Biology subjects

Duennwald, M.

Publications and source records attributed to Duennwald, M..

5 recordsLinked to original sources

bioRxiv2021

A yeast model of the ALS protein Matrin3 uncovers Hsp90 and its co-chaperone Sti1 as modifiers of misfolding and toxicity

The MATR3 gene encoding the protein Matrin3 is implicated in the pathogenesis of the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Matrin3 forms neuronal cytoplasmic and nuclear inclusions in ALS-affected neurons. Additionally, 13 heterozygous missense mutations in MATR3 are identified in ALS patients. To further explore Matrin3 misfolding and toxicity, we established and characterized a yeast model. We demonstrate that wild type Matrin3 and the ALS-associated variant F115C are toxic and form inclusions in yeast. Our further characterization uncovers substantial modification of Matrin3 toxicity and inclusion formation by Hsp90 and its co-chaperones, specifically Sti1. Thus, our study demonstrates how specific branches of cellular protein quality control regulate the misfolding and toxicity of Matrin3. Summary StatementWe established and characterized a yeast model expressing human Matrin3, a protein implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). Using this yeast model and mammalian neuronal cells, we showed that Matrin3 mislocalizes and forms inclusions, is cytotoxic, and increases sensitivity to cellular stress. We also uncovered that Hsp90 and particularly its co-chaperone Sti1 alter Matrin3 toxicity.

molecular biology↗

bioRxiv2020

Hsp90 and its co-chaperone Sti1 control TDP-43 misfolding and toxicity

Protein misfolding is a central feature of most neurodegenerative diseases. Molecular chaperones can modulate the toxicity associated with protein misfolding, but it remains elusive which molecular chaperones and co-chaperones interact with specific misfolded proteins. TDP-43 misfolding and inclusion formation is a hallmark of amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases. Using yeast and mammalian neuronal cells we find that Hsp90 and its co-chaperones have a strong capacity to alter TDP-43 misfolding, inclusion formation, aggregation, and cellular toxicity. Our data also demonstrate that impaired Hsp90 function sensitizes cells to TDP-43 toxicity. We further show that the co-chaperone Sti1 specifically interacts with and modulates TDP-43 toxicity in a dose-dependent manner. Our study thus uncovers a previously unrecognized tie between Hsp90, Sti1, TDP-43 misfolding, and its cellular toxicity.

cell biology↗

bioRxiv2019

Automated Quantification of Enlarged Perivascular Spaces in Clinical Brain MRI across Sites

Enlarged perivascular spaces (PVS) are structural brain changes visible in MRI, and are a marker of cerebral small vessel disease. Most studies use time-consuming and subjective visual scoring to assess these structures. Recently, automated methods to quantify enlarged perivascular spaces have been proposed. Most of these methods have been evaluated only in high resolution scans acquired in controlled research settings. We evaluate and compare two recently published automated methods for the quantification of enlarged perivascular spaces in 76 clinical scans acquired from 9 different scanners. Both methods are neural networks trained on high resolution research scans and are applied without fine-tuning the networks parameters. By adapting the preprocessing of clinical scans, regions of interest similar to those computed from research scans can be processed. The first method estimates only the number of PVS, while the second method estimates simultaneously also a high resolution attention map that can be used to detect and segment PVS. The Pearson correlations between visual and automated scores of enlarged perivascular spaces were higher with the second method. With this method, in the centrum semiovale, the correlation was similar to the inter-rater agreement, and also similar to the performance in high resolution research scans. Results were slightly lower than the inter-rater agreement for the hippocampi, and noticeably lower in the basal ganglia. By computing attention maps, we show that the neural networks focus on the enlarged perivascular spaces. Assessing the burden of said structures in the centrum semiovale with the automated scores reached a satisfying performance, could be implemented in the clinic and, e.g., help predict the bleeding risk related to cerebral amyloid angiopathy.

neuroscience↗

bioRxiv2018

Sfp1 regulates the SAGA component Tra1 in response to proteotoxic stress in Saccharomyces cerevisiae

Proteotoxic stress triggers transcriptional responses that allow cells to compensate for the accumulation of toxic misfolded proteins. Chromatin remodeling regulates gene expression in response to the accumulation of misfolded polyQ proteins associated with Huntingtons disease (HD). Tra1 is an essential component of both the SAGA/SLIK and NuA4 transcription co-activator complexes and is linked to multiple cellular processes associated with misfolded protein stress, including the heat shock response. Cells with compromised Tra1 activity display phenotypes distinct from deletions encoding components of the SAGA and NuA4 complexes, indicating a potentially unique regulatory role of Tra1 in the cellular response to protein misfolding. Here, we employed a yeast model of HD to define how the expression of toxic polyQ expansion proteins affects Tra1 expression and function. Expression of expanded polyQ proteins, mimics deletion of SAGA/NuA4 components and results in growth defects under stress conditions. Moreover, deleting genes encoding SAGA and, to a lesser extent, NuA4 components exacerbates polyQ toxicity. Also, cells carrying a mutant Tra1 allele displayed increased sensitivity to polyQ toxicity. Interestingly, expression of polyQ proteins also upregulated the expression of TRA1 and other genes encoding SAGA components, revealing a feedback mechanism aimed at maintaining Tra1and SAGA functional integrity. Moreover, deleting the TORC1 (Target of Rapamycin) effector SFP1 specifically abolished upregulation of TRA1 upon expression of polyQ proteins. While Sfp1 is known to adjust ribosome biogenesis and cell size in response to stress, we identified a new role for Sfp1 in the control of Tra1, linking TORC1 and cell growth regulation to functions of the SAGA acetyltransferase complex during misfolded protein stress.

genetics↗

bioRxiv2018

A hypomorphic Stip1 allele reveals the requirement for chaperone networks in mouse development and aging

Chaperone networks are dysregulated with aging and neurodegenerative disease, but whether compromised Hsp70/Hsp90 chaperone function directly contributes to neuronal degeneration is unknown. Stress-inducible phosphoprotein-1 (STI1; STIP1; HOP) is a co-chaperone that simultaneously interacts with Hsp70 and Hsp90, but whose function in vivo remains poorly understood. To investigate the requirement of STI1-mediated regulation of the chaperone machinery in aging we combined analysis of a mouse line with a hypomorphic Stip1 allele, with a neuronal cell line lacking STI1 and in-depth analyses of chaperone genes in human datasets. Loss of STI1 function severely disturbed the Hsp70/Hsp90 machinery in vivo, and all client proteins tested and a subset of cochaperones presented decreased levels. Importantly, mice expressing a hypomorphic STI1 allele showed spontaneous age-dependent hippocampal neurodegeneration, with consequent spatial memory deficits. STI1 is a critical node for the chaperone network and it can contribute to age-dependent hippocampal neurodegeneration.

cell biology↗