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52 Publications visible to you, out of a total of 52
The Alzheimer's disease-linked protease BACE2 cleaves VEGFR3 and modulates its signaling.

Abstract (Expand)

The beta-secretase BACE1 is a central drug target for Alzheimer's disease. Clinically tested, BACE1-directed inhibitors also block the homologous protease BACE2. Yet, little is known about physiological … BACE2 substrates and functions in vivo. Here, we identify BACE2 as the protease shedding the lymphangiogenic vascular endothelial growth factor receptor 3 (VEGFR3). Inactivation of BACE2, but not BACE1, inhibited shedding of VEGFR3 from primary human lymphatic endothelial cells (LECs) and reduced release of the shed, soluble VEGFR3 (sVEGFR3) ectodomain into the blood of mice, non-human primates and humans. Functionally, BACE2 inactivation increased full-length VEGFR3 and enhanced VEGFR3 signaling in LECs and also in vivo in zebrafish, where enhanced migration of LECs was observed. Thus, this study identifies BACE2 as a modulator of lymphangiogenic VEGFR3 signaling and demonstrates the utility of sVEGFR3 as a pharmacodynamic plasma marker for BACE2 activity in vivo, a prerequisite for developing BACE1-selective inhibitors for a safer prevention of Alzheimer's disease.

Authors: A. Schmidt, B. Hrupka, F. van Bebber, S. Sunil Kumar, X. Feng, S. K. Tschirner, M. Assfalg, S. A. Muller, L. S. Hilger, L. I. Hofmann, M. Pigoni, G. Jocher, I. Voytyuk, E. L. Self, M. Ito, K. Hyakkoku, A. Yoshimura, N. Horiguchi, R. Feederle, B. De Strooper, S. Schulte-Merker, E. Lammert, D. Moechars, B. Schmid, S. F. Lichtenthaler

Date Published: 18th Jun 2024

Publication Type: Journal

A TBK1 variant causes autophagolysosomal and motoneuron pathology without neuroinflammation in mice.

Abstract (Expand)

Heterozygous mutations in the TBK1 gene can cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The majority of TBK1-ALS/FTD patients carry deleterious loss-of-expression … mutations, and it is still unclear which TBK1 function leads to neurodegeneration. We investigated the impact of the pathogenic TBK1 missense variant p.E696K, which does not abolish protein expression, but leads to a selective loss of TBK1 binding to the autophagy adaptor protein and TBK1 substrate optineurin. Using organelle-specific proteomics, we found that in a knock-in mouse model and human iPSC-derived motor neurons, the p.E696K mutation causes presymptomatic onset of autophagolysosomal dysfunction in neurons precipitating the accumulation of damaged lysosomes. This is followed by a progressive, age-dependent motor neuron disease. Contrary to the phenotype of mice with full Tbk1 knock-out, RIPK/TNF-alpha-dependent hepatic, neuronal necroptosis, and overt autoinflammation were not detected. Our in vivo results indicate autophagolysosomal dysfunction as a trigger for neurodegeneration and a promising therapeutic target in TBK1-ALS/FTD.

Authors: D. Brenner, K. Sieverding, J. Srinidhi, S. Zellner, C. Secker, R. Yilmaz, J. Dyckow, S. Amr, A. Ponomarenko, E. Tunaboylu, Y. Douahem, J. S. Schlag, L. Rodriguez Martinez, G. Kislinger, C. Niemann, K. Nalbach, W. P. Ruf, J. Uhl, J. Hollenbeck, L. Schirmer, A. Catanese, C. S. Lobsiger, K. M. Danzer, D. Yilmazer-Hanke, C. Munch, P. Koch, A. Freischmidt, M. Fetting, C. Behrends, R. Parlato, J. H. Weishaupt

Date Published: 6th May 2024

Publication Type: Journal

Proteomics of mouse brain endothelium uncovers dysregulation of vesicular transport pathways during aging.

Abstract (Expand)

Age-related decline in brain endothelial cell (BEC) function contributes critically to neurological disease. Comprehensive atlases of the BEC transcriptome have become available, but results from … proteomic profiling are lacking. To gain insights into endothelial pathways affected by aging, we developed a magnetic-activated cell sorting-based mouse BEC enrichment protocol compatible with proteomics and resolved the profiles of protein abundance changes during aging. Unsupervised cluster analysis revealed a segregation of age-related protein dynamics with biological functions, including a downregulation of vesicle-mediated transport. We found a dysregulation of key regulators of endocytosis and receptor recycling (most prominently Arf6), macropinocytosis and lysosomal degradation. In gene deletion and overexpression experiments, Arf6 affected endocytosis pathways in endothelial cells. Our approach uncovered changes not picked up by transcriptomic studies, such as accumulation of vesicle cargo and receptor ligands, including Apoe. Proteomic analysis of BECs from Apoe-deficient mice revealed a signature of accelerated aging. Our findings provide a resource for analysing BEC function during aging.

Authors: K. Todorov-Volgyi, J. Gonzalez-Gallego, S. A. Muller, N. Beaufort, R. Malik, M. Schifferer, M. I. Todorov, D. Crusius, S. Robinson, A. Schmidt, J. Korbelin, F. Bareyre, A. Erturk, C. Haass, M. Simons, D. Paquet, S. F. Lichtenthaler, M. Dichgans

Date Published: 22nd Apr 2024

Publication Type: Journal

Direct neuronal reprogramming of NDUFS4 patient cells identifies the unfolded protein response as a novel general reprogramming hurdle.

Abstract (Expand)

Mitochondria account for essential cellular pathways, from ATP production to nucleotide metabolism, and their deficits lead to neurological disorders and contribute to the onset of age-related diseases. … Direct neuronal reprogramming aims at replacing neurons lost in such conditions, but very little is known about the impact of mitochondrial dysfunction on the direct reprogramming of human cells. Here, we explore the effects of mitochondrial dysfunction on the neuronal reprogramming of induced pluripotent stem cell (iPSC)-derived astrocytes carrying mutations in the NDUFS4 gene, important for Complex I and associated with Leigh syndrome. This led to the identification of the unfolded protein response as a major hurdle in the direct neuronal conversion of not only astrocytes and fibroblasts from patients but also control human astrocytes and fibroblasts. Its transient inhibition potently improves reprogramming by influencing the mitochondria-endoplasmic-reticulum-stress-mediated pathways. Taken together, disease modeling using patient cells unraveled novel general hurdles and ways to overcome these in human astrocyte-to-neuron reprogramming.

Authors: G. Sonsalla, A. B. Malpartida, T. Riedemann, M. Gusic, E. Rusha, G. Bulli, S. Najas, A. Janjic, B. A. Hersbach, P. Smialowski, M. Drukker, W. Enard, J. H. M. Prehn, H. Prokisch, M. Gotz, G. Masserdotti

Date Published: 3rd Apr 2024

Publication Type: Journal

Microglia-mediated demyelination protects against CD8(+) T cell-driven axon degeneration in mice carrying PLP defects.

Abstract (Expand)

Axon degeneration and functional decline in myelin diseases are often attributed to loss of myelin but their relation is not fully understood. Perturbed myelinating glia can instigate chronic … neuroinflammation and contribute to demyelination and axonal damage. Here we study mice with distinct defects in the proteolipid protein 1 gene that develop axonal damage which is driven by cytotoxic T cells targeting myelinating oligodendrocytes. We show that persistent ensheathment with perturbed myelin poses a risk for axon degeneration, neuron loss, and behavioral decline. We demonstrate that CD8(+) T cell-driven axonal damage is less likely to progress towards degeneration when axons are efficiently demyelinated by activated microglia. Mechanistically, we show that cytotoxic T cell effector molecules induce cytoskeletal alterations within myelinating glia and aberrant actomyosin constriction of axons at paranodal domains. Our study identifies detrimental axon-glia-immune interactions which promote neurodegeneration and possible therapeutic targets for disorders associated with myelin defects and neuroinflammation.

Authors: J. Groh, T. Abdelwahab, Y. Kattimani, M. Horner, S. Loserth, V. Gudi, R. Adalbert, F. Imdahl, A. E. Saliba, M. Coleman, M. Stangel, M. Simons, R. Martini

Date Published: 30th Oct 2023

Publication Type: Journal

Deciphering sources of PET signals in the tumor microenvironment of glioblastoma at cellular resolution.

Abstract (Expand)

Various cellular sources hamper interpretation of positron emission tomography (PET) biomarkers in the tumor microenvironment (TME). We developed an approach of immunomagnetic cell sorting after in … vivo radiotracer injection (scRadiotracing) with three-dimensional (3D) histology to dissect the cellular allocation of PET signals in the TME. In mice with implanted glioblastoma, translocator protein (TSPO) radiotracer uptake per tumor cell was higher compared to tumor-associated microglia/macrophages (TAMs), validated by protein levels. Translation of in vitro scRadiotracing to patients with glioma immediately after tumor resection confirmed higher single-cell TSPO tracer uptake of tumor cells compared to immune cells. Across species, cellular radiotracer uptake explained the heterogeneity of individual TSPO-PET signals. In consideration of cellular tracer uptake and cell type abundance, tumor cells were the main contributor to TSPO enrichment in glioblastoma; however, proteomics identified potential PET targets highly specific for TAMs. Combining cellular tracer uptake measures with 3D histology facilitates precise allocation of PET signals and serves to validate emerging novel TAM-specific radioligands.

Authors: L. M. Bartos, S. V. Kirchleitner, Z. I. Kolabas, S. Quach, A. Beck, J. Lorenz, J. Blobner, S. A. Mueller, S. Ulukaya, L. Hoeher, I. Horvath, K. Wind-Mark, A. Holzgreve, V. C. Ruf, L. Gold, L. H. Kunze, S. T. Kunte, P. Beumers, H. E. Park, M. Antons, A. Zatcepin, N. Briel, L. Hoermann, R. Schaefer, D. Messerer, P. Bartenstein, M. J. Riemenschneider, S. Lindner, S. Ziegler, J. Herms, S. F. Lichtenthaler, A. Erturk, J. C. Tonn, L. von Baumgarten, N. L. Albert, M. Brendel

Date Published: 27th Oct 2023

Publication Type: Journal

A genome-wide in vivo CRISPR screen identifies essential regulators of T cell migration to the CNS in a multiple sclerosis model.

Abstract (Expand)

Multiple sclerosis (MS) involves the infiltration of autoreactive T cells into the CNS, yet we lack a comprehensive understanding of the signaling pathways that regulate this process. Here, we conducted … a genome-wide in vivo CRISPR screen in a rat MS model and identified 5 essential brakes and 18 essential facilitators of T cell migration to the CNS. While the transcription factor ETS1 limits entry to the CNS by controlling T cell responsiveness, three functional modules, centered around the adhesion molecule alpha4-integrin, the chemokine receptor CXCR3 and the GRK2 kinase, are required for CNS migration of autoreactive CD4(+) T cells. Single-cell analysis of T cells from individuals with MS confirmed that the expression of these essential regulators correlates with the propensity of CD4(+) T cells to reach the CNS. Our data thus reveal key regulators of the fundamental step in the induction of MS lesions.

Authors: A. Kendirli, C. de la Rosa, K. F. Lammle, K. Eglseer, I. J. Bauer, V. Kavaka, S. Winklmeier, L. Zhuo, C. Wichmann, L. A. Gerdes, T. Kumpfel, K. Dornmair, E. Beltran, M. Kerschensteiner, N. Kawakami

Date Published: 4th Oct 2023

Publication Type: Journal

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