ABSTRACT
Huntington's disease (HD) is an incurable neurodegenerative disorder caused by a CAG expansion in the huntingtin gene (HTT). Post-translational modifications of huntingtin protein (HTT), such as phosphorylation, acetylation and ubiquitination, have been implicated in HD pathogenesis. Arginine methylation/dimethylation is an important modification with an emerging role in neurodegeneration; however, arginine methylation of HTT remains largely unexplored. Here we report nearly two dozen novel arginine methylation/dimethylation sites on the endogenous HTT from human and mouse brain and human cells suggested by mass spectrometry with data-dependent acquisition. Targeted quantitative mass spectrometry identified differential arginine methylation at specific sites in HD patient-derived striatal precursor cell lines compared to normal controls. We found that HTT can interact with several type I protein arginine methyltransferases (PRMTs) via its N-terminal domain. Using a combination of in vitro methylation and cell-based experiments, we identified PRMT4 (CARM1) and PRMT6 as major enzymes methylating HTT at specific arginines. Alterations of these methylation sites had a profound effect on biochemical properties of HTT rendering it less soluble in cells and affected its liquid-liquid phase separation and phase transition patterns in vitro. We found that expanded HTT 1-586 fragment can form liquid-like assemblies, which converted into solid-like assemblies when the R200/205 methylation sites were altered. Methyl-null alterations increased HTT toxicity to neuronal cells, while overexpression of PRMT 4 and 6 was beneficial for neuronal survival. Thus, arginine methylation pathways that involve specific HTT-modifying PRMT enzymes and modulate HTT biochemical and toxic properties could provide targets for HD-modifying therapies.
Subject(s)
Arginine , Huntington Disease , Animals , Arginine/genetics , Arginine/metabolism , Humans , Huntingtin Protein/genetics , Huntingtin Protein/metabolism , Huntington Disease/pathology , Methylation , Mice , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Protein Processing, Post-Translational/genetics , Protein-Arginine N-Methyltransferases/genetics , Protein-Arginine N-Methyltransferases/metabolism , SolubilityABSTRACT
Manufacturing technologies for biologics rely on large, centralized, good-manufacturing-practice (GMP) production facilities and on a cumbersome product-distribution network. Here, we report the development of an automated and portable medicines-on-demand device that enables consistent, small-scale GMP manufacturing of therapeutic-grade biologics on a timescale of hours. The device couples the in vitro translation of target proteins from ribosomal DNA, using extracts from reconstituted lyophilized Chinese hamster ovary cells, with the continuous purification of the proteins. We used the device to reproducibly manufacture His-tagged granulocyte-colony stimulating factor, erythropoietin, glucose-binding protein and diphtheria toxoid DT5. Medicines-on-demand technology may enable the rapid manufacturing of biologics at the point of care.
