title: The Dictyostelium discoideum RACK1 orthologue has roles in growth and development.
abstract: BACKGROUND
  The receptor for activated C-kinase 1 (RACK1) is a conserved protein belonging to the WD40 repeat family of proteins. It folds into a beta propeller with seven blades which allow interactions with many proteins. Thus it can serve as a scaffolding protein and have roles in several cellular processes.
  
  
  RESULTS
  We identified the product of the Dictyostelium discoideum gpbB gene as the Dictyostelium RACK1 homolog. The protein is mainly cytosolic but can also associate with cellular membranes. DdRACK1 binds to phosphoinositides (PIPs) in protein-lipid overlay and liposome-binding assays. The basis of this activity resides in a basic region located in the extended loop between blades 6 and 7 as revealed by mutational analysis. Similar to RACK1 proteins from other organisms DdRACK1 interacts with G protein subunits alpha, beta and gamma as shown by yeast two-hybrid, pulldown, and immunoprecipitation assays. Unlike the Saccharomyces cerevisiae and Cryptococcus neoformans RACK1 proteins it does not appear to take over Gβ function in D. discoideum as developmental and other defects were not rescued in Gβ null mutants overexpressing GFP-DdRACK1. Overexpression of GFP-tagged DdRACK1 and a mutant version (DdRACK1mut) which carried a charge-reversal mutation in the basic region in wild type cells led to changes during growth and development.
  
  
  CONCLUSIONS
  DdRACK1 interacts with heterotrimeric G proteins and can through these interactions impact on processes specifically regulated by these proteins.
authors.forename: Napoleon Nosa
authors.initials: NN
authors.lastname: Omosigho
authors.forename: Karthic
authors.initials: K
authors.lastname: Swaminathan
authors.forename: Markus
authors.initials: M
authors.lastname: Plomann
authors.forename: Annette
authors.initials: A
authors.lastname: Müller-Taubenberger
authors.affiliation: Institute of Biochemistry I, Medical Faculty, Center for Molecular Medicine Cologne (CMMC) and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Köln, Germany. noegel@uni-koeln.de.
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
authors.forename: Tanja Y
authors.initials: TY
authors.lastname: Riyahi
mesh_terms: D000595:Amino Acid Sequence; D004023:Dictyostelium / Q000254:growth & development / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010716:Phosphatidylinositols / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D010716:Phosphatidylinositols; D021122:Protein Subunits; D015800:Protozoan Proteins; D012333:RNA, Messenger; D019204:GTP-Binding Proteins