Biology subjects

Lichtenthaler, S. F.

Publications and source records attributed to Lichtenthaler, S. F..

27 records · Page 2Linked to original sources

bioRxiv2021

Proteomics of spatially identified tissues in whole organs

Spatial molecular profiling of complex tissues is essential to investigate cellular function in physiological and pathological states. However, methods for molecular analysis of biological specimens imaged in 3D as a whole are lacking. Here, we present DISCO-MS, a technology combining whole-organ imaging, deep learning-based image analysis, and ultra-high sensitivity mass spectrometry. DISCO-MS yielded qualitative and quantitative proteomics data indistinguishable from uncleared samples in both rodent and human tissues. Using DISCO-MS, we investigated microglia activation locally along axonal tracts after brain injury and revealed known and novel biomarkers. Furthermore, we identified initial individual amyloid-beta plaques in the brains of a young familial Alzheimers disease mouse model, characterized the core proteome of these aggregates, and highlighted their compositional heterogeneity. Thus, DISCO-MS enables quantitative, unbiased proteome analysis of target tissues following unbiased imaging of entire organs, providing new diagnostic and therapeutic opportunities for complex diseases, including neurodegeneration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/466753v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1e37035org.highwire.dtl.DTLVardef@dbaa98org.highwire.dtl.DTLVardef@19cece1org.highwire.dtl.DTLVardef@183c032_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIDISCO-MS combines tissue clearing, whole-organ imaging, deep learning-based image analysis, and ultra-high sensitivity mass spectrometry C_LIO_LIDISCO-MS yielded qualitative and quantitative proteomics data indistinguishable from fresh tissues C_LIO_LIDISCO-MS enables identification of rare pathological regions & their subsequent molecular analysis C_LIO_LIDISCO-MS revealed core proteome of plaques in 6 weeks old Alzheimer s disease mouse model Supplementary Video can be seen at: http://discotechnologies.org/DISCO-MS/ C_LI

bioengineering↗

bioRxiv2020

Highly efficient intercellular spreading of protein misfolding mediated by viral ligand - receptor interactions

Pathological protein aggregates associated with neurodegenerative diseases have the ability to transmit to unaffected cells, thereby templating their own aberrant conformation onto soluble proteins of the same kind. Proteopathic seeds can be released into the extracellular space, secreted in association with extracellular vesicles (EV) or exchanged by direct cell-to-cell contact. The extent to which each of these pathways contributes to the prion-like spreading of protein misfolding is unclear. Exchange of cellular cargo by both direct cell-to-cell contact as well as via EV depends on receptor-ligand interactions and subsequent release of cargo into the cytosol. We hypothesized that enabling these interactions through viral ligands enhances the aggregate-inducing capacity of EV-associated proteopathic seeds. Using different cellular models propagating model prion-like protein aggregates, mouse-adapted prions or pathogenic Tau aggregates, we demonstrate that vesicular stomatitis virus glycoprotein and SARS-CoV-2 spike S increase protein aggregate induction by direct cell-to-cell contact or via viral glycoprotein-decorated EV. Thus, receptor-ligand interactions are major determinants of intercellular aggregate dissemination. Further, our data raise the intriguing possibility that acute or latent viral infections contribute to proteopathic seed spreading by facilitating intercellular cargo transfer. HIGHLIGHTSO_LIDifferent types of proteopathic seeds are secreted in association with extracellular vesicles C_LIO_LIReceptor-ligand interactions are important drivers of direct cell-to-cell and extracellular vesicle-mediated spreading of protein misfolding C_LIO_LIViral glycoproteins mediating attachment and membrane fusion strongly enhance aggregate inducing capacity in recipient cells C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=191 HEIGHT=200 SRC="FIGDIR/small/173070v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1735b86org.highwire.dtl.DTLVardef@7ddaf5org.highwire.dtl.DTLVardef@b222aborg.highwire.dtl.DTLVardef@1022dd6_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Amyloid-beta mediates homeostatic synaptic plasticity

The physiological role of the amyloid-precursor protein (APP) is insufficiently understood. Recent work has implicated APP in the regulation of synaptic plasticity. Substantial evidence exists for a role of APP and its secreted ectodomain APPs in Hebbian plasticity. Here, we addressed the relevance of APP in homeostatic synaptic plasticity using organotypic tissue cultures of APP-/- mice. In the absence of APP, dentate granule cells failed to strengthen their excitatory synapses homeostatically. Homeostatic plasticity is rescued by amyloid-{beta} (A{beta}) and not by APPs, and it is neither observed in APP+/+ tissue treated with {beta}- or {gamma}-secretase inhibitors nor in synaptopodin-deficient cultures lacking the Ca2+-dependent molecular machinery of the spine apparatus. Together, these results suggest a role of APP processing via the amyloidogenic pathway in homeostatic synaptic plasticity, representing a function of relevance for brain physiology as well as for brain states associated with increased A{beta} levels.

neuroscience↗

bioRxiv2020

Quantitative secretome analysis establishes the cell type-resolved mouse brain secretome

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 method (hiSPECS). 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, brain function and to identify cell type-specific biomarkers for CNS diseases.

neuroscience↗

bioRxiv2020

Furin controls β cell function via mTORC1 signaling

Furin is a proprotein convertase (PC) responsible for proteolytic activation of a wide array of precursor proteins within the secretory pathway. It maps to the PRC1 locus, a type 2 diabetes susceptibility locus, yet its specific role in pancreatic {beta} cells is largely unknown. The aim of this study was to determine the role of furin in glucose homeostasis. We show that furin is highly expressed in human islets, while PCs that potentially could provide redundancy are expressed at considerably lower levels. {beta} cell-specific furin knockout ({beta}furKO) mice are glucose intolerant, due to smaller islets with lower insulin content and abnormal dense core secretory granule morphology. RNA expression analysis and differential proteomics on {beta}furKO islets revealed activation of Activating Transcription Factor 4 (ATF4), which was mediated by mammalian target of rapamycin C1 (mTORC1). {beta}furKO cells show impaired cleavage of the essential V-ATPase subunit Ac45, and by blocking this pump in {beta} cells the mTORC1 pathway is activated. Furthermore, {beta}furKO cells show lack of insulin receptor cleavage and impaired response to insulin. Taken together, these results suggest a model of mTORC1-ATF4 hyperactivation in {beta} cells lacking furin, which causes {beta} cell dysfunction.

physiology↗

bioRxiv2019

Fibrillar Aβ triggers microglial proteome alterations and dysfunction in Alzheimer mouse models

Microglial dysfunction is a key pathological feature of Alzheime[r]s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their functional consequences. Here, we performed an in-depth and time-resolved proteomic characterization of microglia in two mouse models of amyloid {beta} (A{beta}) pathology, the overexpression APPPS1 and the knock-in APP-NL-G-F (APP-KI) model. We identified a large panel of Microglial A{beta} Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations during early, middle and advanced stages of A{beta} deposition. Although both mouse models display severe microglial alterations at late stages of amyloid pathology, MARP signatures occur earlier in the APPPS1 mice. Strikingly, the kinetic differences in proteomic profiles correlated with the presence of fibrillar A{beta}, rather than dystrophic neurites, suggesting that fibrillar A{beta} aggregates are the main drivers of the AD-associated microglial phenotype and the observed functional decline. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.

neuroscience↗

bioRxiv2019

Tetraspanin Tspan15 is an essential subunit of an ADAM10 scissor complex

A disintegrin and metalloprotease 10 (ADAM10) is essential for embryonic development and impacts on diseases such as cancer, Alzheimers and inflammatory diseases. ADAM10 is a molecular scissor that proteolytically cleaves the extracellular region from over 100 substrates, including Notch, amyloid precursor protein, cadherins, growth factors and chemokines. ADAM10 was recently proposed to function as six distinct scissors with different substrates, depending on its association with one of six regulatory tetraspanins, termed TspanC8s. However, it remains unclear to what degree ADAM10 function is critically dependent on a TspanC8 partner. To address this, we generated the first monoclonal antibodies to Tspan15 as a model TspanC8. These were used to show that ADAM10 is the principal Tspan15-interacting protein, that Tspan15 expression requires ADAM10 in cell lines and primary cells, and that a synthetic ADAM10/Tspan15 fusion protein is a functional scissor. Together these findings suggest that ADAM10 exists as an intimate ADAM10/TspanC8 scissor complex.

cell biology↗

bioRxiv2019

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

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, consequences of NPC1 loss on microglial function remain uncharacterized. Here, we provide an in-depth characterization of microglial proteomic signatures and phenotypes in a NPC1-deficient (Npc1-/-) murine model and patient blood-derived macrophages. We demonstrate enhanced phagocytic uptake and impaired lipid trafficking in Npc1-/- microglia that precede neuronal death. Loss of NPC1 compromises microglial developmental functions as revealed by increased synaptic pruning and deficient myelin turnover. Undigested myelin accumulates within multi-vesicular bodies of Npc1-/- microglia while lysosomal degradation remains preserved. To translate our findings to human disease, we generated novel ex vivo assays using patient macrophages that displayed similar proteomic disease signatures and lipid trafficking defects as murine Npc1-/- microglia. Thus, peripheral macrophages provide a novel promising clinical tool for monitoring disease progression and therapeutic efficacy in NPC patients. Our study underscores an essential role for NPC1 in immune cells and implies microglial therapeutic potential.

neuroscience↗

bioRxiv2019

CNTNAP2 ectodomain, detected in neuronal and CSF sheddomes, modulates Ca2+ dynamics and network synchrony

SUMMARYWhile many neuronal membrane-anchored proteins undergo proteolytic cleavage, little is known about the biological significance of neuronal ectodomain shedding. Using mass spectrometry (MS)-based proteomics, we showed that the neuronal sheddome mirrors human cerebrospinal fluid (hCSF). Among shed synaptic proteins in hCSF was the ectodomain of CNTNAP2 (CNTNAP2-ecto), a risk factor for neurodevelopmental disorders (NDD). Using structured-illumination microscopy (SIM), we mapped the spatial organization of neuronal CNTNAP2-ecto shedding. Using affinity chromatography followed by MS, we identified the ATP2B/PMCA Ca2+ extrusion pumps as novel CNTNAP2-ecto binding partners. CNTNAP2-ecto coimmunoprecipitates with PMCA2, a known autism risk factor, and enhances its activity, thereby modulating neuronal Ca2+ levels. Finally, we showed that CNTNAP2-ecto regulates neuronal network synchrony in primary cultures and brain slices. These data provide new insights into the biology of synaptic ectodomain shedding and reveal a novel mechanism of regulation of Ca2+ homeostasis and neuronal network synchrony.

neuroscience↗