{"doi":"10.1016/j.jbc.2025.110350","title":"Molecular consequences of SCA5 mutations in the spectrin-repeat domains of β-III-spectrin","abstract":"Spinocerebellar ataxia type 5 (SCA5) mutations in the protein β-III-spectrin cluster to the N-terminal actin-binding domain (ABD) and the central spectrin-repeat domains (SRDs). We previously reported that a common molecular consequence of ABD-localized SCA5 mutations is increased actin binding. However, little is known about the molecular consequences of the SRD-localized mutations. It is known that the SRDs of β-spectrin proteins interact with α-spectrin to form an α/β-spectrin dimer. In addition, it is known that SRDs neighboring the β-spectrin ABD enhance actin binding. Here, we tested the impact of the SRD-localized R480W and E532_M544del mutations on the binding of β-III-spectrin to α-II-spectrin and actin. R480W is associated with a severe infantile onset form of SCA5, while E532_M544del is associated with milder symptoms that begin in adulthood. We show that both the R480W and E532_M544del mutants can bind α-II-spectrin. However, E532_M544del causes partial uncoupling of complementary SRDs in the α/β-spectrin dimer. Further, the R480W mutant forms large intracellular inclusions when coexpressed with α-II-spectrin in cells, supporting that R480W grossly disrupts the α-II/β-III-spectrin complex. Moreover, actin-binding assays show that E532_M544del, but not R480W, increases β-III-spectrin actin binding. Additionally, we demonstrate that R480W α-II/β-III-spectrin inclusions contain F-actin, accumulate the spectrin-binding protein ankyrin-R, and localize immediately adjacent to the Golgi complex. Two additional infantile onset mutations, R437W and R437Q, but not the adult onset T472M mutation, also cause formation of large α-II/β-III-spectrin inclusions. We suggest that the intracellular inclusions caused by R480W, R437W, and R437Q drive the more severe disease symptoms associated with these mutations.","journal":"Journal of Biological Chemistry","year":2025,"id":544643,"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":0.9507,"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":1353838,"name":"Naomi R. DeLaet","orcid":null,"position":1,"is_corresponding":false},{"id":1353839,"name":"Abeer W. Abukamil","orcid":null,"position":2,"is_corresponding":false},{"id":1353840,"name":"Angelica N. Alexopoulos","orcid":null,"position":3,"is_corresponding":false},{"id":1011231,"name":"Amanda R. Keller","orcid":null,"position":4,"is_corresponding":false},{"id":1435174,"name":"Matthew T. Thiel","orcid":null,"position":5,"is_corresponding":false},{"id":943990,"name":"Alexandra E. Atang","orcid":"0009-0008-9686-9742","position":6,"is_corresponding":false},{"id":430806,"name":"Adam W. Avery","orcid":"0000-0001-8085-1822","position":7,"is_corresponding":false},{"id":431507,"name":"Sarah A. Denha","orcid":null,"position":0,"is_corresponding":true}],"reference_count":63,"raw_metadata":null,"created_at":"2026-07-19T02:53:12.864581Z","pmid":"40484375","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":[]}