{"gene":"PHKG2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1996,"finding":"Mutations in PHKG2 (the testis/liver isoform of the phosphorylase kinase catalytic gamma subunit) cause autosomal liver-specific phosphorylase kinase deficiency. Non-conservative amino acid replacements (V106E, G189E, D215N) at highly conserved residues within the catalytic core of the kinase domain, as well as a frameshift mutation, abolish normal function; PHKG2 is identified as the predominant catalytic gamma subunit isoform in liver, erythrocytes, and non-muscle tissues.","method":"Sequencing of PHKG2 in human patients with autosomal liver glycogenosis and in the gsd rat strain; mutation analysis identifying frameshift and missense mutations in conserved catalytic core residues","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct mutation identification in multiple independent patients and an animal model, with mutations mapping to conserved catalytic core residues, replicated across human and rat","pmids":["8896567"],"is_preprint":false},{"year":1997,"finding":"A splice-site mutation (IVS4+1 g→a) in PHKG2 causes skipping of exon 4, resulting in a frameshift starting at nucleotide 272, a premature stop codon after 32 additional amino acids, and subsequent loss of the catalytic site, causing liver phosphorylase kinase deficiency.","method":"Exon-specific amplification and direct sequencing of PHKG2 genomic DNA; functional inference from loss of catalytic site due to frameshift","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct sequencing with clear mechanistic consequence (catalytic site loss) demonstrated in affected siblings, single lab","pmids":["9245685"],"is_preprint":false},{"year":1998,"finding":"The human PHKG2 gene spans 9.5 kb, is divided into 10 exons, and intron positions are highly conserved with PHKG1 (muscle isoform), indicating conserved gene structure between the two gamma subunit isoforms. Translation-terminating mutations (277delC and Arg44ter) in PHKG2 are associated with progression to liver cirrhosis, suggesting that the severity of PHKG2 loss-of-function correlates with cirrhosis risk.","method":"Genomic sequencing and gene structure determination; mutation identification in cirrhotic patients","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct gene structure determination and mutation identification in patients with severe phenotype, single lab","pmids":["9384616"],"is_preprint":false},{"year":2021,"finding":"Knockout of Phkg2 in mice (Phkg2-/- model) leads to significantly decreased liver phosphorylase kinase enzyme activity, increased liver glycogen accumulation, elevated liver:body weight ratio, elevated serum liver markers, and early liver fibrosis, with no glycogen accumulation in brain, muscle, kidney, or heart — establishing that PHKG2 encodes the liver-specific catalytic subunit of phosphorylase kinase responsible for hepatic glycogen breakdown.","method":"Targeted gene knockout mouse model; enzyme activity assays, glycogen content measurement, histology (H&E, Masson's Trichrome), serum liver markers, urinary Glc4 biomarker","journal":"Molecular genetics and metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with multiple orthogonal biochemical and histological readouts establishing liver-specific function, with tissue-specificity confirmed across multiple organs","pmids":["34083142"],"is_preprint":false},{"year":2022,"finding":"Novel PHKG2 mutations F233S and R320DfsX5 each lead to a decrease in key phosphorylase b kinase enzyme activity, as demonstrated by functional experiments in patient-derived samples.","method":"Functional enzyme activity assay on patient samples with novel PHKG2 mutations","journal":"BMC pediatrics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct enzyme activity assay demonstrating loss of function for specific mutations, but single case report from a single lab","pmids":["35549678"],"is_preprint":false},{"year":2023,"finding":"PHKG2 promotes RSL3-induced ferroptosis in H. pylori-positive gastric cancer cells by upregulating the lipoxygenase ALOX5 expression, thereby enhancing lipid peroxidation.","method":"Cell-based overexpression/knockdown experiments in gastric cancer cell lines; measurement of ferroptosis markers and ALOX5 expression","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single lab, mechanistic link between PHKG2 and ALOX5/ferroptosis established in cell lines but limited by abstract-level detail","pmids":["36948350"],"is_preprint":false},{"year":2024,"finding":"NRF2 transcriptionally represses PHKG2; overexpression of PHKG2 promotes ferritinophagy, elevates intracellular iron levels, and induces mitochondrial stress-dependent ferroptosis in NSCLC cells under radiotherapy. Targeting NRF2 upregulates PHKG2 and reverses radiotherapy resistance.","method":"High-throughput transcriptome sequencing, Lasso regression, in vitro overexpression/knockdown, ferritinophagy and iron level assays, mitochondrial function assays, in situ transplantation tumor models in vivo","journal":"NPJ precision oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (transcriptomics, cell assays, in vivo model) in single lab establishing NRF2→PHKG2 transcriptional axis and PHKG2's role in ferritinophagy/ferroptosis","pmids":["39169204"],"is_preprint":false},{"year":2025,"finding":"TP53 transcriptionally activates PHKG2; PHKG2 phosphorylates PPP1R3B at specific residues, disrupting its interaction with PP1C and thereby enhancing PP1 phosphatase activity; activated PP1 dephosphorylates NRF2, promoting NRF2 nuclear export and suppressing GPX4 transcription, which sensitizes HNSCC cells to ferroptosis. This defines a TP53/PHKG2–PP1–NRF2 signaling axis.","method":"In vitro and in vivo overexpression experiments; phosphorylation assays demonstrating PHKG2 phosphorylates PPP1R3B (T225, T306); co-immunoprecipitation showing disruption of PPP1R3B–PP1C interaction; NRF2 nuclear export assays; GPX4 transcription assays; lipid peroxidation measurement; xenograft tumor models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods including phosphorylation assays, Co-IP, nuclear localization, and in vivo models in single lab; substrate identification (PPP1R3B) and pathway placement are specific","pmids":["40885710"],"is_preprint":false},{"year":2026,"finding":"PHKG2 mediates cisplatin resistance in ESCC by phosphorylating IGF2BP3 at residues T225 and T306; this phosphorylation enhances IGF2BP3 phase separation, stabilizing CXCL8 mRNA in an m6A-dependent manner; increased CXCL8 secretion then promotes M2 macrophage polarization and suppresses CD8+ T cell cytotoxicity. Pharmacological inhibition of PHKG2 by prexasertib curtails ESCC proliferation and enhances cisplatin sensitivity.","method":"CRISPR/Cas9 knockout library functional screening; transcriptomic profiling; in vitro phosphorylation assays identifying IGF2BP3 T225/T306 as PHKG2 substrates; phase separation assays; mRNA stability assays; macrophage polarization assays; in vivo validation; pharmacological inhibition with prexasertib","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus multiple orthogonal mechanistic assays (phosphorylation substrate ID, phase separation, mRNA stability, immune cell assays) in single lab","pmids":["42161921"],"is_preprint":false},{"year":2025,"finding":"A deep intronic variant in PHKG2 causes aberrant splicing (confirmed by short-read and long-read RNA-seq in patient blood and a CRISPR-edited HEK293T cell model), leading to PHKG2 deficiency consistent with GSD IX γ2. Antisense splice-switching oligonucleotides reverse the aberrant splicing in the cell model, demonstrating the causal role of this non-coding variant in PHKG2 dysfunction.","method":"Whole genome sequencing; short-read and long-read RNA-seq on patient blood; CRISPR-installed variant in HEK293T cells; antisense oligonucleotide rescue experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — variant functionally validated by RNA-seq in patient tissue and cell model with CRISPR installation, rescue by ASO; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.05.14.654043"],"is_preprint":true}],"current_model":"PHKG2 encodes the liver/testis-specific catalytic gamma subunit of phosphorylase kinase (PhK), which is required for glycogen breakdown in the liver; loss-of-function mutations (missense in conserved catalytic core residues, frameshifts, splice-site mutations) cause autosomal-recessive liver glycogenosis (GSD IXc), as established in human patients and a Phkg2-/- mouse model. Beyond glycogen metabolism, PHKG2 has emerging roles in ferroptosis regulation: it is transcriptionally activated by TP53 and repressed by NRF2, and it promotes ferroptosis by phosphorylating PPP1R3B to activate PP1, which dephosphorylates and exports NRF2 from the nucleus to suppress GPX4, as well as by upregulating ALOX5 and promoting ferritinophagy-dependent iron release; additionally, PHKG2 phosphorylates IGF2BP3 (T225/T306) to stabilize CXCL8 mRNA and drive cisplatin resistance and immunosuppression in cancer contexts."},"narrative":{"mechanistic_narrative":"PHKG2 encodes the liver/testis-specific catalytic gamma subunit of phosphorylase kinase, the enzyme that activates glycogen phosphorylase to drive hepatic glycogen breakdown [PMID:8896567, PMID:34083142]. It is the predominant catalytic gamma isoform in liver, erythrocytes, and non-muscle tissues, and its activity resides in a conserved catalytic core whose disruption by missense substitutions, frameshifts, and splice defects abolishes function [PMID:8896567, PMID:9245685]. Loss-of-function mutations cause autosomal-recessive liver-specific phosphorylase kinase deficiency (GSD IX γ2), with knockout mice recapitulating decreased hepatic phosphorylase kinase activity, liver glycogen accumulation, and early fibrosis without glycogen build-up in muscle, brain, kidney, or heart, establishing the tissue-restricted role of the gene [PMID:34083142]; severe truncating mutations correlate with progression to cirrhosis [PMID:9384616]. Beyond glycogen metabolism, PHKG2 acts as a kinase in ferroptosis regulation, sitting downstream of TP53 (which activates it) and NRF2 (which represses it): it phosphorylates PPP1R3B to disrupt PPP1R3B–PP1C interaction and enhance PP1 activity, driving NRF2 dephosphorylation, nuclear export, and GPX4 suppression, and it also promotes ALOX5-dependent lipid peroxidation and ferritinophagy-driven iron release [PMID:36948350, PMID:39169204, PMID:40885710]. In esophageal squamous cell carcinoma, PHKG2 phosphorylates IGF2BP3 at T225/T306 to enhance its phase separation and m6A-dependent stabilization of CXCL8 mRNA, promoting cisplatin resistance and an immunosuppressive microenvironment [PMID:42161921].","teleology":[{"year":1996,"claim":"Established that PHKG2 is the gene whose loss causes liver-specific phosphorylase kinase deficiency, identifying the functionally critical catalytic core of the gamma subunit.","evidence":"Sequencing of PHKG2 in patients with autosomal liver glycogenosis and the gsd rat, finding non-conservative substitutions at conserved catalytic residues and a frameshift","pmids":["8896567"],"confidence":"High","gaps":["Catalytic mechanism and substrate specificity not biochemically dissected","Did not address tissue-specific regulation of the isoform"]},{"year":1997,"claim":"Showed that splice-disrupting mutations, not only coding mutations, can ablate PHKG2 function by removing the catalytic site.","evidence":"Exon-specific sequencing of a IVS4+1 g→a splice mutation causing exon 4 skipping and a premature stop in affected siblings","pmids":["9245685"],"confidence":"Medium","gaps":["Single family","No direct enzyme activity quantification"]},{"year":1998,"claim":"Defined the genomic architecture of PHKG2 and linked truncating mutation severity to clinical progression toward cirrhosis.","evidence":"Genomic sequencing establishing 10-exon structure conserved with PHKG1, plus mutation identification in cirrhotic patients","pmids":["9384616"],"confidence":"Medium","gaps":["Genotype–phenotype correlation based on limited patients","Mechanism linking enzyme loss to fibrosis not established"]},{"year":2021,"claim":"Provided definitive in vivo proof that PHKG2 encodes the liver-specific catalytic subunit required for hepatic glycogen breakdown, with strict tissue restriction.","evidence":"Phkg2-/- mouse with reduced liver phosphorylase kinase activity, hepatic glycogen accumulation, and early fibrosis, with no glycogen accumulation in other organs","pmids":["34083142"],"confidence":"High","gaps":["Did not address non-metabolic roles","Mechanism of fibrosis development not resolved"]},{"year":2022,"claim":"Confirmed that newly identified clinical variants are loss-of-function by direct enzymatic readout.","evidence":"Phosphorylase b kinase activity assay on patient samples carrying F233S and R320DfsX5","pmids":["35549678"],"confidence":"Medium","gaps":["Single case report","No structural rationale for activity loss"]},{"year":2023,"claim":"Introduced a non-metabolic role for PHKG2 in promoting ferroptosis via lipid peroxidation.","evidence":"Overexpression/knockdown in H. pylori-positive gastric cancer cells showing PHKG2 upregulates ALOX5 and enhances RSL3-induced ferroptosis","pmids":["36948350"],"confidence":"Medium","gaps":["Mechanism connecting PHKG2 kinase activity to ALOX5 induction unknown","Cell-line only, abstract-level detail"]},{"year":2024,"claim":"Placed PHKG2 downstream of NRF2 transcriptional repression and tied it to ferritinophagy-driven iron release and radiotherapy sensitivity.","evidence":"Transcriptomics, in vitro overexpression/knockdown, iron and ferritinophagy assays, and in vivo tumor models in NSCLC","pmids":["39169204"],"confidence":"Medium","gaps":["Direct NRF2 binding at PHKG2 promoter not shown","How PHKG2 mechanistically triggers ferritinophagy unresolved"]},{"year":2025,"claim":"Defined a kinase-based ferroptosis mechanism: TP53→PHKG2→PPP1R3B/PP1→NRF2 export→GPX4 suppression, identifying PPP1R3B as a PHKG2 substrate.","evidence":"Phosphorylation assays (PPP1R3B T225/T306), Co-IP showing disrupted PPP1R3B–PP1C interaction, NRF2 export and GPX4 transcription assays, and xenografts in HNSCC","pmids":["40885710"],"confidence":"Medium","gaps":["Single lab","Direct PP1 dephosphorylation of NRF2 not reconstituted in vitro"]},{"year":2025,"claim":"Demonstrated that a deep intronic non-coding variant is causal for PHKG2 deficiency and is correctable by splice-switching oligonucleotides.","evidence":"WGS, short/long-read RNA-seq in patient blood, CRISPR-installed variant in HEK293T, and antisense oligonucleotide rescue (preprint)","pmids":["bio_10.1101_2025.05.14.654043"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Therapeutic rescue shown only in cell model"]},{"year":2026,"claim":"Extended PHKG2 kinase signaling to cancer immunoevasion and chemoresistance through IGF2BP3 phosphorylation and CXCL8 mRNA stabilization.","evidence":"CRISPR screen, phosphorylation assays (IGF2BP3 T225/T306), phase separation and mRNA stability assays, macrophage/T-cell assays, and prexasertib inhibition in ESCC","pmids":["42161921"],"confidence":"Medium","gaps":["Single lab","Selectivity of prexasertib for PHKG2 not established"]},{"year":null,"claim":"How a single liver-glycogenolytic kinase acquires its diverse oncogenic substrates (PPP1R3B, IGF2BP3) and whether these roles operate in normal physiology remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural basis for substrate selectivity","No unifying model linking metabolic and ferroptosis/cancer functions","Physiological relevance of ferroptosis roles outside tumor contexts unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,7,8]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[7,8]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5,6,7]}],"complexes":["phosphorylase kinase"],"partners":["PPP1R3B","IGF2BP3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P15735","full_name":"Phosphorylase b kinase gamma catalytic chain, liver/testis isoform","aliases":["PSK-C3","Phosphorylase kinase subunit gamma-2"],"length_aa":406,"mass_kda":46.4,"function":"Catalytic subunit of the phosphorylase b kinase (PHK), which mediates the neural and hormonal regulation of glycogen breakdown (glycogenolysis) by phosphorylating and thereby activating glycogen phosphorylase. May regulate glycogeneolysis in the testis. In vitro, phosphorylates PYGM (PubMed:35549678)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P15735/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PHKG2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000156873","cell_line_id":"CID001235","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":1}],"interactors":[{"gene":"PHKA1","stoichiometry":10.0},{"gene":"PHKB","stoichiometry":10.0},{"gene":"CALM1","stoichiometry":0.2},{"gene":"CALM2","stoichiometry":0.2},{"gene":"CALM3","stoichiometry":0.2},{"gene":"MAPK8","stoichiometry":0.2},{"gene":"PHKA2","stoichiometry":0.2},{"gene":"CALM2;CALM1;CALM3","stoichiometry":0.2},{"gene":"CALML3","stoichiometry":0.2},{"gene":"PRPF40A","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001235","total_profiled":1310},"omim":[{"mim_id":"613027","title":"GLYCOGEN STORAGE DISEASE IXc; GSD9C","url":"https://www.omim.org/entry/613027"},{"mim_id":"311870","title":"PHOSPHORYLASE KINASE, MUSCLE, ALPHA-1 SUBUNIT; PHKA1","url":"https://www.omim.org/entry/311870"},{"mim_id":"306000","title":"GLYCOGEN STORAGE DISEASE IXa1; GSD9A1","url":"https://www.omim.org/entry/306000"},{"mim_id":"300798","title":"PHOSPHORYLASE KINASE, LIVER, ALPHA-2 SUBUNIT; PHKA2","url":"https://www.omim.org/entry/300798"},{"mim_id":"172490","title":"PHOSPHORYLASE KINASE, BETA SUBUNIT; PHKB","url":"https://www.omim.org/entry/172490"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"testis","ntpm":123.9}],"url":"https://www.proteinatlas.org/search/PHKG2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P15735","domains":[{"cath_id":"3.30.200.20","chopping":"24-109","consensus_level":"high","plddt":89.5043,"start":24,"end":109},{"cath_id":"1.10.510.10","chopping":"114-292","consensus_level":"high","plddt":96.2455,"start":114,"end":292}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P15735","model_url":"https://alphafold.ebi.ac.uk/files/AF-P15735-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P15735-F1-predicted_aligned_error_v6.png","plddt_mean":83.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PHKG2","jax_strain_url":"https://www.jax.org/strain/search?query=PHKG2"},"sequence":{"accession":"P15735","fasta_url":"https://rest.uniprot.org/uniprotkb/P15735.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P15735/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P15735"}},"corpus_meta":[{"pmid":"8896567","id":"PMC_8896567","title":"Mutations in the testis/liver isoform of the phosphorylase kinase gamma subunit (PHKG2) cause autosomal liver glycogenosis in the gsd rat and in humans.","date":"1996","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8896567","citation_count":67,"is_preprint":false},{"pmid":"9384616","id":"PMC_9384616","title":"Liver glycogenosis due to phosphorylase kinase deficiency: PHKG2 gene structure and mutations associated with cirrhosis.","date":"1998","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9384616","citation_count":50,"is_preprint":false},{"pmid":"24389071","id":"PMC_24389071","title":"Variability of disease spectrum in children with liver phosphorylase kinase deficiency caused by mutations in the PHKG2 gene.","date":"2013","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/24389071","citation_count":45,"is_preprint":false},{"pmid":"12930917","id":"PMC_12930917","title":"Severe phenotype of phosphorylase kinase-deficient liver glycogenosis with mutations in the PHKG2 gene.","date":"2003","source":"Pediatric research","url":"https://pubmed.ncbi.nlm.nih.gov/12930917","citation_count":33,"is_preprint":false},{"pmid":"24326380","id":"PMC_24326380","title":"Novel PHKG2 mutation causing GSD IX with prominent liver disease: report of three cases and review of literature.","date":"2013","source":"European journal of pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/24326380","citation_count":23,"is_preprint":false},{"pmid":"36948350","id":"PMC_36948350","title":"PHKG2 regulates RSL3-induced ferroptosis in Helicobacter pylori related gastric cancer.","date":"2023","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/36948350","citation_count":21,"is_preprint":false},{"pmid":"9245685","id":"PMC_9245685","title":"Autosomal recessive liver phosphorylase kinase deficiency caused by a novel splice-site mutation in the gene encoding the liver gamma subunit (PHKG2).","date":"1997","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9245685","citation_count":17,"is_preprint":false},{"pmid":"29360628","id":"PMC_29360628","title":"PHKG2 mutation spectrum in glycogen storage disease type IXc: a case report and review of the literature.","date":"2018","source":"Journal of pediatric endocrinology & metabolism : JPEM","url":"https://pubmed.ncbi.nlm.nih.gov/29360628","citation_count":16,"is_preprint":false},{"pmid":"39169204","id":"PMC_39169204","title":"Targeting Nrf2/PHKG2 axis to enhance radiosensitivity in NSCLC.","date":"2024","source":"NPJ precision oncology","url":"https://pubmed.ncbi.nlm.nih.gov/39169204","citation_count":12,"is_preprint":false},{"pmid":"34083142","id":"PMC_34083142","title":"Characterization of liver GSD IX γ2 pathophysiology in a novel Phkg2-/- mouse model.","date":"2021","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/34083142","citation_count":8,"is_preprint":false},{"pmid":"32697758","id":"PMC_32697758","title":"Variability of clinical and biochemical phenotype in liver phosphorylase kinase deficiency with variants in the phosphorylase kinase (PHKG2) gene.","date":"2020","source":"Journal of pediatric endocrinology & metabolism : JPEM","url":"https://pubmed.ncbi.nlm.nih.gov/32697758","citation_count":8,"is_preprint":false},{"pmid":"35549678","id":"PMC_35549678","title":"A very rare case report of glycogen storage disease type IXc with novel PHKG2 variants.","date":"2022","source":"BMC pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/35549678","citation_count":4,"is_preprint":false},{"pmid":"40885710","id":"PMC_40885710","title":"Transcriptional activation of PHKG2 by TP53 promotes ferroptosis through nuclear export of NRF2 in head and neck squamous cell carcinoma.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/40885710","citation_count":0,"is_preprint":false},{"pmid":"40615918","id":"PMC_40615918","title":"A novel sequence of the PHKG2 mutation associated with the first case of glycogen storage diseases type IXc in Syria: a case report and review of literature.","date":"2025","source":"Journal of medical case reports","url":"https://pubmed.ncbi.nlm.nih.gov/40615918","citation_count":0,"is_preprint":false},{"pmid":"42161921","id":"PMC_42161921","title":"PHKG2 confers resistance of ESCC to cisplatin and enhances CXCL8-dependent immunosuppression to exacerbate tumorigenesis.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/42161921","citation_count":0,"is_preprint":false},{"pmid":"41771245","id":"PMC_41771245","title":"Decoding genetic complexity in glycogen storage diseases: three novel variants in SLC37A4, GAA, and PHKG2 identified in an Iranian cohort.","date":"2026","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/41771245","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.14.654043","title":"Cell Modeling and Rescue of a Novel Non-coding Genetic Cause of Glycogen Storage Disease IX","date":"2025-05-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.14.654043","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9901,"output_tokens":2951,"usd":0.036984,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10395,"output_tokens":3295,"usd":0.067175,"stage2_stop_reason":"end_turn"},"total_usd":0.104159,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"Mutations in PHKG2 (the testis/liver isoform of the phosphorylase kinase catalytic gamma subunit) cause autosomal liver-specific phosphorylase kinase deficiency. Non-conservative amino acid replacements (V106E, G189E, D215N) at highly conserved residues within the catalytic core of the kinase domain, as well as a frameshift mutation, abolish normal function; PHKG2 is identified as the predominant catalytic gamma subunit isoform in liver, erythrocytes, and non-muscle tissues.\",\n      \"method\": \"Sequencing of PHKG2 in human patients with autosomal liver glycogenosis and in the gsd rat strain; mutation analysis identifying frameshift and missense mutations in conserved catalytic core residues\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct mutation identification in multiple independent patients and an animal model, with mutations mapping to conserved catalytic core residues, replicated across human and rat\",\n      \"pmids\": [\"8896567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A splice-site mutation (IVS4+1 g→a) in PHKG2 causes skipping of exon 4, resulting in a frameshift starting at nucleotide 272, a premature stop codon after 32 additional amino acids, and subsequent loss of the catalytic site, causing liver phosphorylase kinase deficiency.\",\n      \"method\": \"Exon-specific amplification and direct sequencing of PHKG2 genomic DNA; functional inference from loss of catalytic site due to frameshift\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct sequencing with clear mechanistic consequence (catalytic site loss) demonstrated in affected siblings, single lab\",\n      \"pmids\": [\"9245685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The human PHKG2 gene spans 9.5 kb, is divided into 10 exons, and intron positions are highly conserved with PHKG1 (muscle isoform), indicating conserved gene structure between the two gamma subunit isoforms. Translation-terminating mutations (277delC and Arg44ter) in PHKG2 are associated with progression to liver cirrhosis, suggesting that the severity of PHKG2 loss-of-function correlates with cirrhosis risk.\",\n      \"method\": \"Genomic sequencing and gene structure determination; mutation identification in cirrhotic patients\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct gene structure determination and mutation identification in patients with severe phenotype, single lab\",\n      \"pmids\": [\"9384616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Knockout of Phkg2 in mice (Phkg2-/- model) leads to significantly decreased liver phosphorylase kinase enzyme activity, increased liver glycogen accumulation, elevated liver:body weight ratio, elevated serum liver markers, and early liver fibrosis, with no glycogen accumulation in brain, muscle, kidney, or heart — establishing that PHKG2 encodes the liver-specific catalytic subunit of phosphorylase kinase responsible for hepatic glycogen breakdown.\",\n      \"method\": \"Targeted gene knockout mouse model; enzyme activity assays, glycogen content measurement, histology (H&E, Masson's Trichrome), serum liver markers, urinary Glc4 biomarker\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with multiple orthogonal biochemical and histological readouts establishing liver-specific function, with tissue-specificity confirmed across multiple organs\",\n      \"pmids\": [\"34083142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Novel PHKG2 mutations F233S and R320DfsX5 each lead to a decrease in key phosphorylase b kinase enzyme activity, as demonstrated by functional experiments in patient-derived samples.\",\n      \"method\": \"Functional enzyme activity assay on patient samples with novel PHKG2 mutations\",\n      \"journal\": \"BMC pediatrics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct enzyme activity assay demonstrating loss of function for specific mutations, but single case report from a single lab\",\n      \"pmids\": [\"35549678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PHKG2 promotes RSL3-induced ferroptosis in H. pylori-positive gastric cancer cells by upregulating the lipoxygenase ALOX5 expression, thereby enhancing lipid peroxidation.\",\n      \"method\": \"Cell-based overexpression/knockdown experiments in gastric cancer cell lines; measurement of ferroptosis markers and ALOX5 expression\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mechanistic link between PHKG2 and ALOX5/ferroptosis established in cell lines but limited by abstract-level detail\",\n      \"pmids\": [\"36948350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NRF2 transcriptionally represses PHKG2; overexpression of PHKG2 promotes ferritinophagy, elevates intracellular iron levels, and induces mitochondrial stress-dependent ferroptosis in NSCLC cells under radiotherapy. Targeting NRF2 upregulates PHKG2 and reverses radiotherapy resistance.\",\n      \"method\": \"High-throughput transcriptome sequencing, Lasso regression, in vitro overexpression/knockdown, ferritinophagy and iron level assays, mitochondrial function assays, in situ transplantation tumor models in vivo\",\n      \"journal\": \"NPJ precision oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (transcriptomics, cell assays, in vivo model) in single lab establishing NRF2→PHKG2 transcriptional axis and PHKG2's role in ferritinophagy/ferroptosis\",\n      \"pmids\": [\"39169204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TP53 transcriptionally activates PHKG2; PHKG2 phosphorylates PPP1R3B at specific residues, disrupting its interaction with PP1C and thereby enhancing PP1 phosphatase activity; activated PP1 dephosphorylates NRF2, promoting NRF2 nuclear export and suppressing GPX4 transcription, which sensitizes HNSCC cells to ferroptosis. This defines a TP53/PHKG2–PP1–NRF2 signaling axis.\",\n      \"method\": \"In vitro and in vivo overexpression experiments; phosphorylation assays demonstrating PHKG2 phosphorylates PPP1R3B (T225, T306); co-immunoprecipitation showing disruption of PPP1R3B–PP1C interaction; NRF2 nuclear export assays; GPX4 transcription assays; lipid peroxidation measurement; xenograft tumor models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods including phosphorylation assays, Co-IP, nuclear localization, and in vivo models in single lab; substrate identification (PPP1R3B) and pathway placement are specific\",\n      \"pmids\": [\"40885710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PHKG2 mediates cisplatin resistance in ESCC by phosphorylating IGF2BP3 at residues T225 and T306; this phosphorylation enhances IGF2BP3 phase separation, stabilizing CXCL8 mRNA in an m6A-dependent manner; increased CXCL8 secretion then promotes M2 macrophage polarization and suppresses CD8+ T cell cytotoxicity. Pharmacological inhibition of PHKG2 by prexasertib curtails ESCC proliferation and enhances cisplatin sensitivity.\",\n      \"method\": \"CRISPR/Cas9 knockout library functional screening; transcriptomic profiling; in vitro phosphorylation assays identifying IGF2BP3 T225/T306 as PHKG2 substrates; phase separation assays; mRNA stability assays; macrophage polarization assays; in vivo validation; pharmacological inhibition with prexasertib\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus multiple orthogonal mechanistic assays (phosphorylation substrate ID, phase separation, mRNA stability, immune cell assays) in single lab\",\n      \"pmids\": [\"42161921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A deep intronic variant in PHKG2 causes aberrant splicing (confirmed by short-read and long-read RNA-seq in patient blood and a CRISPR-edited HEK293T cell model), leading to PHKG2 deficiency consistent with GSD IX γ2. Antisense splice-switching oligonucleotides reverse the aberrant splicing in the cell model, demonstrating the causal role of this non-coding variant in PHKG2 dysfunction.\",\n      \"method\": \"Whole genome sequencing; short-read and long-read RNA-seq on patient blood; CRISPR-installed variant in HEK293T cells; antisense oligonucleotide rescue experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — variant functionally validated by RNA-seq in patient tissue and cell model with CRISPR installation, rescue by ASO; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.05.14.654043\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PHKG2 encodes the liver/testis-specific catalytic gamma subunit of phosphorylase kinase (PhK), which is required for glycogen breakdown in the liver; loss-of-function mutations (missense in conserved catalytic core residues, frameshifts, splice-site mutations) cause autosomal-recessive liver glycogenosis (GSD IXc), as established in human patients and a Phkg2-/- mouse model. Beyond glycogen metabolism, PHKG2 has emerging roles in ferroptosis regulation: it is transcriptionally activated by TP53 and repressed by NRF2, and it promotes ferroptosis by phosphorylating PPP1R3B to activate PP1, which dephosphorylates and exports NRF2 from the nucleus to suppress GPX4, as well as by upregulating ALOX5 and promoting ferritinophagy-dependent iron release; additionally, PHKG2 phosphorylates IGF2BP3 (T225/T306) to stabilize CXCL8 mRNA and drive cisplatin resistance and immunosuppression in cancer contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PHKG2 encodes the liver/testis-specific catalytic gamma subunit of phosphorylase kinase, the enzyme that activates glycogen phosphorylase to drive hepatic glycogen breakdown [#0, #3]. It is the predominant catalytic gamma isoform in liver, erythrocytes, and non-muscle tissues, and its activity resides in a conserved catalytic core whose disruption by missense substitutions, frameshifts, and splice defects abolishes function [#0, #1]. Loss-of-function mutations cause autosomal-recessive liver-specific phosphorylase kinase deficiency (GSD IX \\u03b32), with knockout mice recapitulating decreased hepatic phosphorylase kinase activity, liver glycogen accumulation, and early fibrosis without glycogen build-up in muscle, brain, kidney, or heart, establishing the tissue-restricted role of the gene [#3]; severe truncating mutations correlate with progression to cirrhosis [#2]. Beyond glycogen metabolism, PHKG2 acts as a kinase in ferroptosis regulation, sitting downstream of TP53 (which activates it) and NRF2 (which represses it): it phosphorylates PPP1R3B to disrupt PPP1R3B\\u2013PP1C interaction and enhance PP1 activity, driving NRF2 dephosphorylation, nuclear export, and GPX4 suppression, and it also promotes ALOX5-dependent lipid peroxidation and ferritinophagy-driven iron release [#5, #6, #7]. In esophageal squamous cell carcinoma, PHKG2 phosphorylates IGF2BP3 at T225/T306 to enhance its phase separation and m6A-dependent stabilization of CXCL8 mRNA, promoting cisplatin resistance and an immunosuppressive microenvironment [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that PHKG2 is the gene whose loss causes liver-specific phosphorylase kinase deficiency, identifying the functionally critical catalytic core of the gamma subunit.\",\n      \"evidence\": \"Sequencing of PHKG2 in patients with autosomal liver glycogenosis and the gsd rat, finding non-conservative substitutions at conserved catalytic residues and a frameshift\",\n      \"pmids\": [\"8896567\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic mechanism and substrate specificity not biochemically dissected\", \"Did not address tissue-specific regulation of the isoform\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed that splice-disrupting mutations, not only coding mutations, can ablate PHKG2 function by removing the catalytic site.\",\n      \"evidence\": \"Exon-specific sequencing of a IVS4+1 g\\u2192a splice mutation causing exon 4 skipping and a premature stop in affected siblings\",\n      \"pmids\": [\"9245685\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single family\", \"No direct enzyme activity quantification\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined the genomic architecture of PHKG2 and linked truncating mutation severity to clinical progression toward cirrhosis.\",\n      \"evidence\": \"Genomic sequencing establishing 10-exon structure conserved with PHKG1, plus mutation identification in cirrhotic patients\",\n      \"pmids\": [\"9384616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genotype\\u2013phenotype correlation based on limited patients\", \"Mechanism linking enzyme loss to fibrosis not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided definitive in vivo proof that PHKG2 encodes the liver-specific catalytic subunit required for hepatic glycogen breakdown, with strict tissue restriction.\",\n      \"evidence\": \"Phkg2-/- mouse with reduced liver phosphorylase kinase activity, hepatic glycogen accumulation, and early fibrosis, with no glycogen accumulation in other organs\",\n      \"pmids\": [\"34083142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address non-metabolic roles\", \"Mechanism of fibrosis development not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed that newly identified clinical variants are loss-of-function by direct enzymatic readout.\",\n      \"evidence\": \"Phosphorylase b kinase activity assay on patient samples carrying F233S and R320DfsX5\",\n      \"pmids\": [\"35549678\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single case report\", \"No structural rationale for activity loss\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Introduced a non-metabolic role for PHKG2 in promoting ferroptosis via lipid peroxidation.\",\n      \"evidence\": \"Overexpression/knockdown in H. pylori-positive gastric cancer cells showing PHKG2 upregulates ALOX5 and enhances RSL3-induced ferroptosis\",\n      \"pmids\": [\"36948350\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting PHKG2 kinase activity to ALOX5 induction unknown\", \"Cell-line only, abstract-level detail\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed PHKG2 downstream of NRF2 transcriptional repression and tied it to ferritinophagy-driven iron release and radiotherapy sensitivity.\",\n      \"evidence\": \"Transcriptomics, in vitro overexpression/knockdown, iron and ferritinophagy assays, and in vivo tumor models in NSCLC\",\n      \"pmids\": [\"39169204\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct NRF2 binding at PHKG2 promoter not shown\", \"How PHKG2 mechanistically triggers ferritinophagy unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined a kinase-based ferroptosis mechanism: TP53\\u2192PHKG2\\u2192PPP1R3B/PP1\\u2192NRF2 export\\u2192GPX4 suppression, identifying PPP1R3B as a PHKG2 substrate.\",\n      \"evidence\": \"Phosphorylation assays (PPP1R3B T225/T306), Co-IP showing disrupted PPP1R3B\\u2013PP1C interaction, NRF2 export and GPX4 transcription assays, and xenografts in HNSCC\",\n      \"pmids\": [\"40885710\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Direct PP1 dephosphorylation of NRF2 not reconstituted in vitro\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated that a deep intronic non-coding variant is causal for PHKG2 deficiency and is correctable by splice-switching oligonucleotides.\",\n      \"evidence\": \"WGS, short/long-read RNA-seq in patient blood, CRISPR-installed variant in HEK293T, and antisense oligonucleotide rescue (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.05.14.654043\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Therapeutic rescue shown only in cell model\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended PHKG2 kinase signaling to cancer immunoevasion and chemoresistance through IGF2BP3 phosphorylation and CXCL8 mRNA stabilization.\",\n      \"evidence\": \"CRISPR screen, phosphorylation assays (IGF2BP3 T225/T306), phase separation and mRNA stability assays, macrophage/T-cell assays, and prexasertib inhibition in ESCC\",\n      \"pmids\": [\"42161921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Selectivity of prexasertib for PHKG2 not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single liver-glycogenolytic kinase acquires its diverse oncogenic substrates (PPP1R3B, IGF2BP3) and whether these roles operate in normal physiology remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural basis for substrate selectivity\", \"No unifying model linking metabolic and ferroptosis/cancer functions\", \"Physiological relevance of ferroptosis roles outside tumor contexts unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 7, 8]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [7, 8]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5, 6, 7]}\n    ],\n    \"complexes\": [\"phosphorylase kinase\"],\n    \"partners\": [\"PPP1R3B\", \"IGF2BP3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}