Efa6 protects axons and regulates their growth and branching by inhibiting microtubule polymerisation at the cortex.



Qu, Yue ORCID: 0000-0002-2593-3654, Hahn, Ines ORCID: 0000-0001-7703-8160, Lees, Meredith, Parkin, Jill, Voelzmann, André ORCID: 0000-0002-7682-5637, Dorey, Karel ORCID: 0000-0003-0846-5286, Rathbone, Alex ORCID: 0000-0003-1871-7686, Friel, Claire T ORCID: 0000-0001-8395-5301, Allan, Victoria J ORCID: 0000-0003-4583-0836, Okenve-Ramos, Pilar ORCID: 0000-0002-7513-6557
et al (show 2 more authors) (2019) Efa6 protects axons and regulates their growth and branching by inhibiting microtubule polymerisation at the cortex. eLife, 8. e50319 - ?.

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Abstract

Cortical collapse factors affect microtubule (MT) dynamics at the plasma membrane. They play important roles in neurons, as suggested by inhibition of axon growth and regeneration through the ARF activator Efa6 in C. elegans, and by neurodevelopmental disorders linked to the mammalian kinesin Kif21A. How cortical collapse factors influence axon growth is little understood. Here we studied them, focussing on the function of Drosophila Efa6 in experimentally and genetically amenable fly neurons. First, we show that Drosophila Efa6 can inhibit MTs directly without interacting molecules via an N-terminal 18 amino acid motif (MT elimination domain/MTED) that binds tubulin and inhibits microtubule growth in vitro and cells. If N-terminal MTED-containing fragments are in the cytoplasm they abolish entire microtubule networks of mouse fibroblasts and whole axons of fly neurons. Full-length Efa6 is membrane-attached, hence primarily blocks MTs in the periphery of fibroblasts, and explorative MTs that have left axonal bundles in neurons. Accordingly, loss of Efa6 causes an increase of explorative MTs: in growth cones they enhance axon growth, in axon shafts they cause excessive branching, as well as atrophy through perturbations of MT bundles. Efa6 over-expression causes the opposite phenotypes. Taken together, our work conceptually links molecular and sub-cellular functions of cortical collapse factors to axon growth regulation and reveals new roles in axon branching and in the prevention of axonal atrophy. Furthermore, the MTED delivers a promising tool that can be used to inhibit MTs in a compartmentalised fashion when fusing it to specifically localising protein domains.

Item Type: Article
Uncontrolled Keywords: Growth Cones, Axons, Cells, Cultured, NIH 3T3 Cells, Cell Membrane, Pseudopodia, Microtubules, Fibroblasts, Animals, Mice, Drosophila melanogaster, Peptides, Guanine Nucleotide Exchange Factors, Drosophila Proteins, Green Fluorescent Proteins, Membrane Proteins, Amino Acid Motifs, Polymerization, Protein Domains
Depositing User: Symplectic Admin
Date Deposited: 18 Nov 2019 08:53
Last Modified: 05 Sep 2022 18:10
DOI: 10.7554/elife.50319
URI: https://livrepository.liverpool.ac.uk/id/eprint/3062266