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Curr Biol. 2016 Jul 11;26(13):1728-1736. doi: 10.1016/j.cub.2016.04.069. Epub 2016 Jun 9.

Isolation of Functional Tubulin Dimers and of Tubulin-Associated Proteins from Mammalian Cells.

Author information

1
Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, the Netherlands.
2
Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, the Netherlands; Department of Radiation Oncology, Erasmus Medical Center, Rotterdam, the Netherlands.
3
Biomedical Imaging Group Rotterdam, Erasmus Medical Center, 3015 GE, Rotterdam, the Netherlands.
4
Proteomics Centre, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, the Netherlands.
5
Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, the Netherlands. Electronic address: n.galjart@erasmusmc.nl.

Abstract

The microtubule (MT) cytoskeleton forms a dynamic filamentous network that is essential for many processes, including mitosis, cell polarity and shape, neurite outgrowth and migration, and ciliogenesis [1, 2]. MTs are built up of α/β-tubulin heterodimers, and their dynamic behavior is in part regulated by tubulin-associated proteins (TAPs). Here we describe a novel system to study mammalian tubulins and TAPs. We co-expressed equimolar amounts of triple-tagged α-tubulin and β-tubulin using a 2A "self-cleaving" peptide and isolated functional fluorescent tubulin dimers from transfected HEK293T cells with a rapid two-step approach. We also produced two mutant tubulins that cause brain malformations in tubulinopathy patients [3]. We then applied a paired mass-spectrometry-based method to identify tubulin-binding proteins in HEK293T cells and describe both novel and known TAPs. We find that CKAP5 and the CLASPs, which are MT plus-end-tracking proteins with TOG(L)-domains [4], bind tubulin efficiently, as does the Golgi-associated protein GCC185, which interacts with the CLASPs [5]. The N-terminal TOGL domain of CLASP1 contributes to tubulin binding and allows CLASP1 to function as an autonomous MT-growth-promoting factor. Interestingly, mutant tubulins bind less well to a number of TAPs, including CLASPs and GCC185, and incorporate less efficiently into cellular MTs. Moreover, expression of these mutants in cells impairs several MT-growth-related processes involving TAPs. Thus, stable tubulin-TAP interactions regulate MT nucleation and growth in cells. Combined, our results provide a resource for investigating tubulin interactions and functions and widen the spectrum of tubulin-related disease mechanisms.

PMID:
27291054
DOI:
10.1016/j.cub.2016.04.069
[Indexed for MEDLINE]
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