Axonal G3BP1 stress granule protein limits axonal mRNA translation and nerve regeneration

Pabitra K Sahoo,Sharmina Miller-Randolph,Terika Smith,Edsel A Pena,Seung Joon Lee,Tammy Szu-Yu Ho,Poonam B Jaiswal,Elizabeth E Taylor,Arthur W English,Stefanie Alber,Anatoly Urisman,Amar N Kar,Bhagat Singh,Jeffery L Twiss,Clifford J Woolf,Shreya Chand,Alma L Burlingame,Mike Fainzilber

doi:10.1038/s41467-018-05647-x

Abstract

Critical functions of intra-axonally synthesized proteins are thought to depend on regulated recruitment of mRNA from storage depots in axons. Here we show that axotomy of mammalian neurons induces translation of stored axonal mRNAs via regulation of the stress granule protein G3BP1, to support regeneration of peripheral nerves. G3BP1 aggregates within peripheral nerve axons in stress granule-like structures that decrease during regeneration, with a commensurate increase in phosphorylated G3BP1. Colocalization of G3BP1 with axonal mRNAs is also correlated with the growth state of the neuron. Disrupting G3BP functions by overexpressing a dominant-negative protein activates intra-axonal mRNA translation, increases axon growth in cultured neurons, disassembles axonal stress granule-like structures, and accelerates rat nerve regeneration in vivo.

Highlights

Critical functions of intra-axonally synthesized proteins are thought to depend on regulated recruitment of mRNA from storage depots in axons
Axonal G3BP1 signals appeared to show higher colocalization with other Stress granules (SG) components compared with components of processing bodies (PB) that are linked to RNA degradation (Fig. 1b)
Colocalization of axonal G3BP1 with the SG protein HuR but not the PB protein DCP1a was further confirmed by proximity ligation assay (PLA; Fig. 1d)

Summary

Introduction

Critical functions of intra-axonally synthesized proteins are thought to depend on regulated recruitment of mRNA from storage depots in axons. We show that axotomy of mammalian neurons induces translation of stored axonal mRNAs via regulation of the stress granule protein G3BP1, to support regeneration of peripheral nerves. G3BP1 aggregates within peripheral nerve axons in stress granule-like structures that decrease during regeneration, with a commensurate increase in phosphorylated G3BP1. Disrupting G3BP functions by overexpressing a dominant-negative protein activates intra-axonal mRNA translation, increases axon growth in cultured neurons, disassembles axonal stress granule-like structures, and accelerates rat nerve regeneration in vivo. Disrupting G3BP1 function with a dominant-negative approach activates intra-axonal mRNA translation, increases axon growth in cultured neurons and accelerates nerve regeneration in vivo, and represents a new pro-regenerative therapeutic approach

Methods

Results

Conclusion