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Doublecortin recognizes the 13-protofilament microtubule cooperatively and tracks microtubule ends

Susanne Bechstedt1, Gary J Brouhard

  • 1Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montréal, Québec, Canada.

Developmental Cell
|June 26, 2012
PubMed

Insights

Doublecortin (DCX) stabilizes developing neurons by nucleating 13-protofilament microtubules. DCX binding sensitivity and cooperative interactions are key to templating new microtubules.

Area of Science:

  • Cell Biology
  • Neuroscience
  • Biochemistry

Background:

  • Microtubules, essential for cell structure and function, exhibit protofilament heterogeneity.
  • The γ-tubulin ring complex typically nucleates 13-protofilament microtubules.
  • Doublecortin (DCX) is a neuronal protein known to stabilize microtubules and has shown *in vitro* nucleation of 13-protofilament microtubules.

Purpose of the Study:

  • To investigate the mechanism by which Doublecortin (DCX) nucleates and stabilizes 13-protofilament microtubules.
  • To determine the structural basis for DCX's specificity towards 13-protofilament microtubules.
  • To elucidate the role of cooperative interactions in DCX's microtubule binding and stabilization.

Main Methods:

  • Fluorescence microscopy assays to observe DCX binding to microtubules.
  • In vitro assays using dynamic microtubules to study polymerization intermediates.
  • Analysis of mutant DCX proteins associated with subcortical band heterotopia.

Main Results:

  • DCX binding is optimized for the specific lateral curvature of the 13-protofilament microtubule lattice.
  • DCX exhibits cooperative binding, where bound molecules reduce the dissociation rate of neighboring DCX molecules.
  • Mutations in DCX linked to subcortical band heterotopia impair these cooperative interactions.
  • DCX was observed to bind to polymerization intermediates at the growing ends of dynamic microtubules.

Conclusions:

  • DCX actively stabilizes 13-protofilament microtubules through optimized binding and cooperative interactions.
  • DCX's ability to template new 13-protofilament microtubules involves interactions with the sides of the microtubule lattice.
  • Understanding DCX's mechanism provides insight into microtubule regulation in neuronal development and associated disorders.

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