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The RNA-binding protein TDP-43 forms intranuclear or cytoplasmic aggregates in age-related neurodegenerative diseases. Here we found that RNA-binding deficient TDP-43 (produced by neurodegeneration-causing mutations or post-translational acetylation in its RNA recognition motifs) drove TDP-43 de-mixing into intranuclear liquid spherical shells with liquid cores. We named these droplets anisosomes, whose shells exhibited birefringence, evidence of liquid crystal formation. Guided by mathematical modeling, we identified the major components of the liquid core to be HSP70 family chaperones, whose ATP-dependent activity maintained the liquidity of shells and cores. In vivo proteasome inhibition within neurons, to mimic aging-related reduction of proteasome activity, induced TDP-43-containing spherical shells. These structures converted into aggregates when ATP levels were reduced. Thus, acetylation, HSP70, and proteasome activities regulate TDP-43 phase separation and conversion into a gel/solid phase. 

In hypoxic stress conditions, glycolysis enzymes assemble into singular cytoplasmic granules called glycolytic (G) bodies. G body formation in yeast correlates with increased glucose consumption and cell survival. However, the physical properties and organizing principles that define G body formation are unclear. We demonstrate that glycolysis enzymes are non-canonical RNA binding proteins, sharing many common mRNA substrates that are also integral constituents of G bodies. Targeting nonspecific endoribonucleases to G bodies reveals that RNA nucleates G body formation and maintains its structural integrity. Consistent with a phase separation mechanism of biogenesis, recruitment of glycolysis enzymes to G bodies relies on multivalent homotypic and heterotypic interactions. Furthermore, G bodies fuse in vivo and are largely insensitive to 1,6-hexanediol, consistent with a hydrogel-like composition. Taken together, our results elucidate the biophysical nature of G bodies and demonstrate that RNA nucleates phase separation of the glycolysis machinery in response to hypoxic stress.