Identification of DmTTLL5 as a Major Tubulin Glutamylase in the Drosophila Nervous System

Isabelle Devambez,Yves Grau,Sophie Layalle,Juliette Van Dijk,Krzysztof Rogowski,Laurent Soustelle,Salim Benlefki,Marie-Laure Parmentier

doi:10.1038/s41598-017-16586-w

Abstract

Microtubules (MTs) play crucial roles during neuronal life. They are formed by heterodimers of alpha and beta-tubulins, which are subjected to several post-translational modifications (PTMs). Amongst them, glutamylation consists in the reversible addition of a variable number of glutamate residues to the C-terminal tails of tubulins. Glutamylation is the most abundant MT PTM in the mammalian adult brain, suggesting that it plays an important role in the nervous system (NS). Here, we show that the previously uncharacterized CG31108 gene encodes an alpha-tubulin glutamylase acting in the Drosophila NS. We show that this glutamylase, which we named DmTTLL5, initiates MT glutamylation specifically on alpha-tubulin, which are the only glutamylated tubulin in the Drosophila brain. In DmTTLL5 mutants, MT glutamylation was not detected in the NS, allowing for determining its potential function. DmTTLL5 mutants are viable and we did not find any defect in vesicular axonal transport, synapse morphology and larval locomotion. Moreover, DmTTLL5 mutant flies display normal negative geotaxis behavior and their lifespan is not altered. Thus, our work identifies DmTTLL5 as the major enzyme responsible for initiating neuronal MT glutamylation specifically on alpha-tubulin and we show that the absence of MT glutamylation is not detrimental for Drosophila NS function.

Highlights

MTs are composed of heterodimers of alpha and beta-tubulins whose carboxy-terminal regions project outward from the MT surface making them accessible for the interaction with MAPs and motor proteins[10]
As CG31108 is expressed in the nervous system (Flybase data), we focused our attention on this gene
Our data show that DmTTLL5 initiates MT glutamylation on alpha-tubulin, the only glutamylated tubulin in the Drosophila central nervous system (CNS), as we could not detect glutamylation on beta-tubulin by using two different antibodies

Summary

Introduction

MTs are composed of heterodimers of alpha and beta-tubulins whose carboxy-terminal regions project outward from the MT surface making them accessible for the interaction with MAPs and motor proteins[10]. Such interactions may be modulated by variations in the C-terminal tails of tubulin isotypes, which generate functional MT heterogeneity[11]. Some TTLLs initiate tubulin glutamylation by adding the first glutamate, while others elongate the chain by adding glutamate residues to the first one[19,20,21]. The aim of our study was to identify the enzyme initiating MT glutamylation in order to investigate in vivo the role of MT glutamylation in the Drosophila nervous system

Objectives

Methods

Results

Conclusion