title: Doublecortin Is Excluded from Growing Microtubule Ends and Recognizes the GDP-Microtubule Lattice.
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.
authors.affiliation: Department of Cell and Tissue Biology, University of California San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ettinger
authors.affiliation: Department of Cell and Tissue Biology, University of California San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: van Haren
authors.affiliation: Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA.
authors.forename: Susana A
authors.initials: SA
authors.lastname: Ribeiro
authors.affiliation: 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.
authors.forename: Torsten
authors.initials: T
authors.lastname: Wittmann
mesh_terms: D045744:Cell Line, Tumor; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*
chemical_list: C000714328:DCX protein, human; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D006153:Guanosine Diphosphate