Tyrosine phosphorylation regulates hnRNPA2 granule protein partitioning & reduces neurodegeneration

Summary

mRNA transport in neurons is a ubiquitous process but has been often overlooked as a contributor to disease. Mutations of transport granule protein hnRNPA2 cause hereditary proteinopathy of neurons, myocytes, and bone. Here, we examine transport granule component specificity, assembly/disassembly, and the link to neurodegeneration. hnRNPA2 transport granule components hnRNPF and ch-TOG interact weakly with hnRNPA2 yet they each partition specifically into hnRNPA2 liquid phases. hnRNPA2 tyrosine phosphorylation dissociates granule interactions by reducing hnRNPA2 phase separation and preventing partitioning of hnRNPF and ch-TOG; tyrosine phosphorylation also decreases aggregation of hnRNPA2 disease mutants. A C. elegans model of hnRNPA2 D290V-associated neurodegeneration exhibits TDP-43 ortholog-dependent glutamatergic neurodegeneration. Expression of the tyrosine kinase that phosphorylates hnRNPA2 reduces glutamatergic neurodegeneration. The evidence for specific partitioning of granule components as well as disruption of these interactions and reduction of neurodegeneration by tyrosine phosphorylation suggest transport granule biology has a role in the pathogenesis of neurodegeneration.