Environmental responsiveness of tubulin glutamylation in sensory cilia is regulated by the p38 MAPK pathway

Yoshishige Kimura,Takayuki Teramoto,Koji Tsutsumi,Manabi Fujiwara,Alu Konno,Mitsutoshi Setou,Takeshi Ishihara,Koji Ikegami,Tomomi Kaneko,Oktay Ismail Kaplan,Oliver E Blacque,Saira Hameed

doi:10.1038/s41598-018-26694-w

Abstract

Glutamylation is a post-translational modification found on tubulin that can alter the interaction between microtubules (MTs) and associated proteins. The molecular mechanisms regulating tubulin glutamylation in response to the environment are not well understood. Here, we show that in the sensory cilia of Caenorhabditis elegans, tubulin glutamylation is upregulated in response to various signals such as temperature, osmolality, and dietary conditions. Similarly, tubulin glutamylation is modified in mammalian photoreceptor cells following light adaptation. A tubulin glutamate ligase gene ttll-4, which is essential for tubulin glutamylation of axonemal MTs in sensory cilia, is activated by p38 MAPK. Amino acid substitution of TTLL-4 has revealed that a Thr residue (a putative MAPK-phosphorylation site) is required for enhancement of tubulin glutamylation. Intraflagellar transport (IFT), a bidirectional trafficking system specifically observed along axonemal MTs, is required for the formation, maintenance, and function of sensory cilia. Measurement of the velocity of IFT particles revealed that starvation accelerates IFT, which was also dependent on the Thr residue of TTLL-4. Similarly, starvation-induced attenuation of avoidance behaviour from high osmolality conditions was also dependent on ttll-4. Our data suggest that a novel evolutionarily conserved regulatory system exists for tubulin glutamylation in sensory cilia in response to the environment.

Highlights

Glutamylation, a post-translational modification (PTM) found on tubulin and other substrates[1,2], is performed by a reversible regulatory mechanism controlled by evolutionarily conserved enzymatic systems
We previously showed reversible enzymatic regulation of tubulin glutamylation is conserved in C. elegans and mammals[5]
We studied the responsiveness of tubulin glutamylation to the environment in two organisms

Summary

Introduction

Glutamylation, a post-translational modification (PTM) found on tubulin and other substrates[1,2], is performed by a reversible regulatory mechanism controlled by evolutionarily conserved enzymatic systems. Signal intensities were compared between control (b) and worms exposed to environmental stimuli (c–g). All stimuli except physical vibration induced a significant increase in tubulin glutamylation. Environmental stimuli of “heat”, “cold”, “osmotic”, and “starvation” but not of “shake” induced a significant increase in glutamylation. In C. elegans, tubulin glutamylation is predominantly observed in axonemal MTs of non-motile cilia located at the ends of dendritic processes of sensory neurons. We and another group have reported the molecular identity of ciliary tubulin glutamylase and deglutamylase enzymes in C. elegans[5,6,7]. Knockdown of an orthologue of CCP5 increases ciliary tubulin glutamylation and induces ciliopathy phenotypes[8]. The physiological plasticity and regulatory mechanisms underpinning tubulin glutamylation are not well understood

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