Gratzer, S. | bioRxiv Science

bioRxiv2025

GPR17 modulates oligodendrocyte precursor cell maturation during development but has limited impact on myelin regeneration following demyelinating insults

Pharmacological enhancement of myelin regeneration is broadly recognized as the next frontier in therapeutic approaches for demyelinating diseases of the CNS such as multiple sclerosis. However, although several molecular targets for remyelination have been tested preclinically and in clinical trials, an efficacious and safe myelin repair treatment is yet to be developed. One promising molecular target to enhance myelin repair is the G protein-coupled receptor (GPCR) GPR17, which has been proposed to play a central role in the transition from early oligodendrocyte progenitor cells (OPC) into pre-myelinating oligodendrocytes. These findings are largely supported by studies using transgenic mice where GPR17 deletion results in developmental hypermyelination. Additionally, pharmacological modulation of GPR17 activity has been reported to enhance oligodendrocyte precursor cell (OPC) maturation and myelination. In our studies aimed to characterize and pharmacologically validate GPR17 as a viable target for drug development, we established by means of transcriptional profiling of GPR17 knockout versus wild type OPCs, that absence of this GPCR results in a gene signature revealing minor changes in myelin protein gene expression. Furthermore, blocking GPR17 receptor activity in OPC cultures using selective and potent antagonists or inverse agonists, results in limited enhancement of maturation and myelination in vitro. Importantly, remyelination in both the cuprizone and lysolecithin-induced demyelination models was not enhanced in the absence of GPR17. Our data demonstrate that GPR17 plays a minor role in OPC differentiation during development, and pharmacological modulation of its activity has a marginal effect on oligodendrocyte precursor maturation and myelin regeneration after injury.

neuroscience↗

bioRxiv2021

Time-resolved FRET screening identifies small molecular modifiers of mutant Huntingtin conformational inflexibility in patient-derived cells

Huntingtons disease (HD) is the most common monogenic neurodegenerative disease and is fatal. CAG repeat expansions in mutant Huntingtin (mHTT) exon 1 encode for polyglutamine (polyQ) stretches and influence age of onset and disease severity, depending on their length. mHTT is more structured compared to wild-type (wt) HTT, resulting in a decreased N-terminal conformational flexibility. mHTT inflexibility may contribute to both gain of function toxicity, due to increased mHTT aggregation propensity, but also to loss of function phenotypes, due to decreased interactions with binding partners. High-throughput-screening techniques to identify mHTT flexibility states and potential flexibility modifying small molecules are currently lacking. Here, we propose a novel approach for identifying small molecules that restore mHTTs conformational flexibility in human patient fibroblasts. We applied an antibody-based time-resolved Forster resonance energy transfer (TR-FRET) immunoassay, measuring endogenous HTT flexibility using two validated HTT-specific antibodies. The ratio of TR-FRET signal at 4{degrees}C and 20{degrees}C differs between wtHTT and mHTT and allowed to perform a high-throughput screening using HTT flexibility as a read-out. We identified several small molecules that can partially rescue mHTT inflexibility, presumably by altering HTT post-translational modifications. This novel screening approach has the potential to identify previously unknown HD drugs and drug targets.

neuroscience↗