{"gene":"PRKG2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2007,"finding":"PRKG2 (cGKII) binds directly to the GluR1 (GluA1) C-terminal domain adjacent to the kinase catalytic site; this interaction is increased when cGKII is activated by cGMP. Within the complex, cGKII phosphorylates GluR1 at Ser845. Activation of cGKII by cGMP increases surface expression of AMPARs at extrasynaptic sites, and inhibition of cGKII blocks GluR1 surface increase during chemLTP and reduces LTP in hippocampal slices.","method":"Co-immunoprecipitation from brain tissue, in vitro binding assays, phosphorylation assays, surface biotinylation, pharmacological inhibition in hippocampal slice electrophysiology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP from brain, in vitro phosphorylation assay, surface biotinylation, and electrophysiological LTP readout; multiple orthogonal methods in one study","pmids":["18031684"],"is_preprint":false},{"year":2014,"finding":"cGKII inhibits NHE3 Na+/H+ exchanger activity by phosphorylating it at three sites (rabbit Ser554, Ser607, Ser663; mouse Ser552, Ser605, Ser659), all of which must be simultaneously present for cGMP/cGKII-mediated inhibition. This phosphorylation is associated with reduced NHE3 surface expression (internalization). Ser663 phosphorylation is also required for dexamethasone-stimulated NHE3 activity and surface expression, representing a multifunctional phosphorylation site.","method":"iTRAQ/LC-MS/MS phosphoproteomics with TiO2 enrichment, site-directed mutagenesis, 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 / Strong — in vitro phosphorylation site identification by MS, mutagenesis of all three sites, functional activity assay, and surface expression quantification; multiple orthogonal methods","pmids":["25480791"],"is_preprint":false},{"year":2009,"finding":"A nonsense mutation (R678X) in PRKG2 truncates 85 C-terminal amino acids including most of the kinase domain and causes dwarfism in Angus cattle. The R678X mutant protein fails to regulate COL2A1 expression normally (COL2 and COL10 mRNA are overexpressed), establishing that the PRKG2 kinase domain is required for its regulation of collagen gene expression downstream of SOX9.","method":"Genetic fine-mapping, sequencing, cell culture overexpression of WT vs. R678X PRKG2, real-time PCR for COL2 and COL10 mRNA","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function mutation with defined molecular phenotype (collagen gene expression) confirmed in cell culture; single lab, two methods (genetic and expression)","pmids":["19887637"],"is_preprint":false},{"year":2008,"finding":"PRKG2 is fused to PDGFRB via t(4;5)(q21.1;q31.3), incorporating the first two exons of PRKG2 fused to truncated exon 12 of PDGFRB, disrupting the juxtamembrane auto-inhibitory domain of PDGFRβ. Functional studies confirmed that the transforming and kinase activity of the PRKG2-PDGFRβ fusion protein depends on disruption of this auto-inhibitory domain.","method":"FISH, molecular cloning of fusion transcript, functional cell-based transformation and kinase activity assays","journal":"Haematologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — molecular characterization of fusion gene with functional validation of auto-inhibitory domain disruption; single lab","pmids":["18166785"],"is_preprint":false},{"year":2020,"finding":"PRKG2 promotes phosphorylation of the oligodendrocyte transcription factor MYRF at Ser259. This phosphorylation increases MYRF binding to mutant huntingtin and reduces expression of myelin-associated genes. Knockdown of PRKG2 in HD mice decreased MYRF Ser259 phosphorylation and increased myelin-associated protein expression, placing PRKG2 upstream of MYRF in a demyelination pathway.","method":"Phospho-specific immunoblotting, PRKG2 shRNA knockdown in HD mouse model, co-immunoprecipitation of MYRF and mutant huntingtin, myelin gene expression analysis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with defined phosphorylation and gene-expression readout in vivo; single lab, multiple methods","pmids":["32270922"],"is_preprint":false},{"year":2014,"finding":"In developing chick retina, cGKII mediates NO/cGMP-dependent cell death (E6) and cell survival (E8) via opposing regulation of nuclear AKT activation and downstream CREB1 phosphorylation. shRNA knockdown of cGKII prevented NO-induced cell death at E6 and cell survival at E8, and abrogated CREB phosphorylation changes at both stages; AKT inhibition blocked cGKII-dependent CREB regulation.","method":"shRNA-mediated cGKII knockdown in vivo and in vitro, phospho-CREB immunostaining, AKT pharmacological inhibition, caspase activation assay","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockdown with phosphorylation readout and rescue experiments; single lab, multiple orthogonal methods","pmids":["24531539"],"is_preprint":false},{"year":2020,"finding":"In retinal cells, cGKII is required for NO-induced AKT activation and nuclear AKT accumulation downstream of soluble guanylyl cyclase. Knockdown of cGKII prevented cycloheximide/anisomycin-induced AKT phosphorylation, and cGKII knockout mice showed no AKT enhancement upon cycloheximide treatment, establishing cGKII as an obligate relay between NO/cGMP signaling and AKT activation.","method":"cGKII shRNA knockdown, cGKII knockout mouse retinas, pharmacological inhibition of soluble guanylyl cyclase, immunoblotting for phospho-AKT and phospho-ERK","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — both genetic knockdown and knockout, with orthogonal pharmacological confirmation; single lab","pmids":["32360667"],"is_preprint":false},{"year":2020,"finding":"Truncated PRKG2 mutant proteins lacking most or all of the kinase domain (nonsense and frameshift variants identified in human patients) fail to phosphorylate c-Raf1 at Ser43, resulting in reduced ERK1/2 activation in response to FGF2, and alter downstream MAPK signaling. These mutant proteins also dysregulate SOX9-mediated transcription by downregulating COL10A1 and upregulating COL2A1.","method":"Exome sequencing, functional expression of truncated mutant PRKG2 in cells, phospho-Raf1 and phospho-ERK1/2 immunoblotting, COL10A1/COL2A1 expression analysis","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function variants with defined substrate phosphorylation (c-Raf1 Ser43) and downstream signaling readout; single lab, multiple methods","pmids":["33106379"],"is_preprint":false},{"year":2018,"finding":"cGKII regulates epileptic seizure activity by phosphorylating GluA1 at Ser845, thereby modulating GluA1 expression and function at the postsynaptic membrane. Pharmacological activation of cGKII in vivo increased epileptic behaviors and AMPAR-mediated excitatory synaptic transmission, while inhibition reduced them.","method":"Pharmacological cGKII activation/inhibition in pilocarpine-induced rat model, behavioral analysis, electrophysiology, immunoblotting for GluA1 and phospho-Ser845","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological gain- and loss-of-function with electrophysiological and phosphorylation readouts; single lab","pmids":["29587280"],"is_preprint":false},{"year":2017,"finding":"cGKII plays a presynaptic role in controlling the homeostatic balance of synaptic vesicle exocytosis and endocytosis in cerebellar granule cells. Genetic knockout of cGKII slows endocytosis in a subset of boutons under strong stimulation and causes structural changes to synapses in cultured cells and cerebellar cortex in vivo.","method":"cGKII knockout mouse model, live imaging of vesicle cycling, electron microscopy ultrastructural analysis, pharmacological inhibition with KT5823","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with ultrastructural and live-imaging functional readout; single lab, multiple methods","pmids":["29084181"],"is_preprint":false},{"year":2010,"finding":"Transcription of the cGKII (PRKG2) gene in chondrocytes is regulated by an Nkx homeodomain binding site located between -292 and -286 bp upstream of the transcription start site. Deletion or mutagenesis of this site markedly reduced promoter activity, and cGKII mRNA expression increased dramatically at the prehypertrophic stage of ATDC5 chondrogenic differentiation.","method":"5'-flanking region cloning and deletion analysis, site-directed mutagenesis of Nkx-binding site, promoter-reporter assays in ATDC5 cells during chondrogenic differentiation","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter deletion and mutagenesis with reporter assay; single lab, two orthogonal methods","pmids":["20057151"],"is_preprint":false},{"year":2021,"finding":"PKG2 interacts with PLCβ1 (phospholipase Cβ1) as identified by proteomic analysis. Upregulation of PKG2 (by lentiviral overexpression or cinaciguat) inhibits PLCβ1 activation, thereby reducing intracellular calcium overload and suppressing endoplasmic reticulum stress in osteoblasts under diabetic conditions.","method":"Co-immunoprecipitation, proteomic analysis, lentiviral PKG2 overexpression, calcium measurement, ER stress marker immunoblotting in primary rat osteoblasts","journal":"Oxidative medicine and cellular longevity","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP and proteomic identification with functional overexpression data; single lab, limited mechanistic follow-up on PKG2-PLCβ1 direct interaction","pmids":["34221234"],"is_preprint":false},{"year":2025,"finding":"SMURF1 (an E3 ubiquitin ligase) ubiquitinates PKG2 and targets it for proteasomal degradation in the context of high-glucose/diabetic conditions. Co-immunoprecipitation confirmed the interaction between SMURF1 and PKG2; proteasome inhibitor MG132 restored PKG2 levels reduced by SMURF1 overexpression; SMURF1 overexpression reduced osteogenic differentiation in a PKG2-dependent manner.","method":"Co-immunoprecipitation of SMURF1 and PKG2, ubiquitination assay, proteasome inhibitor (MG132) treatment, SMURF1 overexpression with PKG2 expression rescue, osteogenic differentiation assays in BMSCs and diabetic rat implant model","journal":"Applied biochemistry and biotechnology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP confirmed SMURF1-PKG2 interaction, ubiquitination assay, and MG132 rescue; single lab, multiple orthogonal methods","pmids":["40682619"],"is_preprint":false},{"year":2019,"finding":"PKG2 overexpression in ovarian cancer cells (SKOV3) inhibits phosphorylation of AKT and ERK in the EGFR downstream signaling pathway and suppresses EGFR expression, while PKG2 siRNA knockdown has the opposite effect, establishing PKG2 as a negative regulator of EGFR/AKT/ERK signaling in this context.","method":"PKG2 plasmid overexpression and siRNA knockdown in SKOV3 cells, western blot for phospho-AKT, phospho-ERK, EGFR","journal":"Journal of B.U.ON.","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method (western blot) with overexpression/knockdown; limited mechanistic resolution","pmids":["32521860"],"is_preprint":false}],"current_model":"PRKG2 (cGKII) is a cGMP-activated serine/threonine kinase that, upon cGMP binding, directly interacts with and phosphorylates multiple substrates including GluA1/GluR1 (at Ser845) to regulate AMPA receptor surface trafficking and synaptic plasticity, NHE3 (at Ser554/607/663) to inhibit epithelial Na+/H+ exchange, MYRF (at Ser259) to promote demyelination, and c-Raf1 (at Ser43) to modulate FGF2-ERK signaling in chondrocytes; it also controls presynaptic vesicle endocytosis in cerebellar neurons, regulates AKT/CREB signaling downstream of NO in retinal development, interacts with PLCβ1 to suppress calcium-dependent ER stress in osteoblasts, and is itself subject to SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions; loss of PRKG2 kinase function across multiple species causes disproportionate dwarfism by blocking the proliferative-to-hypertrophic chondrocyte transition and dysregulating SOX9-mediated collagen gene expression."},"narrative":{"mechanistic_narrative":"PRKG2 (cGKII) is a cGMP-activated serine/threonine protein kinase that transduces nitric oxide/cGMP signals into substrate phosphorylation across neuronal, epithelial, and skeletal tissues [PMID:18031684, PMID:25480791]. In neurons, cGMP-activated cGKII binds the GluA1/GluR1 C-terminus adjacent to its catalytic site and phosphorylates GluR1 at Ser845 to drive AMPA receptor surface expression and synaptic potentiation, a mechanism that also modulates epileptic excitatory transmission [PMID:18031684, PMID:29587280], and it acts presynaptically to maintain the homeostatic balance of synaptic vesicle exocytosis and endocytosis in cerebellar granule cells [PMID:29084181]. In retinal development, cGKII serves as an obligate relay between NO/cGMP and AKT/CREB signaling, controlling stage-specific cell death and survival decisions [PMID:24531539, PMID:32360667]. In epithelia, cGKII phosphorylates the NHE3 Na+/H+ exchanger at three required sites to drive its internalization and inhibit exchange activity [PMID:25480791]. A major role is in chondrocyte biology and skeletal growth: the cGKII kinase domain is required to regulate SOX9-driven collagen gene expression (COL2A1/COL10A1) and to phosphorylate c-Raf1 at Ser43 for FGF2-dependent ERK activation, and loss-of-function truncating mutations cause disproportionate dwarfism in cattle and humans [PMID:19887637, PMID:33106379]. cGKII also phosphorylates the oligodendrocyte transcription factor MYRF at Ser259 to repress myelin genes [PMID:32270922], and its abundance is controlled by SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions [PMID:40682619].","teleology":[{"year":2007,"claim":"Established a direct mechanistic link between cGKII and synaptic plasticity by showing it binds and phosphorylates an AMPA receptor subunit to control receptor trafficking.","evidence":"Reciprocal Co-IP from brain, in vitro binding and phosphorylation assays, surface biotinylation, and LTP electrophysiology in hippocampal slices","pmids":["18031684"],"confidence":"High","gaps":["Does not resolve whether cGKII acts at synaptic vs only extrasynaptic GluR1 pools in vivo","Upstream guanylyl cyclase source generating cGMP not defined"]},{"year":2008,"claim":"Characterized a PRKG2-PDGFRB fusion in which the PRKG2 5' portion drives a constitutively active PDGFRβ, defining a disease-causing rearrangement of the locus.","evidence":"FISH, fusion transcript cloning, cell-based transformation and kinase activity assays","pmids":["18166785"],"confidence":"Medium","gaps":["The fusion reflects PDGFRβ activity, not native PRKG2 kinase function","Contribution of the PRKG2 sequence beyond providing a promoter/dimerization element not dissected"]},{"year":2009,"claim":"Demonstrated that the PRKG2 kinase domain is required for normal regulation of SOX9-driven collagen genes, linking kinase loss-of-function to dwarfism.","evidence":"Genetic fine-mapping and sequencing in cattle plus WT vs R678X overexpression with COL2/COL10 qPCR","pmids":["19887637"],"confidence":"Medium","gaps":["Direct substrate connecting cGKII to SOX9 not identified in this study","Mechanism of collagen gene dysregulation downstream of kinase activity unresolved"]},{"year":2010,"claim":"Identified an Nkx homeodomain element controlling stage-specific PRKG2 transcription, explaining its induction at the prehypertrophic chondrocyte transition.","evidence":"Promoter deletion/mutagenesis and reporter assays in differentiating ATDC5 chondrocytes","pmids":["20057151"],"confidence":"Medium","gaps":["The specific Nkx factor binding in vivo not identified","Link between transcriptional induction and downstream chondrocyte phenotype not tested"]},{"year":2014,"claim":"Defined the epithelial substrate code by showing cGKII inhibits NHE3 via simultaneous phosphorylation of three sites driving exchanger internalization.","evidence":"iTRAQ/LC-MS/MS phosphoproteomics, mutagenesis of all three sites, NHE3 activity and surface biotinylation in cell lines and mouse ileum","pmids":["25480791"],"confidence":"High","gaps":["Physiological context driving cGMP/cGKII activation of this pathway not defined","How Ser663 serves both cGKII-inhibitory and dexamethasone-stimulatory roles mechanistically unclear"]},{"year":2014,"claim":"Placed cGKII as a stage-dependent switch in NO/cGMP control of retinal cell death versus survival through AKT and CREB.","evidence":"shRNA knockdown in vivo/in vitro, phospho-CREB immunostaining, AKT inhibition, caspase assays in chick retina","pmids":["24531539"],"confidence":"Medium","gaps":["Direct cGKII substrate upstream of AKT not identified","Molecular basis for opposing E6 vs E8 outcomes unresolved"]},{"year":2017,"claim":"Revealed a presynaptic role for cGKII in maintaining the exo/endocytosis balance of synaptic vesicles.","evidence":"cGKII knockout mouse, live vesicle-cycling imaging, EM ultrastructure, KT5823 inhibition in cerebellar granule cells","pmids":["29084181"],"confidence":"Medium","gaps":["Presynaptic substrate(s) of cGKII not identified","Whether the structural synapse changes are direct kinase effects unclear"]},{"year":2018,"claim":"Extended the GluA1/Ser845 mechanism to disease by linking cGKII activity to epileptic excitatory transmission.","evidence":"Pharmacological cGKII gain/loss-of-function in pilocarpine rat model with behavior, electrophysiology, phospho-Ser845 immunoblotting","pmids":["29587280"],"confidence":"Medium","gaps":["Pharmacological agents may have off-target effects on related kinases","Genetic confirmation in epilepsy model not provided"]},{"year":2020,"claim":"Identified MYRF Ser259 as a cGKII-dependent phosphorylation site coupling cGKII to myelin gene repression in Huntington disease.","evidence":"Phospho-specific immunoblotting, PRKG2 shRNA knockdown in HD mice, MYRF/mutant huntingtin Co-IP, myelin gene expression","pmids":["32270922"],"confidence":"Medium","gaps":["Direct cGKII-MYRF phosphorylation not demonstrated in vitro","Whether effect is specific to HD context or general to oligodendrocytes unclear"]},{"year":2020,"claim":"Confirmed cGKII as an obligate relay from NO/cGMP to AKT in retinal cells using both knockdown and knockout.","evidence":"cGKII shRNA and knockout mouse retinas, soluble guanylyl cyclase inhibition, phospho-AKT/ERK immunoblotting","pmids":["32360667"],"confidence":"Medium","gaps":["Direct kinase target between cGKII and AKT not identified","Generalizability beyond retina untested"]},{"year":2020,"claim":"Identified c-Raf1 Ser43 as a cGKII substrate explaining how kinase loss-of-function impairs FGF2-ERK signaling and SOX9-mediated collagen regulation in human dwarfism.","evidence":"Exome sequencing of patients, expression of truncated mutants, phospho-Raf1/ERK immunoblotting, COL10A1/COL2A1 analysis","pmids":["33106379"],"confidence":"Medium","gaps":["Direct in vitro cGKII phosphorylation of c-Raf1 Ser43 not isolated from cellular context","How c-Raf1/ERK output converges on SOX9 transcription not fully mapped"]},{"year":2021,"claim":"Proposed a PKG2-PLCβ1 interaction by which PKG2 suppresses calcium-dependent ER stress in diabetic osteoblasts.","evidence":"Co-IP, proteomic identification, lentiviral overexpression, calcium and ER stress marker assays in rat osteoblasts","pmids":["34221234"],"confidence":"Low","gaps":["Single Co-IP/proteomic identification without reciprocal or in vitro validation of direct binding","Whether PKG2 phosphorylates PLCβ1 not tested"]},{"year":2025,"claim":"Established that PKG2 protein abundance is controlled by SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions, affecting osteogenic differentiation.","evidence":"Co-IP, ubiquitination assay, MG132 rescue, SMURF1 overexpression with PKG2 rescue in BMSCs and diabetic rat implant model","pmids":["40682619"],"confidence":"Medium","gaps":["Ubiquitination site(s) on PKG2 not mapped","Whether SMURF1 directly ubiquitinates PKG2 vs via adaptor unclear"]},{"year":null,"claim":"A unified picture of how cGKII selects among its diverse substrates in different tissues, and the upstream cues controlling its compartmentalized activation, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of substrate-specific docking across GluR1, NHE3, MYRF, c-Raf1","Tissue-specific determinants of cGKII signaling output not defined","Mechanism connecting kinase activity to SOX9 transcriptional control not fully established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,4,7]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,6,7]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,8,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,7,10]}],"complexes":[],"partners":["GRIA1","NHE3","MYRF","RAF1","PLCB1","SMURF1"],"other_free_text":[]}},"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":25,"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":15,"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 notes","url":"https://pubmed.ncbi.nlm.nih.gov/25924610","citation_count":11,"is_preprint":false},{"pmid":"19149413","id":"PMC_19149413","title":"Phenotypic characterization of the Komeda miniature rat Ishikawa, an animal model of dwarfism caused by a mutation in Prkg2.","date":"2008","source":"Comparative medicine","url":"https://pubmed.ncbi.nlm.nih.gov/19149413","citation_count":11,"is_preprint":false},{"pmid":"35313961","id":"PMC_35313961","title":"Prkg2 regulates alveolar type 2-mediated re-alveolarization.","date":"2022","source":"Stem cell research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/35313961","citation_count":9,"is_preprint":false},{"pmid":"36600198","id":"PMC_36600198","title":"Polymorphism detection of PRKG2 gene and its association with the number of thoracolumbar vertebrae and carcass traits in Dezhou donkey.","date":"2023","source":"BMC genomic data","url":"https://pubmed.ncbi.nlm.nih.gov/36600198","citation_count":9,"is_preprint":false},{"pmid":"34680883","id":"PMC_34680883","title":"PRKG2 Splice Site Variant in Dogo Argentino Dogs with Disproportionate Dwarfism.","date":"2021","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/34680883","citation_count":8,"is_preprint":false},{"pmid":"35782572","id":"PMC_35782572","title":"RNA Sequencing of the Pituitary Gland and Association Analyses Reveal PRKG2 as a Candidate Gene for Growth and Carcass Traits in Chinese Ningdu Yellow Chickens.","date":"2022","source":"Frontiers in veterinary science","url":"https://pubmed.ncbi.nlm.nih.gov/35782572","citation_count":7,"is_preprint":false},{"pmid":"32360667","id":"PMC_32360667","title":"Protein synthesis inhibition promotes nitric oxide generation and activation of CGKII-dependent downstream signaling pathways in the retina.","date":"2020","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/32360667","citation_count":6,"is_preprint":false},{"pmid":"34221234","id":"PMC_34221234","title":"Pharmic Activation of PKG2 Alleviates Diabetes-Induced Osteoblast Dysfunction by Suppressing PLCβ1-Ca2+-Mediated Endoplasmic Reticulum Stress.","date":"2021","source":"Oxidative medicine and cellular longevity","url":"https://pubmed.ncbi.nlm.nih.gov/34221234","citation_count":5,"is_preprint":false},{"pmid":"20057151","id":"PMC_20057151","title":"Transcriptional regulation of cGMP-dependent protein kinase II (cGK-II) in chondrocytes.","date":"2010","source":"Bioscience, biotechnology, and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20057151","citation_count":5,"is_preprint":false},{"pmid":"32521860","id":"PMC_32521860","title":"Expression of PKG2 in ovarian cancer and its effect on epidermal growth factor receptor.","date":"2020","source":"Journal of B.U.ON. : official journal of the Balkan Union of Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/32521860","citation_count":4,"is_preprint":false},{"pmid":"24882840","id":"PMC_24882840","title":"Common variants of cGKII/PRKG2 are not associated with gout susceptibility.","date":"2014","source":"The Journal of rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/24882840","citation_count":4,"is_preprint":false},{"pmid":"25688884","id":"PMC_25688884","title":"Polymorphism of rs7688672 and rs10033237 in cGKII/PRKG2 and gout susceptibility of Han population in northern China.","date":"2015","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/25688884","citation_count":3,"is_preprint":false},{"pmid":"29587280","id":"PMC_29587280","title":"Inhibition of Cgkii Suppresses Seizure Activity and Hippocampal Excitation by Regulating the Postsynaptic Delivery of Glua1.","date":"2018","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29587280","citation_count":3,"is_preprint":false},{"pmid":"38471404","id":"PMC_38471404","title":"Aggressive systemic mastocytosis with the co-occurrence of PRKG2::PDGFRB, KAT6A::NCOA2, and RXRA::NOTCH1 fusion transcripts and a heterozygous RUNX1 frameshift mutation.","date":"2024","source":"Cancer genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38471404","citation_count":3,"is_preprint":false},{"pmid":"29084181","id":"PMC_29084181","title":"Altered Synaptic Membrane Retrieval after Strong Stimulation of Cerebellar Granule Neurons in Cyclic GMP-Dependent Protein Kinase II (cGKII) Knockout Mice.","date":"2017","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29084181","citation_count":3,"is_preprint":false},{"pmid":"33887582","id":"PMC_33887582","title":"Generation of induced pluripotent stem cell line (IGIBi007-A) from a patient with a novel acromesomelic dysplasia, PRKG2 type (AMDP).","date":"2021","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/33887582","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 one","url":"https://pubmed.ncbi.nlm.nih.gov/41296694","citation_count":0,"is_preprint":false},{"pmid":"40682619","id":"PMC_40682619","title":"SMURF1 Affects Dental Implant Integration in Diabetes By Regulating PKG2 Expression.","date":"2025","source":"Applied biochemistry and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/40682619","citation_count":0,"is_preprint":false},{"pmid":"38072398","id":"PMC_38072398","title":"Diagnostic exome identifies a novel PRKG2 mutation in a proband with skeletal dysplasia.","date":"2023","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38072398","citation_count":0,"is_preprint":false},{"pmid":"41574272","id":"PMC_41574272","title":"Case Report: Dual pathogenic mechanism of a PRKG2 missense variant underlies an attenuated phenotype of acromesomelic dysplasia.","date":"2026","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41574272","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17170,"output_tokens":4160,"usd":0.056955,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11986,"output_tokens":4179,"usd":0.082202,"stage2_stop_reason":"end_turn"},"total_usd":0.139157,"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\": 2007,\n      \"finding\": \"PRKG2 (cGKII) binds directly to the GluR1 (GluA1) C-terminal domain adjacent to the kinase catalytic site; this interaction is increased when cGKII is activated by cGMP. Within the complex, cGKII phosphorylates GluR1 at Ser845. Activation of cGKII by cGMP increases surface expression of AMPARs at extrasynaptic sites, and inhibition of cGKII blocks GluR1 surface increase during chemLTP and reduces LTP in hippocampal slices.\",\n      \"method\": \"Co-immunoprecipitation from brain tissue, in vitro binding assays, phosphorylation assays, surface biotinylation, pharmacological inhibition in hippocampal slice electrophysiology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP from brain, in vitro phosphorylation assay, surface biotinylation, and electrophysiological LTP readout; multiple orthogonal methods in one study\",\n      \"pmids\": [\"18031684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"cGKII inhibits NHE3 Na+/H+ exchanger activity by phosphorylating it at three sites (rabbit Ser554, Ser607, Ser663; mouse Ser552, Ser605, Ser659), all of which must be simultaneously present for cGMP/cGKII-mediated inhibition. This phosphorylation is associated with reduced NHE3 surface expression (internalization). Ser663 phosphorylation is also required for dexamethasone-stimulated NHE3 activity and surface expression, representing a multifunctional phosphorylation site.\",\n      \"method\": \"iTRAQ/LC-MS/MS phosphoproteomics with TiO2 enrichment, site-directed mutagenesis, 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 / Strong — in vitro phosphorylation site identification by MS, mutagenesis of all three sites, functional activity assay, and surface expression quantification; multiple orthogonal methods\",\n      \"pmids\": [\"25480791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A nonsense mutation (R678X) in PRKG2 truncates 85 C-terminal amino acids including most of the kinase domain and causes dwarfism in Angus cattle. The R678X mutant protein fails to regulate COL2A1 expression normally (COL2 and COL10 mRNA are overexpressed), establishing that the PRKG2 kinase domain is required for its regulation of collagen gene expression downstream of SOX9.\",\n      \"method\": \"Genetic fine-mapping, sequencing, cell culture overexpression of WT vs. R678X PRKG2, real-time PCR for COL2 and COL10 mRNA\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function mutation with defined molecular phenotype (collagen gene expression) confirmed in cell culture; single lab, two methods (genetic and expression)\",\n      \"pmids\": [\"19887637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PRKG2 is fused to PDGFRB via t(4;5)(q21.1;q31.3), incorporating the first two exons of PRKG2 fused to truncated exon 12 of PDGFRB, disrupting the juxtamembrane auto-inhibitory domain of PDGFRβ. Functional studies confirmed that the transforming and kinase activity of the PRKG2-PDGFRβ fusion protein depends on disruption of this auto-inhibitory domain.\",\n      \"method\": \"FISH, molecular cloning of fusion transcript, functional cell-based transformation and kinase activity assays\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — molecular characterization of fusion gene with functional validation of auto-inhibitory domain disruption; single lab\",\n      \"pmids\": [\"18166785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRKG2 promotes phosphorylation of the oligodendrocyte transcription factor MYRF at Ser259. This phosphorylation increases MYRF binding to mutant huntingtin and reduces expression of myelin-associated genes. Knockdown of PRKG2 in HD mice decreased MYRF Ser259 phosphorylation and increased myelin-associated protein expression, placing PRKG2 upstream of MYRF in a demyelination pathway.\",\n      \"method\": \"Phospho-specific immunoblotting, PRKG2 shRNA knockdown in HD mouse model, co-immunoprecipitation of MYRF and mutant huntingtin, myelin gene expression analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with defined phosphorylation and gene-expression readout in vivo; single lab, multiple methods\",\n      \"pmids\": [\"32270922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In developing chick retina, cGKII mediates NO/cGMP-dependent cell death (E6) and cell survival (E8) via opposing regulation of nuclear AKT activation and downstream CREB1 phosphorylation. shRNA knockdown of cGKII prevented NO-induced cell death at E6 and cell survival at E8, and abrogated CREB phosphorylation changes at both stages; AKT inhibition blocked cGKII-dependent CREB regulation.\",\n      \"method\": \"shRNA-mediated cGKII knockdown in vivo and in vitro, phospho-CREB immunostaining, AKT pharmacological inhibition, caspase activation assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockdown with phosphorylation readout and rescue experiments; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"24531539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In retinal cells, cGKII is required for NO-induced AKT activation and nuclear AKT accumulation downstream of soluble guanylyl cyclase. Knockdown of cGKII prevented cycloheximide/anisomycin-induced AKT phosphorylation, and cGKII knockout mice showed no AKT enhancement upon cycloheximide treatment, establishing cGKII as an obligate relay between NO/cGMP signaling and AKT activation.\",\n      \"method\": \"cGKII shRNA knockdown, cGKII knockout mouse retinas, pharmacological inhibition of soluble guanylyl cyclase, immunoblotting for phospho-AKT and phospho-ERK\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — both genetic knockdown and knockout, with orthogonal pharmacological confirmation; single lab\",\n      \"pmids\": [\"32360667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Truncated PRKG2 mutant proteins lacking most or all of the kinase domain (nonsense and frameshift variants identified in human patients) fail to phosphorylate c-Raf1 at Ser43, resulting in reduced ERK1/2 activation in response to FGF2, and alter downstream MAPK signaling. These mutant proteins also dysregulate SOX9-mediated transcription by downregulating COL10A1 and upregulating COL2A1.\",\n      \"method\": \"Exome sequencing, functional expression of truncated mutant PRKG2 in cells, phospho-Raf1 and phospho-ERK1/2 immunoblotting, COL10A1/COL2A1 expression analysis\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function variants with defined substrate phosphorylation (c-Raf1 Ser43) and downstream signaling readout; single lab, multiple methods\",\n      \"pmids\": [\"33106379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"cGKII regulates epileptic seizure activity by phosphorylating GluA1 at Ser845, thereby modulating GluA1 expression and function at the postsynaptic membrane. Pharmacological activation of cGKII in vivo increased epileptic behaviors and AMPAR-mediated excitatory synaptic transmission, while inhibition reduced them.\",\n      \"method\": \"Pharmacological cGKII activation/inhibition in pilocarpine-induced rat model, behavioral analysis, electrophysiology, immunoblotting for GluA1 and phospho-Ser845\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological gain- and loss-of-function with electrophysiological and phosphorylation readouts; single lab\",\n      \"pmids\": [\"29587280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"cGKII plays a presynaptic role in controlling the homeostatic balance of synaptic vesicle exocytosis and endocytosis in cerebellar granule cells. Genetic knockout of cGKII slows endocytosis in a subset of boutons under strong stimulation and causes structural changes to synapses in cultured cells and cerebellar cortex in vivo.\",\n      \"method\": \"cGKII knockout mouse model, live imaging of vesicle cycling, electron microscopy ultrastructural analysis, pharmacological inhibition with KT5823\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with ultrastructural and live-imaging functional readout; single lab, multiple methods\",\n      \"pmids\": [\"29084181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Transcription of the cGKII (PRKG2) gene in chondrocytes is regulated by an Nkx homeodomain binding site located between -292 and -286 bp upstream of the transcription start site. Deletion or mutagenesis of this site markedly reduced promoter activity, and cGKII mRNA expression increased dramatically at the prehypertrophic stage of ATDC5 chondrogenic differentiation.\",\n      \"method\": \"5'-flanking region cloning and deletion analysis, site-directed mutagenesis of Nkx-binding site, promoter-reporter assays in ATDC5 cells during chondrogenic differentiation\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter deletion and mutagenesis with reporter assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"20057151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PKG2 interacts with PLCβ1 (phospholipase Cβ1) as identified by proteomic analysis. Upregulation of PKG2 (by lentiviral overexpression or cinaciguat) inhibits PLCβ1 activation, thereby reducing intracellular calcium overload and suppressing endoplasmic reticulum stress in osteoblasts under diabetic conditions.\",\n      \"method\": \"Co-immunoprecipitation, proteomic analysis, lentiviral PKG2 overexpression, calcium measurement, ER stress marker immunoblotting in primary rat osteoblasts\",\n      \"journal\": \"Oxidative medicine and cellular longevity\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP and proteomic identification with functional overexpression data; single lab, limited mechanistic follow-up on PKG2-PLCβ1 direct interaction\",\n      \"pmids\": [\"34221234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMURF1 (an E3 ubiquitin ligase) ubiquitinates PKG2 and targets it for proteasomal degradation in the context of high-glucose/diabetic conditions. Co-immunoprecipitation confirmed the interaction between SMURF1 and PKG2; proteasome inhibitor MG132 restored PKG2 levels reduced by SMURF1 overexpression; SMURF1 overexpression reduced osteogenic differentiation in a PKG2-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation of SMURF1 and PKG2, ubiquitination assay, proteasome inhibitor (MG132) treatment, SMURF1 overexpression with PKG2 expression rescue, osteogenic differentiation assays in BMSCs and diabetic rat implant model\",\n      \"journal\": \"Applied biochemistry and biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP confirmed SMURF1-PKG2 interaction, ubiquitination assay, and MG132 rescue; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40682619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PKG2 overexpression in ovarian cancer cells (SKOV3) inhibits phosphorylation of AKT and ERK in the EGFR downstream signaling pathway and suppresses EGFR expression, while PKG2 siRNA knockdown has the opposite effect, establishing PKG2 as a negative regulator of EGFR/AKT/ERK signaling in this context.\",\n      \"method\": \"PKG2 plasmid overexpression and siRNA knockdown in SKOV3 cells, western blot for phospho-AKT, phospho-ERK, EGFR\",\n      \"journal\": \"Journal of B.U.ON.\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method (western blot) with overexpression/knockdown; limited mechanistic resolution\",\n      \"pmids\": [\"32521860\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PRKG2 (cGKII) is a cGMP-activated serine/threonine kinase that, upon cGMP binding, directly interacts with and phosphorylates multiple substrates including GluA1/GluR1 (at Ser845) to regulate AMPA receptor surface trafficking and synaptic plasticity, NHE3 (at Ser554/607/663) to inhibit epithelial Na+/H+ exchange, MYRF (at Ser259) to promote demyelination, and c-Raf1 (at Ser43) to modulate FGF2-ERK signaling in chondrocytes; it also controls presynaptic vesicle endocytosis in cerebellar neurons, regulates AKT/CREB signaling downstream of NO in retinal development, interacts with PLCβ1 to suppress calcium-dependent ER stress in osteoblasts, and is itself subject to SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions; loss of PRKG2 kinase function across multiple species causes disproportionate dwarfism by blocking the proliferative-to-hypertrophic chondrocyte transition and dysregulating SOX9-mediated collagen gene expression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PRKG2 (cGKII) is a cGMP-activated serine/threonine protein kinase that transduces nitric oxide/cGMP signals into substrate phosphorylation across neuronal, epithelial, and skeletal tissues [#0, #1]. In neurons, cGMP-activated cGKII binds the GluA1/GluR1 C-terminus adjacent to its catalytic site and phosphorylates GluR1 at Ser845 to drive AMPA receptor surface expression and synaptic potentiation, a mechanism that also modulates epileptic excitatory transmission [#0, #8], and it acts presynaptically to maintain the homeostatic balance of synaptic vesicle exocytosis and endocytosis in cerebellar granule cells [#9]. In retinal development, cGKII serves as an obligate relay between NO/cGMP and AKT/CREB signaling, controlling stage-specific cell death and survival decisions [#5, #6]. In epithelia, cGKII phosphorylates the NHE3 Na+/H+ exchanger at three required sites to drive its internalization and inhibit exchange activity [#1]. A major role is in chondrocyte biology and skeletal growth: the cGKII kinase domain is required to regulate SOX9-driven collagen gene expression (COL2A1/COL10A1) and to phosphorylate c-Raf1 at Ser43 for FGF2-dependent ERK activation, and loss-of-function truncating mutations cause disproportionate dwarfism in cattle and humans [#2, #7]. cGKII also phosphorylates the oligodendrocyte transcription factor MYRF at Ser259 to repress myelin genes [#4], and its abundance is controlled by SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established a direct mechanistic link between cGKII and synaptic plasticity by showing it binds and phosphorylates an AMPA receptor subunit to control receptor trafficking.\",\n      \"evidence\": \"Reciprocal Co-IP from brain, in vitro binding and phosphorylation assays, surface biotinylation, and LTP electrophysiology in hippocampal slices\",\n      \"pmids\": [\"18031684\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve whether cGKII acts at synaptic vs only extrasynaptic GluR1 pools in vivo\", \"Upstream guanylyl cyclase source generating cGMP not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Characterized a PRKG2-PDGFRB fusion in which the PRKG2 5' portion drives a constitutively active PDGFRβ, defining a disease-causing rearrangement of the locus.\",\n      \"evidence\": \"FISH, fusion transcript cloning, cell-based transformation and kinase activity assays\",\n      \"pmids\": [\"18166785\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The fusion reflects PDGFRβ activity, not native PRKG2 kinase function\", \"Contribution of the PRKG2 sequence beyond providing a promoter/dimerization element not dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated that the PRKG2 kinase domain is required for normal regulation of SOX9-driven collagen genes, linking kinase loss-of-function to dwarfism.\",\n      \"evidence\": \"Genetic fine-mapping and sequencing in cattle plus WT vs R678X overexpression with COL2/COL10 qPCR\",\n      \"pmids\": [\"19887637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrate connecting cGKII to SOX9 not identified in this study\", \"Mechanism of collagen gene dysregulation downstream of kinase activity unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified an Nkx homeodomain element controlling stage-specific PRKG2 transcription, explaining its induction at the prehypertrophic chondrocyte transition.\",\n      \"evidence\": \"Promoter deletion/mutagenesis and reporter assays in differentiating ATDC5 chondrocytes\",\n      \"pmids\": [\"20057151\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The specific Nkx factor binding in vivo not identified\", \"Link between transcriptional induction and downstream chondrocyte phenotype not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the epithelial substrate code by showing cGKII inhibits NHE3 via simultaneous phosphorylation of three sites driving exchanger internalization.\",\n      \"evidence\": \"iTRAQ/LC-MS/MS phosphoproteomics, mutagenesis of all three sites, NHE3 activity and surface biotinylation in cell lines and mouse ileum\",\n      \"pmids\": [\"25480791\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological context driving cGMP/cGKII activation of this pathway not defined\", \"How Ser663 serves both cGKII-inhibitory and dexamethasone-stimulatory roles mechanistically unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Placed cGKII as a stage-dependent switch in NO/cGMP control of retinal cell death versus survival through AKT and CREB.\",\n      \"evidence\": \"shRNA knockdown in vivo/in vitro, phospho-CREB immunostaining, AKT inhibition, caspase assays in chick retina\",\n      \"pmids\": [\"24531539\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct cGKII substrate upstream of AKT not identified\", \"Molecular basis for opposing E6 vs E8 outcomes unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed a presynaptic role for cGKII in maintaining the exo/endocytosis balance of synaptic vesicles.\",\n      \"evidence\": \"cGKII knockout mouse, live vesicle-cycling imaging, EM ultrastructure, KT5823 inhibition in cerebellar granule cells\",\n      \"pmids\": [\"29084181\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Presynaptic substrate(s) of cGKII not identified\", \"Whether the structural synapse changes are direct kinase effects unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended the GluA1/Ser845 mechanism to disease by linking cGKII activity to epileptic excitatory transmission.\",\n      \"evidence\": \"Pharmacological cGKII gain/loss-of-function in pilocarpine rat model with behavior, electrophysiology, phospho-Ser845 immunoblotting\",\n      \"pmids\": [\"29587280\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pharmacological agents may have off-target effects on related kinases\", \"Genetic confirmation in epilepsy model not provided\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified MYRF Ser259 as a cGKII-dependent phosphorylation site coupling cGKII to myelin gene repression in Huntington disease.\",\n      \"evidence\": \"Phospho-specific immunoblotting, PRKG2 shRNA knockdown in HD mice, MYRF/mutant huntingtin Co-IP, myelin gene expression\",\n      \"pmids\": [\"32270922\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct cGKII-MYRF phosphorylation not demonstrated in vitro\", \"Whether effect is specific to HD context or general to oligodendrocytes unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Confirmed cGKII as an obligate relay from NO/cGMP to AKT in retinal cells using both knockdown and knockout.\",\n      \"evidence\": \"cGKII shRNA and knockout mouse retinas, soluble guanylyl cyclase inhibition, phospho-AKT/ERK immunoblotting\",\n      \"pmids\": [\"32360667\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct kinase target between cGKII and AKT not identified\", \"Generalizability beyond retina untested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified c-Raf1 Ser43 as a cGKII substrate explaining how kinase loss-of-function impairs FGF2-ERK signaling and SOX9-mediated collagen regulation in human dwarfism.\",\n      \"evidence\": \"Exome sequencing of patients, expression of truncated mutants, phospho-Raf1/ERK immunoblotting, COL10A1/COL2A1 analysis\",\n      \"pmids\": [\"33106379\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct in vitro cGKII phosphorylation of c-Raf1 Ser43 not isolated from cellular context\", \"How c-Raf1/ERK output converges on SOX9 transcription not fully mapped\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Proposed a PKG2-PLCβ1 interaction by which PKG2 suppresses calcium-dependent ER stress in diabetic osteoblasts.\",\n      \"evidence\": \"Co-IP, proteomic identification, lentiviral overexpression, calcium and ER stress marker assays in rat osteoblasts\",\n      \"pmids\": [\"34221234\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP/proteomic identification without reciprocal or in vitro validation of direct binding\", \"Whether PKG2 phosphorylates PLCβ1 not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established that PKG2 protein abundance is controlled by SMURF1-mediated ubiquitination and proteasomal degradation under diabetic conditions, affecting osteogenic differentiation.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, MG132 rescue, SMURF1 overexpression with PKG2 rescue in BMSCs and diabetic rat implant model\",\n      \"pmids\": [\"40682619\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination site(s) on PKG2 not mapped\", \"Whether SMURF1 directly ubiquitinates PKG2 vs via adaptor unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified picture of how cGKII selects among its diverse substrates in different tissues, and the upstream cues controlling its compartmentalized activation, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of substrate-specific docking across GluR1, NHE3, MYRF, c-Raf1\", \"Tissue-specific determinants of cGKII signaling output not defined\", \"Mechanism connecting kinase activity to SOX9 transcriptional control not fully established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 4, 7]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 6, 7]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 8, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 7, 10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GRIA1\", \"NHE3\", \"MYRF\", \"RAF1\", \"PLCB1\", \"SMURF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}