{"doi":"10.1085/jgp.202012617","title":"Pre-assembled Ca2+ entry units and constitutively active Ca2+ entry in skeletal muscle of calsequestrin-1 knockout mice","abstract":"Store-operated Ca2+ entry (SOCE) is a ubiquitous Ca2+ influx mechanism triggered by depletion of Ca2+ stores from the endoplasmic/sarcoplasmic reticulum (ER/SR). We recently reported that acute exercise in WT mice drives the formation of Ca2+ entry units (CEUs), intracellular junctions that contain STIM1 and Orai1, the two key proteins mediating SOCE. The presence of CEUs correlates with increased constitutive- and store-operated Ca2+ entry, as well as sustained Ca2+ release and force generation during repetitive stimulation. Skeletal muscle from mice lacking calsequestrin-1 (CASQ1-null), the primary Ca2+-binding protein in the lumen of SR terminal cisternae, exhibits significantly reduced total Ca2+ store content and marked SR Ca2+ depletion during high-frequency stimulation. Here, we report that CEUs are constitutively assembled in extensor digitorum longus (EDL) and flexor digitorum brevis (FDB) muscles of sedentary CASQ1-null mice. The higher density of CEUs in EDL (39.6 ± 2.1/100 µm2 versus 2.0 ± 0.3/100 µm2) and FDB (16.7 ± 1.0/100 µm2 versus 2.7 ± 0.5/100 µm2) muscles of CASQ1-null compared with WT mice correlated with enhanced constitutive- and store-operated Ca2+ entry and increased expression of STIM1, Orai1, and SERCA. The higher ability to recover Ca2+ ions via SOCE in CASQ1-null muscle served to promote enhanced maintenance of peak Ca2+ transient amplitude, increased dependence of luminal SR Ca2+ replenishment on BTP-2-sensitive SOCE, and increased maintenance of contractile force during repetitive, high-frequency stimulation. Together, these data suggest that muscles from CASQ1-null mice compensate for the lack of CASQ1 and reduction in total releasable SR Ca2+ content by assembling CEUs to promote constitutive and store-operated Ca2+ entry.","journal":"The Journal of General Physiology","year":2020,"id":91182,"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":46,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9574,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":456810,"name":"Simona Boncompagni","orcid":"0000-0001-5308-5069","position":1,"is_corresponding":false},{"id":456811,"name":"Laura Pietrangelo","orcid":"0000-0003-1197-7813","position":2,"is_corresponding":false},{"id":456812,"name":"Takahiro Takano","orcid":"0000-0002-6235-6673","position":3,"is_corresponding":false},{"id":456813,"name":"Feliciano Protasi","orcid":"0000-0002-0213-7591","position":4,"is_corresponding":false},{"id":281651,"name":"Robert T. Dirksen","orcid":"0000-0002-3182-1755","position":5,"is_corresponding":false},{"id":456809,"name":"Antonio Michelucci","orcid":"0000-0002-0720-3009","position":0,"is_corresponding":true}],"reference_count":54,"raw_metadata":null,"created_at":"2026-07-18T22:28:45.409789Z","pmid":"32761048","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":[]}