{"gene":"PRKG2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2007,"finding":"PRKG2 (cGKII) binds directly to the GluR1 (GluA1) C-terminal domain adjacent to the kinase catalytic site; this binding is increased when cGKII is activated by cGMP. Within the complex, cGKII phosphorylates GluR1 at Ser845, increasing surface expression of AMPARs at extrasynaptic sites and contributing to LTP.","method":"Co-immunoprecipitation from brain, pulldown assays, pharmacological activation/inhibition of cGKII, surface biotinylation, hippocampal slice LTP recordings","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP from brain, biochemical phosphorylation assay, surface expression assay, and functional LTP readout; replicated in multiple experimental systems","pmids":["18031684"],"is_preprint":false},{"year":2014,"finding":"PRKG2 (cGKII) inhibits the brush-border Na+/H+ exchanger NHE3 by phosphorylating it at three required sites (Ser554, Ser607, Ser663 in rabbit; equivalent Ser552, Ser605, Ser659 in mouse) and reducing NHE3 surface expression; all three phosphorylation sites must be simultaneously present for cGMP/cGKII-mediated inhibition.","method":"iTRAQ/LC-MS/MS phosphoproteomics with TiO2 enrichment, site-directed mutagenesis, cell surface biotinylation, fluorometric NHE3 activity assay in PS120/NHERF2 and Caco-2/Bbe cells and mouse ileum","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mass spectrometry identification of phosphosites plus mutagenesis plus functional activity assay plus surface trafficking assay; multiple orthogonal methods in one study","pmids":["25480791"],"is_preprint":false},{"year":2009,"finding":"A truncating nonsense mutation (R678X) in PRKG2 that removes 85 C-terminal amino acids including much of the kinase domain causes loss of PRKG2 regulation of COL2 and COL10 expression; wild-type PRKG2 suppresses COL2 expression whereas R678X PRKG2 fails to do so, indicating the kinase domain is required for regulation of SOX9/COL2-mediated transcription.","method":"Cell culture overexpression of WT vs. R678X PRKG2, real-time PCR for COL2/COL10 mRNA; genetic mapping and pedigree analysis in Angus cattle","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function variant with defined molecular phenotype (COL2/COL10 expression) and genetic concordance, single lab","pmids":["19887637"],"is_preprint":false},{"year":2020,"finding":"PRKG2 phosphorylates myelin regulatory factor (MYRF) at Ser259; this phosphorylation promotes MYRF binding to mutant huntingtin and reduces expression of myelin-associated genes, contributing to demyelination. Laquinimod reduces Ser259-MYRF phosphorylation, and PRKG2 knockdown increases myelin-associated protein expression in HD mice.","method":"HD mouse model with oligodendrocyte-selective mutant huntingtin; PRKG2 knockdown (shRNA/siRNA), phospho-specific immunoblotting, co-immunoprecipitation, myelin gene expression analysis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo knockdown with defined phosphorylation site and Co-IP interaction, single lab","pmids":["32270922"],"is_preprint":false},{"year":2014,"finding":"In developing avian retina, cGKII (PRKG2) acts downstream of NO/soluble guanylyl cyclase to dualistically regulate AKT nuclear activation and CREB1 phosphorylation: it decreases nuclear phospho-CREB and promotes cell death at E6, but increases nuclear AKT and CREB phosphorylation and promotes cell survival at E8. shRNA-mediated cGKII knockdown abrogated both effects.","method":"shRNA-mediated cGKII knockdown in chick retina (in vivo and in vitro), pharmacological inhibition of sGC and cGK, immunostaining for nuclear phospho-CREB and phospho-AKT, caspase activation assay","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockdown with specific phosphorylation and viability readouts; multiple pharmacological controls; single lab","pmids":["24531539"],"is_preprint":false},{"year":2020,"finding":"In retinal neurons, cGKII acts downstream of NO/soluble guanylyl cyclase to mediate AKT phosphorylation and nuclear accumulation induced by protein synthesis inhibition; cGKII knockout mice fail to show cycloheximide-induced AKT phosphorylation, placing cGKII between cGMP and AKT/ERK activation.","method":"cGKII knockout mice, shRNA knockdown, pharmacological inhibition of NOS and sGC, immunoblotting for phospho-AKT and phospho-ERK","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO and KD with defined signaling readouts, mechanistic pathway placement; single lab","pmids":["32360667"],"is_preprint":false},{"year":2020,"finding":"Biallelic loss-of-function PRKG2 variants (nonsense and frameshift) cause truncated cGKII proteins that fail to phosphorylate c-Raf1 at Ser43, reducing ERK1/2 activation in response to FGF2, and alter SOX9-mediated regulation of COL10A1 (down) and COL2A1 (up), establishing PRKG2's role in FGF/MAPK signaling during chondrocyte differentiation.","method":"Exome sequencing, functional characterization of mutant proteins in cell culture, phospho-Raf1 and phospho-ERK immunoblotting, COL10A1/COL2A1 mRNA quantification","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function variants with direct phosphorylation assay for c-Raf1 Ser43 and downstream ERK readout; single lab","pmids":["33106379"],"is_preprint":false},{"year":2018,"finding":"cGKII (PRKG2) regulates postsynaptic GluA1 (AMPAR) levels by phosphorylating GluA1 at Ser845, thereby controlling AMPAR-mediated excitatory synaptic transmission; pharmacological activation of cGKII in a pilocarpine epilepsy model increases GluA1 surface expression and seizure activity, while inhibition reduces it.","method":"Pharmacological cGKII activation/inhibition in pilocarpine rat model, in vivo behavioral assay, electrophysiology, immunoblotting for GluA1 and phospho-Ser845-GluA1","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — phosphorylation site identified, functional electrophysiology and behavioral readouts; replicates earlier Ser845 finding","pmids":["29587280"],"is_preprint":false},{"year":2017,"finding":"Pre-synaptic cGKII (PRKG2) controls the homeostatic balance between synaptic vesicle exocytosis and endocytosis in cerebellar granule cells; cGKII knockout slows endocytosis after strong stimulation and causes structural changes to synapses, demonstrating a role in synaptic membrane retrieval.","method":"cGKII knockout mice, live imaging of vesicle recycling, electron microscopy ultrastructural analysis of cerebellar synapses, pharmacological inhibition with KT5823","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with direct ultrastructural and functional vesicle recycling readouts; single lab","pmids":["29084181"],"is_preprint":false},{"year":2008,"finding":"PRKG2 is fused to PDGFRB in a t(4;5)(q21.1;q31.3) translocation in myeloproliferative disease; the PRKG2-PDGFRβ fusion incorporates the first two exons of PRKG2 fused to truncated exon 12 of PDGFRB, disrupting the auto-inhibitory juxtamembrane domain of PDGFRβ and conferring constitutive kinase activity and transforming properties responsive to imatinib.","method":"FISH, molecular cloning of fusion transcript, functional transforming assay, imatinib treatment","journal":"Haematologica","confidence":"Medium","confidence_rationale":"Tier 2 — fusion gene characterized molecularly with functional transforming assay; single case report but with functional validation","pmids":["18166785"],"is_preprint":false},{"year":2021,"finding":"PRKG2 (PKG2) promotes osteoblast function; its overexpression inhibits PLCβ1 activation, reduces intracellular calcium overload, and suppresses endoplasmic reticulum stress. Co-immunoprecipitation identified a physical interaction between PKG2 and PLCβ1, placing PKG2 upstream of the PLCβ1-Ca2+-ER stress pathway in osteoblasts.","method":"Lentiviral PKG2 overexpression in primary rat osteoblasts, co-immunoprecipitation, proteomic analysis, calcium measurement, ER stress marker immunoblotting","journal":"Oxidative medicine and cellular longevity","confidence":"Low","confidence_rationale":"Tier 3 — Co-IP interaction with PLCβ1 and downstream readouts; single lab, limited mechanistic depth","pmids":["34221234"],"is_preprint":false},{"year":2025,"finding":"SMURF1, an E3 ubiquitin ligase, physically interacts with PKG2 (PRKG2) and promotes its ubiquitination and proteasomal degradation; SMURF1 overexpression downregulates PKG2 protein, reducing osteogenic differentiation, while proteasome inhibition (MG132) rescues PKG2 levels.","method":"Co-immunoprecipitation of SMURF1 and PKG2, proteasome inhibitor treatment (MG132), SMURF1 overexpression in BMSCs and diabetic rat model, osteogenic differentiation assays","journal":"Applied biochemistry and biotechnology","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP with functional overexpression data; single lab, limited orthogonal validation","pmids":["40682619"],"is_preprint":false},{"year":2022,"finding":"Prkg2 regulates the lineage fate of alveolar type 2 (AT2) cells; Prkg2-/- AT2 cells form more organoids but generate fewer AT2 and more AT1 cells, indicating PRKG2 suppresses AT2-to-AT1 differentiation, and this is modulated by PKA signaling (H89 treatment reduces organoid formation in both WT and KO).","method":"Prkg2 knockout mice, 3D organoid co-culture of primary AT2 cells with fibroblasts, EdU proliferation assay, immunostaining for AT1 (podoplanin) and AT2 (SPC) markers, PKA inhibitor treatment","journal":"Stem cell research & therapy","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined lineage differentiation phenotype and pharmacological interaction with PKA pathway; single lab","pmids":["35313961"],"is_preprint":false},{"year":2010,"finding":"The cGK-II (PRKG2) gene promoter contains a functional Nkx-binding site (between positions -292 and -286) required for transcriptional activity in chondrocytes; deletion or mutagenesis of this site markedly reduces promoter activity, and cGK-II mRNA is induced prior to hypertrophic differentiation in ATDC5 chondrogenic cells.","method":"Reporter gene (promoter-luciferase) deletion/mutagenesis analysis, RT-PCR during ATDC5 chondrogenic differentiation","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — promoter mutagenesis identifying Nkx-binding site; single lab, no direct Nkx binding confirmed by EMSA or ChIP","pmids":["20057151"],"is_preprint":false},{"year":2026,"finding":"A PRKG2 missense variant (p.Asp544Tyr) in the kinase domain creates a cryptic splice site, generating two aberrant protein products (an in-frame deletion and a missense substitution), causing partial loss of PRKG2 kinase function and an attenuated acromesomelic dysplasia phenotype.","method":"Whole-genome sequencing, RNA splicing analysis, functional characterization of aberrant transcripts","journal":"Frontiers in genetics","confidence":"Low","confidence_rationale":"Tier 3 — RNA splicing analysis with functional inference; single case, limited biochemical validation","pmids":["41574272"],"is_preprint":false}],"current_model":"PRKG2 (cGKII) is a cGMP-activated serine/threonine protein kinase that directly binds and phosphorylates multiple substrates—including GluR1/GluA1 at Ser845 to promote AMPAR surface expression and synaptic plasticity, NHE3 at three required serine residues to inhibit intestinal Na+/H+ exchange, MYRF at Ser259 to suppress myelin gene expression, and c-Raf1 at Ser43 to modulate FGF-induced ERK1/2 signaling in chondrocytes—while also acting upstream of AKT/CREB in retinal neurons and being subject to ubiquitin-mediated proteasomal degradation by SMURF1; loss of its kinase domain disrupts the proliferative-to-hypertrophic transition of growth plate chondrocytes, causing dwarfism across multiple species."},"narrative":{"teleology":[{"year":2007,"claim":"Establishing that cGKII is not merely a cytoplasmic signaling kinase but directly binds its substrate GluA1 and phosphorylates Ser845 to drive AMPAR surface expression and LTP answered how cGMP signaling regulates excitatory synaptic strength.","evidence":"Co-IP from brain, pulldown assays, surface biotinylation, hippocampal slice LTP recordings","pmids":["18031684"],"confidence":"High","gaps":["Identity of additional neuronal cGKII substrates beyond GluA1","Whether cGKII-GluA1 interaction is regulated by other post-translational modifications","Structural basis of the cGKII–GluA1 C-terminal binding interface"]},{"year":2008,"claim":"Discovery of a PRKG2-PDGFRB fusion in myeloproliferative disease revealed that the PRKG2 locus can participate in oncogenic rearrangements, though the fusion's transforming activity derives from constitutive PDGFRB kinase activation rather than cGKII function.","evidence":"FISH, fusion transcript cloning, transforming assay, imatinib sensitivity in a single patient case","pmids":["18166785"],"confidence":"Medium","gaps":["Single case report; frequency of this translocation is unknown","Whether PRKG2 regulatory elements contribute to fusion expression levels"]},{"year":2009,"claim":"Identification of a truncating PRKG2 mutation (R678X) in dwarfed cattle that failed to suppress COL2 expression established that the kinase domain is essential for regulating chondrocyte differentiation programs.","evidence":"Genetic mapping in Angus cattle pedigrees, overexpression of WT vs. R678X PRKG2, RT-PCR for COL2/COL10","pmids":["19887637"],"confidence":"Medium","gaps":["Direct phosphorylation substrate linking cGKII kinase activity to SOX9/collagen regulation was not identified","No rescue experiment restoring WT PRKG2 in mutant chondrocytes"]},{"year":2010,"claim":"Promoter analysis identified a functional Nkx-binding site required for PRKG2 transcription in chondrocytes, providing a first clue to how PRKG2 itself is transcriptionally induced before hypertrophic differentiation.","evidence":"Promoter-luciferase deletion/mutagenesis in chondrogenic ATDC5 cells, RT-PCR time course","pmids":["20057151"],"confidence":"Low","gaps":["No direct Nkx protein binding confirmed by EMSA or ChIP","Identity of the specific Nkx family member driving PRKG2 transcription remains unresolved","Relevance to in vivo chondrocyte differentiation not tested"]},{"year":2014,"claim":"Phosphoproteomic identification of three obligate NHE3 phosphosites and demonstration that all three are simultaneously required for cGKII-mediated inhibition of Na+/H+ exchange resolved the molecular mechanism by which cGMP controls intestinal sodium absorption.","evidence":"iTRAQ/LC-MS/MS with TiO2 enrichment, site-directed mutagenesis, surface biotinylation, fluorometric NHE3 activity assay in cell lines and mouse ileum","pmids":["25480791"],"confidence":"High","gaps":["Structural basis for requirement of all three sites simultaneously","Whether cGKII phosphorylates NHE3 directly or through an intermediate kinase in vivo"]},{"year":2014,"claim":"Showing that cGKII mediates opposing developmental outcomes—promoting apoptosis at E6 but survival at E8—through stage-dependent AKT and CREB phosphorylation revealed that cGKII's downstream signaling output is context-dependent in retinal neurons.","evidence":"shRNA knockdown in chick retina, pharmacological sGC/cGK inhibition, nuclear phospho-CREB and phospho-AKT immunostaining, caspase activation","pmids":["24531539"],"confidence":"Medium","gaps":["Direct substrate linking cGKII to AKT phosphorylation not identified","Mechanism of developmental switch in cGKII signaling output unknown"]},{"year":2017,"claim":"Demonstration that cGKII knockout slows synaptic vesicle endocytosis and alters synapse ultrastructure in cerebellar granule cells established a presynaptic role for cGKII distinct from its postsynaptic GluA1 phosphorylation function.","evidence":"cGKII knockout mice, live vesicle recycling imaging, electron microscopy of cerebellar synapses","pmids":["29084181"],"confidence":"Medium","gaps":["Presynaptic substrates of cGKII mediating endocytosis not identified","Whether this presynaptic role operates in brain regions beyond cerebellum"]},{"year":2018,"claim":"Replication of the cGKII–GluA1 Ser845 phosphorylation axis in an epilepsy model, showing that cGKII activation increases seizure activity via enhanced AMPAR surface expression, translated the earlier biochemical finding into a disease-relevant context.","evidence":"Pharmacological cGKII activation/inhibition in pilocarpine rat model, electrophysiology, phospho-Ser845-GluA1 immunoblotting","pmids":["29587280"],"confidence":"Medium","gaps":["Genetic validation (cGKII knockout in epilepsy model) not performed","Whether cGKII contributes to epileptogenesis or only modulates established seizures"]},{"year":2020,"claim":"Identification of MYRF Ser259 as a cGKII phosphosite that promotes MYRF–mutant huntingtin binding and suppresses myelin gene expression connected cGKII to oligodendrocyte pathology in Huntington's disease and revealed a non-neuronal CNS substrate.","evidence":"PRKG2 knockdown in HD mouse oligodendrocytes, phospho-specific immunoblotting, co-IP, myelin gene expression analysis","pmids":["32270922"],"confidence":"Medium","gaps":["Whether MYRF phosphorylation by cGKII occurs in wild-type myelination or only in HD context","Structural basis of phospho-MYRF–huntingtin interaction unknown"]},{"year":2020,"claim":"Biallelic PRKG2 loss-of-function variants in human acromesomelic dysplasia patients were shown to abolish c-Raf1 Ser43 phosphorylation and ERK1/2 activation, directly linking cGKII kinase activity to FGF/MAPK signaling in chondrocyte hypertrophy and establishing the human disease mechanism.","evidence":"Exome sequencing of affected families, functional characterization of mutant proteins, phospho-Raf1/phospho-ERK immunoblotting, COL10A1/COL2A1 expression","pmids":["33106379"],"confidence":"Medium","gaps":["Whether c-Raf1 is a direct or indirect cGKII substrate in chondrocytes not formally resolved","In vivo rescue of skeletal phenotype by WT PRKG2 not demonstrated"]},{"year":2020,"claim":"Confirmation in cGKII knockout mice that cGKII is required for cycloheximide-induced AKT phosphorylation in retina placed cGKII as a necessary node between cGMP production and AKT/ERK activation under translational stress.","evidence":"cGKII knockout mice, shRNA knockdown, NOS/sGC pharmacological inhibition, phospho-AKT and phospho-ERK immunoblotting","pmids":["32360667"],"confidence":"Medium","gaps":["Direct cGKII substrate connecting to AKT phosphorylation still not identified","Relevance beyond retinal neurons not explored"]},{"year":2022,"claim":"Prkg2 knockout AT2 cells forming more organoids but differentiating preferentially toward AT1 fate revealed a role for cGKII in suppressing alveolar progenitor cell lineage transition, broadening its known biology beyond neurons and cartilage.","evidence":"Prkg2 knockout mice, 3D AT2 organoid co-culture, EdU proliferation, AT1/AT2 marker immunostaining, PKA inhibitor treatment","pmids":["35313961"],"confidence":"Medium","gaps":["Substrates mediating cGKII's effect on AT2-to-AT1 differentiation unknown","Relationship between cGKII and PKA signaling in this context mechanistically undefined"]},{"year":null,"claim":"Key unresolved questions include the structural basis of cGKII substrate selectivity across its diverse tissue-specific targets, the direct substrates linking cGKII to AKT activation, and whether cGKII's role in alveolar and osteoblast differentiation shares a common downstream pathway with its chondrocyte function.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal structure of full-length cGKII or cGKII–substrate complex","No unbiased phosphoproteomics across multiple cGKII-expressing tissues","Mechanism of cGKII turnover by SMURF1-mediated ubiquitination awaits independent confirmation"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,3,6,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4,5]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,5,6,7]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,6,12]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,7,8]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[1]}],"complexes":[],"partners":["GRIA1","SLC9A3","MYRF","RAF1","SMURF1","PLCB1"],"other_free_text":[]},"mechanistic_narrative":"PRKG2 encodes cGMP-dependent protein kinase II (cGKII), a membrane-associated serine/threonine kinase that transduces nitric oxide/cGMP signaling into phosphorylation of diverse substrates across multiple tissues. In neurons, cGKII directly binds and phosphorylates GluA1 at Ser845, promoting AMPAR surface insertion to regulate synaptic plasticity and seizure susceptibility, and controls presynaptic vesicle endocytosis at cerebellar synapses [PMID:18031684, PMID:29587280, PMID:29084181]. In chondrocytes, cGKII phosphorylates c-Raf1 at Ser43 to activate ERK1/2 downstream of FGF signaling and regulates SOX9-dependent collagen gene expression required for the proliferative-to-hypertrophic transition; biallelic loss-of-function mutations cause acromesomelic dysplasia (dwarfism) in humans and cattle [PMID:33106379, PMID:19887637, PMID:41574272]. cGKII additionally phosphorylates NHE3 at three obligate serine residues to inhibit intestinal sodium/hydrogen exchange, phosphorylates MYRF at Ser259 to suppress myelin gene transcription, and signals through AKT/CREB to regulate developmental cell survival in the retina [PMID:25480791, PMID:32270922, PMID:24531539]."},"prefetch_data":{"uniprot":{"accession":"Q13237","full_name":"cGMP-dependent protein kinase 2","aliases":["cGMP-dependent protein kinase II","cGKII"],"length_aa":762,"mass_kda":87.4,"function":"Crucial regulator of intestinal secretion and bone growth. Phosphorylates and activates CFTR on the plasma membrane. Plays a key role in intestinal secretion by regulating cGMP-dependent translocation of CFTR in jejunum (PubMed:33106379). Acts downstream of NMDAR to activate the plasma membrane accumulation of GRIA1/GLUR1 in synapse and increase synaptic plasticity. Phosphorylates GRIA1/GLUR1 at Ser-863 (By similarity). Acts as a regulator of gene expression and activator of the extracellular signal-regulated kinases MAPK3/ERK1 and MAPK1/ERK2 in mechanically stimulated osteoblasts. Under fluid shear stress, mediates ERK activation and subsequent induction of FOS, FOSL1/FRA1, FOSL2/FRA2 and FOSB that play a key role in the osteoblast anabolic response to mechanical stimulation (By similarity)","subcellular_location":"Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q13237/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PRKG2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PRKG2","total_profiled":1310},"omim":[{"mim_id":"619638","title":"SPONDYLOMETAPHYSEAL DYSPLASIA, PAGNAMENTA TYPE; SMDP","url":"https://www.omim.org/entry/619638"},{"mim_id":"619636","title":"ACROMESOMELIC DYSPLASIA 4; AMD4","url":"https://www.omim.org/entry/619636"},{"mim_id":"615039","title":"N-DEACETYLASE/N-SULFOTRANSFERASE 4; NDST4","url":"https://www.omim.org/entry/615039"},{"mim_id":"613509","title":"CHROMOSOME 4q21 DELETION SYNDROME","url":"https://www.omim.org/entry/613509"},{"mim_id":"608160","title":"SRY-BOX 9; SOX9","url":"https://www.omim.org/entry/608160"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"intestine","ntpm":12.9},{"tissue":"prostate","ntpm":9.3}],"url":"https://www.proteinatlas.org/search/PRKG2"},"hgnc":{"alias_symbol":["cGKII","PRKGR2","PKG2"],"prev_symbol":[]},"alphafold":{"accession":"Q13237","domains":[{"cath_id":"2.60.120.10","chopping":"143-265","consensus_level":"high","plddt":88.3797,"start":143,"end":265},{"cath_id":"2.60.120.10","chopping":"286-396","consensus_level":"high","plddt":85.3786,"start":286,"end":396},{"cath_id":"3.30.200.20","chopping":"430-534_746-762","consensus_level":"medium","plddt":90.6072,"start":430,"end":762},{"cath_id":"1.10.510.10","chopping":"536-731","consensus_level":"medium","plddt":93.3878,"start":536,"end":731}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13237","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13237-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13237-F1-predicted_aligned_error_v6.png","plddt_mean":82.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PRKG2","jax_strain_url":"https://www.jax.org/strain/search?query=PRKG2"},"sequence":{"accession":"Q13237","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13237.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13237/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13237"}},"corpus_meta":[{"pmid":"18031684","id":"PMC_18031684","title":"A GluR1-cGKII interaction regulates AMPA receptor trafficking.","date":"2007","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/18031684","citation_count":145,"is_preprint":false},{"pmid":"25480791","id":"PMC_25480791","title":"Cyclic GMP kinase II (cGKII) inhibits NHE3 by altering its trafficking and phosphorylating NHE3 at three required sites: identification of a multifunctional phosphorylation site.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25480791","citation_count":48,"is_preprint":false},{"pmid":"9864307","id":"PMC_9864307","title":"Pkg2, a novel transmembrane protein Ser/Thr kinase of Streptomyces granaticolor.","date":"1999","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/9864307","citation_count":41,"is_preprint":false},{"pmid":"19887637","id":"PMC_19887637","title":"A nonsense mutation in cGMP-dependent type II protein kinase (PRKG2) causes dwarfism in American Angus cattle.","date":"2009","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/19887637","citation_count":41,"is_preprint":false},{"pmid":"18166785","id":"PMC_18166785","title":"Activity of imatinib in systemic mastocytosis with chronic basophilic leukemia and a PRKG2-PDGFRB fusion.","date":"2008","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/18166785","citation_count":39,"is_preprint":false},{"pmid":"18262053","id":"PMC_18262053","title":"Fusion of PRKG2 and SPTBN1 to the platelet-derived growth factor receptor beta gene (PDGFRB) in imatinib-responsive atypical myeloproliferative disorders.","date":"2008","source":"Cancer genetics and cytogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/18262053","citation_count":27,"is_preprint":false},{"pmid":"32270922","id":"PMC_32270922","title":"Phosphorylation of myelin regulatory factor by PRKG2 mediates demyelination in Huntington's disease.","date":"2020","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/32270922","citation_count":24,"is_preprint":false},{"pmid":"24531539","id":"PMC_24531539","title":"The nitric oxide-cGKII system relays death and survival signals during embryonic retinal development via AKT-induced CREB1 activation.","date":"2014","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/24531539","citation_count":22,"is_preprint":false},{"pmid":"33106379","id":"PMC_33106379","title":"Biallelic cGMP-dependent type II protein kinase gene (PRKG2) variants cause a novel acromesomelic dysplasia.","date":"2020","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33106379","citation_count":14,"is_preprint":false},{"pmid":"25924610","id":"PMC_25924610","title":"Transcriptional profiling of PRKG2-null growth plate identifies putative down-stream targets of PRKG2.","date":"2015","source":"BMC research 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heterozygous RUNX1 frameshift mutation.","date":"2024","source":"Cancer genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38471404","citation_count":3,"is_preprint":false},{"pmid":"16681148","id":"PMC_16681148","title":"Effect of phosphate on the expression of protein-Ser/Thr kinase pkg2 in Streptomyces granaticolor.","date":"2005","source":"Folia microbiologica","url":"https://pubmed.ncbi.nlm.nih.gov/16681148","citation_count":2,"is_preprint":false},{"pmid":"39202255","id":"PMC_39202255","title":"ELOVL2, PRKG2, and EDARADD DNA Methylation Strongly Estimate Indonesian Adolescents.","date":"2024","source":"Diagnostics (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/39202255","citation_count":1,"is_preprint":false},{"pmid":"41296694","id":"PMC_41296694","title":"A nonsense mutation in the PRKG2 gene in dalmatian dogs with chondrodysplasia.","date":"2025","source":"PloS 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genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41574272","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16401,"output_tokens":4093,"usd":0.055299},"stage2":{"model":"claude-opus-4-6","input_tokens":7514,"output_tokens":3384,"usd":0.183255},"total_usd":0.238554,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"PRKG2 (cGKII) binds directly to the GluR1 (GluA1) C-terminal domain adjacent to the kinase catalytic site; this binding is increased when cGKII is activated by cGMP. Within the complex, cGKII phosphorylates GluR1 at Ser845, increasing surface expression of AMPARs at extrasynaptic sites and contributing to LTP.\",\n      \"method\": \"Co-immunoprecipitation from brain, pulldown assays, pharmacological activation/inhibition of cGKII, surface biotinylation, hippocampal slice LTP recordings\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP from brain, biochemical phosphorylation assay, surface expression assay, and functional LTP readout; replicated in multiple experimental systems\",\n      \"pmids\": [\"18031684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PRKG2 (cGKII) inhibits the brush-border Na+/H+ exchanger NHE3 by phosphorylating it at three required sites (Ser554, Ser607, Ser663 in rabbit; equivalent Ser552, Ser605, Ser659 in mouse) and reducing NHE3 surface expression; all three phosphorylation sites must be simultaneously present for cGMP/cGKII-mediated inhibition.\",\n      \"method\": \"iTRAQ/LC-MS/MS phosphoproteomics with TiO2 enrichment, site-directed mutagenesis, cell surface biotinylation, fluorometric NHE3 activity assay in PS120/NHERF2 and Caco-2/Bbe cells and mouse ileum\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mass spectrometry identification of phosphosites plus mutagenesis plus functional activity assay plus surface trafficking assay; multiple orthogonal methods in one study\",\n      \"pmids\": [\"25480791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A truncating nonsense mutation (R678X) in PRKG2 that removes 85 C-terminal amino acids including much of the kinase domain causes loss of PRKG2 regulation of COL2 and COL10 expression; wild-type PRKG2 suppresses COL2 expression whereas R678X PRKG2 fails to do so, indicating the kinase domain is required for regulation of SOX9/COL2-mediated transcription.\",\n      \"method\": \"Cell culture overexpression of WT vs. R678X PRKG2, real-time PCR for COL2/COL10 mRNA; genetic mapping and pedigree analysis in Angus cattle\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function variant with defined molecular phenotype (COL2/COL10 expression) and genetic concordance, single lab\",\n      \"pmids\": [\"19887637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRKG2 phosphorylates myelin regulatory factor (MYRF) at Ser259; this phosphorylation promotes MYRF binding to mutant huntingtin and reduces expression of myelin-associated genes, contributing to demyelination. Laquinimod reduces Ser259-MYRF phosphorylation, and PRKG2 knockdown increases myelin-associated protein expression in HD mice.\",\n      \"method\": \"HD mouse model with oligodendrocyte-selective mutant huntingtin; PRKG2 knockdown (shRNA/siRNA), phospho-specific immunoblotting, co-immunoprecipitation, myelin gene expression analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockdown with defined phosphorylation site and Co-IP interaction, single lab\",\n      \"pmids\": [\"32270922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In developing avian retina, cGKII (PRKG2) acts downstream of NO/soluble guanylyl cyclase to dualistically regulate AKT nuclear activation and CREB1 phosphorylation: it decreases nuclear phospho-CREB and promotes cell death at E6, but increases nuclear AKT and CREB phosphorylation and promotes cell survival at E8. shRNA-mediated cGKII knockdown abrogated both effects.\",\n      \"method\": \"shRNA-mediated cGKII knockdown in chick retina (in vivo and in vitro), pharmacological inhibition of sGC and cGK, immunostaining for nuclear phospho-CREB and phospho-AKT, caspase activation assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown with specific phosphorylation and viability readouts; multiple pharmacological controls; single lab\",\n      \"pmids\": [\"24531539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In retinal neurons, cGKII acts downstream of NO/soluble guanylyl cyclase to mediate AKT phosphorylation and nuclear accumulation induced by protein synthesis inhibition; cGKII knockout mice fail to show cycloheximide-induced AKT phosphorylation, placing cGKII between cGMP and AKT/ERK activation.\",\n      \"method\": \"cGKII knockout mice, shRNA knockdown, pharmacological inhibition of NOS and sGC, immunoblotting for phospho-AKT and phospho-ERK\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO and KD with defined signaling readouts, mechanistic pathway placement; single lab\",\n      \"pmids\": [\"32360667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Biallelic loss-of-function PRKG2 variants (nonsense and frameshift) cause truncated cGKII proteins that fail to phosphorylate c-Raf1 at Ser43, reducing ERK1/2 activation in response to FGF2, and alter SOX9-mediated regulation of COL10A1 (down) and COL2A1 (up), establishing PRKG2's role in FGF/MAPK signaling during chondrocyte differentiation.\",\n      \"method\": \"Exome sequencing, functional characterization of mutant proteins in cell culture, phospho-Raf1 and phospho-ERK immunoblotting, COL10A1/COL2A1 mRNA quantification\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function variants with direct phosphorylation assay for c-Raf1 Ser43 and downstream ERK readout; single lab\",\n      \"pmids\": [\"33106379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"cGKII (PRKG2) regulates postsynaptic GluA1 (AMPAR) levels by phosphorylating GluA1 at Ser845, thereby controlling AMPAR-mediated excitatory synaptic transmission; pharmacological activation of cGKII in a pilocarpine epilepsy model increases GluA1 surface expression and seizure activity, while inhibition reduces it.\",\n      \"method\": \"Pharmacological cGKII activation/inhibition in pilocarpine rat model, in vivo behavioral assay, electrophysiology, immunoblotting for GluA1 and phospho-Ser845-GluA1\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — phosphorylation site identified, functional electrophysiology and behavioral readouts; replicates earlier Ser845 finding\",\n      \"pmids\": [\"29587280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Pre-synaptic cGKII (PRKG2) controls the homeostatic balance between synaptic vesicle exocytosis and endocytosis in cerebellar granule cells; cGKII knockout slows endocytosis after strong stimulation and causes structural changes to synapses, demonstrating a role in synaptic membrane retrieval.\",\n      \"method\": \"cGKII knockout mice, live imaging of vesicle recycling, electron microscopy ultrastructural analysis of cerebellar synapses, pharmacological inhibition with KT5823\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with direct ultrastructural and functional vesicle recycling readouts; single lab\",\n      \"pmids\": [\"29084181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PRKG2 is fused to PDGFRB in a t(4;5)(q21.1;q31.3) translocation in myeloproliferative disease; the PRKG2-PDGFRβ fusion incorporates the first two exons of PRKG2 fused to truncated exon 12 of PDGFRB, disrupting the auto-inhibitory juxtamembrane domain of PDGFRβ and conferring constitutive kinase activity and transforming properties responsive to imatinib.\",\n      \"method\": \"FISH, molecular cloning of fusion transcript, functional transforming assay, imatinib treatment\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — fusion gene characterized molecularly with functional transforming assay; single case report but with functional validation\",\n      \"pmids\": [\"18166785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PRKG2 (PKG2) promotes osteoblast function; its overexpression inhibits PLCβ1 activation, reduces intracellular calcium overload, and suppresses endoplasmic reticulum stress. Co-immunoprecipitation identified a physical interaction between PKG2 and PLCβ1, placing PKG2 upstream of the PLCβ1-Ca2+-ER stress pathway in osteoblasts.\",\n      \"method\": \"Lentiviral PKG2 overexpression in primary rat osteoblasts, co-immunoprecipitation, proteomic analysis, calcium measurement, ER stress marker immunoblotting\",\n      \"journal\": \"Oxidative medicine and cellular longevity\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP interaction with PLCβ1 and downstream readouts; single lab, limited mechanistic depth\",\n      \"pmids\": [\"34221234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMURF1, an E3 ubiquitin ligase, physically interacts with PKG2 (PRKG2) and promotes its ubiquitination and proteasomal degradation; SMURF1 overexpression downregulates PKG2 protein, reducing osteogenic differentiation, while proteasome inhibition (MG132) rescues PKG2 levels.\",\n      \"method\": \"Co-immunoprecipitation of SMURF1 and PKG2, proteasome inhibitor treatment (MG132), SMURF1 overexpression in BMSCs and diabetic rat model, osteogenic differentiation assays\",\n      \"journal\": \"Applied biochemistry and biotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with functional overexpression data; single lab, limited orthogonal validation\",\n      \"pmids\": [\"40682619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Prkg2 regulates the lineage fate of alveolar type 2 (AT2) cells; Prkg2-/- AT2 cells form more organoids but generate fewer AT2 and more AT1 cells, indicating PRKG2 suppresses AT2-to-AT1 differentiation, and this is modulated by PKA signaling (H89 treatment reduces organoid formation in both WT and KO).\",\n      \"method\": \"Prkg2 knockout mice, 3D organoid co-culture of primary AT2 cells with fibroblasts, EdU proliferation assay, immunostaining for AT1 (podoplanin) and AT2 (SPC) markers, PKA inhibitor treatment\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined lineage differentiation phenotype and pharmacological interaction with PKA pathway; single lab\",\n      \"pmids\": [\"35313961\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The cGK-II (PRKG2) gene promoter contains a functional Nkx-binding site (between positions -292 and -286) required for transcriptional activity in chondrocytes; deletion or mutagenesis of this site markedly reduces promoter activity, and cGK-II mRNA is induced prior to hypertrophic differentiation in ATDC5 chondrogenic cells.\",\n      \"method\": \"Reporter gene (promoter-luciferase) deletion/mutagenesis analysis, RT-PCR during ATDC5 chondrogenic differentiation\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — promoter mutagenesis identifying Nkx-binding site; single lab, no direct Nkx binding confirmed by EMSA or ChIP\",\n      \"pmids\": [\"20057151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A PRKG2 missense variant (p.Asp544Tyr) in the kinase domain creates a cryptic splice site, generating two aberrant protein products (an in-frame deletion and a missense substitution), causing partial loss of PRKG2 kinase function and an attenuated acromesomelic dysplasia phenotype.\",\n      \"method\": \"Whole-genome sequencing, RNA splicing analysis, functional characterization of aberrant transcripts\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — RNA splicing analysis with functional inference; single case, limited biochemical validation\",\n      \"pmids\": [\"41574272\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PRKG2 (cGKII) is a cGMP-activated serine/threonine protein kinase that directly binds and phosphorylates multiple substrates—including GluR1/GluA1 at Ser845 to promote AMPAR surface expression and synaptic plasticity, NHE3 at three required serine residues to inhibit intestinal Na+/H+ exchange, MYRF at Ser259 to suppress myelin gene expression, and c-Raf1 at Ser43 to modulate FGF-induced ERK1/2 signaling in chondrocytes—while also acting upstream of AKT/CREB in retinal neurons and being subject to ubiquitin-mediated proteasomal degradation by SMURF1; loss of its kinase domain disrupts the proliferative-to-hypertrophic transition of growth plate chondrocytes, causing dwarfism across multiple species.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PRKG2 encodes cGMP-dependent protein kinase II (cGKII), a membrane-associated serine/threonine kinase that transduces nitric oxide/cGMP signaling into phosphorylation of diverse substrates across multiple tissues. In neurons, cGKII directly binds and phosphorylates GluA1 at Ser845, promoting AMPAR surface insertion to regulate synaptic plasticity and seizure susceptibility, and controls presynaptic vesicle endocytosis at cerebellar synapses [PMID:18031684, PMID:29587280, PMID:29084181]. In chondrocytes, cGKII phosphorylates c-Raf1 at Ser43 to activate ERK1/2 downstream of FGF signaling and regulates SOX9-dependent collagen gene expression required for the proliferative-to-hypertrophic transition; biallelic loss-of-function mutations cause acromesomelic dysplasia (dwarfism) in humans and cattle [PMID:33106379, PMID:19887637, PMID:41574272]. cGKII additionally phosphorylates NHE3 at three obligate serine residues to inhibit intestinal sodium/hydrogen exchange, phosphorylates MYRF at Ser259 to suppress myelin gene transcription, and signals through AKT/CREB to regulate developmental cell survival in the retina [PMID:25480791, PMID:32270922, PMID:24531539].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing that cGKII is not merely a cytoplasmic signaling kinase but directly binds its substrate GluA1 and phosphorylates Ser845 to drive AMPAR surface expression and LTP answered how cGMP signaling regulates excitatory synaptic strength.\",\n      \"evidence\": \"Co-IP from brain, pulldown assays, surface biotinylation, hippocampal slice LTP recordings\",\n      \"pmids\": [\"18031684\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of additional neuronal cGKII substrates beyond GluA1\",\n        \"Whether cGKII-GluA1 interaction is regulated by other post-translational modifications\",\n        \"Structural basis of the cGKII–GluA1 C-terminal binding interface\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery of a PRKG2-PDGFRB fusion in myeloproliferative disease revealed that the PRKG2 locus can participate in oncogenic rearrangements, though the fusion's transforming activity derives from constitutive PDGFRB kinase activation rather than cGKII function.\",\n      \"evidence\": \"FISH, fusion transcript cloning, transforming assay, imatinib sensitivity in a single patient case\",\n      \"pmids\": [\"18166785\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single case report; frequency of this translocation is unknown\",\n        \"Whether PRKG2 regulatory elements contribute to fusion expression levels\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of a truncating PRKG2 mutation (R678X) in dwarfed cattle that failed to suppress COL2 expression established that the kinase domain is essential for regulating chondrocyte differentiation programs.\",\n      \"evidence\": \"Genetic mapping in Angus cattle pedigrees, overexpression of WT vs. R678X PRKG2, RT-PCR for COL2/COL10\",\n      \"pmids\": [\"19887637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct phosphorylation substrate linking cGKII kinase activity to SOX9/collagen regulation was not identified\",\n        \"No rescue experiment restoring WT PRKG2 in mutant chondrocytes\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Promoter analysis identified a functional Nkx-binding site required for PRKG2 transcription in chondrocytes, providing a first clue to how PRKG2 itself is transcriptionally induced before hypertrophic differentiation.\",\n      \"evidence\": \"Promoter-luciferase deletion/mutagenesis in chondrogenic ATDC5 cells, RT-PCR time course\",\n      \"pmids\": [\"20057151\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct Nkx protein binding confirmed by EMSA or ChIP\",\n        \"Identity of the specific Nkx family member driving PRKG2 transcription remains unresolved\",\n        \"Relevance to in vivo chondrocyte differentiation not tested\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Phosphoproteomic identification of three obligate NHE3 phosphosites and demonstration that all three are simultaneously required for cGKII-mediated inhibition of Na+/H+ exchange resolved the molecular mechanism by which cGMP controls intestinal sodium absorption.\",\n      \"evidence\": \"iTRAQ/LC-MS/MS with TiO2 enrichment, site-directed mutagenesis, surface biotinylation, fluorometric NHE3 activity assay in cell lines and mouse ileum\",\n      \"pmids\": [\"25480791\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for requirement of all three sites simultaneously\",\n        \"Whether cGKII phosphorylates NHE3 directly or through an intermediate kinase in vivo\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that cGKII mediates opposing developmental outcomes—promoting apoptosis at E6 but survival at E8—through stage-dependent AKT and CREB phosphorylation revealed that cGKII's downstream signaling output is context-dependent in retinal neurons.\",\n      \"evidence\": \"shRNA knockdown in chick retina, pharmacological sGC/cGK inhibition, nuclear phospho-CREB and phospho-AKT immunostaining, caspase activation\",\n      \"pmids\": [\"24531539\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct substrate linking cGKII to AKT phosphorylation not identified\",\n        \"Mechanism of developmental switch in cGKII signaling output unknown\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstration that cGKII knockout slows synaptic vesicle endocytosis and alters synapse ultrastructure in cerebellar granule cells established a presynaptic role for cGKII distinct from its postsynaptic GluA1 phosphorylation function.\",\n      \"evidence\": \"cGKII knockout mice, live vesicle recycling imaging, electron microscopy of cerebellar synapses\",\n      \"pmids\": [\"29084181\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Presynaptic substrates of cGKII mediating endocytosis not identified\",\n        \"Whether this presynaptic role operates in brain regions beyond cerebellum\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Replication of the cGKII–GluA1 Ser845 phosphorylation axis in an epilepsy model, showing that cGKII activation increases seizure activity via enhanced AMPAR surface expression, translated the earlier biochemical finding into a disease-relevant context.\",\n      \"evidence\": \"Pharmacological cGKII activation/inhibition in pilocarpine rat model, electrophysiology, phospho-Ser845-GluA1 immunoblotting\",\n      \"pmids\": [\"29587280\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Genetic validation (cGKII knockout in epilepsy model) not performed\",\n        \"Whether cGKII contributes to epileptogenesis or only modulates established seizures\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of MYRF Ser259 as a cGKII phosphosite that promotes MYRF–mutant huntingtin binding and suppresses myelin gene expression connected cGKII to oligodendrocyte pathology in Huntington's disease and revealed a non-neuronal CNS substrate.\",\n      \"evidence\": \"PRKG2 knockdown in HD mouse oligodendrocytes, phospho-specific immunoblotting, co-IP, myelin gene expression analysis\",\n      \"pmids\": [\"32270922\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MYRF phosphorylation by cGKII occurs in wild-type myelination or only in HD context\",\n        \"Structural basis of phospho-MYRF–huntingtin interaction unknown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Biallelic PRKG2 loss-of-function variants in human acromesomelic dysplasia patients were shown to abolish c-Raf1 Ser43 phosphorylation and ERK1/2 activation, directly linking cGKII kinase activity to FGF/MAPK signaling in chondrocyte hypertrophy and establishing the human disease mechanism.\",\n      \"evidence\": \"Exome sequencing of affected families, functional characterization of mutant proteins, phospho-Raf1/phospho-ERK immunoblotting, COL10A1/COL2A1 expression\",\n      \"pmids\": [\"33106379\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether c-Raf1 is a direct or indirect cGKII substrate in chondrocytes not formally resolved\",\n        \"In vivo rescue of skeletal phenotype by WT PRKG2 not demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Confirmation in cGKII knockout mice that cGKII is required for cycloheximide-induced AKT phosphorylation in retina placed cGKII as a necessary node between cGMP production and AKT/ERK activation under translational stress.\",\n      \"evidence\": \"cGKII knockout mice, shRNA knockdown, NOS/sGC pharmacological inhibition, phospho-AKT and phospho-ERK immunoblotting\",\n      \"pmids\": [\"32360667\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct cGKII substrate connecting to AKT phosphorylation still not identified\",\n        \"Relevance beyond retinal neurons not explored\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Prkg2 knockout AT2 cells forming more organoids but differentiating preferentially toward AT1 fate revealed a role for cGKII in suppressing alveolar progenitor cell lineage transition, broadening its known biology beyond neurons and cartilage.\",\n      \"evidence\": \"Prkg2 knockout mice, 3D AT2 organoid co-culture, EdU proliferation, AT1/AT2 marker immunostaining, PKA inhibitor treatment\",\n      \"pmids\": [\"35313961\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Substrates mediating cGKII's effect on AT2-to-AT1 differentiation unknown\",\n        \"Relationship between cGKII and PKA signaling in this context mechanistically undefined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of cGKII substrate selectivity across its diverse tissue-specific targets, the direct substrates linking cGKII to AKT activation, and whether cGKII's role in alveolar and osteoblast differentiation shares a common downstream pathway with its chondrocyte function.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal structure of full-length cGKII or cGKII–substrate complex\",\n        \"No unbiased phosphoproteomics across multiple cGKII-expressing tissues\",\n        \"Mechanism of cGKII turnover by SMURF1-mediated ubiquitination awaits independent confirmation\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 3, 6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 5, 6, 7]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 6, 12]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"GRIA1\",\n      \"SLC9A3\",\n      \"MYRF\",\n      \"RAF1\",\n      \"SMURF1\",\n      \"PLCB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}