Pseudo‐repeats in doublecortin make distinct mechanistic contributions to microtubule regulation

Abstract

Doublecortin ( DCX ) is a neuronal microtubule‐associated protein ( MAP ) indispensable for brain development. Its flexibly linked doublecortin ( DC ) domains— NDC and CDC —mediate microtubule ( MT ) nucleation and stabilization, but it is unclear how. Using high‐resolution time‐resolved cryo‐ EM , we mapped NDC and CDC interactions with tubulin at different MT polymerization stages and studied their functional effects on MT dynamics using TIRF microscopy. Although coupled, each DC repeat within DCX appears to have a distinct role in MT nucleation and stabilization: CDC is a conformationally plastic module that appears to facilitate MT nucleation and stabilize tubulin–tubulin contacts in the nascent MT lattice, while NDC appears to be favored along the mature lattice, providing MT stabilization. Our structures of MT ‐bound DC domains also explain in unprecedented detail the DCX mutation‐related brain defects observed in the clinic. This modular composition of DCX reflects a common design principle among MAP s where pseudo‐repeats of tubulin/ MT binding elements chaperone or stabilize distinct conformational transitions to regulate distinct stages of MT dynamic instability.

Form follows function: Variable microtubule architecture in the malaria parasite

“…As these polymorphisms are not normally found in cells, stipulation of a uniformly 13-protofilament microtubule population therefore needs to be established during nucleation by external factors. There are four known mechanisms of controlling the number of protofilaments in a microtubule: Templating via the γ-tubulin ring complex (γTuRC) (Oakley et al, 2015; Wieczorek et al, 2020), setting a specific inter-protofilament angle through lateral binding of proteins such as doublecortin (Manka and Moores, 2020; Moores et al, 2004), expression of different tubulin isoforms (Fukushige et al, 1999) or post-translational modifications (Cueva et al, 2012).…”

Structure Determination of Microtubules and Pili: Past, Present, and Future Directions

“…However, this need for fiducials was overcome with additional image processing techniques, when near-atomic structural determination of pseudo-symmetric MTs without binding proteins in different nucleotide states was demonstrated (Zhang et al, 2018) (Figure 2A). Nevertheless, in many cases the MT-binding protein itself was the subject of structural interest, with notable examples solved near-atomic resolutions including the MT-binding regions of disease-related proteins tau (Kellogg et al, 2018) and doublecortin (Manka and Moores, 2020), minus-end binding CAMSAP (Atherton et al, 2019), MTnucleator TPX2 (Zhang et al, 2017) and the MT-depolymerising kinesin-13 (Benoit et al, 2018) (Figure 2A). In recent years, cryo-EM of MTs and binding partners has continued to develop (Figure 1).…”

TUBA1A tubulinopathy mutants disrupt neuron morphogenesis and override XMAP215/Stu2 regulation of microtubule dynamics

“…The ability of tubulin to adopt a range of conformational states not only impacts its intrinsic microtubule dynamics, but also tubulin’s interactions with a wide spectrum of MAPs. For example, doublecortin (DC) is predominantly expressed in the developing brain and its N-terminal DC-like repeat domain binds at the corner of four tubulin subunits in a straight microtubule lattice ( Fourniol et al, 2010 ; Manka and Moores, 2020 ; Moores et al, 2006 ). On the other hand, members of the XMAP215 protein family possess a variable number of TOG (tumor overexpressed gene) domains, some of which preferentially bind to curved tubulin ( Ayaz et al, 2014 ; Ayaz et al, 2012 ; Slep and Vale, 2007 ).…”