title: Resistance to inhibitors of cholinesterase 8A catalyzes release of Galphai-GTP and nuclear mitotic apparatus protein (NuMA) from NuMA/LGN/Galphai-GDP complexes.
abstract: Resistance to inhibitors of cholinesterase (Ric) 8A is a guanine nucleotide exchange factor that activates certain G protein alpha-subunits. Genetic studies in Caenorhabditis elegans and Drosophila melanogaster have placed RIC-8 in a previously uncharacterized G protein signaling pathway that regulates centrosome movements during cell division. Components of this pathway include G protein subunits of the Galphai class, GPR or GoLoco domain-containing proteins, RGS (regulator of G protein signaling) proteins, and accessory factors. These proteins interact to regulate microtubule pulling forces during mitotic movement of chromosomes. It is unclear how the GTP-binding and hydrolysis cycle of Galphai functions in the context of this pathway. In mammals, the GoLoco domain-containing protein LGN (GPSM2), the LGN- and microtubule-binding nuclear mitotic apparatus protein (NuMA), and Galphai regulate a similar process. We find that mammalian Ric-8A dissociates Galphai-GDP/LGN/NuMA complexes catalytically, releasing activated Galphai-GTP in vitro. Ric-8A-stimulated activation of Galphai caused concomitant liberation of NuMA from LGN. We conclude that Ric-8A efficiently utilizes GoLoco/Galphai-GDP complexes as substrates in vitro and suggest that Ric-8A-stimulated release of Galphai-GTP and/or NuMA regulates the microtubule pulling forces on centrosomes during cell division.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA.
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Tall
authors.forename: Alfred G
authors.initials: AG
authors.lastname: Gilman
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002384:Catalysis; D018797:Cell Cycle Proteins; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007700:Kinetics; D019814:Myristic Acid / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002800:Cholinesterase Inhibitors; D009687:Nuclear Proteins; C489081:Numa1 protein, rat; D019814:Myristic Acid; D006160:Guanosine Triphosphate; D019206:GTP-Binding Protein alpha Subunits, Gi-Go