title: Contribution of guanine exchange factor H1 in phorbol ester-induced apoptosis.
abstract: Phorbol-12-myristate-13-acetate (PMA) treatment induces erythroblastoma D2 cells kept in suspension to undergo RhoA-dependent contraction and to become proapoptotic, while attached cells are induced to differentiate accompanied by the reduction of RhoA activity. In this study, we found that guanine exchange factor H1 (GEF-H1) is highly expressed in D2 cells. Depletion of GEF-H1 expression in D2 cells decreased RhoA activity and prevented PMA-induced contraction and apoptosis. Upon PMA stimulation, GEF-H1 became associated with microtubules in cells that were induced to differentiate. As a contrast, in the proapoptotic population of cells GEF-H1 stayed in the cytoplasm without showing PMA-responsive microtubule translocation. Given that GEF-H1 is inactivated when associated with microtubules and its release into cytosol due to depolymerization of microtubules activates RhoA, our results demonstrated that nonmicrotubule-associated GEF-H1 in D2 cells contributes to the sustained activation of RhoA/ROCK signaling in suspension cells, making cells susceptible to PMA-induced apoptosis.
authors.affiliation: Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1 Section 1 Jen-Ai Road, Taipei, Taiwan, ROC.
authors.forename: Y-C
authors.initials: YC
authors.lastname: Chang
authors.forename: H-H
authors.initials: HH
authors.lastname: Lee
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Chen
authors.forename: G M
authors.initials: GM
authors.lastname: Bokoch
authors.forename: Z-F
authors.initials: ZF
authors.lastname: Chang
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000502:physiology; D009154:Mutation / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C577356:ARHGEF2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D013755:Tetradecanoylphorbol Acetate