title: Dynamic regulation of GEF-H1 localization at microtubules by Par1b/MARK2.
abstract: Par1b/MARK2 is a serine/threonine kinase that plays key roles in the development of cell polarity, but its precise mechanism of action remains unknown. Here we report that GEF-H1, a guanine nucleotide exchange factor for Rho-family small GTPases, is a novel substrate for Par1b. GEF-H1 directly associates with microtubules via its N-terminal C1 domain, which is known to regulate the activity of GEF-H1. Ectopically expressed GEF-H1 markedly promotes stabilization of microtubules, resulting in acetylation of microtubules. We find that Par1b phosphorylates GEF-H1 at three serine residues conserved in vertebrates and releases GEF-H1 from microtubules, which abrogates stabilization and acetylation of microtubules induced by GEF-H1 overexpression. The alanine mutant for the three phosphorylation sites (3SA) of GEF-H1 strongly induces stabilization and acetylation of microtubules, which was resistant to Par1b. Time-lapse imaging analyses reveal that GFP-fused GEF-H1 dynamically moved on microtubules from one protrusion to another, whereas the 3SA mutant was static. These data suggest that Par1b-phosphorylation regulates turnover of GEF-H1 localization by regulating its interaction with microtubules, which may contribute to cell polarization.
authors.affiliation: Laboratory of Intracellular Signaling, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Miki
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D004285:Dogs; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D014404:Tubulin / Q000378:metabolism
chemical_list: C577356:ARHGEF2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D014404:Tubulin; C094670:MARK2 protein, human; D017346:Protein Serine-Threonine Kinases