{"doi":"10.1016/j.jbc.2025.110999","title":"Binding of the brain G protein G⍺o to its potential effector RASA3 is promoted by Ca2+","abstract":"G⍺ o , the alpha subunit of the most abundant heterotrimeric G protein in the brain, mediates signaling by opioids and by many neuromodulators to inhibit neural function. An open question is whether activated G⍺ o -GTP directly binds to and regulates effector molecules, like all other animal G⍺ proteins, or if it signals solely by releasing Gβ γ subunits. Using mouse brain lysates as native source of G⍺ o and its potential effectors, we analyzed immunopurified G⍺ o protein complexes by mass spectrometry. Pre-activating G⍺ o in the lysates with GTP γ S resulted in a ∼6 fold increase in the amount of the small G protein GTPase activators RASA3 and RASA2 in the purified complexes, the largest increase among all G⍺ o -associated proteins, making RASA2/3 candidate G⍺ o effectors. Using purified recombinant proteins, we found that RASA3 binds directly to G⍺ o -GTP γ S more strongly than it does to G⍺ o -GDP. We also found that the addition of Ca 2+ , a second messenger produced by the G⍺ q pathway that opposes G⍺ o signaling, strengthened binding of RASA3 to G⍺ o -GDP . A C-terminal fragment of RASA3 containing a predicted Ca 2+ site was sufficient to bind G⍺ o , albeit more weakly and without a preference for the activated state of G⍺ o . We present a model in which RASA3 could mediate G⍺ o signaling using two distinct G⍺ o -binding sites: one on full-length RASA3 that preferentially binds active G⍺ o -GTP, and a second on the RASA3 C-terminus that binds inactive G⍺ o in the presence of Ca 2+ .","journal":"Journal of Biological Chemistry","year":2025,"id":584017,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9657,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":461296,"name":"Andrew Olson","orcid":"0000-0001-8882-3359","position":1,"is_corresponding":false},{"id":831300,"name":"Juliana E Gentile","orcid":"0000-0002-8389-4489","position":2,"is_corresponding":false},{"id":271366,"name":"TuKiet T. Lam","orcid":"0000-0002-4850-3462","position":3,"is_corresponding":false},{"id":461301,"name":"Michael R. Koelle","orcid":"0000-0001-9486-8481","position":4,"is_corresponding":false},{"id":1496928,"name":"H. Bell","orcid":null,"position":0,"is_corresponding":true}],"reference_count":53,"raw_metadata":null,"created_at":"2026-07-19T02:59:07.970345Z","pmid":"41349768","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}