Galanin overexpressing mice showed an attenuated plasma extravasation, an increased pain response in the formalin test, and changes in muscle physiology, but did not differ from wild type mice in sudomotor function. These findings suggest that overexpressed galanin in some tissues of these mice can be released and via a receptor-mediated action influence pathophysiological processes.
Publisher: Public Library of Science (PLoS)
Date: 19-03-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-08-2007
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-06-2000
DOI: 10.1126/SCIENCE.288.5471.1660
Abstract: The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation of chimeric chick and mouse embryos and give rise to cells of all germ layers. This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases.
Publisher: No publisher found
Date: 2007
DOI: 10.1111/J.1471-4159.2007.04571.X
Abstract: Presenilins (PSs) are involved in processing several proteins such as the amyloid precursor protein (APP), as well as in pathways for cell death and survival. We previously showed that some familial Alzheimer's disease PS mutations cause increased basal and acetylcholine muscarinic receptor-stimulated phospholipase C (PLC) activity which was gamma-secretase dependent. To further evaluate the dependence of PLC on PSs we measured PLC activity and the activation of variant protein kinase C (PKC) isoforms in mouse embryonic fibroblasts (MEFs) lacking either PS1, PS2, or both. PLC activity and PKCalpha and PKCgamma activations were significantly lower in PS1 and PS2 double knockout MEFs after PLC stimulation. Protein levels of PKCalpha and PKCgamma were lower in PS1 and PS2 double knockout MEFs. In contrast, PKCdelta levels were significantly elevated in PS1 and PS2 double knockout as well as in PS1 knockout MEFs. Also, PKCdelta levels were lowered after transfection of PS1 into PS1 knockout or PS double knockout MEFs. Using APP knockout MEFs we showed that the expression of PKCalpha, but not the other PKC isoforms is partially dependent on APP and can be regulated by APP intracellular domain (AICD). These results show that PLC and PKC activations are modulated by PS and also that PSs differentially regulate the expression of PKC isoforms by both APP/AICD-dependent and independent mechanisms.
Publisher: Wiley
Date: 28-10-2010
DOI: 10.1002/ANA.22274
Abstract: Frontotemporal lobar degeneration (FTLD) is the most common cause of early-onset dementia. Pathological ubiquitinated inclusion bodies observed in FTLD and motor neuron disease (MND) comprise trans-activating response element (TAR) DNA binding protein (TDP-43) and/or fused in sarcoma (FUS) protein. Our objective was to identify the causative gene in an FTLD-MND pedigree with no mutations in known dementia genes. A mutation screen of candidate genes, luciferase assays, and quantitative polymerase chain reaction (PCR) was performed to identify the biological role of the putative mutation. Neuropathological characterization of affected in iduals and western blot studies of cell lines were performed to identify the pathological mechanism of the mutation. We identified a nonpolymorphic mutation (c.672*51G>T) in the 3'-untranslated region (UTR) of the Sigma nonopioid intracellular receptor 1 (SIGMAR1) gene in affected in iduals from the FTLD-MND pedigree. The c.672*51G>T mutation increased gene expression by 1.4-fold, corresponding with a significant 1.5-fold to 2-fold change in the SIGMAR1 transcript or Sigma-1 protein in lymphocyte or brain tissue. Brains of SIGMAR1 mutation carriers displayed a unique pathology with cytoplasmic inclusions immunopositive for either TDP-43 or FUS but not Sigma-1. Overexpression of SIGMAR1 shunted TDP-43 and FUS from the nucleus to the cytoplasm by 2.3-fold and 5.2-fold, respectively. Treatment of cells with Sigma-1 ligands significantly altered translocation of TDP-43 by up to 2-fold. SIGMAR1 is a causative gene for familial FTLD-MND with a unique neuropathology that differs from other FTLD and MND cases. Our findings also suggest Sigma-1 drugs as potential treatments for the TDP-43/FUS proteinopathies.
Publisher: Elsevier BV
Date: 06-2004
Publisher: Proceedings of the National Academy of Sciences
Date: 12-03-2002
Abstract: Notch receptors undergo three distinct proteolytic cleavages during maturation and activation. The third cleavage occurs within the plasma membrane and results in the release and translocation of the intracellular domain into the nucleus to execute Notch signaling. This so-called γ-secretase cleavage is under the control of presenilins, but it is not known whether presenilins themselves carry out the cleavage or whether they act by means of yet-unidentified γ-secretase(s). In this article, we show that Notch intracellular cleavage in intact cells completely depends on presenilins. In contrast, partial purification of the Notch cleavage activity reveals an activity, which is present only in protein extracts from presenilin-containing cells, and which does not comigrate with presenilin. This finding provides evidence for the existence of a specific Notch-processing activity, which is physically distinct from presenilins. We conclude from these experiments that presenilins are critically required for Notch intracellular cleavage but are not themselves directly mediating the cleavage.
Publisher: Elsevier BV
Date: 07-2003
DOI: 10.1016/S0014-4827(03)00117-4
Abstract: One of the cardinal neuropathological findings in brains from Alzheimer's disease (AD) patients is the occurrence of amyloid beta-peptide (Abeta) deposits. The gamma-secretase-mediated intramembrane proteolysis event generating Abeta also results in the release of the APP intracellular domain (AICD), which may mediate nuclear signaling. It was recently shown that AICD starts at a position distal to the site predicted from gamma-secretase cleavage within the membrane. This novel site, the epsilon site, is located close to the inner leaflet of the membrane bilayer. The relationship between proteolysis at the gamma and epsilon sites has not been fully characterized. Here we studied AICD signaling in intact cells using a chimeric C99 molecule and a luciferase reporter system. We show that the release of AICD from the membrane takes place in a compartment downstream of the endoplasmic reticulum, is dependent on presenilin proteins, and can be inhibited by treatment with established gamma-secretase inhibitors. Moreover, we find that AICD signaling remains unaltered from C99 derivatives containing mutations associated with increased Abeta42 production and familial AD. These findings indicate that there are very similar routes for Abeta and AICD formation but that FAD-linked mutations in APP primarily affect gamma-secretase-mediated Abeta42 formation, and not AICD signaling.
Publisher: BMJ
Date: 09-2006
Publisher: Proceedings of the National Academy of Sciences
Date: 13-12-2002
Abstract: Notch receptors are single transmembrane receptors that contain a large number of epidermal growth factor-like repeats (EGF repeats) in their extracellular domains. Mutations in the EGF repeats of the human Notch 3 receptor lead to the vascular dementia disease Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL). The vast majority of CADASIL mutations are missense mutations removing or inserting cysteine residues in the EGF repeats, but it is not yet clear whether these mutations primarily affect receptor trafficking, maturation, and/or signaling. To address this issue, we have generated and analyzed stable cell lines expressing either wild-type murine Notch 3 (mNotch 3) or the mutant mNotch 3 R142C , which corresponds to the prevalent CADASIL form of Notch 3, Notch 3 R141C in humans. We find that a lower proportion of mNotch 3 R142C is expressed in the site 1-cleaved configuration, and that reduced amounts of mNotch 3 R142C appear at the cell surface, as compared with wild-type mNotch 3. This observation is accompanied by a higher propensity for mNotch 3 R142C to form intracellular aggregates, which may be a result of increased accumulation or slowed transport in the secretory pathway. In contrast to the impaired cell surface expression, mNotch 3 R142C signals equally well in response to Delta 1 and Jagged 1 as wild-type mNotch 3. Taken together, these data suggest that trafficking and localization rather than signaling of mNotch 3 are affected in mNotch 3 R142C .
Publisher: Cold Spring Harbor Laboratory
Date: 09-2021
DOI: 10.1101/2021.08.31.458349
Abstract: The blood-brain barrier (BBB) is central to separate blood from the extracellular fluids of the brain. To understand disease-related changes in the BBB is pivotal and such changes can increasingly be studied by single-cell RNA sequencing (scRNAseq), which provides high-resolution insight into gene expression changes related to the pathophysiological response of the vasculature. However, analysis of the vascular cells in the brain is challenging due to the low abundance of these cells relative to neuronal and glial cells, and improved techniques for enrichment of the vascular component is therefore warranted. The present study describes a method whereby panning with CD31-coated magnetic beads allows isolation of brain vasculature without the need for transgenic reporter lines or FACS sorting. The protocol was tested in three modalities: isolation of cells for scRNAseq, western blot (WB) analysis, and primary cell culture. For scRNAseq, a total of 22,515 single-cell transcriptomes were generated from 12-months old mice and separated into 23 clusters corresponding to all known vascular and perivascular cell types. The most abundant cell type was endothelial cells (EC) ( Pecam1 - and Cdh5 -positive), which dispersed into clusters of arterial, capillary, and venous EC according to previously established BBB arterio-venous zonation markers. Furthermore, we identified clusters of microglia ( Aif1- positive), one cluster of fenestrated endothelial cells ( Plvap -positive Cldn5 -negative), a cluster of pericytes ( Kcnj8 - and Abcc9- positive) and a cluster of vascular smooth muscle cells (VSMC) ( Acta2 - and Tagln -positive). WB analysis using established markers for the different cell types (CD31 (EC), SM22 (VSMC), PDGFRB (pericytes), GFAP (astrocytes), and IBA1 (microglia) confirmed their presence in the isolated vascular component and suggests that the protocol is suitable for future proteomic analysis. Finally, we adapted the isolation protocol to accommodate primary culture of brain vascular cells. In conclusion, we have successfully established a simple and fast method for isolating microvasculature from the murine brain independent of cell sorting and alleviating the need to use reporter mouse lines. The protocol is suitable for a multitude of testing modalities, including single-cell analyses, WB and primary cell culture.
Publisher: Elsevier BV
Date: 03-2010
Publisher: Wiley
Date: 20-12-2021
DOI: 10.1111/JCMM.17146
Abstract: The aggregation of β‐amyloid peptide 42 results in the formation of toxic oligomers and plaques, which plays a pivotal role in Alzheimer's disease pathogenesis. Aβ42 is one of several Aβ peptides, all of Aβ30 to Aβ43 that are produced as a result of γ‐secretase–mediated regulated intramembrane proteolysis of the amyloid precursor protein. γ‐Secretase modulators (GSMs) represent a promising class of Aβ42‐lowering anti‐amyloidogenic compounds for the treatment of AD. Gamma‐secretase modulators change the relative proportion of secreted Aβ peptides, while sparing the γ‐secretase–mediated processing event resulting in the release of the cytoplasmic APP intracellular domain. In this study, we have characterized how GSMs affect the γ‐secretase cleavage of three γ‐secretase substrates, E‐cadherin, ephrin type A receptor 4 (EphA4) and ephrin type B receptor 2 (EphB2), which all are implicated in important contexts of cell signalling. By using a reporter gene assay, we demonstrate that the γ‐secretase–dependent generation of EphA4 and EphB2 intracellular domains is unaffected by GSMs. We also show that γ‐secretase processing of EphA4 and EphB2 results in the release of several Aβ‐like peptides, but that only the production of Aβ‐like proteins from EphA4 is modulated by GSMs, but with an order of magnitude lower potency as compared to Aβ modulation. Collectively, these results suggest that GSMs are selective for γ‐secretase–mediated Aβ production.
Publisher: Wiley
Date: 2005
DOI: 10.1002/GENE.20091
Abstract: CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy, MIM 125310) is a genetic vascular dementia disease that is linked to missense mutations, small in-frame deletions, and splice site mutations in the human Notch 3 gene. Here we describe the generation of a mouse knockin model for one of the most prevalent CADASIL mutations, an arginine to cysteine transition at position 141, R141C, which corresponds to mutation R142C in mouse NOTCH 3. CADASIL(R142C) mice show no apparent CADASIL-like phenotype after histological and MRI analysis. The NOTCH 3 (R142C) receptor is processed normally and does not appear to accumulate the ectodomain, which has been observed in CADASIL patients. We discuss possible reasons for the different outcomes of the same germline CADASIL mutation in mice and humans.
Publisher: Wiley
Date: 08-10-2008
DOI: 10.1111/J.1471-4159.2007.05038.X
Abstract: Pedigrees with familial Alzheimer's disease (AD) show considerable phenotypic variability. Spastic paraparesis (SP), or progressive spasticity of the lower limbs is frequently hereditary and exists either as uncomplicated (paraparesis alone) or complicated (paraparesis and other neurological features) disease subtypes. In some AD families, with presenilin-1 (PSEN1) mutations, affected in iduals also have SP. These PSEN1 AD pedigrees frequently have a distinctive and variant neuropathology, namely large, non-cored plaques without neuritic dystrophy called cotton wool plaques (CWP). The PSEN1 AD mutations giving rise to CWP produce unusually high levels of the amyloid beta peptide (Abeta) ending at position 42 or 43, and the main component of CWP is amino-terminally truncated forms of amyloid beta peptide starting after the alternative beta-secretase cleavage site at position 11. This suggests a molecular basis for the formation of CWP and an association with both SP and AD. The SP phenotype in some PSEN1 AD pedigrees also appears to be associated with a delayed onset of dementia compared with affected in iduals who present with dementia only, suggesting the existence of a protective factor in some in iduals with SP. Variations in neuropathology and neurological symptoms in PSEN1 AD raise the prospect that modifier genes may underlie this phenotypic heterogeneity.
Publisher: Wiley
Date: 26-09-2011
Publisher: Elsevier BV
Date: 09-2011
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.BBRC.2010.12.029
Abstract: γ-Secretase plays an important function in the development of Alzheimer disease, since it participates in the production of the toxic amyloid β-peptide (Aβ) from the amyloid precursor protein (APP). Besides APP, γ-secretase cleaves many other substrates resulting in adverse side effects when γ-secretase inhibitors are used in clinical trials. γ-Secretase is a membrane bound protein complex consisting of at least four subunits, presenilin (PS), nicastrin, Aph-1 and Pen-2. PS and Aph-1 exist as different homologs (PS1/PS2 and Aph-1a/Aph-1b, respectively), which generates a variation in complex composition. PS1 and PS2 appears to have distinct roles since PS1 is essential during embryonic development whereas PS2 deficient mice are viable with a mild phenotype. The molecular mechanism behind this ersity is, however, largely unknown. In order to investigate whether PS1 and PS2 show different substrate specificity, we used PS1 or PS2 deficient mouse embryonic fibroblasts to study the processing on the γ-secretase substrates APP, Notch, N-cadherin, and ephrinB. We found that whereas depletion of PS1 severely affected the cleavage of all substrates, the effect of PS2 depletion was minor. In addition, less PS2 was found in active γ-secretase complexes. We also studied the effect of PS2 depletion in adult mouse brain and, in concordance with the results from the mouse embryonic fibroblasts, PS2 deficiency did not alter the cleavage of the two most important substrates, APP and Notch. In summary, this study shows that the contribution of PS2 on γ-secretase activity is of less importance, explaining the mild phenotype of PS2-deficient mice.
No related grants have been discovered for Helena Karlström.