Protein Synthesis, Post-Translation Modification, and Degradation
Mutations of Tubulin Glycylation Sites Reveal Cross-talk between the C Termini of α- and β-Tubulin and Affect the Ciliary Matrix in Tetrahymena*

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Two types of polymeric post-translational modifications of α/β-tubulin, glycylation and glutamylation, occur widely in cilia and flagella. Their respective cellular functions are poorly understood. Mass spectrometry and immunoblotting showed that two closely related species, the ciliates Tetrahymena and Paramecium, have dramatically different compositions of tubulin post-translational modifications in structurally identical axonemes. Whereas the axonemal tubulin of Paramecium is highly glycylated and has a very low glutamylation content, the axonemal tubulin of Tetrahymena is glycylated and extensively glutamylated. In addition, only the α-tubulin of Tetrahymena undergoes detyrosination. Mutations of the known glycylation sites in Tetrahymena tubulin affected the level of each polymeric modification type in both the mutated and nonmutated subunits, revealing cross-talk between α- and β-tubulin. Ultrastructural analyses of glycylation site mutants uncovered defects in the doublet B-subfiber of axonemes and revealed an accumulation of dense material in the ciliary matrix, reminiscent of intraflagellar transport particles seen by others in Chlamydomonas. We propose that polyglycylation and/or polyglutamylation stabilize the B-subfiber of outer doublets and regulate the intraflagellar transport.

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b

Present address: Laboratoire d'Enzymologie et de Biochimie Structurales, UPR 9063 CNRS, 91198 Gif-sur-Yvette, France.

e

Present address: Unité de Régulation Enzymatique des Activités Cellulaires, URA 2185 CNRS, Institut Pasteur, 75724 Paris Cedex 15, France.

h

Present address: Dept. of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520.

*

This work was supported by CNRS, the Association pour la Recherche contre le Cancer, and the Université Paris-Sud. Activities at the University of Georgia were supported by the National Institutes of Health Grant GM54017 and National Science Foundation Grant 235826 (to J. G.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

c

The authors contributed equally to the work.

© 2005 ASBMB. Currently published by Elsevier Inc; originally published by American Society for Biochemistry and Molecular Biology.