Biology subjects

Hellwig, A.

Publications and source records attributed to Hellwig, A..

7 recordsLinked to original sources

bioRxiv2023

Growth/differentiation factor 15 controls primary cilia morphology in the murine ventricular-subventricular zone thereby affecting progenitor proliferation.

Growth/differentiation factor 15 (GDF15) and its receptor GDNF Family Receptor Alpha-Like (GFRAL) are expressed from embryonic development onwards in the germinal epithelium of the ganglionic eminence (GE), regulating proliferation and number of apical progenitors. However, the mechanisms underlying this regulation are not yet clear. We here show that GDF15 exerts this regulation by affecting ciliary signalling. Not only was GFRAL localized to primary cilia but, constitutive GDF15 ablation also led to shorter and thicker primary cilia. Lack of GDF15 affected the expression of histone deacetylase 6 (HDAC6) and ciliary adenylate cyclase 3 (ADCY3), thereby modifying acetylation of microtubules and endogenous Sonic Hedgehog (SHH) activation in neural progenitors. Application of exogenous GDF15 or pharmacological antagonism of HDAC6 or ADCY3 all increased cilia length and rescued proliferation and SHH signalling in mutant but not WT progenitors. Notably, HDAC6 expression and cilia length were changed only in the GE, were ciliary GFRAL localization was observed. In contrast, GFRAL was absent from primary cilia of hippocampal progenitors where GDF15 affected ADCY3 and SHH signalling, but not HDAC6 expression or cilia morphology. We conclude that ciliary GDF15 signalling regulates HDAC6 thereby affecting primary cilia elongation and proliferation in apical progenitors.

neuroscience↗

bioRxiv2022

Quantitative live cell imaging of a tauopathy model enables the identification of a polypharmacological drug candidate that restores physiological microtubule regulation

Tauopathies such as Alzheimers disease are characterized by the aggregation and increased phosphorylation of the microtubule-associated protein tau. The pathological changes in tau are closely linked to neurodegeneration, making tau a prime candidate for intervention. However, the multiple facets of tau function and the lack of cellular tauopathy models that could support mechanism-based drug development hampers progress. Here we report the development of a live-cell imaging approach to quantitatively monitor pathological changes of human tau as it interacts with axonal microtubules. We show that a full-length aggregation-prone tau construct exhibits reduced interaction with microtubules as it increasingly aggregates. Through chemoinformatic analyses, we identified 2-phenyloxazole (PHOX) derivatives as putative polypharmacological small molecules that inhibit tau aggregation and modulate tau phosphorylation. We found that PHOX15 restores the physiological microtubule interaction of aggregation-prone tau in neurons and inhibits the first phase of tau aggregation in vitro. Furthermore, we report that PHOX15 inhibits the tau kinases GSK3{beta} and Cdk5, alters the kinome activity of model neurons, and reduces tau phosphorylation at disease-relevant sites. Molecular dynamics simulations highlight cryptic channel-like pockets crossing tau protofilaments and indicate that the binding of PHOX15 in one of the channels reduces the protofilaments ability to adopt a PHF-like conformation. The data show that our imaging approach provides a useful tool for identifying compounds that modulate tau-microtubule interaction in axons. We demonstrate that a polypharmacological approach to simultaneously treat tau aggregation and tau phosphorylation is able to restore physiological microtubule regulation, identifying PHOX15 as a promising drug candidate to counteract tau-induced neurodegeneration.

neuroscience↗

bioRxiv2022

Challenges in Improving Genomic Literacy: Results from National and Regional Surveys of Genomic Knowledge, Attitudes, Concerns, and Behaviors

PurposeInformation about genomics is increasingly available to mainstream society, with more and more emphasis on using genomic information to make health care decisions. To determine how prepared people are to use this knowledge to make critical health-related decisions, we assessed the publics level of genomic literacy and whether this knowledge affects their engagement in behaviors related to genomics, such as getting genetic testing. MethodsA survey assessing perceived and actual knowledge, attitudes, concerns, sources of information, and behaviors related to genomics was administered to national and regional samples of participants. A hierarchical linear regression tested whether knowledge and attitudes predicted engagement in behaviors related to genomics. ResultsParticipants had good basic knowledge of genetics, though they were less familiar with the term "the human genome." They also displayed positive attitudes towards genomic research, despite expressing many concerns. Both greater knowledge and more positive attitudes significantly and independently predicted greater engagement in genetic testing and other related proactive health behaviors. ConclusionKnowledge and concerns about genomics impact the publics ability and willingness to obtain genetic testing and engage in other proactive health behaviors. The publics genomic literacy could be enhanced by integrating their knowledge (e.g of DNA) with broader concepts (e.g. the human genome and genomics) and how they relate to health. Future research is needed on interventions that do this, to improve the publics genomic literacy through relationships that build trust

scientific communication and education↗

bioRxiv2022

New motifs in Ndc1 mediating interaction with the Nup84 complex and nuclear membranes

The nuclear pore complex (NPC) embedded in the double nuclear membrane is built from ~30 different nucleoporins (Nups) in multiple copies, of which a few are integral nuclear membrane proteins. One of these transmembrane Nups is Ndc1, which is thought to play a role in interphase NPC assembly at the fused inner and outer nuclear membrane. In this study, we discovered a direct interaction of Ndc1s transmembrane domain with Nup120 and Nup133, members of the Y-complex that coats the nuclear pore membrane. In addition, we identified a so far unrecognized amphipathic helix (AH) in the C-terminal domain of Ndc1, which can bind to high curvature liposomes. When overexpressed in yeast this amphipathic motif is toxic and dramatically alters the intracellular membrane organization. Further genetic investigations revealed that Ndc1-AH functionally interacts with related motifs in the C-terminus of Nups Nup53 and Nup59, known to serve in nuclear pore membrane binding and link between NPC modules. This relationship could explain why the essential function of Ndc1 can be suppressed by deleting the amphipathic helix from Nup53. Our data indicate that nuclear membrane biogenesis dependent on a balanced ratio between amphipathic motifs in diverse nucleoporins is essential for interphase NPC biogenesis.

cell biology↗

bioRxiv2021

NECAB2 orchestrates an endosomal pathway of mitochondrial quality control at striatal synapses

Synaptic signaling depends on ATP generated by mitochondria. Due to extensive connectivity, the striatum is especially vulnerable to mitochondrial dysfunction and thus requires efficient mitochondrial quality control and repair. We found that global knockout of the neuronal calcium-binding protein 2 (NECAB2) in the mouse causes loss of striatal synapses and behavioral phenotypes related to striatal dysfunction such as reduced motivation and altered sensory gating. Striatal mitochondria from Necab2 knockout mice are more abundant and smaller. They are characterized by increased respiration and superoxide production resulting in oxidative stress. This accumulation of dysfunctional mitochondria is caused by a defective assembly of mitochondria with early endosomes in a pathway that involves the small GTPase Rab5 and its guanine nucleotide exchange factor Alsin/ALS2. NECAB2 therefore participates in an endosomal pathway of mitochondrial stress response and repair important for striatal function.

neuroscience↗

bioRxiv2018

Core Proteome and Architecture of COPI Vesicles

Retrieval of escaped ER-residents and intra-Golgi transport is facilitated by coat protein complex I (COPI)-coated vesicles. Their formation requires the activated small GTPase ADP-ribosylation factor (Arf) and the coat complex coatomer. Here we assess the protein composition of COPI vesicles by combining stable isotope labeling with amino acids in cell culture (SILAC) with in vitro reconstitution of COPI vesicles from semi-intact cells (SIC) using the minimal set of recombinant coat proteins. This approach yields an unbiased picture of the proteome of these carriers. We define a set of ~40 proteins common to COPI vesicles produced from different human as well as murine cell lines. Almost all bona fide COPI vesicle proteins are either ER-Golgi cycling proteins or Golgi-residents, while only a minor portion of secreted proteins was found. Moreover, we have investigated a putative role of {gamma}- and {zeta}-COP as well as Arf isoforms in sorting and recruitment of specific proteins into COPI vesicles. As opposed to the related COPII system, all isoforms of coatomer and all COPI-forming isoforms of the small GTPase Arf produce COPI-coated vesicles with strikingly similar protein compositions. We present a model for the core architecture of COPI vesicles.

biochemistry↗

bioRxiv2018

Proteomic Profiling of Mammalian COPII Vesicles

Intracellular transport and homeostasis of the endomembrane system in eukaryotic cells depend on formation and fusion of vesicular carriers. COPII vesicles export newly synthesized secretory proteins from the endoplasmic reticulum (ER). They are formed by sequential recruitment of the small GTP binding protein Sar1, the inner coat complex Sec23/24, and the outer coat complex Sec13/31. In order to investigate the roles of mammalian Sec24 isoforms in cargo sorting, we have combined in vitro COPII vesicle reconstitutions with SILAC-based mass spectrometric analysis. This approach enabled us to identify the core proteome of mammalian COPII vesicles. Comparison of the proteomes generated from vesicles with different Sec24 isoforms confirms several established isoform-dependent cargo proteins, and identifies ERGIC1 and CNIH1 as novel Sec24C- and Sec24A-specific cargo proteins, respectively. Proteomic analysis of vesicles reconstituted with a Sec24C mutant, bearing a compromised binding site for the ER-to-Golgi QSNARE Syntaxin5, revealed that the SM/Munc18 protein SCFD1 binds to Syntaxin5 prior to its sorting into COPII vesicles. Furthermore, analysis of Sec24D mutants implicated in the development of a syndromic form of osteogenesis imperfecta showed sorting defects for the three ER-to-Golgi QSNAREs Syntaxin5, GS27, and Bet1.

biochemistry↗