title: GSK3beta phosphorylation modulates CLASP-microtubule association and lamella microtubule attachment.
abstract: Polarity of the microtubule (MT) cytoskeleton is essential for many cell functions. Cytoplasmic linker-associated proteins (CLASPs) are MT-associated proteins thought to organize intracellular MTs and display a unique spatiotemporal regulation. In migrating epithelial cells, CLASPs track MT plus ends in the cell body but bind along MTs in the lamella. In this study, we demonstrate that glycogen synthase kinase 3beta (GSK3beta) directly phosphorylates CLASPs at multiple sites in the domain required for MT plus end tracking. Although complete phosphorylation disrupts both plus end tracking and association along lamella MTs, we show that partial phosphorylation of the identified GSK3beta motifs determines whether CLASPs track plus ends or associate along MTs. In addition, we find that expression of constitutively active GSK3beta destabilizes lamella MTs by disrupting lateral MT interactions with the cell cortex. GSK3beta-induced lamella MT destabilization was partially rescued by expression of CLASP2 with mutated phosphorylation sites. This indicates that CLASP-mediated stabilization of peripheral MTs, which likely occurs in the vicinity of focal adhesions, may be regulated by local GSK3beta inactivation.
authors.affiliation: Department of Cell and Tissue Biology, University of California-San Francisco, San Francisco, CA 94143, USA.
authors.forename: Praveen
authors.initials: P
authors.lastname: Kumar
authors.forename: Karen S
authors.initials: KS
authors.lastname: Lyle
authors.forename: Sarah
authors.initials: S
authors.lastname: Gierke
authors.forename: Alexandre
authors.initials: A
authors.lastname: Matov
authors.forename: Gaudenz
authors.initials: G
authors.lastname: Danuser
authors.forename: Torsten
authors.initials: T
authors.lastname: Wittmann
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002448:Cell Adhesion; D002465:Cell Movement; D016764:Cell Polarity; D004847:Epithelial Cells / Q000201:enzymology*; D022001:Focal Adhesions / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000201:enzymology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: C497851:CLASP2 protein, human; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3