title: Enhancement of β-catenin activity by BIG1 plus BIG2 via Arf activation and cAMP signals.
abstract: Multifunctional β-catenin, with critical roles in both cell-cell adhesion and Wnt-signaling pathways, was among HeLa cell proteins coimmunoprecipitated by antibodies against brefeldin A-inhibited guanine nucleotide-exchange factors 1 and 2 (BIG1 or BIG2) that activate ADP-ribosylation factors (Arfs) by accelerating the replacement of bound GDP with GTP. BIG proteins also contain A-kinase anchoring protein (AKAP) sequences that can act as scaffolds for multimolecular assemblies that facilitate and limit cAMP signaling temporally and spatially. Direct interaction of BIG1 N-terminal sequence with β-catenin was confirmed using yeast two-hybrid assays and in vitro synthesized proteins. Depletion of BIG1 and/or BIG2 or overexpression of guanine nucleotide-exchange factor inactive mutant, but not wild-type, proteins interfered with β-catenin trafficking, leading to accumulation at perinuclear Golgi structures. Both phospholipase D activity and vesicular trafficking were required for effects of BIG1 and BIG2 on β-catenin activation. Levels of PKA-phosphorylated β-catenin S675 and β-catenin association with PKA, BIG1, and BIG2 were also diminished after BIG1/BIG2 depletion. Inferring a requirement for BIG1 and/or BIG2 AKAP sequence in PKA modification of β-catenin and its effect on transcription activation, we confirmed dependence of S675 phosphorylation and transcription coactivator function on BIG2 AKAP-C sequence.
authors.affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892; Department of Life Science, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Chun-Chun
authors.initials: CC
authors.lastname: Li
authors.affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Kang
authors.initials: K
authors.lastname: Le
authors.affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Jiro
authors.initials: J
authors.lastname: Kato
authors.affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892; vaughanm@nih.gov.
authors.forename: Martha
authors.initials: M
authors.lastname: Vaughan
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D000072417:Protein Domains; D015290:Second Messenger Systems / Q000502:physiology*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D054758:A Kinase Anchor Proteins; C119087:ARFGEF1 protein, human; C119088:ARFGEF2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D051176:beta Catenin; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D010739:Phospholipase D; D020727:ADP-Ribosylation Factors
keywords: ADP-ribosylation factor; AKAP; cell migration; phospholipase D