Abstract
ABSTRACTMicrotubule glutamylation is an important modulator of microtubule function and has been implicated in the regulation of centriole stability, neuronal outgrowth and cilia motility. Glutamylation of the microtubules is catalyzed by a family of tubulin tyrosine ligase-like (TTLL) enzymes. Analysis of individual TTLL enzymes has led to an understanding of their specific functions, but how activities of the TTLL enzymes are coordinated to spatially and temporally regulate glutamylation remains relatively unexplored. We have undertaken an analysis of the glutamylating TTLL enzymes in C. elegans. We find that although all five TTLL enzymes are expressed in the embryo and adult worm, loss of individual enzymes does not perturb microtubule function in embryonic cell divisions. Moreover, normal dye-filling, osmotic avoidance and male mating behavior indicate the presence of functional amphid cilia and male-specific neurons. A ttll-4(tm3310); ttll-11(tm4059); ttll-5(tm3360) triple mutant, however, shows reduced male mating efficiency due to a defect in the response step, suggesting that these three enzymes function redundantly, and that glutamylation is required for proper function of the male-specific neurons.
Highlights
Microtubules are a major component of the cellular cytoskeleton and play essential roles in intracellular transport, cell division and cilia structure
Domain structure of the C. elegans tubulin tyrosine ligase-like (TTLL) proteins Bioinformatics searches have revealed that the C. elegans genome encodes six TTLL enzymes (Janke et al, 2005)
We have focused our analyses on the five C. elegans glutamylating enzymes: TTLL-4, -5, -9, -11 and -15
Summary
Microtubules are a major component of the cellular cytoskeleton and play essential roles in intracellular transport, cell division and cilia structure. The microtubules are subject to a vast array of posttranslational modifications, including acetylation, glutamylation, tyrosination, and glycylation, and this extraordinary complexity has led to the proposal that it forms a ‘tubulin code’ (Garnham et al, 2015; Verhey and Gaertig, 2007). The tubulin code, it has been suggested, differentiates subpopulations of microtubules and regulates the binding of proteins that modulate microtubule function. The expression of enzymes that post-translationally modify the microtubules and the availability of cellular effectors would converge to regulate microtubule function.
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