Structural characterization of the D290V mutation site in hnRNPA2 low-complexity–domain polymers

Abstract

SignificanceGenetic studies have shown that mutations of conserved Asp residues in three analogous heterogeneous ribonucleoproteins are causative of three neurological diseases. All three Asp residues map to domains of low complexity (LC) or intrinsic disorder. These domains form labile self-associated polymers as normal functional states, and the mutations abnormally enhance the stability of the polymers via heretofore unknown mechanisms. The present study gives evidence that the charged Asp residues are closely aligned in the polymer core and removal of electrostatic repulsion enhances polymer stability. These results may provide insight into other neurodegenerative diseases also caused by mutations in LC domains.

Transiently structured head domains control intermediate filament assembly

“…It has been interpreted that these aspartic acid residues impart repulsive, charge:charge interactions that are structure-destabilizing. Upon mutational change, often times to valine, the destabilizing interactions are removed, leading to enhanced selfassociation of the hnRNP LC domains and age-related neurodegenerative disease (Gui et al, 2019;Murray et al, 2018). We offer that human genetic studies are helping us to understand that evolution has established a proper balance of "designed instability" to self-associative, β-strand-enriched interactions that are of biologic utility to both RNA-binding proteins and intermediate filament proteins.…”

“…Expression of all GFP and mCherry fusion proteins was induced with 0.6 mM IPTG at 16 °C and cells were harvested 16 hours post-induction. Universal and amino acid-specific 13 C, 15 N labeling of NFL and desmin head domains was carried out as previously described (Murray et al, 2017;Murray et al, 2018).…”

“…The observation that crosspeak signals from individual residues cannot be resolved in the 2D ss-NMR spectra of head domain polymers suggests that the level of structural order within these polymers is lower than in cross-β polymers formed by the low-complexity domains of FUS and hnRNPA2 (Murray et al, 2017;Murray et al, 2018) or in certain pathogenic amyloid fibrils (Colvin et al, 2016;Tuttle et al, 2016;Van Melckebeke et al, 2010), where better-resolved crosspeaks were observed. The precise level of order in NFL and desmin head domain polymers cannot be determined.…”

“…Most amyloid-like, cross-β protein assemblies contain in-register parallel β-sheets (Colvin et al, 2016;Murray et al, 2017;Murray et al, 2018;Tuttle et al, 2016). Exceptions to this rule include β-solenoidal fibrils (Van Melckebeke et al, 2010), worm-like metastable "protofibrils" (Qiang et al, 2012), and fibrils formed by certain short peptides (Petkova et al, 2004).…”

Toxic PR poly-dipeptides encoded by the C9orf72 repeat expansion target Kapβ2 and dysregulate phase separation of low-complexity domains

“…Human genetics has provided us with some clues to how LC polymers become pathogenic. Specific mutations [D-to-V] in the LC domain of hnRNPs from amyotrophic lateral sclerosis (ALS) and multisystem proteinopathy (MSP) cause stable cross-β polymers (2,9). A hexanucleotide repeat expansion in C9orf72, the most prevalent form of familial ALS and frontotemporal dementia (FTD), produces the most toxic products-poly-dipeptides, proline:arginine (PR) and glycine:arginine (GR) (10,11).…”