{"gene":"ATP11C","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2011,"finding":"ATP11C functions as an aminophospholipid flippase that internalizes phosphatidylserine in pro-B cells; loss-of-function mutations cause defective PS translocation and developmental arrest of B lymphopoiesis, establishing a direct link between flippase activity and B cell differentiation.","method":"Mouse genetics (ENU mutagenesis), flow cytometry for PS translocation, transgenic rescue experiments (pre-rearranged Ig, Bcl-2, IL-7 transgenes)","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent labs, multiple orthogonal genetic rescue experiments, direct PS translocation assay, replicated across two simultaneous papers","pmids":["21423173","21423172"],"is_preprint":false},{"year":2011,"finding":"ATP11C mutations cause X-linked intrahepatic cholestasis in mice, originating from a non-hematopoietic (liver) cell defect; mutant mice show elevated serum cholic acid and are hypersensitive to dietary cholic acid supplementation, establishing ATP11C as a hepatic transporter preventing cholestasis.","method":"Mouse genetics, liver function tests, bile acid measurements, dietary supplementation challenge, bone marrow chimeras to distinguish hematopoietic vs. non-hematopoietic origin","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (chimeras, biochemistry, dietary challenge) in a focused single study with clear mechanistic readout","pmids":["21518881"],"is_preprint":false},{"year":2016,"finding":"ATP11C is the major phosphatidylserine flippase in human erythrocytes; a loss-of-function mutation reduces PS internalization 10-fold and causes X-linked congenital hemolytic anemia, establishing ATP11C as the principal erythrocyte flippase.","method":"Patient genetics, PS internalization assay in patient erythrocytes vs. controls, flow cytometry for PS exposure","journal":"Haematologica","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional PS flipping assay in patient-derived cells, confirmed by genetic mutation identification, replicated by later studies","pmids":["26944472"],"is_preprint":false},{"year":2016,"finding":"ATP11C mediates significant flippase activity (PS and PE internalization) in all murine leukocyte subsets; loss of ATP11C results in increased PS exposure on viable pro-B and developing T cells, but only B cell development is blocked.","method":"Flow cytometry with fluorescent PS/PE analogs in leukocyte subsets from ATP11C-deficient mice, 7-AAD viability gating","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct flipping assay across multiple cell types in knockout mice, single lab","pmids":["26799398"],"is_preprint":false},{"year":2016,"finding":"ATP11C localizes to the basolateral membrane of central hepatocytes and is required for basolateral localization of multiple bile salt uptake transporters (OATP1B2, OATP1A1, OATP1A4, NTCP); its loss causes proteasome-dependent degradation of these transporters and impairs hepatic uptake of unconjugated bile salts.","method":"Immunofluorescence, western blotting, pharmacokinetic analysis with radiolabeled substrates, proteasome inhibitor rescue (bortezomib) in ATP11C-deficient mice","journal":"Hepatology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (IHC localization, western blot, in vivo pharmacokinetics, pharmacological rescue) in a focused mechanistic study","pmids":["26926206"],"is_preprint":false},{"year":2015,"finding":"A nonsense mutation in ATP11C is responsible for the PS uptake defect in UPS-1 cells; exogenous expression of wild-type ATP11C restores PS flipping, establishing ATP11C as the essential flippase for PS in CHO-K1 cells.","method":"mRNA quantification, mutation identification by sequencing, rescue by exogenous ATP11C expression, fluorescent PS analog uptake assay","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutation identification plus functional rescue, single lab, two orthogonal methods","pmids":["26420878"],"is_preprint":false},{"year":2015,"finding":"ATP11C deficiency in mice impairs hepatic sinusoidal uptake of organic anions and reduces expression of OATP transporters in liver plasma membranes, without affecting biliary secretion or canalicular transporter expression.","method":"In vivo pharmacokinetic analysis with radiolabeled substrates, isolated hepatocyte uptake assays, liver plasma membrane fractionation and western blotting","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo pharmacokinetics plus ex vivo hepatocyte assays, single lab","pmids":["26399598"],"is_preprint":false},{"year":2017,"finding":"ATP11C is internalized from the plasma membrane via clathrin-mediated endocytosis upon Ca2+-mediated PKC activation; a di-leucine motif (SVRPLL) in the cytoplasmic C-terminus of ATP11C becomes functional upon PKC activation, and this regulation is triggered by Ca2+ signaling through Gq-coupled receptors. ATP11A does not undergo the same endocytosis.","method":"Live-cell imaging, endocytosis assays, PKC activation experiments, mutagenesis of di-leucine motif, pharmacological inhibition of clathrin-mediated endocytosis, Gq-coupled receptor stimulation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, imaging, pharmacological inhibition, receptor stimulation), clear mechanistic dissection of motif function","pmids":["29123098"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structures of ATP11C in six states at 3.0–4.0 Å resolution reveal the complete transport cycle: phosphorylation-driven domain movements couple with phospholipid binding; three phospholipid-bound states detail head group recognition and acyl chain accommodation in transmembrane grooves; invariant Lys880 and surrounding hydrogen-bond network serve as a pivot for helix bending and dephosphorylation.","method":"Single-particle cryo-EM, structure determination in five conformational states","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM structures with multiple transport intermediates and functional validation of key residues","pmids":["32997992"],"is_preprint":false},{"year":2019,"finding":"The C-terminal cytoplasmic region determines splice variant-specific localization: ATP11C-a distributes over the entire plasma membrane, while ATP11C-b localizes to a polarized membrane region; LLXY residues in the ATP11C-b C-terminus are critical for polarized localization. ATP11C-b and ATP11C-a do not undergo endocytosis upon PKC activation, in contrast to ATP11C-a.","method":"Fluorescence microscopy of splice variant localization in polarized and non-polarized cells, site-directed mutagenesis of LLXY motif, PKC activation assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct imaging plus mutagenesis of targeting motif, single lab","pmids":["31371488"],"is_preprint":false},{"year":2019,"finding":"The ATP11C T418N disease-causing mutation reduces flippase activity by causing ER retention and proteasome-mediated degradation rather than catalytic inactivation: mutant protein fails to traffic to the plasma membrane even in the presence of CDC50A, and is partially rescued by proteasome inhibitors.","method":"Monoclonal antibody generation, immunoblotting of patient erythrocyte membranes, transfection of mutant vs. wild-type in cultured cells, immunofluorescence for localization, proteasome inhibitor rescue, PS flippase activity assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (patient sample, cell transfection, pharmacological rescue, localization), single lab","pmids":["31253392"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM of ATP11C reconstituted in Nanodiscs reveals distended inner membrane around transmembrane helix 2 in the BeF-stabilized intermediate, suggesting local membrane perturbation facilitates phospholipid release to the lipid bilayer; membrane boundary varies with enzyme conformational state.","method":"Single-particle cryo-EM at 3.4 Å and 3.9 Å of Nanodisc-reconstituted ATP11C, ATPase activity measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution cryo-EM in native lipid environment with functional ATPase validation, single lab","pmids":["34922944"],"is_preprint":false},{"year":2021,"finding":"The polarized localization of ATP11C-b at the plasma membrane is mediated through direct interaction with ezrin; the LLxY motif in the ATP11C-b C-terminus is required for both ezrin binding and polarized localization. ERM proteins (especially ezrin) contribute to ATP11C-b polarization, and ATP11C-b loss causes mislocalization of C-terminally phosphorylated (active) ERM proteins, restored only by ATP11C-b but not ATP11C-a.","method":"Co-immunoprecipitation, mutagenesis of LLxY motif, ERM knockdown, fluorescence microscopy, ATP11C knockout with rescue experiments","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction demonstrated, mutagenesis, knockdown/rescue, single lab","pmids":["34528675"],"is_preprint":false},{"year":2023,"finding":"ATP11C loss in pre-B cells does not impair IL-7-dependent proliferation but is required for differentiation of pre-B cells into immature B cells upon IL-7 withdrawal, indicating ATP11C-mediated lipid asymmetry controls the switch from proliferation to differentiation.","method":"CRISPR/Cas9 knockout of ATP11C in pre-B cell line, PS flippase activity assay, proliferation and differentiation assays in vitro","journal":"Immunologic research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR knockout with direct functional and differentiation readouts, single lab","pmids":["36753036"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of the ATP11C Q79E mutant in the PC-occluded E2-Pi state reveals a reshaped substrate binding pocket: Q79E mutation plus conformational changes in Ser91 and Asn352 create additional space accommodating the bulky choline headgroup, thereby expanding substrate specificity from PS/PE to include PC.","method":"Cryo-EM structure determination, ATPase activity assay with PS and PC substrates, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure plus functional ATPase assay, mutagenesis, mechanistic dissection of substrate specificity, single lab","pmids":["41237907"],"is_preprint":false},{"year":2025,"finding":"The ATP11C-CDC50A complex maintains PS in the inner membrane leaflet; CRISPR knockout of ATP11C reduces PS flipping efficiency, impairs Newcastle disease virus (NDV) replication, and disrupts virion release; CDC50A mutations D193G/K319E compromise ATP11C activity and reduce PS redistribution by 60%, establishing CDC50A as an essential subunit for ATP11C function.","method":"CRISPR/Cas9 knockout, PS flipping assay, viral replication quantification, CDC50A site-directed mutagenesis, virus-like particle production assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with direct functional readouts plus mutagenesis of co-subunit, single lab","pmids":["40812423"],"is_preprint":false},{"year":2023,"finding":"A missense variant ATP11C p.Leu789Phe reduces ATP11C protein expression by 58% in patient RBC ghosts and reduces PS flippase activity to 26% of normal; recombinant mutant expression in HEK293T cells confirms reduced protein expression (27%) and decreased PS-stimulated ATPase activity (57%), establishing loss-of-function as the mechanism causing hemolytic anemia.","method":"Patient RBC ghost immunoblotting, PS flippase activity assay, recombinant protein expression in HEK293T cells, ATPase activity measurement","journal":"American journal of hematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient-derived material plus recombinant cell expression with direct enzymatic assay, single lab","pmids":["37671681"],"is_preprint":false}],"current_model":"ATP11C is a P4-type ATPase flippase that forms a complex with CDC50A and actively translocates phosphatidylserine (and phosphatidylethanolamine) from the exoplasmic to the cytoplasmic leaflet of the plasma membrane; cryo-EM structures reveal phosphorylation-driven domain movements, a substrate-binding pocket whose specificity is determined by key residues (Q79, S91, N352), and an invariant Lys880 pivot for dephosphorylation. At the plasma membrane, ATP11C undergoes clathrin-mediated endocytosis upon Ca2+/PKC activation via a C-terminal di-leucine motif, while the polarized splice variant ATP11C-b is anchored to specific membrane domains through interaction with ezrin via an LLxY motif. Loss of ATP11C function causes defective B lymphopoiesis, congenital hemolytic anemia, intrahepatic cholestasis (through impaired basolateral localization of bile acid transporters OATP1B2/1A1/1A4/NTCP in central hepatocytes), and pre-B to immature B cell differentiation arrest."},"narrative":{"mechanistic_narrative":"ATP11C is a P4-type ATPase aminophospholipid flippase that, in complex with its essential subunit CDC50A, actively translocates phosphatidylserine and phosphatidylethanolamine from the exoplasmic to the cytoplasmic leaflet of the plasma membrane, thereby establishing and maintaining membrane lipid asymmetry across erythrocytes, leukocytes, and hepatocytes [PMID:21423173, PMID:21423172, PMID:26944472, PMID:40812423]. Cryo-EM structures captured across the transport cycle define a phosphorylation-driven catalytic mechanism in which domain movements couple to phospholipid binding, with an invariant Lys880 serving as the pivot for helix bending and dephosphorylation, and the substrate-binding pocket (Q79, S91, N352) dictating head-group selectivity such that engineered changes expand specificity from PS/PE to phosphatidylcholine [PMID:32997992, PMID:41237907]; native-membrane structures further show local bilayer distortion around transmembrane helix 2 that facilitates lipid release [PMID:34922944]. Surface activity of ATP11C is dynamically controlled: a C-terminal di-leucine motif (SVRPLL) drives Ca2+/PKC-triggered clathrin-mediated endocytosis, while the splice variant ATP11C-b is anchored to a polarized membrane domain through direct binding of its C-terminal LLxY motif to ezrin [PMID:29123098, PMID:31371488, PMID:34528675]. Loss of ATP11C function causes defective B lymphopoiesis through a block in the pre-B to immature B cell differentiation switch, X-linked congenital hemolytic anemia, and X-linked intrahepatic cholestasis arising from a hepatocyte-intrinsic defect in which ATP11C is required for basolateral localization and stability of bile-salt uptake transporters (OATP1B2/1A1/1A4, NTCP) [PMID:21423173, PMID:21423172, PMID:21518881, PMID:26944472, PMID:26926206, PMID:36753036]. Disease-associated mutations act through loss of function, either by ER retention and proteasomal degradation (T418N) or reduced protein expression and ATPase activity (L789F) [PMID:31253392, PMID:37671681].","teleology":[{"year":2011,"claim":"Established that ATP11C is an aminophospholipid flippase whose PS-translocating activity is required for B lymphopoiesis, linking a biophysical lipid-transport function to a developmental program.","evidence":"ENU mutagenesis mouse genetics with PS translocation flow cytometry and transgenic rescue in pro-B cells","pmids":["21423173","21423172"],"confidence":"High","gaps":["Did not resolve why only B cells arrest despite flippase activity in other lineages","Molecular structure and catalytic mechanism not addressed"]},{"year":2011,"claim":"Showed the cholestasis phenotype originates from a non-hematopoietic liver defect, establishing ATP11C as a hepatic factor preventing bile-acid toxicity.","evidence":"Bone marrow chimeras, bile acid measurements, and dietary cholic acid challenge in mutant mice","pmids":["21518881"],"confidence":"High","gaps":["Mechanism connecting flippase activity to bile-acid handling unresolved","Identity of affected hepatic transporters not yet known"]},{"year":2015,"claim":"Defined the hepatic mechanism: ATP11C deficiency reduces sinusoidal organic-anion uptake and OATP transporter levels at the basolateral membrane without affecting canalicular secretion.","evidence":"In vivo pharmacokinetics with radiolabeled substrates, isolated hepatocyte uptake, and liver plasma membrane fractionation/western blot","pmids":["26399598"],"confidence":"Medium","gaps":["Whether transporter loss is degradation or mistrafficking not yet distinguished","Single lab"]},{"year":2015,"claim":"Confirmed ATP11C as the essential PS flippase in a cultured cell line via mutation identification and functional rescue, generalizing its role beyond immune and hepatic cells.","evidence":"Mutation sequencing and exogenous wild-type rescue with fluorescent PS-analog uptake in CHO-K1/UPS-1 cells","pmids":["26420878"],"confidence":"Medium","gaps":["Does not address regulation or structural basis","Single lab"]},{"year":2016,"claim":"Established ATP11C as the principal erythrocyte PS flippase and causally linked its loss to X-linked congenital hemolytic anemia in humans.","evidence":"Patient genetics with PS internalization and PS exposure assays in patient-derived erythrocytes","pmids":["26944472"],"confidence":"High","gaps":["Mechanism linking PS exposure to hemolysis not fully dissected","Effect on protein stability not addressed in this study"]},{"year":2016,"claim":"Showed flippase activity is broad across leukocyte subsets yet only B cell development is blocked, sharpening the lineage-specificity question.","evidence":"Flow cytometry with fluorescent PS/PE analogs in leukocytes from knockout mice with viability gating","pmids":["26799398"],"confidence":"Medium","gaps":["Lineage-specific dependence remains unexplained","Single lab"]},{"year":2016,"claim":"Resolved the hepatic mechanism by showing ATP11C is required for basolateral localization of bile-salt uptake transporters, with their loss driven by proteasomal degradation.","evidence":"Immunofluorescence, western blot, in vivo pharmacokinetics, and bortezomib proteasome-inhibitor rescue in deficient mice","pmids":["26926206"],"confidence":"High","gaps":["How a flippase governs transporter trafficking mechanistically unresolved","Direct physical interaction with transporters not shown"]},{"year":2017,"claim":"Revealed dynamic regulation of surface ATP11C: a C-terminal di-leucine motif drives Ca2+/PKC-triggered clathrin-mediated endocytosis downstream of Gq-coupled receptors.","evidence":"Live-cell imaging, endocytosis and PKC-activation assays, di-leucine motif mutagenesis, clathrin inhibition, and Gq receptor stimulation","pmids":["29123098"],"confidence":"High","gaps":["Physiological contexts triggering this endocytosis in vivo not defined","Adaptor proteins reading the motif not identified"]},{"year":2019,"claim":"Showed splice-variant C-termini determine subcellular distribution, with ATP11C-b targeted to a polarized membrane domain via an LLXY motif and resistant to PKC-induced endocytosis.","evidence":"Fluorescence microscopy of splice variants and LLXY motif mutagenesis with PKC-activation assays","pmids":["31371488"],"confidence":"Medium","gaps":["Binding partner mediating polarized targeting not yet identified","Single lab"]},{"year":2019,"claim":"Defined a disease mutation mechanism distinct from catalytic loss: T418N causes ER retention and proteasomal degradation, preventing plasma-membrane trafficking.","evidence":"Patient erythrocyte immunoblotting, mutant transfection, immunofluorescence localization, and proteasome-inhibitor rescue","pmids":["31253392"],"confidence":"Medium","gaps":["Whether CDC50A folding interaction is altered not fully resolved","Single lab"]},{"year":2020,"claim":"Provided the structural basis for transport by capturing six states of the cycle, defining phosphorylation-coupled domain movements, head-group recognition, and the Lys880 dephosphorylation pivot.","evidence":"Single-particle cryo-EM in multiple conformational states with functional residue validation","pmids":["32997992"],"confidence":"High","gaps":["Role of native lipid environment in the cycle not addressed","Splice-variant and regulatory C-terminus not resolved structurally"]},{"year":2021,"claim":"Showed in a native lipid environment that the enzyme distorts the inner membrane around TM2 in a phosphointermediate, providing a physical basis for phospholipid release into the bilayer.","evidence":"Cryo-EM of Nanodisc-reconstituted ATP11C with ATPase activity measurement","pmids":["34922944"],"confidence":"High","gaps":["Kinetics of membrane deformation during transport not measured","Single lab"]},{"year":2021,"claim":"Identified ezrin as the direct partner anchoring polarized ATP11C-b, and showed ATP11C-b reciprocally controls localization of active ERM proteins.","evidence":"Co-immunoprecipitation, LLxY motif mutagenesis, ERM knockdown, and knockout/rescue microscopy","pmids":["34528675"],"confidence":"Medium","gaps":["Structural detail of the LLxY-ezrin interface not defined","Single lab"]},{"year":2023,"claim":"Pinpointed ATP11C's role in B cell development to the IL-7-withdrawal-driven pre-B to immature B differentiation switch rather than proliferation.","evidence":"CRISPR/Cas9 knockout in a pre-B cell line with PS flippase, proliferation, and differentiation assays","pmids":["36753036"],"confidence":"Medium","gaps":["Signaling link between lipid asymmetry and the differentiation switch unresolved","Single lab"]},{"year":2023,"claim":"Demonstrated a human L789F variant acts by reducing protein expression and PS-stimulated ATPase activity, confirming loss-of-function as the basis of hemolytic anemia.","evidence":"Patient RBC ghost immunoblotting, PS flippase assay, and recombinant HEK293T expression with ATPase measurement","pmids":["37671681"],"confidence":"Medium","gaps":["Whether reduced expression reflects misfolding or degradation not dissected","Single lab"]},{"year":2025,"claim":"Established CDC50A as an essential subunit for ATP11C activity and linked ATP11C-maintained PS asymmetry to enveloped virus replication and release.","evidence":"CRISPR knockout, PS flipping and viral replication assays, CDC50A D193G/K319E mutagenesis, and virus-like particle assays","pmids":["40812423"],"confidence":"Medium","gaps":["Direct structural role of CDC50A residues in catalysis not resolved","Single lab"]},{"year":2025,"claim":"Structurally defined the determinants of substrate specificity by showing Q79E with conformational shifts of Ser91 and Asn352 reshape the pocket to admit the bulky choline head group, expanding selectivity to PC.","evidence":"Cryo-EM of the Q79E mutant in the PC-occluded E2-Pi state with PS/PC ATPase assays and mutagenesis","pmids":["41237907"],"confidence":"High","gaps":["Whether native ATP11C ever transports PC physiologically not established","Single lab"]},{"year":null,"claim":"How lipid asymmetry generated by ATP11C is transduced into specific cell-fate and trafficking outcomes (B cell differentiation switch, basolateral transporter retention) remains mechanistically undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No molecular link between cytoplasmic PS enrichment and downstream signaling identified","Physical basis for ATP11C control of partner transporter trafficking unknown","Lineage-specific developmental dependence unexplained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[8,11,14]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[8,11,16]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,2,14]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[0,2,3,15]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,7,9,12]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[10]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[4,6]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,13]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[7]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,4]}],"complexes":["ATP11C-CDC50A flippase complex"],"partners":["CDC50A","EZRIN","OATP1B2","NTCP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NB49","full_name":"Phospholipid-transporting ATPase IG","aliases":["ATPase IQ","ATPase class VI type 11C","P4-ATPase flippase complex alpha subunit ATP11C"],"length_aa":1132,"mass_kda":129.5,"function":"Catalytic component of a P4-ATPase flippase complex which catalyzes the hydrolysis of ATP coupled to the transport of aminophospholipids, phosphatidylserines (PS) and phosphatidylethanolamines (PE), from the outer to the inner leaflet of the plasma membrane (PubMed:24904167, PubMed:25315773, PubMed:26567335, PubMed:32493773). Major PS-flippase in immune cell subsets. In erythrocyte plasma membrane, it is required to maintain PS in the inner leaflet preventing its exposure on the surface. This asymmetric distribution is critical for the survival of erythrocytes in circulation since externalized PS is a phagocytic signal for erythrocyte clearance by splenic macrophages (PubMed:26944472). Required for B cell differentiation past the pro-B cell stage (By similarity). Seems to mediate PS flipping in pro-B cells (By similarity). May be involved in the transport of cholestatic bile acids (By similarity)","subcellular_location":"Cell membrane; Endoplasmic reticulum membrane; Early endosome membrane; Recycling endosome membrane","url":"https://www.uniprot.org/uniprotkb/Q8NB49/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ATP11C","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"OSBP","stoichiometry":0.2},{"gene":"STX12","stoichiometry":0.2},{"gene":"VAMP3","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ATP11C","total_profiled":1310},"omim":[{"mim_id":"611028","title":"TRANSMEMBRANE PROTEIN 30A; TMEM30A","url":"https://www.omim.org/entry/611028"},{"mim_id":"307700","title":"HYPOPARATHYROIDISM, X-LINKED; HYPX","url":"https://www.omim.org/entry/307700"},{"mim_id":"301053","title":"MICRO RNA 505; MIR505","url":"https://www.omim.org/entry/301053"},{"mim_id":"301015","title":"HEMOLYTIC ANEMIA, CONGENITAL, X-LINKED; HACXL","url":"https://www.omim.org/entry/301015"},{"mim_id":"300516","title":"ATPase, CLASS VI, TYPE 11C; ATP11C","url":"https://www.omim.org/entry/300516"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"liver","ntpm":45.4}],"url":"https://www.proteinatlas.org/search/ATP11C"},"hgnc":{"alias_symbol":["ATPIG","ATPIQ"],"prev_symbol":[]},"alphafold":{"accession":"Q8NB49","domains":[{"cath_id":"2.70.150.10","chopping":"145-274","consensus_level":"high","plddt":85.3265,"start":145,"end":274},{"cath_id":"3.40.50.1000","chopping":"408-418_657-731_748-831","consensus_level":"high","plddt":84.1649,"start":408,"end":831},{"cath_id":"3.40.1110.10","chopping":"423-436_459-482_491-655","consensus_level":"high","plddt":86.313,"start":423,"end":655}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NB49","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NB49-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NB49-F1-predicted_aligned_error_v6.png","plddt_mean":82.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ATP11C","jax_strain_url":"https://www.jax.org/strain/search?query=ATP11C"},"sequence":{"accession":"Q8NB49","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NB49.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NB49/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NB49"}},"corpus_meta":[{"pmid":"21423173","id":"PMC_21423173","title":"ATP11C is critical for the internalization of phosphatidylserine and differentiation of B lymphocytes.","date":"2011","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21423173","citation_count":119,"is_preprint":false},{"pmid":"21423172","id":"PMC_21423172","title":"The P4-type ATPase ATP11C is essential for B lymphopoiesis in adult bone marrow.","date":"2011","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21423172","citation_count":81,"is_preprint":false},{"pmid":"26944472","id":"PMC_26944472","title":"ATP11C is a major flippase in human erythrocytes and its defect causes congenital hemolytic anemia.","date":"2016","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/26944472","citation_count":76,"is_preprint":false},{"pmid":"32997992","id":"PMC_32997992","title":"Transport Cycle of Plasma Membrane Flippase ATP11C by Cryo-EM.","date":"2020","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/32997992","citation_count":58,"is_preprint":false},{"pmid":"21518881","id":"PMC_21518881","title":"X-linked cholestasis in mouse due to mutations of the P4-ATPase ATP11C.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21518881","citation_count":51,"is_preprint":false},{"pmid":"29123098","id":"PMC_29123098","title":"Phospholipid flippase ATP11C is endocytosed and downregulated following Ca2+-mediated protein kinase C activation.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29123098","citation_count":46,"is_preprint":false},{"pmid":"26926206","id":"PMC_26926206","title":"ATP11C targets basolateral bile salt transporter proteins in mouse central hepatocytes.","date":"2016","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/26926206","citation_count":21,"is_preprint":false},{"pmid":"26799398","id":"PMC_26799398","title":"ATP11C Facilitates Phospholipid Translocation across the Plasma Membrane of All Leukocytes.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26799398","citation_count":21,"is_preprint":false},{"pmid":"26420878","id":"PMC_26420878","title":"ATP11C mutation is responsible for the defect in phosphatidylserine uptake in UPS-1 cells.","date":"2015","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/26420878","citation_count":20,"is_preprint":false},{"pmid":"26399598","id":"PMC_26399598","title":"Impaired Hepatic Uptake by Organic Anion-Transporting Polypeptides Is Associated with Hyperbilirubinemia and Hypercholanemia in Atp11c Mutant Mice.","date":"2015","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26399598","citation_count":19,"is_preprint":false},{"pmid":"34922944","id":"PMC_34922944","title":"Cryo-EM of the ATP11C flippase reconstituted in Nanodiscs shows a distended phospholipid bilayer inner membrane around transmembrane helix 2.","date":"2021","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34922944","citation_count":15,"is_preprint":false},{"pmid":"31371488","id":"PMC_31371488","title":"The cytoplasmic C-terminal region of the ATP11C variant determines its localization at the polarized plasma membrane.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/31371488","citation_count":9,"is_preprint":false},{"pmid":"26045263","id":"PMC_26045263","title":"ATP8B1 and ATP11C: Two Lipid Flippases Important for Hepatocyte Function.","date":"2015","source":"Digestive diseases (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/26045263","citation_count":9,"is_preprint":false},{"pmid":"37671681","id":"PMC_37671681","title":"A novel missense variant in ATP11C is associated with reduced red blood cell phosphatidylserine flippase activity and mild hereditary hemolytic anemia.","date":"2023","source":"American journal of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/37671681","citation_count":8,"is_preprint":false},{"pmid":"31253392","id":"PMC_31253392","title":"ATP11C T418N, a gene mutation causing congenital hemolytic anemia, reduces flippase activity due to improper membrane trafficking.","date":"2019","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/31253392","citation_count":7,"is_preprint":false},{"pmid":"34528675","id":"PMC_34528675","title":"The interaction of ATP11C-b with ezrin contributes to its polarized localization.","date":"2021","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/34528675","citation_count":5,"is_preprint":false},{"pmid":"32344036","id":"PMC_32344036","title":"Expression of three P4-phospholipid flippases-atp11a, atp11b, and atp11c in zebrafish (Danio rerio).","date":"2020","source":"Gene expression patterns : GEP","url":"https://pubmed.ncbi.nlm.nih.gov/32344036","citation_count":4,"is_preprint":false},{"pmid":"37892263","id":"PMC_37892263","title":"Case of Congenital Hemolytic Anemia with ATP11C and ANK1 Variants.","date":"2023","source":"Children (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/37892263","citation_count":3,"is_preprint":false},{"pmid":"34651249","id":"PMC_34651249","title":"The ratio of ATP11C/PLSCR1 mRNA transcripts has clinical significance in sickle cell anemia.","date":"2021","source":"Annals of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/34651249","citation_count":2,"is_preprint":false},{"pmid":"40869043","id":"PMC_40869043","title":"Not-So-Rare Defects of RBC Lipidic Composition: Four New Cases of Flippase Deficiency Due to ATP11C Mutations.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40869043","citation_count":2,"is_preprint":false},{"pmid":"40812423","id":"PMC_40812423","title":"Newcastle disease virus exploits the phospholipid flippase ATP11c-CDC50A complex to promote viral infection.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/40812423","citation_count":1,"is_preprint":false},{"pmid":"36753036","id":"PMC_36753036","title":"ATP11C promotes the differentiation of pre-B cells into immature B cells but does not affect their IL-7-dependent proliferation.","date":"2023","source":"Immunologic research","url":"https://pubmed.ncbi.nlm.nih.gov/36753036","citation_count":1,"is_preprint":false},{"pmid":"41237907","id":"PMC_41237907","title":"Cryo-EM structure of the ATP11C Q79E mutant reveals the structural basis for altered Phospholipid recognition.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41237907","citation_count":1,"is_preprint":false},{"pmid":"42018644","id":"PMC_42018644","title":"Clinical variability of ATP11C-related hemolytic anemia: expanding the phenotypic and diagnostic spectrum.","date":"2026","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/42018644","citation_count":0,"is_preprint":false},{"pmid":"41523080","id":"PMC_41523080","title":"Hypomorphic ATP11c is a novel regulator of decreased efficacy of transfused red blood cells in humans and mice.","date":"2026","source":"HemaSphere","url":"https://pubmed.ncbi.nlm.nih.gov/41523080","citation_count":0,"is_preprint":false},{"pmid":"42024132","id":"PMC_42024132","title":"Beyond Gilbert's syndrome: hyperbilirubinaemia due to combined UGT1A1 mutation associated with an ATP11C variant.","date":"2026","source":"Revista espanola de enfermedades digestivas","url":"https://pubmed.ncbi.nlm.nih.gov/42024132","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.24.634764","title":"Phosphatidylserine (PS)-targeting chimeric Interferon (IFN) fusion proteins for anti-tumor applications","date":"2025-01-26","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.24.634764","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15132,"output_tokens":4181,"usd":0.054055,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12222,"output_tokens":4987,"usd":0.092893,"stage2_stop_reason":"end_turn"},"total_usd":0.146948,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"ATP11C functions as an aminophospholipid flippase that internalizes phosphatidylserine in pro-B cells; loss-of-function mutations cause defective PS translocation and developmental arrest of B lymphopoiesis, establishing a direct link between flippase activity and B cell differentiation.\",\n      \"method\": \"Mouse genetics (ENU mutagenesis), flow cytometry for PS translocation, transgenic rescue experiments (pre-rearranged Ig, Bcl-2, IL-7 transgenes)\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent labs, multiple orthogonal genetic rescue experiments, direct PS translocation assay, replicated across two simultaneous papers\",\n      \"pmids\": [\"21423173\", \"21423172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ATP11C mutations cause X-linked intrahepatic cholestasis in mice, originating from a non-hematopoietic (liver) cell defect; mutant mice show elevated serum cholic acid and are hypersensitive to dietary cholic acid supplementation, establishing ATP11C as a hepatic transporter preventing cholestasis.\",\n      \"method\": \"Mouse genetics, liver function tests, bile acid measurements, dietary supplementation challenge, bone marrow chimeras to distinguish hematopoietic vs. non-hematopoietic origin\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (chimeras, biochemistry, dietary challenge) in a focused single study with clear mechanistic readout\",\n      \"pmids\": [\"21518881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ATP11C is the major phosphatidylserine flippase in human erythrocytes; a loss-of-function mutation reduces PS internalization 10-fold and causes X-linked congenital hemolytic anemia, establishing ATP11C as the principal erythrocyte flippase.\",\n      \"method\": \"Patient genetics, PS internalization assay in patient erythrocytes vs. controls, flow cytometry for PS exposure\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional PS flipping assay in patient-derived cells, confirmed by genetic mutation identification, replicated by later studies\",\n      \"pmids\": [\"26944472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ATP11C mediates significant flippase activity (PS and PE internalization) in all murine leukocyte subsets; loss of ATP11C results in increased PS exposure on viable pro-B and developing T cells, but only B cell development is blocked.\",\n      \"method\": \"Flow cytometry with fluorescent PS/PE analogs in leukocyte subsets from ATP11C-deficient mice, 7-AAD viability gating\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct flipping assay across multiple cell types in knockout mice, single lab\",\n      \"pmids\": [\"26799398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ATP11C localizes to the basolateral membrane of central hepatocytes and is required for basolateral localization of multiple bile salt uptake transporters (OATP1B2, OATP1A1, OATP1A4, NTCP); its loss causes proteasome-dependent degradation of these transporters and impairs hepatic uptake of unconjugated bile salts.\",\n      \"method\": \"Immunofluorescence, western blotting, pharmacokinetic analysis with radiolabeled substrates, proteasome inhibitor rescue (bortezomib) in ATP11C-deficient mice\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (IHC localization, western blot, in vivo pharmacokinetics, pharmacological rescue) in a focused mechanistic study\",\n      \"pmids\": [\"26926206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A nonsense mutation in ATP11C is responsible for the PS uptake defect in UPS-1 cells; exogenous expression of wild-type ATP11C restores PS flipping, establishing ATP11C as the essential flippase for PS in CHO-K1 cells.\",\n      \"method\": \"mRNA quantification, mutation identification by sequencing, rescue by exogenous ATP11C expression, fluorescent PS analog uptake assay\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutation identification plus functional rescue, single lab, two orthogonal methods\",\n      \"pmids\": [\"26420878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ATP11C deficiency in mice impairs hepatic sinusoidal uptake of organic anions and reduces expression of OATP transporters in liver plasma membranes, without affecting biliary secretion or canalicular transporter expression.\",\n      \"method\": \"In vivo pharmacokinetic analysis with radiolabeled substrates, isolated hepatocyte uptake assays, liver plasma membrane fractionation and western blotting\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo pharmacokinetics plus ex vivo hepatocyte assays, single lab\",\n      \"pmids\": [\"26399598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ATP11C is internalized from the plasma membrane via clathrin-mediated endocytosis upon Ca2+-mediated PKC activation; a di-leucine motif (SVRPLL) in the cytoplasmic C-terminus of ATP11C becomes functional upon PKC activation, and this regulation is triggered by Ca2+ signaling through Gq-coupled receptors. ATP11A does not undergo the same endocytosis.\",\n      \"method\": \"Live-cell imaging, endocytosis assays, PKC activation experiments, mutagenesis of di-leucine motif, pharmacological inhibition of clathrin-mediated endocytosis, Gq-coupled receptor stimulation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, imaging, pharmacological inhibition, receptor stimulation), clear mechanistic dissection of motif function\",\n      \"pmids\": [\"29123098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cryo-EM structures of ATP11C in six states at 3.0–4.0 Å resolution reveal the complete transport cycle: phosphorylation-driven domain movements couple with phospholipid binding; three phospholipid-bound states detail head group recognition and acyl chain accommodation in transmembrane grooves; invariant Lys880 and surrounding hydrogen-bond network serve as a pivot for helix bending and dephosphorylation.\",\n      \"method\": \"Single-particle cryo-EM, structure determination in five conformational states\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM structures with multiple transport intermediates and functional validation of key residues\",\n      \"pmids\": [\"32997992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The C-terminal cytoplasmic region determines splice variant-specific localization: ATP11C-a distributes over the entire plasma membrane, while ATP11C-b localizes to a polarized membrane region; LLXY residues in the ATP11C-b C-terminus are critical for polarized localization. ATP11C-b and ATP11C-a do not undergo endocytosis upon PKC activation, in contrast to ATP11C-a.\",\n      \"method\": \"Fluorescence microscopy of splice variant localization in polarized and non-polarized cells, site-directed mutagenesis of LLXY motif, PKC activation assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct imaging plus mutagenesis of targeting motif, single lab\",\n      \"pmids\": [\"31371488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The ATP11C T418N disease-causing mutation reduces flippase activity by causing ER retention and proteasome-mediated degradation rather than catalytic inactivation: mutant protein fails to traffic to the plasma membrane even in the presence of CDC50A, and is partially rescued by proteasome inhibitors.\",\n      \"method\": \"Monoclonal antibody generation, immunoblotting of patient erythrocyte membranes, transfection of mutant vs. wild-type in cultured cells, immunofluorescence for localization, proteasome inhibitor rescue, PS flippase activity assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (patient sample, cell transfection, pharmacological rescue, localization), single lab\",\n      \"pmids\": [\"31253392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM of ATP11C reconstituted in Nanodiscs reveals distended inner membrane around transmembrane helix 2 in the BeF-stabilized intermediate, suggesting local membrane perturbation facilitates phospholipid release to the lipid bilayer; membrane boundary varies with enzyme conformational state.\",\n      \"method\": \"Single-particle cryo-EM at 3.4 Å and 3.9 Å of Nanodisc-reconstituted ATP11C, ATPase activity measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution cryo-EM in native lipid environment with functional ATPase validation, single lab\",\n      \"pmids\": [\"34922944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The polarized localization of ATP11C-b at the plasma membrane is mediated through direct interaction with ezrin; the LLxY motif in the ATP11C-b C-terminus is required for both ezrin binding and polarized localization. ERM proteins (especially ezrin) contribute to ATP11C-b polarization, and ATP11C-b loss causes mislocalization of C-terminally phosphorylated (active) ERM proteins, restored only by ATP11C-b but not ATP11C-a.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis of LLxY motif, ERM knockdown, fluorescence microscopy, ATP11C knockout with rescue experiments\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction demonstrated, mutagenesis, knockdown/rescue, single lab\",\n      \"pmids\": [\"34528675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ATP11C loss in pre-B cells does not impair IL-7-dependent proliferation but is required for differentiation of pre-B cells into immature B cells upon IL-7 withdrawal, indicating ATP11C-mediated lipid asymmetry controls the switch from proliferation to differentiation.\",\n      \"method\": \"CRISPR/Cas9 knockout of ATP11C in pre-B cell line, PS flippase activity assay, proliferation and differentiation assays in vitro\",\n      \"journal\": \"Immunologic research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR knockout with direct functional and differentiation readouts, single lab\",\n      \"pmids\": [\"36753036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of the ATP11C Q79E mutant in the PC-occluded E2-Pi state reveals a reshaped substrate binding pocket: Q79E mutation plus conformational changes in Ser91 and Asn352 create additional space accommodating the bulky choline headgroup, thereby expanding substrate specificity from PS/PE to include PC.\",\n      \"method\": \"Cryo-EM structure determination, ATPase activity assay with PS and PC substrates, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure plus functional ATPase assay, mutagenesis, mechanistic dissection of substrate specificity, single lab\",\n      \"pmids\": [\"41237907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The ATP11C-CDC50A complex maintains PS in the inner membrane leaflet; CRISPR knockout of ATP11C reduces PS flipping efficiency, impairs Newcastle disease virus (NDV) replication, and disrupts virion release; CDC50A mutations D193G/K319E compromise ATP11C activity and reduce PS redistribution by 60%, establishing CDC50A as an essential subunit for ATP11C function.\",\n      \"method\": \"CRISPR/Cas9 knockout, PS flipping assay, viral replication quantification, CDC50A site-directed mutagenesis, virus-like particle production assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with direct functional readouts plus mutagenesis of co-subunit, single lab\",\n      \"pmids\": [\"40812423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A missense variant ATP11C p.Leu789Phe reduces ATP11C protein expression by 58% in patient RBC ghosts and reduces PS flippase activity to 26% of normal; recombinant mutant expression in HEK293T cells confirms reduced protein expression (27%) and decreased PS-stimulated ATPase activity (57%), establishing loss-of-function as the mechanism causing hemolytic anemia.\",\n      \"method\": \"Patient RBC ghost immunoblotting, PS flippase activity assay, recombinant protein expression in HEK293T cells, ATPase activity measurement\",\n      \"journal\": \"American journal of hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived material plus recombinant cell expression with direct enzymatic assay, single lab\",\n      \"pmids\": [\"37671681\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ATP11C is a P4-type ATPase flippase that forms a complex with CDC50A and actively translocates phosphatidylserine (and phosphatidylethanolamine) from the exoplasmic to the cytoplasmic leaflet of the plasma membrane; cryo-EM structures reveal phosphorylation-driven domain movements, a substrate-binding pocket whose specificity is determined by key residues (Q79, S91, N352), and an invariant Lys880 pivot for dephosphorylation. At the plasma membrane, ATP11C undergoes clathrin-mediated endocytosis upon Ca2+/PKC activation via a C-terminal di-leucine motif, while the polarized splice variant ATP11C-b is anchored to specific membrane domains through interaction with ezrin via an LLxY motif. Loss of ATP11C function causes defective B lymphopoiesis, congenital hemolytic anemia, intrahepatic cholestasis (through impaired basolateral localization of bile acid transporters OATP1B2/1A1/1A4/NTCP in central hepatocytes), and pre-B to immature B cell differentiation arrest.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATP11C is a P4-type ATPase aminophospholipid flippase that, in complex with its essential subunit CDC50A, actively translocates phosphatidylserine and phosphatidylethanolamine from the exoplasmic to the cytoplasmic leaflet of the plasma membrane, thereby establishing and maintaining membrane lipid asymmetry across erythrocytes, leukocytes, and hepatocytes [#0, #2, #15]. Cryo-EM structures captured across the transport cycle define a phosphorylation-driven catalytic mechanism in which domain movements couple to phospholipid binding, with an invariant Lys880 serving as the pivot for helix bending and dephosphorylation, and the substrate-binding pocket (Q79, S91, N352) dictating head-group selectivity such that engineered changes expand specificity from PS/PE to phosphatidylcholine [#8, #14]; native-membrane structures further show local bilayer distortion around transmembrane helix 2 that facilitates lipid release [#11]. Surface activity of ATP11C is dynamically controlled: a C-terminal di-leucine motif (SVRPLL) drives Ca2+/PKC-triggered clathrin-mediated endocytosis, while the splice variant ATP11C-b is anchored to a polarized membrane domain through direct binding of its C-terminal LLxY motif to ezrin [#7, #9, #12]. Loss of ATP11C function causes defective B lymphopoiesis through a block in the pre-B to immature B cell differentiation switch, X-linked congenital hemolytic anemia, and X-linked intrahepatic cholestasis arising from a hepatocyte-intrinsic defect in which ATP11C is required for basolateral localization and stability of bile-salt uptake transporters (OATP1B2/1A1/1A4, NTCP) [#0, #1, #2, #4, #13]. Disease-associated mutations act through loss of function, either by ER retention and proteasomal degradation (T418N) or reduced protein expression and ATPase activity (L789F) [#10, #16].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established that ATP11C is an aminophospholipid flippase whose PS-translocating activity is required for B lymphopoiesis, linking a biophysical lipid-transport function to a developmental program.\",\n      \"evidence\": \"ENU mutagenesis mouse genetics with PS translocation flow cytometry and transgenic rescue in pro-B cells\",\n      \"pmids\": [\"21423173\", \"21423172\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve why only B cells arrest despite flippase activity in other lineages\", \"Molecular structure and catalytic mechanism not addressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed the cholestasis phenotype originates from a non-hematopoietic liver defect, establishing ATP11C as a hepatic factor preventing bile-acid toxicity.\",\n      \"evidence\": \"Bone marrow chimeras, bile acid measurements, and dietary cholic acid challenge in mutant mice\",\n      \"pmids\": [\"21518881\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting flippase activity to bile-acid handling unresolved\", \"Identity of affected hepatic transporters not yet known\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the hepatic mechanism: ATP11C deficiency reduces sinusoidal organic-anion uptake and OATP transporter levels at the basolateral membrane without affecting canalicular secretion.\",\n      \"evidence\": \"In vivo pharmacokinetics with radiolabeled substrates, isolated hepatocyte uptake, and liver plasma membrane fractionation/western blot\",\n      \"pmids\": [\"26399598\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether transporter loss is degradation or mistrafficking not yet distinguished\", \"Single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Confirmed ATP11C as the essential PS flippase in a cultured cell line via mutation identification and functional rescue, generalizing its role beyond immune and hepatic cells.\",\n      \"evidence\": \"Mutation sequencing and exogenous wild-type rescue with fluorescent PS-analog uptake in CHO-K1/UPS-1 cells\",\n      \"pmids\": [\"26420878\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address regulation or structural basis\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established ATP11C as the principal erythrocyte PS flippase and causally linked its loss to X-linked congenital hemolytic anemia in humans.\",\n      \"evidence\": \"Patient genetics with PS internalization and PS exposure assays in patient-derived erythrocytes\",\n      \"pmids\": [\"26944472\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking PS exposure to hemolysis not fully dissected\", \"Effect on protein stability not addressed in this study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed flippase activity is broad across leukocyte subsets yet only B cell development is blocked, sharpening the lineage-specificity question.\",\n      \"evidence\": \"Flow cytometry with fluorescent PS/PE analogs in leukocytes from knockout mice with viability gating\",\n      \"pmids\": [\"26799398\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Lineage-specific dependence remains unexplained\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved the hepatic mechanism by showing ATP11C is required for basolateral localization of bile-salt uptake transporters, with their loss driven by proteasomal degradation.\",\n      \"evidence\": \"Immunofluorescence, western blot, in vivo pharmacokinetics, and bortezomib proteasome-inhibitor rescue in deficient mice\",\n      \"pmids\": [\"26926206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a flippase governs transporter trafficking mechanistically unresolved\", \"Direct physical interaction with transporters not shown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed dynamic regulation of surface ATP11C: a C-terminal di-leucine motif drives Ca2+/PKC-triggered clathrin-mediated endocytosis downstream of Gq-coupled receptors.\",\n      \"evidence\": \"Live-cell imaging, endocytosis and PKC-activation assays, di-leucine motif mutagenesis, clathrin inhibition, and Gq receptor stimulation\",\n      \"pmids\": [\"29123098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological contexts triggering this endocytosis in vivo not defined\", \"Adaptor proteins reading the motif not identified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed splice-variant C-termini determine subcellular distribution, with ATP11C-b targeted to a polarized membrane domain via an LLXY motif and resistant to PKC-induced endocytosis.\",\n      \"evidence\": \"Fluorescence microscopy of splice variants and LLXY motif mutagenesis with PKC-activation assays\",\n      \"pmids\": [\"31371488\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding partner mediating polarized targeting not yet identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined a disease mutation mechanism distinct from catalytic loss: T418N causes ER retention and proteasomal degradation, preventing plasma-membrane trafficking.\",\n      \"evidence\": \"Patient erythrocyte immunoblotting, mutant transfection, immunofluorescence localization, and proteasome-inhibitor rescue\",\n      \"pmids\": [\"31253392\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CDC50A folding interaction is altered not fully resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided the structural basis for transport by capturing six states of the cycle, defining phosphorylation-coupled domain movements, head-group recognition, and the Lys880 dephosphorylation pivot.\",\n      \"evidence\": \"Single-particle cryo-EM in multiple conformational states with functional residue validation\",\n      \"pmids\": [\"32997992\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of native lipid environment in the cycle not addressed\", \"Splice-variant and regulatory C-terminus not resolved structurally\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed in a native lipid environment that the enzyme distorts the inner membrane around TM2 in a phosphointermediate, providing a physical basis for phospholipid release into the bilayer.\",\n      \"evidence\": \"Cryo-EM of Nanodisc-reconstituted ATP11C with ATPase activity measurement\",\n      \"pmids\": [\"34922944\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetics of membrane deformation during transport not measured\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified ezrin as the direct partner anchoring polarized ATP11C-b, and showed ATP11C-b reciprocally controls localization of active ERM proteins.\",\n      \"evidence\": \"Co-immunoprecipitation, LLxY motif mutagenesis, ERM knockdown, and knockout/rescue microscopy\",\n      \"pmids\": [\"34528675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural detail of the LLxY-ezrin interface not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Pinpointed ATP11C's role in B cell development to the IL-7-withdrawal-driven pre-B to immature B differentiation switch rather than proliferation.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in a pre-B cell line with PS flippase, proliferation, and differentiation assays\",\n      \"pmids\": [\"36753036\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling link between lipid asymmetry and the differentiation switch unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated a human L789F variant acts by reducing protein expression and PS-stimulated ATPase activity, confirming loss-of-function as the basis of hemolytic anemia.\",\n      \"evidence\": \"Patient RBC ghost immunoblotting, PS flippase assay, and recombinant HEK293T expression with ATPase measurement\",\n      \"pmids\": [\"37671681\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether reduced expression reflects misfolding or degradation not dissected\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established CDC50A as an essential subunit for ATP11C activity and linked ATP11C-maintained PS asymmetry to enveloped virus replication and release.\",\n      \"evidence\": \"CRISPR knockout, PS flipping and viral replication assays, CDC50A D193G/K319E mutagenesis, and virus-like particle assays\",\n      \"pmids\": [\"40812423\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct structural role of CDC50A residues in catalysis not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Structurally defined the determinants of substrate specificity by showing Q79E with conformational shifts of Ser91 and Asn352 reshape the pocket to admit the bulky choline head group, expanding selectivity to PC.\",\n      \"evidence\": \"Cryo-EM of the Q79E mutant in the PC-occluded E2-Pi state with PS/PC ATPase assays and mutagenesis\",\n      \"pmids\": [\"41237907\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether native ATP11C ever transports PC physiologically not established\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How lipid asymmetry generated by ATP11C is transduced into specific cell-fate and trafficking outcomes (B cell differentiation switch, basolateral transporter retention) remains mechanistically undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular link between cytoplasmic PS enrichment and downstream signaling identified\", \"Physical basis for ATP11C control of partner transporter trafficking unknown\", \"Lineage-specific developmental dependence unexplained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [8, 11, 14]},\n      {\"term_id\": \"GO:0140359\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [8, 11, 16]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 2, 14]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [0, 2, 3, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 7, 9, 12]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 13]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"complexes\": [\"ATP11C-CDC50A flippase complex\"],\n    \"partners\": [\"CDC50A\", \"ezrin\", \"OATP1B2\", \"NTCP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}