{"doi":"10.1101/2025.05.28.656654","title":"Disease-causing mutations in the G protein β5 β-propeller disrupt its chaperonin-mediated folding trajectory","abstract":"Abstract The Chaperonin Containing Tailless polypeptide 1 (CCT or TRiC) is an essential cytosolic chaperone that folds multiple protein substrates, including many with β-propeller folds. One β-propeller substrate is the G protein β 5 subunit (Gβ 5 ) of Regulator of G protein Signaling (RGS) complexes that determine the duration of G protein signals in neurons. In recent work, we used cryo-electron microscopy (cryo-EM) to visualize the complete CCT-mediated folding trajectory for Gβ 5 , from an initiating electrostatic interaction of a single β-strand in Gβ 5 with the CCT5 subunit to a completely folded β-propeller structure. Here, we employed biochemistry and cryo-EM to determine key interactions with CCT that initiate Gβ 5 folding and how missense mutations in Gβ 5 that cause severe neurological diseases alter the Gβ 5 folding trajectory and lead to incompletely folded, trapped intermediates. These findings highlight how CCT recognizes folding substrates, how defects in chaperonin-mediated folding contribute to disease, and how strategies might be designed to stabilize misfolded proteins to restore function. Significance Electrostatic interactions between the CCT chaperonin and its protein substrates initiate the folding process. Using cryo-EM structure determinations, we found a striking specificity for these interactions that allow CCT-mediated Gβ 5 folding. Moreover, certain missense mutations in Gβ 5 lead to misfolding and are associated with neurological disorders. We tracked how these mutations disrupt the normal folding of Gβ 5 by CCT. Although mutant Gβ 5 still binds the complex, folding stalls mid-process, leaving the protein trapped in partially folded, non-functional states. These defects arise from disrupted packing of the Gβ 5 core that interferes with formation of the native structure. Our findings reveal a molecular basis for Gβ 5 misfolding in disease and suggest pharmacological chaperones that stabilize the folded state might restore proper function.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2025,"id":558088,"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":1,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9648,"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":1301375,"name":"Deirdre Mack","orcid":null,"position":1,"is_corresponding":false},{"id":1458533,"name":"Riley A. Nickles","orcid":null,"position":2,"is_corresponding":false},{"id":545197,"name":"Caelen A. Jones","orcid":null,"position":3,"is_corresponding":false},{"id":1458534,"name":"Rex L. Brunsdale","orcid":null,"position":4,"is_corresponding":false},{"id":1301376,"name":"Samuel L. Cottam","orcid":null,"position":5,"is_corresponding":false},{"id":778544,"name":"Barry M. Willardson","orcid":"0000-0002-8503-2268","position":7,"is_corresponding":false},{"id":1458535,"name":"Liam J. Moss","orcid":null,"position":9,"is_corresponding":false},{"id":942281,"name":"Stefano Maggi","orcid":"0000-0003-4853-5840","position":10,"is_corresponding":false},{"id":709239,"name":"Peter Shen","orcid":"0000-0002-6256-6910","position":11,"is_corresponding":false},{"id":1002809,"name":"Mikaila Sass","orcid":null,"position":0,"is_corresponding":true}],"reference_count":58,"raw_metadata":null,"created_at":"2026-07-19T02:55:21.727661Z","pmid":"40501749","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":[]}