title: Differences in the Phosphorylation-Dependent Regulation of Prenylation of Rap1A and Rap1B.
abstract: Two isoforms of the small GTPase Rap1, Rap1A and Rap1B, participate in cell adhesion; Rap1A promotes steady state adhesion, while Rap1B regulates dynamic changes in cell adhesion. These events depend on the prenylation of Rap1, which promotes its membrane localization. Here, we identify previously unsuspected differences in the regulation of prenylation of Rap1A versus Rap1B, due in part to their different phosphorylation-dependent interactions with the chaperone protein SmgGDS-607. Previous studies indicate that the activation of Gαsprotein-coupled receptors (GPCRs) phosphorylates S-179 and S-180 in the polybasic region (PBR) of Rap1B, which inhibits Rap1B binding to SmgGDS-607 and diminishes Rap1B prenylation and membrane localization. In this study, we investigate how phosphorylation in the PBR of multiple small GTPases, including K-Ras4B, RhoA, Rap1A, and Rap1B, affects their binding to SmgGDS, with emphasis on differences between Rap1A and Rap1B. We identify the amino acids in SmgGDS-607 necessary for binding of Rap1A and Rap1B, and present homology models examining the binding between Rap1A or Rap1B and SmgGDS-607. Unlike Rap1B, phosphorylation in the PBR of Rap1A does not detectably inhibit its prenylation or its binding to SmgGDS-607. Activation of GPCRs suppresses Rap1A prenylation, but unlike this effect on Rap1B, the GPCR-mediated suppression of Rap1A prenylation can occur independently of Rap1A phosphorylation and does not detectably diminish Rap1A membrane localization. These data demonstrate unexpected evolutionarily conserved differences in the ability of GPCRs to regulate the prenylation of Rap1B compared to Rap1A.
authors.affiliation: Department of Pharmacology and Toxicology, Cancer Center and Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Wilson
authors.affiliation: HudsonAlpha Institute for Biotechnology, 601 Genome Way NW, Huntsville, AL 35806, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Prokop
authors.affiliation: Department of Pharmacology and Toxicology, Cancer Center and Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
authors.forename: Ellen
authors.initials: E
authors.lastname: Lorimer
authors.affiliation: College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, 1415 South Martin Luther King Jr. Boulevard, Tallahassee, FL 32307, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ntantie
authors.affiliation: Department of Pharmacology and Toxicology, Cancer Center and Cardiovascular Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA. Electronic address: williams@mcw.edu.
authors.forename: Carol L
authors.initials: CL
authors.lastname: Williams
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054876:Prenylation; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D016415:Sequence Alignment; D020668:rap GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; C430803:RAP1A protein, human; C115955:RAP1GDS1 protein, human; C116753:RAP1B protein, human; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins
keywords: G protein-coupled receptor; Rap1GDS1; SmgGDS; polybasic region; protein isoprenylation