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31 Publications visible to you, out of a total of 31
Experimental evidence for temporal uncoupling of brain Abeta deposition and neurodegenerative sequelae.

Abstract (Expand)

Brain Abeta deposition is a key early event in the pathogenesis of Alzheimer s disease (AD), but the long presymptomatic phase and poor correlation between Abeta deposition and clinical symptoms remain … puzzling. To elucidate the dependency of downstream pathologies on Abeta, we analyzed the trajectories of cerebral Abeta accumulation, Abeta seeding activity, and neurofilament light chain (NfL) in the CSF (a biomarker of neurodegeneration) in Abeta-precursor protein transgenic mice. We find that Abeta deposition increases linearly until it reaches an apparent plateau at a late age, while Abeta seeding activity increases more rapidly and reaches a plateau earlier, coinciding with the onset of a robust increase of CSF NfL. Short-term inhibition of Abeta generation in amyloid-laden mice reduced Abeta deposition and associated glial changes, but failed to reduce Abeta seeding activity, and CSF NfL continued to increase although at a slower pace. When short-term or long-term inhibition of Abeta generation was started at pre-amyloid stages, CSF NfL did not increase despite some Abeta deposition, microglial activation, and robust brain Abeta seeding activity. A dissociation of Abeta load and CSF NfL trajectories was also found in familial AD, consistent with the view that Abeta aggregation is not kinetically coupled to neurotoxicity. Rather, neurodegeneration starts when Abeta seeding activity is saturated and before Abeta deposition reaches critical (half-maximal) levels, a phenomenon reminiscent of the two pathogenic phases in prion disease.

Authors: C. Rother, R. E. Uhlmann, S. A. Muller, J. Schelle, A. Skodras, U. Obermuller, L. M. Hasler, M. Lambert, F. Baumann, Y. Xu, C. Bergmann, G. Salvadori, M. Loos, I. Brzak, D. Shimshek, U. Neumann, L. C. Walker, S. A. Schultz, J. P. Chhatwal, S. A. Kaeser, S. F. Lichtenthaler, M. Staufenbiel, M. Jucker

Date Published: 28th Nov 2022

Publication Type: Journal

Signatures of glial activity can be detected in the CSF proteome.

Abstract (Expand)

Single-cell transcriptomics has revealed specific glial activation states associated with the pathogenesis of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. While these … findings may eventually lead to new therapeutic opportunities, little is known about how these glial responses are reflected by biomarker changes in bodily fluids. Such knowledge, however, appears crucial for patient stratification, as well as monitoring disease progression and treatment responses in clinical trials. Here, we took advantage of well-described mouse models of beta-amyloidosis and alpha-synucleinopathy to explore cerebrospinal fluid (CSF) proteome changes related to their respective proteopathic lesions. Nontargeted liquid chromatography-mass spectrometry revealed that the majority of proteins that undergo age-related changes in CSF of either mouse model were linked to microglia and astrocytes. Specifically, we identified a panel of more than 20 glial-derived proteins that were increased in CSF of aged beta-amyloid precursor protein- and alpha-synuclein-transgenic mice and largely overlap with previously described disease-associated glial genes identified by single-cell transcriptomics. Our results also show that enhanced shedding is responsible for the increase of several of the identified glial CSF proteins as exemplified for TREM2. Notably, the vast majority of these proteins can also be quantified in human CSF and reveal changes in Alzheimer's disease cohorts. The finding that cellular transcriptome changes translate into corresponding changes of CSF proteins is of clinical relevance, supporting efforts to identify fluid biomarkers that reflect the various functional states of glial responses in cerebral proteopathies, such as Alzheimer's and Parkinson's disease.

Authors: T. Eninger, S. A. Muller, M. Bacioglu, M. Schweighauser, M. Lambert, L. F. Maia, J. J. Neher, S. M. Hornfeck, U. Obermuller, G. Kleinberger, C. Haass, P. J. Kahle, M. Staufenbiel, L. Ping, D. M. Duong, A. I. Levey, N. T. Seyfried, S. F. Lichtenthaler, M. Jucker, S. A. Kaeser

Date Published: 14th Jun 2022

Publication Type: Journal

Proteomic profiling in cerebral amyloid angiopathy reveals an overlap with CADASIL highlighting accumulation of HTRA1 and its substrates.

Abstract (Expand)

Cerebral amyloid angiopathy (CAA) is an age-related condition and a major cause of intracerebral hemorrhage and cognitive decline that shows close links with Alzheimer's disease (AD). CAA is … characterized by the aggregation of amyloid-beta (Abeta) peptides and formation of Abeta deposits in the brain vasculature resulting in a disruption of the angioarchitecture. Capillaries are a critical site of Abeta pathology in CAA type 1 and become dysfunctional during disease progression. Here, applying an advanced protocol for the isolation of parenchymal microvessels from post-mortem brain tissue combined with liquid chromatography tandem mass spectrometry (LC-MS/MS), we determined the proteomes of CAA type 1 cases (n = 12) including a patient with hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D), and of AD cases without microvascular amyloid pathology (n = 13) in comparison to neurologically healthy controls (n = 12). ELISA measurements revealed microvascular Abeta(1-40) levels to be exclusively enriched in CAA samples (mean: > 3000-fold compared to controls). The proteomic profile of CAA type 1 was characterized by massive enrichment of multiple predominantly secreted proteins and showed significant overlap with the recently reported brain microvascular proteome of patients with cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebral small vessel disease (SVD) characterized by the aggregation of the Notch3 extracellular domain. We found this overlap to be largely attributable to the accumulation of high-temperature requirement protein A1 (HTRA1), a serine protease with an established role in the brain vasculature, and several of its substrates. Notably, this signature was not present in AD cases. We further show that HTRA1 co-localizes with Abeta deposits in brain capillaries from CAA type 1 patients indicating a pathologic recruitment process. Together, these findings suggest a central role of HTRA1-dependent protein homeostasis in the CAA microvasculature and a molecular connection between multiple types of brain microvascular disease.

Authors: A. Zellner, S. A. Muller, B. Lindner, N. Beaufort, A. J. M. Rozemuller, T. Arzberger, N. C. Gassen, S. F. Lichtenthaler, B. Kuster, C. Haffner, M. Dichgans

Date Published: 24th Jan 2022

Publication Type: Journal

Proteomic and lipidomic profiling of demyelinating lesions identifies fatty acids as modulators in lesion recovery.

Abstract (Expand)

After demyelinating injury of the central nervous system, resolution of the mounting acute inflammation is crucial for the initiation of a regenerative response. Here, we aim to identify fatty acids … and lipid mediators that govern the balance of inflammatory reactions within demyelinating lesions. Using lipidomics, we identify bioactive lipids in the resolution phase of inflammation with markedly elevated levels of n-3 polyunsaturated fatty acids. Using fat-1 transgenic mice, which convert n-6 fatty acids to n-3 fatty acids, we find that reduction of the n-6/n-3 ratio decreases the phagocytic infiltrate. In addition, we observe accelerated decline of microglia/macrophages and enhanced generation of oligodendrocytes in aged mice when n-3 fatty acids are shuttled to the brain. Thus, n-3 fatty acids enhance lesion recovery and may, therefore, provide the basis for pro-regenerative medicines of demyelinating diseases in the central nervous system.

Authors: H. Penkert, A. Bertrand, V. Tiwari, S. Breimann, S. A. Muller, P. M. Jordan, M. J. Gerl, C. Klose, L. Cantuti-Castelvetri, M. Bosch-Queralt, I. Levental, S. F. Lichtenthaler, O. Werz, M. Simons

Date Published: 26th Oct 2021

Publication Type: Journal

The pseudoprotease iRhom1 controls ectodomain shedding of membrane proteins in the nervous system.

Abstract (Expand)

Proteolytic ectodomain shedding of membrane proteins is a fundamental mechanism to control the communication between cells and their environment. A key protease for membrane protein shedding is ADAM17, … which requires a non-proteolytic subunit, either inactive Rhomboid 1 (iRhom1) or iRhom2 for its activity. While iRhom1 and iRhom2 are co-expressed in most tissues and appear to have largely redundant functions, the brain is an organ with predominant expression of iRhom1. Yet, little is known about the spatio-temporal expression of iRhom1 in mammalian brain and about its function in controlling membrane protein shedding in the nervous system. Here, we demonstrate that iRhom1 is expressed in mouse brain from the prenatal stage to adulthood with a peak in early postnatal development. In the adult mouse brain iRhom1 was widely expressed, including in cortex, hippocampus, olfactory bulb, and cerebellum. Proteomic analysis of the secretome of primary neurons using the hiSPECS method and of cerebrospinal fluid, obtained from iRhom1-deficient and control mice, identified several membrane proteins that require iRhom1 for their shedding in vitro or in vivo. One of these proteins was 'multiple-EGF-like-domains protein 10' (MEGF10), a phagocytic receptor in the brain that is linked to the removal of amyloid beta and apoptotic neurons. MEGF10 was further validated as an ADAM17 substrate using ADAM17-deficient mouse embryonic fibroblasts. Taken together, this study discovers a role for iRhom1 in controlling membrane protein shedding in the mouse brain, establishes MEGF10 as an iRhom1-dependent ADAM17 substrate and demonstrates that iRhom1 is widely expressed in murine brain.

Authors: J. Tushaus, S. A. Muller, J. Shrouder, M. Arends, M. Simons, N. Plesnila, C. P. Blobel, S. F. Lichtenthaler

Date Published: 6th Oct 2021

Publication Type: Journal

ADAM10-Mediated Ectodomain Shedding Is an Essential Driver of Podocyte Damage.

Abstract (Expand)

BACKGROUND: Podocytes embrace the glomerular capillaries with foot processes, which are interconnected by a specialized adherens junction to ultimately form the filtration barrier. Altered adhesion and … loss are common features of podocyte injury, which could be mediated by shedding of cell-adhesion molecules through the regulated activity of cell surface-expressed proteases. A Disintegrin and Metalloproteinase 10 (ADAM10) is such a protease known to mediate ectodomain shedding of adhesion molecules, among others. Here we evaluate the involvement of ADAM10 in the process of antibody-induced podocyte injury. METHODS: Membrane proteomics, immunoblotting, high-resolution microscopy, and immunogold electron microscopy were used to analyze human and murine podocyte ADAM10 expression in health and kidney injury. The functionality of ADAM10 ectodomain shedding for podocyte development and injury was analyzed, in vitro and in vivo, in the anti-podocyte nephritis (APN) model in podocyte-specific, ADAM10-deficient mice. RESULTS: ADAM10 is selectively localized at foot processes of murine podocytes and its expression is dispensable for podocyte development. Podocyte ADAM10 expression is induced in the setting of antibody-mediated injury in humans and mice. Podocyte ADAM10 deficiency attenuates the clinical course of APN and preserves the morphologic integrity of podocytes, despite subepithelial immune-deposit formation. Functionally, ADAM10-related ectodomain shedding results in cleavage of the cell-adhesion proteins N- and P-cadherin, thus decreasing their injury-related surface levels. This favors podocyte loss and the activation of downstream signaling events through the Wnt signaling pathway in an ADAM10-dependent manner. CONCLUSIONS: ADAM10-mediated ectodomain shedding of injury-related cadherins drives podocyte injury.

Authors: M. Sachs, S. Wetzel, J. Reichelt, W. Sachs, L. Schebsdat, S. Zielinski, L. Seipold, L. Heintz, S. A. Muller, O. Kretz, M. Lindenmeyer, T. Wiech, T. B. Huber, R. Lullmann-Rauch, S. F. Lichtenthaler, P. Saftig, C. Meyer-Schwesinger

Date Published: 1st Jun 2021

Publication Type: Journal

Loss of NPC1 enhances phagocytic uptake and impairs lipid trafficking in microglia.

Abstract (Expand)

Niemann-Pick type C disease is a rare neurodegenerative disorder mainly caused by mutations in NPC1, resulting in abnormal late endosomal/lysosomal lipid storage. Although microgliosis is a prominent … pathological feature, direct consequences of NPC1 loss on microglial function remain not fully characterized. We discovered pathological proteomic signatures and phenotypes in NPC1-deficient murine models and demonstrate a cell autonomous function of NPC1 in microglia. Loss of NPC1 triggers enhanced phagocytic uptake and impaired myelin turnover in microglia that precede neuronal death. Npc1(-/-) microglia feature a striking accumulation of multivesicular bodies and impaired trafficking of lipids to lysosomes while lysosomal degradation function remains preserved. Molecular and functional defects were also detected in blood-derived macrophages of NPC patients that provide a potential tool for monitoring disease. Our study underscores an essential cell autonomous role for NPC1 in immune cells and implies microglial therapeutic potential.

Authors: A. Colombo, L. Dinkel, S. A. Muller, L. Sebastian Monasor, M. Schifferer, L. Cantuti-Castelvetri, J. Konig, L. Vidatic, T. Bremova-Ertl, A. P. Lieberman, S. Hecimovic, M. Simons, S. F. Lichtenthaler, M. Strupp, S. A. Schneider, S. Tahirovic

Date Published: 24th Feb 2021

Publication Type: Journal

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