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Curr Biol. 2016 Jun 20;26(12):1549-1555. doi: 10.1016/j.cub.2016.04.020. Epub 2016 May 26.

Doublecortin Is Excluded from Growing Microtubule Ends and Recognizes the GDP-Microtubule Lattice.

Author information

1
Department of Cell and Tissue Biology, University of California San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
2
Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA.
3
Department of Cell and Tissue Biology, University of California San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA. Electronic address: torsten.wittmann@ucsf.edu.

Abstract

Many microtubule (MT) functions are mediated by a diverse class of proteins (+TIPs) at growing MT plus ends that control intracellular MT interactions and dynamics and depend on end-binding proteins (EBs) [1]. Cryoelectron microscopy has recently identified the EB binding site as the interface of four tubulin dimers that undergoes a conformational change in response to β-tubulin GTP hydrolysis [2, 3]. Doublecortin (DCX), a MT-associated protein (MAP) required for neuronal migration during cortical development [4, 5], binds to the same site as EBs [6], and recent in vitro studies proposed DCX localization to growing MT ends independent of EBs [7]. Because this conflicts with observations in neurons [8, 9] and the molecular function of DCX is not well understood, we revisited intracellular DCX dynamics at low expression levels. Here, we report that DCX is not a +TIP in cells but, on the contrary, is excluded from the EB1 domain. In addition, we find that DCX-MT interactions are highly sensitive to MT geometry. In cells, DCX binding was greatly reduced at MT segments with high local curvature. Remarkably, this geometry-dependent binding to MTs was completely reversed in the presence of taxanes, which reconciles incompatible observations in cells [9] and in vitro [10]. We propose a model explaining DCX specificity for different MT geometries based on structural changes induced by GTP hydrolysis that decreases the spacing between adjacent tubulin dimers [11]. Our data are consistent with a unique mode of MT interaction in which DCX specifically recognizes this compacted GDP-like MT lattice.

PMID:
27238282
PMCID:
PMC5023073
DOI:
10.1016/j.cub.2016.04.020
[Indexed for MEDLINE]
Free PMC Article

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