{"gene":"ALPK3","run_date":"2026-06-09T22:02:43","timeline":{"discoveries":[{"year":2001,"finding":"MIDORI (ALPK3) protein is localized to the nucleus in cardiomyocytes, and overexpression of Midori induces expression of endogenous Midori itself, suggesting it acts as a transcriptional regulator. Overexpression promotes differentiation of P19CL6 cells into cardiomyocytes, while antisense suppression reduces differentiation efficiency.","method":"Differential display, Northern blot, whole-mount in situ hybridization, overexpression/antisense stable cell lines, immunolocalization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — nuclear localization confirmed by direct imaging, gain- and loss-of-function in P19CL6 cells with defined differentiation phenotype; single lab, multiple orthogonal methods","pmids":["11418590"],"is_preprint":false},{"year":2011,"finding":"ALPK3-deficient (knockout) mice develop cardiomyopathy featuring both hypertrophic and dilated characteristics. Light and electron microscopy revealed altered cardiomyocyte architecture with reduced numbers of abnormal intercalated discs and mild myofibrillar disarray, establishing ALPK3 as required for normal intercalated disc organization and myofibrillar architecture in vivo.","method":"Knockout mouse model, MRI, histology, electron microscopy","journal":"Veterinary pathology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO model with multiple orthogonal structural and functional readouts; replicated by subsequent human studies showing same intercalated disc defects","pmids":["21441111"],"is_preprint":false},{"year":2016,"finding":"ALPK3-deficient cardiomyocytes (from patient iPSCs and CRISPR-engineered human ESCs lacking ALPK3) display disordered sarcomeres and intercalated discs by ultrastructural analysis, extended field potential duration by multi-electrode array, and abnormal calcium handling by calcium imaging, establishing loss of function as the underlying disease mechanism and identifying calcium handling defects as a feature of ALPK3 deficiency.","method":"Patient iPSC-derived cardiomyocytes, human ESC CRISPR knockouts, ultrastructural analysis (EM), multi-electrode array, calcium imaging","journal":"European heart journal","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — isogenic human stem cell models with multiple orthogonal functional readouts (ultrastructure, electrophysiology, calcium imaging); replicates mouse KO findings","pmids":["27106955"],"is_preprint":false},{"year":2022,"finding":"Multiple sequence alignment and phosphoproteomic evaluation of ALPK3 kinase domain inhibition and overexpression revealed no significant changes in catalytic phosphorylation activity, establishing ALPK3 as a pseudokinase. ALPK3 co-localizes with myomesin proteins (MYOM1, MYOM2) at both the nuclear envelope and the sarcomere M-band. Loss-of-function ALPK3 variants cause mislocalization of myomesin proteins and dysregulation of additional M-band proteins involved in sarcomere protein turnover, impairing cardiomyocyte structure and function.","method":"Multiple sequence alignment of alpha-kinase domains, phosphoproteomics (kinase domain inhibition and overexpression), co-localization imaging, isogenic human iPSC-derived cardiomyocytes, mouse models, human patient tissue analysis","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 1 / Strong — phosphoproteomic evidence for pseudokinase status combined with co-localization and functional mislocalization studies in isogenic iPSC-CMs and mouse models; multiple orthogonal methods in single rigorous study","pmids":["36321451"],"is_preprint":false},{"year":2022,"finding":"miR-384-5p was found to be decreased in cardiac hypertrophic tissues and cells; overexpression of miR-384-5p ameliorates pressure overload-induced cardiac hypertrophy by downregulating ALPK3 expression, positioning ALPK3 as a downstream target of miR-384-5p in cardiomyocyte hypertrophy signaling.","method":"ISO/Ang-II cardiac hypertrophy models (in vivo and in vitro), miR-384-5p overexpression, RT-qPCR, western blot, echocardiography","journal":"Journal of biochemical and molecular toxicology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, indirect evidence that ALPK3 is a miR-384-5p target via expression assays; no direct binding or reporter assay data described in abstract","pmids":["35510648"],"is_preprint":false},{"year":2025,"finding":"Knock-in mice carrying an ALPK3 truncating variant (K201X) show reduced basal sarcomere length, prolonged relaxation, increased diastolic calcium levels, decreased protein kinase A-mediated phosphorylation (including cardiac troponin I), and reduced myosin super-relaxed state fraction. These contractile and calcium handling defects were partially corrected by mavacamten (myosin inhibitor), implicating ALPK3 as a modulator of protein kinase A signaling and myosin regulation.","method":"Knock-in mouse model (K201X), isolated cardiomyocyte sarcomere length/relaxation measurements, calcium imaging, phosphorylation assays (western blot), myosin super-relaxed state measurement, mavacamten pharmacological rescue","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vivo knock-in model with multiple orthogonal cellular assays (calcium, sarcomere, kinase activity, myosin state) plus pharmacological rescue; peer-reviewed publication","pmids":["40128237"],"is_preprint":false},{"year":2025,"finding":"Delivery of full-length ALPK3 via adeno-associated virus (AAV) restored contractile function in human cardiac organoids and in vivo mouse models carrying ALPK3 truncating mutations. AAV-ALPK3 gene therapy also completely restored contractile deficits in human cardiac organoids carrying TTN truncating variants, suggesting ALPK3 scaffolds an M-band protein quality control network relevant to multiple cardiomyopathy causes.","method":"AAV gene delivery, human cardiac organoids, in vivo mouse knockout/knock-in models, contractile function measurements","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — preprint; in vivo and ex vivo rescue experiments with defined functional readouts; single study, not yet peer-reviewed","pmids":["bio_10.1101_2025.07.31.667858"],"is_preprint":true},{"year":2025,"finding":"Comprehensive systematic review with experimental modeling confirms that ALPK3 lacks catalytic kinase activity (pseudokinase) and maintains sarcomeric proteostasis by scaffolding myomesins (MYOM1/MYOM2), MuRF (muscle ring-finger protein) E3 ubiquitin ligases, and SQSTM1/p62 at the sarcomere M-band and nuclear envelope. Loss of this scaffolding displaces myomesins and drives thick-filament protein aggregation, causing contractile dysfunction.","method":"Integrative review synthesizing phosphoproteomics, co-localization, iPSC-derived cardiomyocyte models, mouse models, and patient tissue data","journal":"Circulation. Genomic and precision medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — comprehensive synthesis of existing experimental data; mechanistic claims grounded in prior primary studies; not a new primary experiment but a rigorous curation","pmids":["41221624"],"is_preprint":false}],"current_model":"ALPK3 (Midori) is a cardiac-enriched pseudokinase that lacks catalytic phosphotransferase activity and instead functions as a structural scaffold at the sarcomere M-band and nuclear envelope, where it anchors myomesin force-buffering proteins (MYOM1/MYOM2), MuRF E3 ubiquitin ligases, and SQSTM1/p62 to maintain sarcomere proteostasis; loss of ALPK3 displaces myomesins, disrupts M-band protein turnover, impairs intercalated disc organization, causes abnormal calcium handling and reduced protein kinase A-mediated phosphorylation, and ultimately produces cardiomyopathy whose contractile defects can be partially rescued by the myosin inhibitor mavacamten or by AAV-mediated gene replacement."},"narrative":{"mechanistic_narrative":"ALPK3 is a cardiac-enriched pseudokinase that functions as a structural scaffold required for sarcomere integrity and cardiomyocyte architecture, with loss of function producing cardiomyopathy [PMID:21441111, PMID:36321451]. Phosphoproteomic analysis upon kinase-domain inhibition and overexpression detected no catalytic phosphotransferase activity, establishing ALPK3 as a pseudokinase that instead acts by co-localizing with the myomesin force-buffering proteins MYOM1 and MYOM2 at the sarcomere M-band and nuclear envelope; loss-of-function variants mislocalize myomesins and dysregulate additional M-band proteins controlling sarcomere protein turnover [PMID:36321451]. Through this scaffolding role ALPK3 maintains sarcomeric proteostasis, anchoring MuRF E3 ubiquitin ligases and SQSTM1/p62 at the M-band, and its loss displaces myomesins and drives thick-filament protein aggregation [PMID:41221624]. ALPK3 deficiency disorders sarcomeres and intercalated discs and causes abnormal calcium handling in both knockout mice and isogenic human stem cell-derived cardiomyocytes [PMID:21441111, PMID:27106955]. A truncating knock-in model links ALPK3 to contractile regulation, showing prolonged relaxation, elevated diastolic calcium, reduced protein kinase A-mediated phosphorylation, and a decreased myosin super-relaxed state that is partially corrected by the myosin inhibitor mavacamten [PMID:40128237]. AAV-mediated delivery of full-length ALPK3 restores contractile function in human cardiac organoids and mouse models carrying ALPK3 truncating mutations [PMID:bio_10.1101_2025.07.31.667858].","teleology":[{"year":2001,"claim":"Established the first cellular context for ALPK3 (Midori), asking where the protein acts and whether it influences cardiac cell fate.","evidence":"Differential display, immunolocalization, and gain/loss-of-function in P19CL6 cells","pmids":["11418590"],"confidence":"Medium","gaps":["Proposed transcriptional regulator role rests on overexpression autoinduction, not direct DNA binding","Performed in a single cell-line differentiation model"]},{"year":2011,"claim":"Tested whether ALPK3 is required in vivo, showing its loss causes cardiomyopathy with intercalated disc and myofibrillar defects.","evidence":"Knockout mouse model with MRI, histology, and electron microscopy","pmids":["21441111"],"confidence":"High","gaps":["Did not define the molecular function underlying the structural defects","Mixed hypertrophic/dilated phenotype mechanism unresolved"]},{"year":2016,"claim":"Confirmed loss of function as the disease mechanism in human cells and identified calcium handling as an affected process.","evidence":"Patient iPSC-derived and CRISPR-engineered isogenic human ESC cardiomyocytes with EM, multi-electrode array, and calcium imaging","pmids":["27106955"],"confidence":"High","gaps":["Did not identify molecular partners or the basis of calcium dysregulation","Catalytic status of ALPK3 not addressed"]},{"year":2022,"claim":"Resolved the long-standing assumption that ALPK3 is an active kinase, establishing it as a pseudokinase that scaffolds myomesins at the M-band and nuclear envelope.","evidence":"Alpha-kinase domain alignment, phosphoproteomics under kinase inhibition/overexpression, and co-localization in isogenic iPSC-CMs, mouse models, and patient tissue","pmids":["36321451"],"confidence":"High","gaps":["Structural basis of myomesin anchoring not defined","Whether scaffolding is direct binding or indirect not established"]},{"year":2022,"claim":"Placed ALPK3 in a hypertrophy regulatory circuit as a downstream target whose suppression mitigates pressure-overload hypertrophy.","evidence":"ISO/Ang-II hypertrophy models with miR-384-5p overexpression, RT-qPCR, and echocardiography","pmids":["35510648"],"confidence":"Low","gaps":["No direct miR-384-5p:ALPK3 binding or reporter assay shown","Inferred from expression correlation in a single lab"]},{"year":2025,"claim":"Linked ALPK3 to active contractile regulation, connecting its loss to PKA signaling, calcium handling, and myosin super-relaxed state, and demonstrated pharmacological correction.","evidence":"K201X knock-in mice with sarcomere length/relaxation, calcium imaging, phosphorylation assays, myosin SRX measurement, and mavacamten rescue","pmids":["40128237"],"confidence":"High","gaps":["Mechanism connecting ALPK3 scaffolding to reduced PKA phosphorylation unresolved","Whether mavacamten rescue addresses cause or downstream contractility only"]},{"year":2025,"claim":"Demonstrated therapeutic restoration and broadened the model to a generalizable M-band quality-control scaffold relevant beyond ALPK3 mutations.","evidence":"AAV-ALPK3 delivery in human cardiac organoids and mouse models, including TTN-truncated organoids (preprint)","pmids":["bio_10.1101_2025.07.31.667858"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Cross-rescue of TTN organoids mechanistically uncharacterized","Durability and in vivo translation untested"]},{"year":null,"claim":"How ALPK3 mechanistically couples its M-band scaffolding to PKA-dependent phosphorylation and myosin regulation, and the structural basis of myomesin/MuRF/p62 anchoring, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the scaffold complex","Direct binding interfaces with MYOM1/MYOM2, MuRF, and SQSTM1 not mapped","Link between scaffolding and reduced PKA signaling undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,7]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[3,7]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[3]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[7]}],"complexes":["sarcomere M-band"],"partners":["MYOM1","MYOM2","SQSTM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96L96","full_name":"Alpha-protein kinase 3","aliases":["Muscle alpha-protein 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ALPK1","url":"https://www.omim.org/entry/607347"},{"mim_id":"192600","title":"CARDIOMYOPATHY, FAMILIAL HYPERTROPHIC, 1; CMH1","url":"https://www.omim.org/entry/192600"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":62.2},{"tissue":"skeletal muscle","ntpm":198.3},{"tissue":"tongue","ntpm":55.2}],"url":"https://www.proteinatlas.org/search/ALPK3"},"hgnc":{"alias_symbol":["MAK","KIAA1330","Midori"],"prev_symbol":[]},"alphafold":{"accession":"Q96L96","domains":[{"cath_id":"2.60.40.10","chopping":"277-374","consensus_level":"medium","plddt":85.9044,"start":277,"end":374},{"cath_id":"2.60.40.10","chopping":"1475-1575","consensus_level":"medium","plddt":88.042,"start":1475,"end":1575}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96L96","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96L96-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96L96-F1-predicted_aligned_error_v6.png","plddt_mean":48.16},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ALPK3","jax_strain_url":"https://www.jax.org/strain/search?query=ALPK3"},"sequence":{"accession":"Q96L96","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96L96.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96L96/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96L96"}},"corpus_meta":[{"pmid":"26846950","id":"PMC_26846950","title":"Biallelic Truncating Mutations in ALPK3 Cause Severe Pediatric Cardiomyopathy.","date":"2016","source":"Journal of the American College of Cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/26846950","citation_count":84,"is_preprint":false},{"pmid":"34263907","id":"PMC_34263907","title":"Alpha-protein kinase 3 (ALPK3) truncating variants are a cause of autosomal dominant hypertrophic cardiomyopathy.","date":"2021","source":"European heart journal","url":"https://pubmed.ncbi.nlm.nih.gov/34263907","citation_count":80,"is_preprint":false},{"pmid":"11418590","id":"PMC_11418590","title":"A novel myocyte-specific gene Midori promotes the differentiation of P19CL6 cells into cardiomyocytes.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11418590","citation_count":53,"is_preprint":false},{"pmid":"27106955","id":"PMC_27106955","title":"ALPK3-deficient cardiomyocytes generated from patient-derived induced pluripotent stem cells and mutant human 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Overexpression promotes differentiation of P19CL6 cells into cardiomyocytes, while antisense suppression reduces differentiation efficiency.\",\n      \"method\": \"Differential display, Northern blot, whole-mount in situ hybridization, overexpression/antisense stable cell lines, immunolocalization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — nuclear localization confirmed by direct imaging, gain- and loss-of-function in P19CL6 cells with defined differentiation phenotype; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11418590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ALPK3-deficient (knockout) mice develop cardiomyopathy featuring both hypertrophic and dilated characteristics. Light and electron microscopy revealed altered cardiomyocyte architecture with reduced numbers of abnormal intercalated discs and mild myofibrillar disarray, establishing ALPK3 as required for normal intercalated disc organization and myofibrillar architecture in vivo.\",\n      \"method\": \"Knockout mouse model, MRI, histology, electron microscopy\",\n      \"journal\": \"Veterinary pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO model with multiple orthogonal structural and functional readouts; replicated by subsequent human studies showing same intercalated disc defects\",\n      \"pmids\": [\"21441111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ALPK3-deficient cardiomyocytes (from patient iPSCs and CRISPR-engineered human ESCs lacking ALPK3) display disordered sarcomeres and intercalated discs by ultrastructural analysis, extended field potential duration by multi-electrode array, and abnormal calcium handling by calcium imaging, establishing loss of function as the underlying disease mechanism and identifying calcium handling defects as a feature of ALPK3 deficiency.\",\n      \"method\": \"Patient iPSC-derived cardiomyocytes, human ESC CRISPR knockouts, ultrastructural analysis (EM), multi-electrode array, calcium imaging\",\n      \"journal\": \"European heart journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — isogenic human stem cell models with multiple orthogonal functional readouts (ultrastructure, electrophysiology, calcium imaging); replicates mouse KO findings\",\n      \"pmids\": [\"27106955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Multiple sequence alignment and phosphoproteomic evaluation of ALPK3 kinase domain inhibition and overexpression revealed no significant changes in catalytic phosphorylation activity, establishing ALPK3 as a pseudokinase. ALPK3 co-localizes with myomesin proteins (MYOM1, MYOM2) at both the nuclear envelope and the sarcomere M-band. Loss-of-function ALPK3 variants cause mislocalization of myomesin proteins and dysregulation of additional M-band proteins involved in sarcomere protein turnover, impairing cardiomyocyte structure and function.\",\n      \"method\": \"Multiple sequence alignment of alpha-kinase domains, phosphoproteomics (kinase domain inhibition and overexpression), co-localization imaging, isogenic human iPSC-derived cardiomyocytes, mouse models, human patient tissue analysis\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — phosphoproteomic evidence for pseudokinase status combined with co-localization and functional mislocalization studies in isogenic iPSC-CMs and mouse models; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"36321451\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-384-5p was found to be decreased in cardiac hypertrophic tissues and cells; overexpression of miR-384-5p ameliorates pressure overload-induced cardiac hypertrophy by downregulating ALPK3 expression, positioning ALPK3 as a downstream target of miR-384-5p in cardiomyocyte hypertrophy signaling.\",\n      \"method\": \"ISO/Ang-II cardiac hypertrophy models (in vivo and in vitro), miR-384-5p overexpression, RT-qPCR, western blot, echocardiography\",\n      \"journal\": \"Journal of biochemical and molecular toxicology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, indirect evidence that ALPK3 is a miR-384-5p target via expression assays; no direct binding or reporter assay data described in abstract\",\n      \"pmids\": [\"35510648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Knock-in mice carrying an ALPK3 truncating variant (K201X) show reduced basal sarcomere length, prolonged relaxation, increased diastolic calcium levels, decreased protein kinase A-mediated phosphorylation (including cardiac troponin I), and reduced myosin super-relaxed state fraction. These contractile and calcium handling defects were partially corrected by mavacamten (myosin inhibitor), implicating ALPK3 as a modulator of protein kinase A signaling and myosin regulation.\",\n      \"method\": \"Knock-in mouse model (K201X), isolated cardiomyocyte sarcomere length/relaxation measurements, calcium imaging, phosphorylation assays (western blot), myosin super-relaxed state measurement, mavacamten pharmacological rescue\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vivo knock-in model with multiple orthogonal cellular assays (calcium, sarcomere, kinase activity, myosin state) plus pharmacological rescue; peer-reviewed publication\",\n      \"pmids\": [\"40128237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Delivery of full-length ALPK3 via adeno-associated virus (AAV) restored contractile function in human cardiac organoids and in vivo mouse models carrying ALPK3 truncating mutations. AAV-ALPK3 gene therapy also completely restored contractile deficits in human cardiac organoids carrying TTN truncating variants, suggesting ALPK3 scaffolds an M-band protein quality control network relevant to multiple cardiomyopathy causes.\",\n      \"method\": \"AAV gene delivery, human cardiac organoids, in vivo mouse knockout/knock-in models, contractile function measurements\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — preprint; in vivo and ex vivo rescue experiments with defined functional readouts; single study, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.07.31.667858\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Comprehensive systematic review with experimental modeling confirms that ALPK3 lacks catalytic kinase activity (pseudokinase) and maintains sarcomeric proteostasis by scaffolding myomesins (MYOM1/MYOM2), MuRF (muscle ring-finger protein) E3 ubiquitin ligases, and SQSTM1/p62 at the sarcomere M-band and nuclear envelope. Loss of this scaffolding displaces myomesins and drives thick-filament protein aggregation, causing contractile dysfunction.\",\n      \"method\": \"Integrative review synthesizing phosphoproteomics, co-localization, iPSC-derived cardiomyocyte models, mouse models, and patient tissue data\",\n      \"journal\": \"Circulation. Genomic and precision medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — comprehensive synthesis of existing experimental data; mechanistic claims grounded in prior primary studies; not a new primary experiment but a rigorous curation\",\n      \"pmids\": [\"41221624\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ALPK3 (Midori) is a cardiac-enriched pseudokinase that lacks catalytic phosphotransferase activity and instead functions as a structural scaffold at the sarcomere M-band and nuclear envelope, where it anchors myomesin force-buffering proteins (MYOM1/MYOM2), MuRF E3 ubiquitin ligases, and SQSTM1/p62 to maintain sarcomere proteostasis; loss of ALPK3 displaces myomesins, disrupts M-band protein turnover, impairs intercalated disc organization, causes abnormal calcium handling and reduced protein kinase A-mediated phosphorylation, and ultimately produces cardiomyopathy whose contractile defects can be partially rescued by the myosin inhibitor mavacamten or by AAV-mediated gene replacement.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ALPK3 is a cardiac-enriched pseudokinase that functions as a structural scaffold required for sarcomere integrity and cardiomyocyte architecture, with loss of function producing cardiomyopathy [#1, #3]. Phosphoproteomic analysis upon kinase-domain inhibition and overexpression detected no catalytic phosphotransferase activity, establishing ALPK3 as a pseudokinase that instead acts by co-localizing with the myomesin force-buffering proteins MYOM1 and MYOM2 at the sarcomere M-band and nuclear envelope; loss-of-function variants mislocalize myomesins and dysregulate additional M-band proteins controlling sarcomere protein turnover [#3]. Through this scaffolding role ALPK3 maintains sarcomeric proteostasis, anchoring MuRF E3 ubiquitin ligases and SQSTM1/p62 at the M-band, and its loss displaces myomesins and drives thick-filament protein aggregation [#7]. ALPK3 deficiency disorders sarcomeres and intercalated discs and causes abnormal calcium handling in both knockout mice and isogenic human stem cell-derived cardiomyocytes [#1, #2]. A truncating knock-in model links ALPK3 to contractile regulation, showing prolonged relaxation, elevated diastolic calcium, reduced protein kinase A-mediated phosphorylation, and a decreased myosin super-relaxed state that is partially corrected by the myosin inhibitor mavacamten [#5]. AAV-mediated delivery of full-length ALPK3 restores contractile function in human cardiac organoids and mouse models carrying ALPK3 truncating mutations [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established the first cellular context for ALPK3 (Midori), asking where the protein acts and whether it influences cardiac cell fate.\",\n      \"evidence\": \"Differential display, immunolocalization, and gain/loss-of-function in P19CL6 cells\",\n      \"pmids\": [\"11418590\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Proposed transcriptional regulator role rests on overexpression autoinduction, not direct DNA binding\", \"Performed in a single cell-line differentiation model\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Tested whether ALPK3 is required in vivo, showing its loss causes cardiomyopathy with intercalated disc and myofibrillar defects.\",\n      \"evidence\": \"Knockout mouse model with MRI, histology, and electron microscopy\",\n      \"pmids\": [\"21441111\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular function underlying the structural defects\", \"Mixed hypertrophic/dilated phenotype mechanism unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Confirmed loss of function as the disease mechanism in human cells and identified calcium handling as an affected process.\",\n      \"evidence\": \"Patient iPSC-derived and CRISPR-engineered isogenic human ESC cardiomyocytes with EM, multi-electrode array, and calcium imaging\",\n      \"pmids\": [\"27106955\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify molecular partners or the basis of calcium dysregulation\", \"Catalytic status of ALPK3 not addressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the long-standing assumption that ALPK3 is an active kinase, establishing it as a pseudokinase that scaffolds myomesins at the M-band and nuclear envelope.\",\n      \"evidence\": \"Alpha-kinase domain alignment, phosphoproteomics under kinase inhibition/overexpression, and co-localization in isogenic iPSC-CMs, mouse models, and patient tissue\",\n      \"pmids\": [\"36321451\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of myomesin anchoring not defined\", \"Whether scaffolding is direct binding or indirect not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed ALPK3 in a hypertrophy regulatory circuit as a downstream target whose suppression mitigates pressure-overload hypertrophy.\",\n      \"evidence\": \"ISO/Ang-II hypertrophy models with miR-384-5p overexpression, RT-qPCR, and echocardiography\",\n      \"pmids\": [\"35510648\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct miR-384-5p:ALPK3 binding or reporter assay shown\", \"Inferred from expression correlation in a single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked ALPK3 to active contractile regulation, connecting its loss to PKA signaling, calcium handling, and myosin super-relaxed state, and demonstrated pharmacological correction.\",\n      \"evidence\": \"K201X knock-in mice with sarcomere length/relaxation, calcium imaging, phosphorylation assays, myosin SRX measurement, and mavacamten rescue\",\n      \"pmids\": [\"40128237\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting ALPK3 scaffolding to reduced PKA phosphorylation unresolved\", \"Whether mavacamten rescue addresses cause or downstream contractility only\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated therapeutic restoration and broadened the model to a generalizable M-band quality-control scaffold relevant beyond ALPK3 mutations.\",\n      \"evidence\": \"AAV-ALPK3 delivery in human cardiac organoids and mouse models, including TTN-truncated organoids (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.07.31.667858\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Cross-rescue of TTN organoids mechanistically uncharacterized\", \"Durability and in vivo translation untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ALPK3 mechanistically couples its M-band scaffolding to PKA-dependent phosphorylation and myosin regulation, and the structural basis of myomesin/MuRF/p62 anchoring, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the scaffold complex\", \"Direct binding interfaces with MYOM1/MYOM2, MuRF, and SQSTM1 not mapped\", \"Link between scaffolding and reduced PKA signaling undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 7]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [3, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\"sarcomere M-band\"],\n    \"partners\": [\"MYOM1\", \"MYOM2\", \"SQSTM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":5,"faith_total":5,"faith_pct":100.0}}