title: The betagamma subunit of heterotrimeric G proteins interacts with RACK1 and two other WD repeat proteins.
abstract: A yeast two-hybrid approach was used to discern possible new effectors for the betagamma subunit of heterotrimeric G proteins. Three of the clones isolated are structurally similar to Gbeta, each exhibiting the WD40 repeat motif. Two of these proteins, the receptor for activated C kinase 1 (RACK1) and the dynein intermediate chain, co-immunoprecipitate with Gbetagamma using an anti-Gbeta antibody. The third protein, AAH20044, has no known function; however, sequence analysis indicates that it is a WD40 repeat protein. Further investigation with RACK1 shows that it not only interacts with Gbeta(1)gamma(1) but also unexpectedly with the transducin heterotrimer Galpha(t)beta(1)gamma(1). Galpha(t) alone does not interact, but it must contribute to the interaction because the apparent EC(50) value of RACK1 for Galpha(t)beta(1)gamma(1) is 3-fold greater than that for Gbeta(1)gamma(1) (0.1 versus 0.3 microm). RACK1 is a scaffold that interacts with several proteins, among which are activated betaIIPKC and dynamin-1 (1). betaIIPKC and dynamin-1 compete with Gbeta(1)gamma(1) and Galpha(t)beta(1)gamma(1) for interaction with RACK1. These findings have several implications: 1) that WD40 repeat proteins may interact with each other; 2) that Gbetagamma interacts differently with RACK1 than with its other known effectors; and/or 3) that the G protein-RACK1 complex may constitute a signaling scaffold important for intracellular responses.
mesh_terms: D016475:3T3 Cells; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D003593:Cytoplasm / Q000378:metabolism; D004252:DNA Mutational Analysis; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D034284:Dynamin I / Q000378:metabolism; D004398:Dyneins / Q000378:metabolism; D019204:GTP-Binding Proteins; D005982:Glutathione Transferase / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
chemical_list: D007527:Isoenzymes; D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D005982:Glutathione Transferase; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D034284:Dynamin I; D019204:GTP-Binding Proteins; D004398:Dyneins; D020962:Heterotrimeric GTP-Binding Proteins