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93 Publications visible to you, out of a total of 93
ATG4 family proteins drive phagophore growth independently of the LC3/GABARAP lipidation system.

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

White matter aging drives microglial diversity.

Abstract (Expand)

Aging results in gray and white matter degeneration, but the specific microglial responses are unknown. Using single-cell RNA sequencing from white and gray matter separately, we identified white … matter-associated microglia (WAMs), which share parts of the disease-associated microglia (DAM) gene signature and are characterized by activation of genes implicated in phagocytic activity and lipid metabolism. WAMs depend on triggering receptor expressed on myeloid cells 2 (TREM2) signaling and are aging dependent. In the aged brain, WAMs form independent of apolipoprotein E (APOE), in contrast to mouse models of Alzheimer's disease, in which microglia with the WAM gene signature are generated prematurely and in an APOE-dependent pathway similar to DAMs. Within the white matter, microglia frequently cluster in nodules, where they are engaged in clearing degenerated myelin. Thus, WAMs may represent a potentially protective response required to clear degenerated myelin accumulating during white matter aging and disease.

Authors: S. Safaiyan, S. Besson-Girard, T. Kaya, L. Cantuti-Castelvetri, L. Liu, H. Ji, M. Schifferer, G. Gouna, F. Usifo, N. Kannaiyan, D. Fitzner, X. Xiang, M. J. Rossner, M. Brendel, O. Gokce, M. Simons

Date Published: 7th Apr 2021

Publication Type: Journal

MicroRNAs from extracellular vesicles as a signature for Parkinson's disease.

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

Systematically defining selective autophagy receptor-specific cargo using autophagosome content profiling.

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

CRISPR-Mediated Induction of Neuron-Enriched Mitochondrial Proteins Boosts Direct Glia-to-Neuron Conversion.

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

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

Adult neural stem cell activation in mice is regulated by the day/night cycle and intracellular calcium dynamics.

Abstract (Expand)

Neural stem cells (NSCs) in the adult brain transit from the quiescent state to proliferation to produce new neurons. The mechanisms regulating this transition in freely behaving animals are, however, … poorly understood. We customized in vivo imaging protocols to follow NSCs for several days up to months, observing their activation kinetics in freely behaving mice. Strikingly, NSC division is more frequent during daylight and is inhibited by darkness-induced melatonin signaling. The inhibition of melatonin receptors affected intracellular Ca<sup>2+</sup> dynamics and promoted NSC activation. We further discovered a Ca<sup>2+</sup> signature of quiescent versus activated NSCs and showed that several microenvironmental signals converge on intracellular Ca<sup>2+</sup> pathways to regulate NSC quiescence and activation. In vivo NSC-specific optogenetic modulation of Ca<sup>2+</sup> fluxes to mimic quiescent-state-like Ca<sup>2+</sup> dynamics in freely behaving mice blocked NSC activation and maintained their quiescence, pointing to the regulatory mechanisms mediating NSC activation in freely behaving animals.

Authors: Archana Gengatharan, Sarah Malvaut, Alina Marymonchyk, Majid Ghareghani, Marina Snapyan, Judith Fischer-Sternjak, Jovica Ninkovic, Magdalena Götz, Armen Saghatelyan

Date Published: 4th Feb 2021

Publication Type: Journal

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