Identification of CfNek, a novel member of the NIMA family of cell cycle regulators, as a polypeptide copurifying with tubulin polyglutamylation activity in<i>Crithidia</i>

Section: Discussionmentioning

confidence: 99%

NIMA-related kinaseTbNRKC is involved in basal body separation inTrypanosoma brucei

Pradel

Bonhivers

Landrein

et al. 2006

“…Recently, TPG from Crithidia was proposed to be a NIMArelated protein, called CfNek (Westermann and Weber, 2002). As its most closely related mammalian Nek2 orthologue (Fry et al, 1995), CfNek exhibits a β-casein kinase activity.…”

Section: Tpg Is a Multimeric Enzymementioning

confidence: 99%

“…Such strong differences are rather unexpected but could be related to the more complex functions of polyglutamylation in multi-cellular organisms, compared to flagellates. Nevertheless, it is interesting to note Journal of Cell Science 116 (20) that CfNek is associated with basal bodies in Crithidia (Westermann and Weber, 2002) and Nek2 with centrosomes in higher eukaryotes (Fry et al, 1998), raising the possibility that the latter kinase could be implicated in the regulation of some aspects of polyglutamylation.…”

Section: Tpg Is a Multimeric Enzymementioning

confidence: 99%

Characterisation of PGs1, a subunit of a protein complex co-purifying with tubulin polyglutamylase

Regnard

Fesquet

Janke

et al. 2003

Polyglutamylation is a post-translational modification initially discovered on tubulin. It has been implicated in multiple microtubule functions, including neuronal differentiation, axonemal beating and stability of the centrioles, and shown to modulate the interaction between tubulin and microtubule associated proteins. The enzymes catalysing this modification are not yet known. Starting with a partially purified fraction of mouse brain tubulin polyglutamylase, monoclonal antibodies were raised and used to further purify the enzyme by immunoprecipitation. The purified enzyme complex (Mr 360×103) displayed at least three major polypeptides of 32, 50 and 80×103, present in stochiometric amounts. We show that the 32×103 subunit is encoded by the mouse gene GTRGEO22, the mutation of which has recently been implicated in multiple defects in mice, including male sterility. We demonstrate that this subunit, called PGs1, has no catalytic activity on its own, but is implicated in the localisation of the enzyme at major sites of polyglutamylation, i.e. neurones, axonemes and centrioles.

“…Other homologues of NIMA, such as Fin1 and Kin3 from yeast, also have important cell cycle functions via regulation of microtubule organization and mitotic spindle assembly (Jones and Rosamond, 1990;Krien et al, 1998). In addition, the Chlamydomonas NIMA-family kinases Fa2p and Cnk2p regulate ciliary function and length by promoting cilia disassembly (Bradley and Quarmby, 2005;Bradley et al, 2004;Finst et al, 2000;Finst et al, 1998;Mahjoub et al, 2002;Mahjoub et al, 2004;Parker et al, 2007;Quarmby and Mahjoub, 2005), and Nek from Crithidia displays tubulin polyglutamylation activity (Westermann and Weber, 2002;Westermann and Weber, 2003). Finally, Nek kinases influence organ development and morphogenesis in Arabidopsis through their effects on microtubules (Cloutier et al, 2005;Motose et al, 2008;Sakai et al, 2008;Vigneault et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

The NIMA-family kinase Nek3 regulates microtubule acetylation in neurons

Chang

Baloh

Milbrandt

2009

NIMA-related kinases (Neks) belong to a large family of Ser/Thr kinases that have critical roles in coordinating microtubule dynamics during ciliogenesis and mitotic progression. The Nek kinases are also expressed in neurons, whose axonal projections are, similarly to cilia, microtubule-abundant structures that extend from the cell body. We therefore investigated whether Nek kinases have additional, non-mitotic roles in neurons. We found that Nek3 influences neuronal morphogenesis and polarity through effects on microtubules. Nek3 is expressed in the cytoplasm and axons of neurons and is phosphorylated at Thr475 located in the C-terminal PEST domain, which regulates its catalytic activity. Although exogenous expression of wild-type or phosphomimic (T475D) Nek3 in cultured neurons has no discernible impact, expression of a phospho-defective mutant (T475A) or PEST-truncated Nek3 leads to distorted neuronal morphology with disturbed polarity and deacetylation of microtubules via HDAC6 in its kinase-dependent manner. Thus, the phosphorylation at Thr475 serves as a regulatory switch that alters Nek3 function. The deacetylation of microtubules in neurons by unphosphorylated Nek3 raises the possibility that it could have a role in disorders where axonal degeneration is an important component.