title: cAMP response element-binding protein interacts with and stimulates the proteasomal degradation of the nuclear receptor coactivator GRIP1.
abstract: The glucocorticoid receptor interacting protein (GRIP1) belongs to the p160 steroid receptor coactivator family that plays essential roles in nuclear receptor-dependent transcriptional regulation. Previously, we reported that the cAMP-dependent protein kinase (PKA) induces ubiquitination leading to degradation of GRIP1. Here we show that the cAMP response element-binding protein (CREB) downregulates GRIP1 and is necessary for the PKA-stimulated degradation of GRIP1, which leads to changes in the expression of a subset of genes regulated by estrogen receptor-α in MCF-7 breast cancer cells. Our data of domain-mapping and ubiquitination analyses suggest that CREB promotes the proteasomal breakdown of ubiquitinated GRIP1 through 2 functionally independent protein domains containing amino acids 347 to 758 and 1121 to 1462. We provide evidence that CREB interacts directly with GRIP1 and that CREB Ser-133 phosphorylation or transcriptional activity is not required for GRIP1 interaction and degradation. The basic leucine zipper domain (bZIP) of CREB is important for the interaction with GRIP1, and deletion of this domain led to an inability to downregulate GRIP1. We propose that CREB mediates the PKA-stimulated degradation of GRIP1 through protein-protein interaction and stimulation of proteasomal degradation of ubiquitinated GRIP1.
authors: Department of Clinical Science, University of Bergen, N-5021 Bergen, Norway.
authors: Tuyen
authors: T
authors: Hoang
authors: Ingvild S
authors: IS
authors: Fenne
authors: Andre
authors: A
authors: Madsen
authors: Olivera
authors: O
authors: Bozickovic
authors: Mona
authors: M
authors: Johannessen
authors: Mari
authors: M
authors: Bergsvåg
authors: Ernst Asbjørn
authors: EA
authors: Lien
authors: Michael R
authors: MR
authors: Stallcup
authors: Jørn V
authors: JV
authors: Sagen
authors: Ugo
authors: U
authors: Moens
authors: Gunnar
authors: G
authors: Mellgren
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D047628:Estrogen Receptor alpha / Q000378:metabolism; D006801:Humans; D061986:MCF-7 Cells; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism*; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation; D014162:Transfection; D054875:Ubiquitination / Q000502:physiology
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D047628:Estrogen Receptor alpha; D051958:Nuclear Receptor Coactivator 2; D017868:Cyclic AMP-Dependent Protein Kinases