{"doi":"10.1186/s12964-024-02008-8","title":"Phosphorylation of Bok at Ser-8 blocks its ability to suppress IP3R-mediated calcium mobilization","abstract":"Abstract Background Bok is a poorly characterized Bcl-2 protein family member with roles yet to be clearly defined. It is clear, however, that Bok binds strongly to inositol 1,4,5-trisphosphate (IP 3 ) receptors (IP 3 Rs), which govern the mobilization of Ca 2+ from the endoplasmic reticulum, a signaling pathway required for many cellular processes. Also known is that Bok has a highly conserved phosphorylation site for cAMP-dependent protein kinase at serine-8 (Ser-8). Whether Bok, or phosphorylated Bok, has any direct impact on the Ca 2+ mobilizing function of IP 3 Rs remains to be established. Methods Bok Ser-8 phosphorylation was characterized using purified proteins, G-protein coupled receptor agonists that increase cAMP levels in intact cells, mass spectrometry, and immunoreactivity changes. Also, using mammalian cells that exclusively or predominately express IP 3 R1, to which Bok binds strongly, and a fluorescent Ca 2+ -sensitive dye or a genetically-encoded Ca 2+ sensor, we explored how endogenous and exogenous Bok controls the Ca 2+ mobilizing function of IP 3 R1, and whether Bok phosphorylation at Ser-8, or replacement of Ser-8 with a phosphomimetic amino acid, is regulatory. Results Our results confirm that Ser-8 of Bok is phosphorylated by cAMP-dependent protein kinase, and remarkably that phosphorylation can be detected with Bok specific antibodies. Also, we find that Bok has suppressive effects on IP 3 R-mediated Ca 2+ mobilization in a variety of cell types. Specifically, Bok accelerated the post-maximal decline in G-protein coupled receptor-induced cytosolic Ca 2+ concentration, via a mechanism that involves suppression of IP 3 R-dependent Ca 2+ release from the endoplasmic reticulum. These effects were dependent on the Bok-IP 3 R interaction, as they are only seen with IP 3 Rs that can bind Bok (e.g., IP 3 R1). Surprisingly, Bok phosphorylation at Ser-8 weakened the interaction between Bok and IP 3 R1 and reversed the ability of Bok to suppress IP 3 R1-mediated Ca 2+ mobilization. Conclusions For the first time, Bok was shown to directly suppress IP 3 R1 activity, which was reversed by Ser-8 phosphorylation. We hypothesize that this suppression of IP 3 R1 activity is due to Bok regulation of the conformational changes in IP 3 R1 that mediate channel opening. This study provides new insights on the role of Bok, its interaction with IP 3 Rs, and the impact it has on IP 3 R-mediated Ca 2+ mobilization.","journal":"Cell Communication and Signaling","year":2025,"id":560344,"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":0.9627,"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":948979,"name":"Katherine R. Keller","orcid":"0000-0002-7664-5652","position":1,"is_corresponding":false},{"id":65726,"name":"Richard J.H. Wojcikiewicz","orcid":"0000-0001-8092-6417","position":2,"is_corresponding":false},{"id":708926,"name":"Caden G. Bonzerato","orcid":"0000-0001-6380-8320","position":0,"is_corresponding":true}],"reference_count":84,"raw_metadata":null,"created_at":"2026-07-19T02:55:42.883572Z","pmid":"39810210","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":[]}