Date of Award
Summer 2025
Document Type
Open Access Dissertation
Department
Biological Sciences
First Advisor
Jeffery L. Twiss
Abstract
Local protein synthesis is essential for neuronal function, allowing axons to rapidly and autonomously respond to environmental cues without relying on the distant soma. This spatially restricted mRNA translation supports critical cellular activities including growth cone guidance, synaptic plasticity, and axonal maintenance. Although how axonal protein synthesis is regulated remains largely unknown, research over the past decade points to RNA regulons - functional groups of mRNAs that are co-regulated by specific RNA-binding proteins (RBPs) - as a means to orchestrate the regulation of mRNA cohorts encoding proteins with shared or complimentary functions. Recent evidence suggests that stress granules (SGs) and SG-like protein-RNA aggregates may serve to orchestrate translational mRNA regulons after axonal injury and during axon regeneration. SGs and SG-like aggregate are membraneless assemblies of RNA and RNA-binding proteins (RBPs) that transiently sequester mRNAs from the translational machinery. The core SG protein G3BP1 plays a central role in the SGs dynamic in axons, where it mediates the sequestration of mRNAs before and after axotomy, thereby modulating their translation both in naïve, injury, and regenerating conditions. G3BP1 forms granules through liquid–liquid phase separation (LLPS), and G3BP1’s LLPS threshold is modulated by post-translational modifications. Phosphorylation at serine 149 increases the threshold for LLPS, leading to SG disassembly and promoting axon growth. Acetylation of human G3BP1 at lysine 376 has also been shown to disrupt SG formation in non-neuronal cells; however, whether this modification occurs in neurons or contributes to neuronal growth remains to be determined. Here, I show that rodent G3BP1 undergoes acetylation at lysine 374 (K374) following nerve injury. Expression of an acetyl-mimetic G3BP1K374Q enhances neuronal axon growth in culture and promotes regeneration of injured peripheral nerves in vivo. Notably, this modification selectively increases local protein synthesis within axons. G3BP1 has previously been reported to be deacetylated by HDAC6. In line with this, we find that pharmacological inhibition of HDAC6 increases mouse and rat G3BP1 acetylation at lysine 374 in dorsal root ganglion (DRG) axons and enhances axon growth. In contrast to report that p300/CBP serves as the human G3BP1 acetyl transferase in U2OS cells (Gal, Chen et al. 2019, Hafner, Donlin-Asp et al. 2019), we find that depletion of Elongator Complex Protein 3 (ELP3) from neurons increases axonal G3BP1 granules, decreases acetylated rodent G3BP1 in axons and decreases axon growth in cultured DRG neurons. Following pheripheral nerve injury, ELP3-depleted axons appear to regenerate slower than normal with only few axons regenerating pass the crush site. Surprisingly, ELP3-depleted neurons show degeneration of proximal, cell body-connected axons following axotomy. This axon degeneration is prevented by expression of the acetylmimetic G3BP1. Together, our data emphasize the critical role of ELP3-mediated G3BP1 acetylation in promoting axonal growth, regeneration, and neuronal resilience, highlighting a novel post-transcriptional mechanism with therapeutic potential for enhancing nerve repair.
Rights
© 2025, Irene Dalla Costa
Recommended Citation
Dalla Costa, I.(2025). The Role of G3BP1 Modifications in Modulating Axonal RNA Translation. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/8520