Tyrosine phosphorylation regulates hnRNPA2 granule protein partitioning and reduces neurodegeneration

Abstract

mRNA transport in neurons requires formation of transport granules containing many protein components, and subsequent alterations in phosphorylation status can release transcripts for translation. Further, mutations in a structurally disordered domain of the transport granule protein hnRNPA2 increase its aggregation and cause hereditary proteinopathy of neurons, myocytes, and bone. We examine in vitro hnRNPA2 granule component phase separation, partitioning specificity, assembly/disassembly, and the link to neurodegeneration. Transport granule components hnRNPF and ch-TOG interact weakly with hnRNPA2 yet partition specifically into liquid phase droplets with the low complexity domain (LC) of hnRNPA2, but not FUS LC. In vitro hnRNPA2 tyrosine phosphorylation reduces hnRNPA2 phase separation, prevents partitioning of hnRNPF and ch-TOG into hnRNPA2 LC droplets, and decreases aggregation of hnRNPA2 disease variants. The expression of chimeric hnRNPA2 D290V in Caenorhabditis elegans results in stress-induced glutamatergic neurodegeneration; this neurodegeneration is rescued by loss of tdp-1, suggesting gain-of-function toxicity. The expression of Fyn, a tyrosine kinase that phosphorylates hnRNPA2, reduces neurodegeneration associated with chimeric hnRNPA2 D290V. These data suggest a model where phosphorylation alters LC interaction specificity, aggregation, and toxicity.

Post-Translational Modifications Modulate Proteinopathies of TDP-43, FUS and hnRNP-A/B in Amyotrophic Lateral Sclerosis

“…In the case of hnRNP-A2, Tyr-phosphorylation alters the propensity of the protein to undergo LLPS in vitro , prevents partitioning of granule components and hinders aggregation of mutants associated with neurodegenerative disorders. Moreover, different phosphorylation events in the same domain may elicit different effects offering the possibility of tuning protein assemblies ( Ryan et al, 2021 ). C. elegans experiments have identified FYN kinase as a candidate for hnRNP-A2 phosphorylation ( Ryan et al, 2021 ).…”

“…Moreover, different phosphorylation events in the same domain may elicit different effects offering the possibility of tuning protein assemblies ( Ryan et al, 2021 ). C. elegans experiments have identified FYN kinase as a candidate for hnRNP-A2 phosphorylation ( Ryan et al, 2021 ). Indeed, Tyr phosphomimetic mutations, i.e., substitutions with aspartic or glutamic acid that mimic the phosphate negative charge, prevent partitioning in droplets of hnRNP-F and ch-TOG, two molecular partners of hnRNP-A2, while Ser phosphomimetic ones do not ( Ryan et al, 2021 ).…”

The Intrinsically Disordered Region of Coronins Fine-tunes Oligomerization and Actin Polymerization

“…As none of the contact probability values are larger than 0.5, the maximum value on the scale of contact probability is changed from 0 to 0.5 for better contrast. Following the approach of Ryan et al 145 , the inter-residue distance cut-off for a contact to be formed is 𝜎 𝑖𝑗 as defined above. In addition to the original motif-averaged probability map, a motif contact difference map (Figure 7-figure supplement 2E, F; Figure 7I and J) was constructed to present the contact probability differences at different contact pairs for two proteins (e.g.…”

From Prions to Stress Granules: Defining the Compositional Features of Prion-Like Domains That Promote Different Types of Assemblies

“…Finally, it is important to note that because different PrLDs are likely recruited to stress granules by distinct mechanisms, the general trends that have emerged from screens of stress granule-associated PrLDs, or from studies of individual PrLDs, may not apply to all PrLDs. A recent study examining phase separation by components of hnRNPA2-containing transport granules highlights this challenge [149]. In these experiments, hnRNPF, a PrLDcontaining protein found in hnRNPA2 granules, did not efficiently phase-separate on its own.…”