Dr. Matthew Andrusiak
Biological Sciences, University of California, San Diego
The genetic mutation and de-regulation of prion-like domain (PrLD) containing proteins is over-represented in human disease. Despite their role in human disease, little is known about how PrLD’s regulate protein function. PrLD-containing proteins are often capable of liquid-liquid phase separation (LLPS) resulting in the formation of non-membrane bound cellular compartments. The in vivo function and cellular mechanisms regulated by LLPS remain unknown. My work identified the PrLD coding gene tiar-2, a C. elegans member of the TIA1 family, as an intrinsic inhibitor of axon regeneration. TIAR-2 forms granules and inhibits axon regeneration in a dose-dependent manner. TIAR-2 undergoes LLPS in vitro and granules have liquid-features in vivo. Following axon injury, TIAR-2 granule number increases, and their liquid-like features are significantly reduced. Importantly, the PrLD of TIAR-2 is necessary and sufficient for its ability to inhibit regeneration and form granules. Post-translational modifications, such as phosphorylation, have been shown to act as molecular switches regulating LLPS. TIAR-2 is serine phosphorylated and this modification is required for TIAR-2 granule formation and function in axon regeneration. This work identified axonal injury as an acute cue that modulates the formation of LLPS granules and the function of the PrLD containing protein TIAR-2. Future research efforts will focus on understanding the role of prion-like domains in the regulation of biological outputs during nervous system and organismal development, as well as following neuronal injury.