title: Tubulin cofactors and Arl2 are cage-like chaperones that regulate the soluble αβ-tubulin pool for microtubule dynamics.
abstract: Microtubule dynamics and polarity stem from the polymerization of αβ-tubulin heterodimers. Five conserved tubulin cofactors/chaperones and the Arl2 GTPase regulate α- and β-tubulin assembly into heterodimers and maintain the soluble tubulin pool in the cytoplasm, but their physical mechanisms are unknown. Here, we reconstitute a core tubulin chaperone consisting of tubulin cofactors TBCD, TBCE, and Arl2, and reveal a cage-like structure for regulating αβ-tubulin. Biochemical assays and electron microscopy structures of multiple intermediates show the sequential binding of αβ-tubulin dimer followed by tubulin cofactor TBCC onto this chaperone, forming a ternary complex in which Arl2 GTP hydrolysis is activated to alter αβ-tubulin conformation. A GTP-state locked Arl2 mutant inhibits ternary complex dissociation in vitro and causes severe defects in microtubule dynamics in vivo. Our studies suggest a revised paradigm for tubulin cofactors and Arl2 functions as a catalytic chaperone that regulates soluble αβ-tubulin assembly and maintenance to support microtubule dynamics.
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Stanley
authors.initials: S
authors.lastname: Nithianantham
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Sinh
authors.initials: S
authors.lastname: Le
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Elbert
authors.initials: E
authors.lastname: Seto
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Weitao
authors.initials: W
authors.lastname: Jia
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Julie
authors.initials: J
authors.lastname: Leary
authors.affiliation: Ludwig Institute for Cancer Research, University of California, San Diego, San Diego, United States.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Corbett
authors.affiliation: Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States.
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Moore
authors.affiliation: Department of Molecular Cellular Biology, University of California, Davis, Davis, United States.
authors.forename: Jawdat
authors.initials: J
authors.lastname: Al-Bassam
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*
chemical_list: C107852:CIN1 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D018832:Molecular Chaperones; C000595641:PAC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C000607641:TBCC protein, S cerevisiae; C000607640:TBCD protein, S cerevisiae; C469270:TBCE protein, human; D014404:Tubulin; C492128:ARF3 protein, S cerevisiae; D020727:ADP-Ribosylation Factors
keywords: Arl2; GTPase; S. cerevisiae; biochemistry; biophysics; chaperone; cofactor; microtubule; structural biology; tubulin