{"doi":"10.1016/j.jbc.2021.101398","title":"Sphingomyelin synthases 1 and 2 exhibit phosphatidylcholine phospholipase C activity","abstract":"Many studies have confirmed the enzymatic activity of a mammalian phosphatidylcholine (PC) phospholipase C (PLC) (PC-PLC), which produces diacylglycerol (DAG) and phosphocholine through the hydrolysis of PC in the absence of ceramide. However, the protein(s) responsible for this activity have never yet been identified. Based on the fact that tricyclodecan-9-yl-potassium xanthate can inhibit both PC-PLC and sphingomyelin synthase (SMS) activities, and SMS1 and SMS2 have a conserved catalytic domain that could mediate a nucleophilic attack on the phosphodiester bond of PC, we hypothesized that both SMS1 and SMS2 might have PC-PLC activity. In the present study, we found that purified recombinant SMS1 and SMS2 but not SMS-related protein have PC-PLC activity. Moreover, we prepared liver-specific Sms1/global Sms2 double-KO mice. We found that liver PC-PLC activity was significantly reduced and steady-state levels of PC and DAG in the liver were regulated by the deficiency, in comparison with control mice. Using adenovirus, we expressed Sms1 and Sms2 genes in the liver of the double-KO mice, respectively, and found that expressed SMS1 and SMS2 can hydrolyze PC to produce DAG and phosphocholine. Thus, SMS1 and SMS2 exhibit PC-PLC activity in vitro and in vivo. Many studies have confirmed the enzymatic activity of a mammalian phosphatidylcholine (PC) phospholipase C (PLC) (PC-PLC), which produces diacylglycerol (DAG) and phosphocholine through the hydrolysis of PC in the absence of ceramide. However, the protein(s) responsible for this activity have never yet been identified. Based on the fact that tricyclodecan-9-yl-potassium xanthate can inhibit both PC-PLC and sphingomyelin synthase (SMS) activities, and SMS1 and SMS2 have a conserved catalytic domain that could mediate a nucleophilic attack on the phosphodiester bond of PC, we hypothesized that both SMS1 and SMS2 might have PC-PLC activity. In the present study, we found that purified recombinant SMS1 and SMS2 but not SMS-related protein have PC-PLC activity. Moreover, we prepared liver-specific Sms1/global Sms2 double-KO mice. We found that liver PC-PLC activity was significantly reduced and steady-state levels of PC and DAG in the liver were regulated by the deficiency, in comparison with control mice. Using adenovirus, we expressed Sms1 and Sms2 genes in the liver of the double-KO mice, respectively, and found that expressed SMS1 and SMS2 can hydrolyze PC to produce DAG and phosphocholine. Thus, SMS1 and SMS2 exhibit PC-PLC activity in vitro and in vivo. Phosphatidylcholine (PC) is an essential phospholipid for cell formation, growth, and death (1van Meer G. Voelker D.R. Feigenson G.W. Membrane lipids: Where they are and how they behave.Nat. Rev. Mol. Cell Biol. 2008; 9: 112-124Crossref PubMed Scopus (3973) Google Scholar). The steady-state levels of PC should be controlled by its biosynthesis (Kennedy pathway) and catabolic pathways, including PC-phospholipase C (PC-PLC) (2Wolf R.A. Gross R.W. Identification of neutral active phospholipase C which hydrolyzes choline glycerophospholipids and plasmalogen selective phospholipase A2 in canine myocardium.J. Biol. Chem. 1985; 260: 7295-7303Abstract Full Text PDF PubMed Google Scholar, 3Sheikhnejad R.G. Srivastava P.N. Isolation and properties of a phosphatidylcholine-specific phospholipase C from bull seminal plasma.J. Biol. Chem. 1986; 261: 7544-7549Abstract Full Text PDF PubMed Google Scholar). PLCs are a group of enzymes that produce a diacylglycerol (DAG) and a phosphorylated molecule, such as phosphorylcholine (P-choline) and phosphorylethanolamine (P-ethanolamine) (4Cheng M. Bhujwalla Z.M. Glunde K. Targeting phospholipid metabolism in cancer.Front. Oncol. 2016; 6: 266Crossref PubMed Scopus (76) Google Scholar). It is conceivable that PC-PLC activity is important in maintaining steady-state levels of PC, thus influencing cell membrane integrity and function. Although bacterial PC-PLC was cloned previously (5Vazquez-Boland J.A","journal":"Journal of Biological Chemistry","year":2021,"id":175874,"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":22,"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":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":605843,"name":"Zhiqiang Li","orcid":"0000-0001-9730-2387","position":1,"is_corresponding":false},{"id":717699,"name":"Yang Chen","orcid":"0000-0003-4496-7849","position":2,"is_corresponding":false},{"id":387652,"name":"Yu Cao","orcid":"0000-0003-1409-2068","position":3,"is_corresponding":false},{"id":686213,"name":"Xian‐Cheng Jiang","orcid":"0000-0003-2030-9542","position":4,"is_corresponding":false},{"id":703577,"name":"Yeun-po Chiang","orcid":"0000-0003-0054-596X","position":0,"is_corresponding":true}],"reference_count":31,"raw_metadata":null,"created_at":"2026-07-18T23:47:19.591542Z","pmid":"34774525","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":[]}