Microtubule‐severing proteins are involved in flagellar length control and mitosis in Trypanosomatids

Abstract

SummaryMicrotubules are key players in the biology of Trypanosomatid parasites, not only as classical components of the mitotic spindle, microtubule-organizing centres and flagellum but also as the essential constituent of the cytoskeleton. Their length dynamics are regulated by, among others, microtubule-severing proteins. Four and six genes encoding microtubulesevering proteins can be found bioinformatically in the Leishmania major and Trypanosoma brucei genome respectively. We investigated all these proteins in these organisms, which include the katanin, katanin-like, spastin and fidgetin, and looked at their subcellular localization as well as their putative function by examining 'loss-of-function' phenotypes. The katanin-like KAT60b was found implicated in flagellar length reduction, but not in its size increase, while the katanin p80 subunit appeared clearly involved in cytokinesis. Fidgetin and spastin homologues were both localized in the nucleus: the first as a discrete and variable number of dots during most of the cell cycle, redistributing to the spindle and midbody during mitosis; the second concentrated as Յ 5 perinucleolar punctuations, similar to the electron-dense plaques identified in T. brucei, which were assimilated to kinetochores. This first study of microtubulesevering proteins in 'divergent' eukaryotes gives further insight into the multiple functions of these proteins identified in the hitherto studied models.

Spastin-Interacting Protein NA14/SSNA1 Functions in Cytokinesis and Axon Development

“…4B). Consistent with previous reports [12], [14], [29], [32], spastin similarly localized to midbodies during the abscission phase late in cytokinesis (Fig. 4B).…”

KATNB1 in the human testis and its genetic variants in fertile and oligoasthenoteratozoospermic infertile men

“…The katanin complex is evolutionarily conserved, and orthologues of the p60 severing enzyme and the p80 accessory protein have been identified in species from all five kingdoms, including in C. elegans, Drosophila melanogaster, Arabidopsis thaliana, Chlamydomonas reinhardtii, mice and humans. Of note, katanin has an evolutionarily conserved role in cilia and flagella biogenesis (Sharma et al, 2007;Casanova et al, 2009). In a genome-wide ENU-induced mutagenesis screen for novel regulators of male infertility (Jamsai & O'Bryan, 2010), Katnb1 was identified as a gene with a causative role in severe OAT in mice .…”

“…Katanin can also sever microtubules as they emerge from the nucleating complex to produce short microtubule seeds that can be transported to other sites and re-polymerized in a process known as 'cut and run' . Katanin is essential for a wide range of functions in various organisms including for the regulation of spindle dynamics during cell division in Caenorhabditis elegans (McNally et al, 2006(McNally et al, , 2014, microtubule dynamics in developing rodent neurons (Ahmad et al, 1999;Karabay et al, 2004;Yu et al, 2005) and in plant cells (Nakamura et al, 2010), and for the assembly of flagella in Tetrahymena, Trypanosomes and mice (Sharma et al, 2007;Casanova et al, 2009;O'Donnell et al, 2012). Importantly, both Katnb1 and the p60-severing enzyme homolog Katnal1, have been shown to be essential for male fertility in the mouse Smith et al, 2012).…”

A novel family of katanin-like 2 protein isoforms (KATNAL2), interacting with nucleotide-binding proteins Nubp1 and Nubp2, are key regulators of different MT-based processes in mammalian cells

“…Additionally, severing by katanin at the MT (-) ends at the centrosome promotes the redistribution of c-tubulin rings to enhance new MT nucleation [25]; Katanin-like protein 1 (KATNAL1) also seems to boost the formation of spindle MTs and increase spindle MT density in human cells by altering c-tubulin ring kinetics [20] and is also involved in spermatogenesis [26]. The role of katanin in cytokinesis has been highlighted in protozoa such as Tetrahymena, where kataninnull cells can successfully complete nuclear division but not cytokinesis, resulting in chains of non-separated cells [14], while in Trypanosoma and Leishmania both p60 and p80 are essential for distinct steps of cytokinesis [27,28].…”