title: p21-activated kinase 1 regulates microtubule dynamics by phosphorylating tubulin cofactor B.
abstract: p21-activated kinase 1 (Pak1) induces cytoskeleton reorganization in part by regulating microtubule dynamics through an elusive mechanism. Using a yeast two-hybrid screen, we identified tubulin cofactor B (TCoB) (a cofactor in the assembly of the alpha/beta-tubulin heterodimers) as an interacting substrate of Pak1. Pak1 directly phosphorylated TCoB in vitro and in vivo on serines 65 and 128 and colocalized with TCoB on newly polymerized microtubules and on centrosomes. TCoB interacted with the GTPase-binding domain of Pak1 and activated Pak1 in vitro and in vivo. In contrast to wild-type TCoB, an S65A, S128A double mutant and knock-down of the endogenous TCoB or Pak1 reduced microtubule polymerization, suggesting that Pak1 phosphorylation is necessary for normal TCoB function. Overexpression of TCoB dramatically increased the number of gamma-tubulin-containing microtubule-organizing centers, a phenotype reminiscent of cells overexpressing Pak1. TCoB was overexpressed and phosphorylated in breast tumors. These findings reveal a novel role for TCoB and Pak1 in regulating microtubule dynamics.
authors.affiliation: Box 108, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
authors.forename: Ratna K
authors.initials: RK
authors.lastname: Vadlamudi
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Barnes
authors.forename: Suresh
authors.initials: S
authors.lastname: Rayala
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Seetharaman
authors.initials: S
authors.lastname: Balasenthil
authors.forename: Stevan
authors.initials: S
authors.lastname: Marcus
authors.forename: Holly V
authors.initials: HV
authors.lastname: Goodson
authors.forename: Aysegul A
authors.initials: AA
authors.lastname: Sahin
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
mesh_terms: D001943:Breast Neoplasms / Q000737:chemistry / Q000201:enzymology*; D005260:Female; D015723:Gene Library; D006801:Humans; D042361:Mammary Glands, Human / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D008941:Spindle Apparatus / Q000378:metabolism / Q000502:physiology; D015533:Transcriptional Activation; D014404:Tubulin / Q000032:analysis / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D054462:p21-Activated Kinases
chemical_list: D008869:Microtubule-Associated Proteins; D018832:Molecular Chaperones; D034741:RNA, Small Interfering; D014404:Tubulin; C501073:tubulin cofactor B, human; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases