Effects of Mutations on the Aggregation Propensity of the Human Prion-Like Protein hnRNPA2B1

Abstract

Hundreds of human proteins contain prion-like domains, which are a subset of low-complexity domains with high amino acid compositional similarity to yeast prion domains. A recently characterized mutation in the prion-like domain of the human heterogeneous nuclear ribonucleoprotein hnRNPA2B1 increases the aggregation propensity of the protein and causes multisystem proteinopathy. The mutant protein forms cytoplasmic inclusions when expressed in , the mutation accelerates aggregation, and the mutant prion-like domain can substitute for a portion of a yeast prion domain in supporting prion activity. To examine the relationship between amino acid sequence and aggregation propensity, we made a diverse set of point mutations in the hnRNPA2B1 prion-like domain. We found that the effects on prion formation in and aggregation could be predicted entirely based on amino acid composition. However, composition was an imperfect predictor of inclusion formation in ; while most mutations showed similar behaviors in yeast,, and in , a few showed anomalous behavior. Collectively, these results demonstrate the significant progress that has been made in predicting the effects of mutations on intrinsic aggregation propensity while also highlighting the challenges of predicting the effects of mutations in more complex organisms.

Perfecting prediction of mutational impact on the aggregation propensity of the ALS‐associated hnRNPA2 prion‐like protein

“…In both cases, the D276V mutation behaves as an outlier. This mutation has a much lower impact on the experimental prion propensity of hnRNPA2 PrLD than D290V , which argues against composition alone accounting for the aggregation of this PrLD. Indeed, PAPA predicts the same aggregation potential for both mutations.…”

“…The prion‐promoting activity induced by the different mutations was easily tracked by monitoring the ability of Ade − yeast cells (holding a premature stop codon in the ade1 gene) to grow in adenine‐defective media when they overexpress aggregation‐prone hnRNPA2 PrLD‐Sup35 fusions, rendering an Ade + phenotype. For instance, the D290V mutant supports prion formation, whereas the WT does not . Both ZipperDB and PAPA algorithms were shown previously to predict these relative prion propensities and thus the pathogenic impact of the D290V mutation .…”

“…B). PAPA performed much better and this led the authors to propose that the changes in PrLD composition upon mutation would alone account for the observed phenotypes and thus, in contrast to what occurs in classical amyloids, the presence of strong steric zippers is neither necessary nor sufficient for the pathogenic aggregation of these kinds of human proteins . Here, we reanalyze these data to provide a different view of the determinants underlying the pathogenic aggregation of human prion‐like proteins.…”

Protein Engineering Reveals Mechanisms of Functional Amyloid Formation in Pseudomonas aeruginosa Biofilms

“…Recent advances in prediction tools have enabled accurate prediction of intrinsic aggregation propensity based on specific mutations in mammalian amyloid proteins [45, 46], but here we have extended this approach to the relatively unexplored realm of bacterial amyloids. Taken together, our findings identify segments in the P. aeruginosa FapC sequence that are implicated in amyloid fibril formation.…”

RNA-binding proteins with prion-like domains in health and disease

“…Indeed, both hnRNPA1 and hnRNPA2 form fibrils in vitro that are self-seeding (i.e. can nucleate the aggregation of soluble protein), thereby reducing the lag phase of assembly, and the disease-associated mutations greatly accelerate fibrillization [101,132]. In vitro , the mutant proteins are capable of seeding their own assembly and the assembly of the corresponding wild-type protein [101], providing a potential explanation for the genetic dominance of MSP mutations.…”