Glutamylation Regulates Transport, Specializes Function, and Sculpts the Structure of Cilia

Robert O'Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, Maureen M. Barr

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15 Scopus citations

Abstract

Ciliary microtubules (MTs) are extensively decorated with post-translational modifications (PTMs), such as glutamylation of tubulin tails. PTMs and tubulin isotype diversity act as a “tubulin code” that regulates cytoskeletal stability and the activity of MT-associated proteins such as kinesins. We previously showed that, in C. elegans cilia, the deglutamylase CCPP-1 affects ciliary ultrastructure, localization of the TRP channel PKD-2 and the kinesin-3 KLP-6, and velocity of the kinesin-2 OSM-3/KIF17, whereas a cell-specific α-tubulin isotype regulates ciliary ultrastructure, intraflagellar transport, and ciliary functions of extracellular vesicle (EV)-releasing neurons. Here we examine the role of PTMs and the tubulin code in the ciliary specialization of EV-releasing neurons using genetics, fluorescence microscopy, kymography, electron microscopy, and sensory behavioral assays. Although the C. elegans genome encodes five tubulin tyrosine ligase-like (TTLL) glutamylases, only ttll-11 specifically regulates PKD-2 localization in EV-releasing neurons. In EV-releasing cephalic male (CEM) cilia, TTLL-11 and the deglutamylase CCPP-1 regulate remodeling of 9+0 MT doublets into 18 singlet MTs. Balanced TTLL-11 and CCPP-1 activity fine-tunes glutamylation to control the velocity of the kinesin-2 OSM-3/KIF17 and kinesin-3 KLP-6 without affecting the intraflagellar transport (IFT) kinesin-II. TTLL-11 is transported by ciliary motors. TTLL-11 and CCPP-1 are also required for the ciliary function of releasing bioactive EVs, and TTLL-11 is itself a novel EV cargo. Therefore, MT glutamylation, as part of the tubulin code, controls ciliary specialization, ciliary motor-based transport, and ciliary EV release in a living animal. We suggest that cell-specific control of MT glutamylation may be a conserved mechanism to specialize the form and function of cilia. O'Hagan et al. report that fine-tuning of microtubule glutamylation by the glutamylase TTLL-11 and the deglutamylase CCPP-1 regulates ciliary function by controlling ciliary receptor localization, the velocity of particular kinesin-2 and kinesin-3 motors, and the release of extracellular vesicles and sculpting a specialized axonemal ultrastructure.

Original languageEnglish
Pages (from-to)3430-3441.e6
JournalCurrent Biology
Volume27
Issue number22
DOIs
StatePublished - 20 Nov 2017

Keywords

  • C. elegans
  • cilia
  • extracellular vesicles
  • glutamylation
  • intraflagellar transport
  • kinesin-2
  • kinesin-3
  • microtubule
  • polycystin
  • post-translational modifications

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    O'Hagan, R., Silva, M., Nguyen, K. C. Q., Zhang, W., Bellotti, S., Ramadan, Y. H., Hall, D. H., & Barr, M. M. (2017). Glutamylation Regulates Transport, Specializes Function, and Sculpts the Structure of Cilia. Current Biology, 27(22), 3430-3441.e6. https://doi.org/10.1016/j.cub.2017.09.066