Publications

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74 Publications visible to you, out of a total of 74

Abstract (Expand)

The sequestration of damaged mitochondria within double-membrane structures termed autophagosomes is a key step of PINK1/Parkin mitophagy. The ATG4 family of proteases are thought to regulate autophagosome formation exclusively by processing the ubiquitin-like ATG8 family (LC3/GABARAPs). We discover that human ATG4s promote autophagosome formation independently of their protease activity and of ATG8 family processing. ATG4 proximity networks reveal a role for ATG4s and their proximity partners, including the immune-disease protein LRBA, in ATG9A vesicle trafficking to mitochondria. Artificial intelligence-directed 3D electron microscopy of phagophores shows that ATG4s promote phagophore-ER contacts during the lipid-transfer phase of autophagosome formation. We also show that ATG8 removal during autophagosome maturation does not depend on ATG4 activity. Instead, ATG4s can disassemble ATG8-protein conjugates, revealing a role for ATG4s as deubiquitinating-like enzymes. These findings establish non-canonical roles of the ATG4 family beyond the ATG8 lipidation axis and provide an AI-driven framework for rapid 3D electron microscopy.

Authors: T. N. Nguyen, B. S. Padman, S. Zellner, G. Khuu, L. Uoselis, W. K. Lam, M. Skulsuppaisarn, R. S. J. Lindblom, E. M. Watts, C. Behrends, M. Lazarou

Date Published: 6th May 2021

Publication Type: Journal

Abstract (Expand)

In the present study, we have demonstrated that extracellular vesicles (EVs) derived from cerebrospinal fluid (CSF) represent a promising source for the identification of a novel miRNA signatures in Parkinson's disease (PD). Using next‐generation small‐RNA sequencing, we present for the first time the complete and quantitative microRNAome of EVs isolated from human CSF of PD and age‐correlated controls (CTR). In parallel, we performed CSF proteomic profiling of overlapping patient cohorts, which revealed the deregulation of disease‐relevant pathways similar to the ones obtained with the parallel miRNA analyses, supporting the results for the identified signature.

Authors: Lucas Caldi Gomes, Anna-Elisa Roser, Gaurav Jain, Tonatiuh Pena Centeno, Fabian Maass, Lukas Schilde, Caroline May, Anja Schneider, Mathias Bähr, Katrin Marcus, André Fischer, Paul Lingor

Date Published: 5th Apr 2021

Publication Type: Journal

Abstract (Expand)

Autophagy deficiency in fed conditions leads to the formation of protein inclusions highlighting the contribution of this lysosomal delivery route to cellular proteostasis. Selective autophagy pathways exist that clear accumulated and aggregated ubiquitinated proteins. Receptors for this type of autophagy (aggrephagy) include p62, NBR1, TOLLIP, and OPTN, which possess LC3-interacting regions and ubiquitin-binding domains (UBDs), thus working as a bridge between LC3/GABARAP proteins and ubiquitinated substrates. However, the identity of aggrephagy substrates and the redundancy of aggrephagy and related UBD-containing receptors remains elusive. Here, we combined proximity labeling and organelle enrichment with quantitative proteomics to systematically map the autophagic degradome targeted by UBD-containing receptors under basal and proteostasis-challenging conditions in human cell lines. We identified various autophagy substrates, some of which were differentially engulfed by autophagosomal and endosomal membranes via p62 and TOLLIP, respectively. Overall, this resource will allow dissection of the proteostasis contribution of autophagy to numerous individual proteins.

Authors: Susanne Zellner, Martina Schifferer, Christian Behrends

Date Published: 18th Mar 2021

Publication Type: Journal

Abstract (Expand)

Astrocyte-to-neuron conversion is a promising avenue for neuronal replacement therapy. Neurons are particularly dependent on mitochondrial function, but how well mitochondria adapt to the new fate is unknown. Here, we determined the comprehensive mitochondrial proteome of cortical astrocytes and neurons, identifying about 150 significantly enriched mitochondrial proteins for each cell type, including transporters, metabolic enzymes, and cell-type-specific antioxidants. Monitoring their transition during reprogramming revealed late and only partial adaptation to the neuronal identity. Early dCas9-mediated activation of genes encoding mitochondrial proteins significantly improved conversion efficiency, particularly for neuron-enriched but not astrocyte-enriched antioxidant proteins. For example, Sod1 not only improves the survival of the converted neurons but also elicits a faster conversion pace, indicating that mitochondrial proteins act as enablers and drivers in this process. Transcriptional engineering of mitochondrial proteins with other functions improved reprogramming as well, demonstrating a broader role of mitochondrial proteins during fate conversion.

Authors: Gianluca L Russo, Giovanna Sonsalla, Poornemaa Natarajan, Christopher T Breunig, Giorgia Bulli, Juliane Merl-Pham, Sabine Schmitt, Jessica Giehrl-Schwab, Florian Giesert, Martin Jastroch, Hans Zischka, Wolfgang Wurst, Stefan H Stricker, Stefanie M Hauck, Giacomo Masserdotti, Magdalena Götz

Date Published: 4th Mar 2021

Publication Type: Journal

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

Abstract (Expand)

To understand how cells communicate in the nervous system, it is essential to define their secretome, which is challenging for primary cells because of large cell numbers being required. Here, we miniaturized secretome analysis by developing the "high-performance secretome protein enrichment with click sugars" (hiSPECS) method. To demonstrate its broad utility, hiSPECS was used to identify the secretory response of brain slices upon LPS-induced neuroinflammation and to establish the cell type-resolved mouse brain secretome resource using primary astrocytes, microglia, neurons, and oligodendrocytes. This resource allowed mapping the cellular origin of CSF proteins and revealed that an unexpectedly high number of secreted proteins in vitro and in vivo are proteolytically cleaved membrane protein ectodomains. Two examples are neuronally secreted ADAM22 and CD200, which we identified as substrates of the Alzheimer-linked protease BACE1. hiSPECS and the brain secretome resource can be widely exploited to systematically study protein secretion and brain function and to identify cell type-specific biomarkers for CNS diseases.

Authors: J. Tushaus, S. A. Muller, E. S. Kataka, J. Zaucha, L. Sebastian Monasor, M. Su, G. Guner, G. Jocher, S. Tahirovic, D. Frishman, M. Simons, S. F. Lichtenthaler

Date Published: 15th Oct 2020

Publication Type: Journal

Abstract (Expand)

Neuronal cell lines are important model systems to study mechanisms of neurodegenerative diseases. One example is the Lund Human Mesencephalic (LUHMES) cell line, which can differentiate into dopaminergic-like neurons and is frequently used to study mechanisms of Parkinson's disease and neurotoxicity. Neuronal differentiation of LUHMES cells is commonly verified with selected neuronal markers, but little is known about the proteome-wide protein abundance changes during differentiation. Using mass spectrometry and label-free quantification (LFQ), the proteome of differentiated and undifferentiated LUHMES cells and of primary murine midbrain neurons are compared. Neuronal differentiation induced substantial changes of the LUHMES cell proteome, with proliferation-related proteins being strongly down-regulated and neuronal and dopaminergic proteins, such as L1CAM and alpha-synuclein (SNCA) being up to 1,000-fold up-regulated. Several of these proteins, including MAPT and SYN1, may be useful as new markers for experimentally validating neuronal differentiation of LUHMES cells. Primary midbrain neurons are slightly more closely related to differentiated than to undifferentiated LUHMES cells, in particular with respect to the abundance of proteins related to neurodegeneration. In summary, the analysis demonstrates that differentiated LUHMES cells are a suitable model for studies on neurodegeneration and provides a resource of the proteome-wide changes during neuronal differentiation. (ProteomeXchange identifier PXD020044).

Authors: J. Tushaus, E. S. Kataka, J. Zaucha, D. Frishman, S. A. Muller, S. F. Lichtenthaler

Date Published: 21st Sep 2020

Publication Type: Journal

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