{"gene":"GRK1","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2010,"finding":"Monomeric rhodopsin (in nanodiscs) is sufficient for normal GRK1 phosphorylation; GRK1 phosphorylates light-activated rhodopsin monomer as efficiently as rhodopsin in native disc membranes, and monomeric phosphorylated Rh* binds arrestin-1 with low nanomolar affinity and 1:1 stoichiometry.","method":"Reconstitution in nanodiscs, in vitro phosphorylation assay, fluorescence-based arrestin-binding affinity measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in defined lipid nanodiscs with quantitative binding measurements and multiple orthogonal methods","pmids":["20966068"],"is_preprint":false},{"year":2003,"finding":"GRK1 is required for light-dependent multi-site phosphorylation of both S and M cone opsins in mouse cone photoreceptors; without GRK1, light-activated cone opsins are neither phosphorylated nor bound by cone arrestin (mCAR).","method":"Genetic knockout (Nrl-/- and Nrl-/-Grk1-/- double-KO mice), in situ phosphorylation, isoelectric focusing, immunoprecipitation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — clean double-KO with multiple orthogonal biochemical readouts demonstrating GRK1 dependence of cone opsin phosphorylation","pmids":["12853434"],"is_preprint":false},{"year":2005,"finding":"cAMP-dependent protein kinase (PKA) phosphorylates GRK1 at Ser21, and this phosphorylation attenuates GRK1 enzymatic activity toward rhodopsin; rod outer segment preparations confirm GRK1 is a physiologically relevant PKA substrate.","method":"In vitro PKA phosphorylation assay, site-directed identification of Ser21, FLAG-tagged GRK1 expression in HEK-293 cells treated with forskolin, bovine rod outer segment phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis site identification, confirmed in cell-based and rod outer segment systems","pmids":["15946941"],"is_preprint":false},{"year":2007,"finding":"The prenyl-binding protein PrBP/delta (encoded by Pde6d) is required for transport of farnesylated GRK1 to rod and cone photoreceptor outer segments; Pde6d-/- mice show partial mislocalization of GRK1 and a delay in dark-state recovery consistent with reduced outer-segment GRK1 levels.","method":"Pde6d knockout mouse, immunocytochemistry, single-cell electrophysiology, paired-flash ERG","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with direct localization data and corroborating physiological ERG phenotype","pmids":["17496142"],"is_preprint":false},{"year":2011,"finding":"GRK1 is phosphorylated on Ser21 in a cAMP-dependent manner in dark-adapted retina (high cAMP) and dephosphorylated upon light exposure independently of phototransduction; adenylyl cyclase type 1 is required for dark-dependent GRK1 phosphorylation.","method":"Immunoblot with phospho-specific antibody, adenylyl cyclase 1 knockout mice, rod transducin α-subunit knockout mice, dark/light adaptation paradigms","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple KO models with quantitative phosphorylation measurements establishing cAMP pathway requirement and transducin independence","pmids":["21504899"],"is_preprint":false},{"year":2019,"finding":"Phosphorylation of GRK1 at Ser21 by PKA is required for normal kinetics of rod dark adaptation but not cone dark adaptation; GRK1-S21A knock-in mice show delayed rod recovery after bleaching, consistent with increased rhodopsin phosphorylation slowing chromophore regeneration.","method":"GRK1-S21A knock-in mouse, ex vivo and in vivo ERG, dark adaptation assays, retinal morphology","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 — precise knock-in mutation with physiological phenotype demonstrating cell-type-specific functional consequence","pmids":["31908030"],"is_preprint":false},{"year":2010,"finding":"GRK1 deletion causes retinal degeneration through a transducin-independent, light-independent mechanism; Grk1-/-Gnat1-/- mice still degenerate, demonstrating that the protective role of GRK1 is not solely via quenching opsin/transducin signaling.","method":"Grk1-/-, Rpe65-/-Grk1-/-, and Grk1-/-Gnat1-/- multi-KO mice; histology, opsin phosphorylation assays, rod electrophysiology","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — epistatic triple-KO design with multiple orthogonal readouts identifying a second, non-signaling role for GRK1","pmids":["20164334"],"is_preprint":false},{"year":2015,"finding":"Neuronal calcium sensor-1 (NCS-1) binds a GRK1-derived peptide at the hydrophobic C-lobe crevice; crystal structures show one GRK1 peptide copy binds versus two D2R peptide copies, with differential binding enabled by conformational flexibility of the NCS-1 C-terminal region (Ser178–Val190).","method":"Crystal structure of Ca2+/NCS-1 in complex with GRK1 peptide, ITC/biophysical binding measurements, C-terminal truncation mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional mutagenesis validation defining the GRK1-binding mode on NCS-1","pmids":["25979333"],"is_preprint":false},{"year":1998,"finding":"Human retina expresses GRK1 in both rod and cone photoreceptors; a splice variant GRK1b retains the last intron, produces mRNA exported to the cytosol, but the protein is expressed at low levels and has very low catalytic activity compared to GRK1a.","method":"Molecular cloning, RT-PCR, immunolocalization of GRK1 in rod and cone photoreceptors, catalytic activity assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct cloning and localization with activity comparison, single lab","pmids":["9478965"],"is_preprint":false},{"year":2006,"finding":"In zebrafish, GRK1A localizes to rod outer segments and GRK7-1 to cone outer segments; GRK7-1 has a 32-fold higher Vmax than GRK1A in phosphorylating light-activated rhodopsin, explaining the faster cone shutoff kinetics.","method":"In situ hybridization, immunohistochemistry, in vitro phosphorylation assay with recombinant GRK1A vs GRK7-1","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinetic reconstitution with direct localization data, multiple orthogonal methods","pmids":["16787417"],"is_preprint":false},{"year":2001,"finding":"Species-specific differences exist in GRK1 and GRK7 cone expression: pigs and dogs express only GRK7 in cones; mice and rats express only GRK1 in cones; humans and monkeys co-express both, implying either GRK1 or GRK7 can mediate cone opsin desensitization depending on species.","method":"Immunocytochemistry with kinase-selective antibodies across multiple species retinas","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 3 — direct localization across species by immunocytochemistry, single lab, no functional rescue","pmids":["11717351"],"is_preprint":false},{"year":2015,"finding":"RP2 deletion in zebrafish reduces protein levels and causes abnormal retinal localization of GRK1 (and rod transducin subunits), linking RP2's role as an ARL3 GAP to the proper trafficking of farnesylated GRK1 in photoreceptors.","method":"TALEN-based RP2 knockout zebrafish, immunohistochemistry, immunoblot","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — KO with direct localization and protein quantification; single lab but mechanistic link via farnesylated protein trafficking established","pmids":["26034134"],"is_preprint":false},{"year":2009,"finding":"GRK1 overexpression (~3-fold) in transgenic mice produces proportionally higher rhodopsin phosphorylation activity but does not protect against light-induced photoreceptor apoptosis; instead, excess opsin channeled through the GRK1 deactivation pathway increases susceptibility to stress-induced cell death.","method":"BAC transgenic mouse overexpressing GRK1, in vitro phosphorylation assay, ERG, morphometry, nucleosome release apoptosis assay","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic gain-of-function with enzymatic activity confirmation and multiple phenotypic readouts","pmids":["19834036"],"is_preprint":false},{"year":2022,"finding":"In zebrafish, cone-expressed Grk1b does not undergo cAMP-dependent phosphorylation in vivo, whereas Grk7a does; PKA activity (via dominant-negative PKA transgene in cones) is required for Grk7a phosphorylation but not for Grk1b phosphorylation, revealing cell-type-specific regulation of GRK isoforms.","method":"Grk1a-/- and Grk1b-/- zebrafish, cone-specific dominant-negative PKA transgene, ERG with forskolin treatment, immunoblot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple KO and transgenic models with pharmacological intervention and electrophysiological readouts","pmids":["36273582"],"is_preprint":false},{"year":2005,"finding":"The conserved ~0.2 kb enhancer/promoter immediately upstream of the GRK1 transcription start site is sufficient to drive expression specifically in rod photoreceptors, cone photoreceptors, and pinealocytes in transgenic mice, with developmental onset paralleling outer segment maturation.","method":"GFP reporter transgenic mice, fluorescence microscopy, RT-PCR, immunostaining during postnatal retinal development","journal":"Molecular vision","confidence":"Medium","confidence_rationale":"Tier 2 — direct in vivo cis-regulatory mapping with spatiotemporal validation, single lab","pmids":["16357827"],"is_preprint":false}],"current_model":"GRK1 (rhodopsin kinase) is a photoreceptor-specific serine/threonine kinase that phosphorylates light-activated rhodopsin and cone opsins at multiple C-terminal sites to initiate visual signal termination; its activity is negatively regulated by PKA-mediated phosphorylation at Ser21 in the dark (high cAMP), is modulated by NCS-1 binding, depends on PrBP/delta and RP2/ARL3 for farnesyl-dependent transport to outer segments, and operates on monomeric receptor with 1:1 stoichiometry, while also serving a second, light- and transducin-independent neuroprotective role in photoreceptor homeostasis."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing that GRK1 is expressed in both human rods and cones — and that a splice variant (GRK1b) exists but has minimal catalytic activity — defined the isoform landscape and implied GRK1a as the functionally dominant kinase in human photoreceptors.","evidence":"Molecular cloning, RT-PCR, immunolocalization and catalytic activity assays in human retina","pmids":["9478965"],"confidence":"Medium","gaps":["Single-lab characterization without independent replication","Functional significance of GRK1b splice variant in vivo unresolved","Whether GRK1 is the sole kinase for cone opsins in human cones was unknown"]},{"year":2001,"claim":"Cross-species immunolocalization revealed that cone GRK identity is species-dependent — mice use GRK1, pigs/dogs use GRK7, and primates co-express both — resolving confusion about cone opsin deactivation mechanisms.","evidence":"Immunocytochemistry with kinase-selective antibodies across mammalian retinas","pmids":["11717351"],"confidence":"Medium","gaps":["No functional rescue to confirm sufficiency of either kinase alone","Relative contributions of GRK1 vs GRK7 in primate cones unknown"]},{"year":2003,"claim":"Genetic ablation of GRK1 in a cone-only mouse model proved that GRK1 is required for light-dependent phosphorylation of S and M cone opsins and for cone arrestin binding, establishing GRK1 as the essential cone opsin kinase in mice.","evidence":"Nrl−/− and Nrl−/−Grk1−/− double-KO mice with isoelectric focusing and immunoprecipitation","pmids":["12853434"],"confidence":"High","gaps":["Whether GRK7 can substitute in species that express it in cones","Downstream consequences of unphosphorylated cone opsin for cone survival"]},{"year":2005,"claim":"Identification of Ser21 as a PKA phosphorylation site that attenuates GRK1 activity answered how GRK1 is kept partially inhibited in the dark, providing a molecular mechanism for dark-state modulation of phototransduction deactivation.","evidence":"In vitro PKA phosphorylation, site-directed mutagenesis, confirmation in bovine rod outer segments and HEK-293 cells","pmids":["15946941"],"confidence":"High","gaps":["In vivo physiological consequence of Ser21 phosphorylation not yet tested","Identity of the phosphatase that dephosphorylates Ser21 in light unknown"]},{"year":2006,"claim":"Kinetic comparison of zebrafish GRK1A and GRK7-1 showed a 32-fold higher Vmax for GRK7-1, explaining why cones that express GRK7 achieve faster signal shutoff than rods relying on GRK1.","evidence":"Recombinant kinase in vitro phosphorylation assays with in situ hybridization/immunohistochemistry in zebrafish retina","pmids":["16787417"],"confidence":"High","gaps":["Whether Vmax differences fully account for in vivo shutoff speed differences","Structural basis for GRK7's higher activity unresolved"]},{"year":2007,"claim":"Demonstrating that PrBP/δ is required for farnesylated GRK1 transport to outer segments identified the trafficking machinery for GRK1, linking prenyl-binding chaperone biology to phototransduction.","evidence":"Pde6d knockout mouse with immunocytochemistry and paired-flash ERG","pmids":["17496142"],"confidence":"High","gaps":["Whether additional chaperones are needed for full GRK1 delivery","How GRK1 is released from PrBP/δ at the outer segment"]},{"year":2010,"claim":"Two key advances: (1) reconstitution in nanodiscs proved that monomeric rhodopsin is the functional GRK1 substrate with 1:1 stoichiometry, and (2) epistatic KO analysis revealed a transducin- and light-independent neuroprotective role for GRK1 distinct from signal quenching.","evidence":"Nanodisc reconstitution with fluorescence-based arrestin binding (PMID:20966068); Grk1−/−Gnat1−/− and Rpe65−/−Grk1−/− multi-KO mice with histology and electrophysiology (PMID:20164334)","pmids":["20966068","20164334"],"confidence":"High","gaps":["Identity of the non-opsin GRK1 substrate mediating neuroprotection unknown","Structural basis for GRK1 recognition of monomeric rhodopsin unresolved"]},{"year":2011,"claim":"Demonstrating that dark-state GRK1-Ser21 phosphorylation requires adenylyl cyclase 1 but is independent of phototransduction (transducin) established that GRK1 regulation occurs via a parallel cAMP signaling axis.","evidence":"Phospho-specific immunoblotting in adenylyl cyclase 1 KO and rod transducin α-subunit KO mice under dark/light adaptation","pmids":["21504899"],"confidence":"High","gaps":["How light triggers Ser21 dephosphorylation independently of transducin not fully resolved","Whether other cAMP effectors modulate GRK1 in parallel"]},{"year":2015,"claim":"Two findings refined GRK1 regulation and trafficking: crystal structure of NCS-1 bound to a GRK1 peptide defined the interaction interface, and RP2 knockout in zebrafish linked ARL3 GTPase regulation to farnesylated GRK1 trafficking.","evidence":"Crystal structure of Ca²⁺/NCS-1–GRK1 peptide complex with ITC (PMID:25979333); TALEN-based RP2 KO zebrafish with immunolocalization (PMID:26034134)","pmids":["25979333","26034134"],"confidence":"High","gaps":["Functional consequence of NCS-1–GRK1 interaction on kinase activity in photoreceptors unknown","Whether RP2/ARL3 acts directly on PrBP/δ-GRK1 complexes not confirmed in mammalian retina"]},{"year":2019,"claim":"GRK1-S21A knock-in mice demonstrated that Ser21 phosphorylation is physiologically required for normal rod — but not cone — dark adaptation, establishing cell-type-specific PKA regulation of GRK1.","evidence":"GRK1-S21A knock-in mouse with ex vivo and in vivo ERG dark adaptation assays","pmids":["31908030"],"confidence":"High","gaps":["Mechanism by which excess rhodopsin phosphorylation slows chromophore regeneration not molecularly defined","Whether cone-expressed GRK1 is regulated by alternative post-translational modifications"]},{"year":2022,"claim":"Zebrafish genetic dissection showed that cone-expressed Grk1b escapes cAMP/PKA-dependent phosphorylation, unlike Grk7a, revealing isoform-specific regulatory logic in cones.","evidence":"Grk1a−/−, Grk1b−/− zebrafish with cone-specific dominant-negative PKA transgene, ERG and immunoblotting","pmids":["36273582"],"confidence":"High","gaps":["Structural basis for differential PKA sensitivity among GRK isoforms unknown","Relevance to mammalian cone biology where GRK1 is the cone kinase remains to be tested"]},{"year":null,"claim":"The molecular identity of the non-opsin GRK1 substrate(s) mediating its transducin-independent neuroprotective function, the structural basis for GRK1 recognition of activated rhodopsin, and the mechanism coupling light to Ser21 dephosphorylation remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No substrate beyond opsins identified for the neuroprotective function","No full-length GRK1–rhodopsin complex structure available","Phosphatase responsible for light-dependent Ser21 dephosphorylation not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,5,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,8,11]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,11]}],"pathway":[{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[0,1,5,9]}],"complexes":[],"partners":["RHO","OPN1SW","OPN1MW","ARR1","NCS1","PDE6D","RP2"],"other_free_text":[]},"mechanistic_narrative":"GRK1 (rhodopsin kinase) is a photoreceptor-specific serine/threonine kinase that phosphorylates light-activated rhodopsin and cone opsins at multiple C-terminal sites, initiating receptor deactivation and visual signal termination in both rod and cone photoreceptors [PMID:20966068, PMID:12853434]. GRK1 acts on monomeric rhodopsin with 1:1 stoichiometry and its catalytic activity is negatively regulated by PKA-mediated phosphorylation at Ser21 under dark-adapted (high cAMP) conditions, a modification required for normal rod dark adaptation kinetics [PMID:15946941, PMID:21504899, PMID:31908030]. Proper delivery of farnesylated GRK1 to photoreceptor outer segments depends on the prenyl-binding protein PrBP/δ and the RP2–ARL3 GTPase pathway [PMID:17496142, PMID:26034134]. Beyond its canonical role in signal quenching, GRK1 exerts a light- and transducin-independent neuroprotective function, as Grk1 deletion causes photoreceptor degeneration even when phototransduction is genetically abolished [PMID:20164334]."},"prefetch_data":{"uniprot":{"accession":"Q15835","full_name":"Rhodopsin kinase GRK1","aliases":["G protein-coupled receptor kinase 1"],"length_aa":563,"mass_kda":63.5,"function":"Retina-specific kinase involved in the signal turnoff via phosphorylation of rhodopsin (RHO), the G protein- coupled receptor that initiates the phototransduction cascade (PubMed:15946941). This rapid desensitization is essential for scotopic vision and permits rapid adaptation to changes in illumination (By similarity). May play a role in the maintenance of the outer nuclear layer in the retina (By similarity)","subcellular_location":"Membrane; Cell projection, cilium, photoreceptor outer segment","url":"https://www.uniprot.org/uniprotkb/Q15835/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GRK1","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":73,"dependency_fraction":0.0821917808219178},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GRK1","total_profiled":1310},"omim":[{"mim_id":"613411","title":"OGUCHI DISEASE 2","url":"https://www.omim.org/entry/613411"},{"mim_id":"606987","title":"G PROTEIN-COUPLED RECEPTOR KINASE 7; GRK7","url":"https://www.omim.org/entry/606987"},{"mim_id":"606575","title":"MEMBRANE PROTEIN, PALMITOYLATED 4; MPP4","url":"https://www.omim.org/entry/606575"},{"mim_id":"600870","title":"G PROTEIN-COUPLED RECEPTOR KINASE 5; GRK5","url":"https://www.omim.org/entry/600870"},{"mim_id":"310500","title":"NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1A; CSNB1A","url":"https://www.omim.org/entry/310500"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Principal piece","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"retina","ntpm":39.5}],"url":"https://www.proteinatlas.org/search/GRK1"},"hgnc":{"alias_symbol":["GPRK1","RK"],"prev_symbol":["RHOK"]},"alphafold":{"accession":"Q15835","domains":[{"cath_id":"3.30.200.20","chopping":"4-21_187-272_488-511","consensus_level":"high","plddt":91.1995,"start":4,"end":511},{"cath_id":"1.10.167.10","chopping":"45-183","consensus_level":"high","plddt":93.1238,"start":45,"end":183},{"cath_id":"1.10.510.10","chopping":"274-476","consensus_level":"high","plddt":96.3545,"start":274,"end":476}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15835","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15835-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15835-F1-predicted_aligned_error_v6.png","plddt_mean":91.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GRK1","jax_strain_url":"https://www.jax.org/strain/search?query=GRK1"},"sequence":{"accession":"Q15835","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15835.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15835/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15835"}},"corpus_meta":[{"pmid":"8617238","id":"PMC_8617238","title":"The p38/RK mitogen-activated protein kinase pathway regulates interleukin-6 synthesis response to tumor necrosis factor.","date":"1996","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/8617238","citation_count":570,"is_preprint":false},{"pmid":"8755992","id":"PMC_8755992","title":"Stimulation of the stress-activated mitogen-activated protein kinase subfamilies in perfused heart. p38/RK mitogen-activated protein kinases and c-Jun N-terminal kinases are activated by ischemia/reperfusion.","date":"1996","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/8755992","citation_count":467,"is_preprint":false},{"pmid":"8670865","id":"PMC_8670865","title":"Differential regulation of the MAP, SAP and RK/p38 kinases by Pyst1, a novel cytosolic dual-specificity phosphatase.","date":"1996","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/8670865","citation_count":359,"is_preprint":false},{"pmid":"8603987","id":"PMC_8603987","title":"Role of CSB/p38/RK stress response kinase in LPS and cytokine signaling mechanisms.","date":"1996","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/8603987","citation_count":348,"is_preprint":false},{"pmid":"9029150","id":"PMC_9029150","title":"Activation of stress-activated protein kinase-3 (SAPK3) by cytokines and cellular stresses is mediated via SAPKK3 (MKK6); comparison of the specificities of SAPK3 and SAPK2 (RK/p38).","date":"1997","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/9029150","citation_count":327,"is_preprint":false},{"pmid":"9003778","id":"PMC_9003778","title":"MLK-3 activates the SAPK/JNK and p38/RK pathways via SEK1 and MKK3/6.","date":"1996","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/9003778","citation_count":281,"is_preprint":false},{"pmid":"8805335","id":"PMC_8805335","title":"p38/RK is essential for stress-induced nuclear responses: JNK/SAPKs and c-Jun/ATF-2 phosphorylation are insufficient.","date":"1996","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/8805335","citation_count":204,"is_preprint":false},{"pmid":"8902523","id":"PMC_8902523","title":"Differential activation of ERK, JNK/SAPK and P38/CSBP/RK map kinase family members during the cellular response to arsenite.","date":"1996","source":"Free radical biology & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/8902523","citation_count":185,"is_preprint":false},{"pmid":"9148940","id":"PMC_9148940","title":"Cdc42Hs, but not Rac1, inhibits serum-stimulated cell cycle progression at G1/S through a mechanism requiring p38/RK.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9148940","citation_count":167,"is_preprint":false},{"pmid":"28623072","id":"PMC_28623072","title":"Commentary on \"Integrative clinical genomics of advanced prostate cancer\". Robinson D, Van Allen EM, Wu YM, Schultz N, Lonigro RJ, Mosquera JM, Montgomery B, Taplin ME, Pritchard CC, Attard G, Beltran H, Abida W, Bradley RK, Vinson J, Cao X, Vats P, Kunju LP, Hussain M, Feng FY, Tomlins SA, Cooney KA, Smith DC, Brennan C, Siddiqui J, Mehra R, Chen Y, Rathkopf DE, Morris MJ, Solomon SB, Durack JC, Reuter VE, Gopalan A, Gao J, Loda M, Lis RT, Bowden M, Balk SP, Gaviola G, Sougnez C, Gupta M, Yu EY, Mostaghel EA, Cheng HH, Mulcahy H, True LD, Plymate SR, Dvinge H, Ferraldeschi R, Flohr P, Miranda S, Zafeiriou Z, Tunariu N, Mateo J, Perez-Lopez R, Demichelis F, Robinson BD, Schiffman M, Nanus DM, Tagawa ST, Sigaras A, Eng KW, Elemento O, Sboner A, Heath EI, Scher HI, Pienta KJ, Kantoff P, de Bono JS, Rubin MA, Nelson PS, Garraway LA, Sawyers CL, Chinnaiyan AM.Cell. 21 May 2015;161(5):1215-1228.","date":"2017","source":"Urologic oncology","url":"https://pubmed.ncbi.nlm.nih.gov/28623072","citation_count":157,"is_preprint":false},{"pmid":"20966068","id":"PMC_20966068","title":"Monomeric rhodopsin is sufficient for normal rhodopsin kinase (GRK1) phosphorylation and arrestin-1 binding.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20966068","citation_count":154,"is_preprint":false},{"pmid":"25722443","id":"PMC_25722443","title":"Between Rho(k) and a hard place: the relation between vessel wall stiffness, endothelial contractility, and cardiovascular disease.","date":"2015","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/25722443","citation_count":152,"is_preprint":false},{"pmid":"9733728","id":"PMC_9733728","title":"Regulation of human involucrin promoter activity by a protein kinase C, Ras, MEKK1, MEK3, p38/RK, AP1 signal transduction pathway.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9733728","citation_count":144,"is_preprint":false},{"pmid":"17496142","id":"PMC_17496142","title":"Deletion of PrBP/delta impedes transport of GRK1 and PDE6 catalytic subunits to photoreceptor outer segments.","date":"2007","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17496142","citation_count":143,"is_preprint":false},{"pmid":"24987011","id":"PMC_24987011","title":"The plant RWP-RK transcription factors: key regulators of nitrogen responses and of gametophyte development.","date":"2014","source":"Journal of experimental botany","url":"https://pubmed.ncbi.nlm.nih.gov/24987011","citation_count":130,"is_preprint":false},{"pmid":"7556642","id":"PMC_7556642","title":"RK-682, a potent inhibitor of tyrosine phosphatase, arrested the mammalian cell cycle progression at G1phase.","date":"1995","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/7556642","citation_count":126,"is_preprint":false},{"pmid":"18560757","id":"PMC_18560757","title":"Adenosine kinase and ribokinase--the RK family of proteins.","date":"2008","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/18560757","citation_count":119,"is_preprint":false},{"pmid":"8861944","id":"PMC_8861944","title":"Purification and cDNA cloning of SAPKK3, the major activator of RK/p38 in stress- and cytokine-stimulated monocytes and epithelial cells.","date":"1996","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/8861944","citation_count":117,"is_preprint":false},{"pmid":"25089011","id":"PMC_25089011","title":"The growth-defense pivot: crisis management in plants mediated by LRR-RK surface receptors.","date":"2014","source":"Trends in biochemical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/25089011","citation_count":116,"is_preprint":false},{"pmid":"9211946","id":"PMC_9211946","title":"Involvement of stress-activated protein kinase and p38/RK mitogen-activated protein kinase signaling pathways in the enhanced phosphorylation of initiation factor 4E in NIH 3T3 cells.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9211946","citation_count":116,"is_preprint":false},{"pmid":"12853434","id":"PMC_12853434","title":"GRK1-dependent phosphorylation of S and M opsins and their binding to cone arrestin during cone phototransduction in the mouse retina.","date":"2003","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/12853434","citation_count":103,"is_preprint":false},{"pmid":"11717351","id":"PMC_11717351","title":"Species-specific differences in expression of G-protein-coupled receptor kinase (GRK) 7 and GRK1 in mammalian cone photoreceptor cells: implications for cone cell phototransduction.","date":"2001","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/11717351","citation_count":99,"is_preprint":false},{"pmid":"9393876","id":"PMC_9393876","title":"Effects of the inhibition of p38/RK MAP kinase on induction of five fos and jun genes by diverse stimuli.","date":"1997","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/9393876","citation_count":89,"is_preprint":false},{"pmid":"23860768","id":"PMC_23860768","title":"Resistance to neuraminidase inhibitors conferred by an R292K mutation in a human influenza virus H7N9 isolate can be masked by a mixed R/K viral population.","date":"2013","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/23860768","citation_count":87,"is_preprint":false},{"pmid":"9478965","id":"PMC_9478965","title":"Molecular forms of human rhodopsin kinase (GRK1).","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9478965","citation_count":75,"is_preprint":false},{"pmid":"7750576","id":"PMC_7750576","title":"Activation of the MAP kinase homologue RK requires the phosphorylation of Thr-180 and Tyr-182 and both residues are phosphorylated in chemically stressed KB cells.","date":"1995","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/7750576","citation_count":74,"is_preprint":false},{"pmid":"27634756","id":"PMC_27634756","title":"RK-33 Radiosensitizes Prostate Cancer Cells by Blocking the RNA Helicase DDX3.","date":"2016","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/27634756","citation_count":72,"is_preprint":false},{"pmid":"35176382","id":"PMC_35176382","title":"The r/K selection theory and its application in biological wastewater treatment processes.","date":"2022","source":"The Science of the total environment","url":"https://pubmed.ncbi.nlm.nih.gov/35176382","citation_count":71,"is_preprint":false},{"pmid":"21802295","id":"PMC_21802295","title":"The RWP-RK factor GROUNDED promotes embryonic polarity by facilitating YODA MAP kinase signaling.","date":"2011","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/21802295","citation_count":70,"is_preprint":false},{"pmid":"30238564","id":"PMC_30238564","title":"RK-287107, a potent and specific tankyrase inhibitor, blocks colorectal cancer cell growth in a preclinical model.","date":"2018","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/30238564","citation_count":68,"is_preprint":false},{"pmid":"9581785","id":"PMC_9581785","title":"The DNA sequence of the RK strain of human herpesvirus 7.","date":"1998","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/9581785","citation_count":67,"is_preprint":false},{"pmid":"20081823","id":"PMC_20081823","title":"In vitro reconstruction of tetronate RK-682 biosynthesis.","date":"2009","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/20081823","citation_count":61,"is_preprint":false},{"pmid":"31450667","id":"PMC_31450667","title":"Plant Leucine-Rich Repeat Receptor Kinase (LRR-RK): Structure, Ligand Perception, and Activation Mechanism.","date":"2019","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/31450667","citation_count":59,"is_preprint":false},{"pmid":"27870062","id":"PMC_27870062","title":"RWP-RK domain-containing transcription factors control cell differentiation during female gametophyte development in Arabidopsis.","date":"2016","source":"The New phytologist","url":"https://pubmed.ncbi.nlm.nih.gov/27870062","citation_count":55,"is_preprint":false},{"pmid":"16787417","id":"PMC_16787417","title":"GRK1 and GRK7: unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones.","date":"2006","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16787417","citation_count":54,"is_preprint":false},{"pmid":"168818","id":"PMC_168818","title":"Fine structural changes at Entamoeba histolytica rabbit kidney cell (RK 13) interface.","date":"1975","source":"Annals of tropical medicine and parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/168818","citation_count":53,"is_preprint":false},{"pmid":"14982459","id":"PMC_14982459","title":"Total synthesis of the polyene-polyol macrolide RK-397, featuring cross-couplings of alkynylepoxide modules.","date":"2004","source":"Journal of the American Chemical Society","url":"https://pubmed.ncbi.nlm.nih.gov/14982459","citation_count":48,"is_preprint":false},{"pmid":"30540790","id":"PMC_30540790","title":"Genome-wide identification and characterization of gene family for RWP-RK transcription factors in wheat (Triticum aestivum L.).","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/30540790","citation_count":46,"is_preprint":false},{"pmid":"17822394","id":"PMC_17822394","title":"Integration of CellDesigner and SABIO-RK.","date":"2007","source":"In silico biology","url":"https://pubmed.ncbi.nlm.nih.gov/17822394","citation_count":45,"is_preprint":false},{"pmid":"15946941","id":"PMC_15946941","title":"Phosphorylation of GRK1 and GRK7 by cAMP-dependent protein kinase attenuates their enzymatic activities.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15946941","citation_count":41,"is_preprint":false},{"pmid":"31695568","id":"PMC_31695568","title":"Studies of the effects and mechanisms of ginsenoside Re and Rk3 on myelosuppression induced by cyclophosphamide.","date":"2018","source":"Journal of ginseng research","url":"https://pubmed.ncbi.nlm.nih.gov/31695568","citation_count":39,"is_preprint":false},{"pmid":"30103701","id":"PMC_30103701","title":"MITE insertion-dependent expression of CitRKD1 with a RWP-RK domain regulates somatic embryogenesis in citrus nucellar tissues.","date":"2018","source":"BMC plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/30103701","citation_count":39,"is_preprint":false},{"pmid":"30292066","id":"PMC_30292066","title":"Targeting DDX3 in Medulloblastoma Using the Small Molecule Inhibitor RK-33.","date":"2018","source":"Translational oncology","url":"https://pubmed.ncbi.nlm.nih.gov/30292066","citation_count":38,"is_preprint":false},{"pmid":"31936642","id":"PMC_31936642","title":"RK-33 Is a Broad-Spectrum Antiviral Agent That Targets DEAD-Box RNA Helicase DDX3X.","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/31936642","citation_count":36,"is_preprint":false},{"pmid":"26034134","id":"PMC_26034134","title":"Knockout of RP2 decreases GRK1 and rod transducin subunits and leads to photoreceptor degeneration in zebrafish.","date":"2015","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26034134","citation_count":35,"is_preprint":false},{"pmid":"1556009","id":"PMC_1556009","title":"A new inhibitor of protein kinase C, RK-1409 (7-oxostaurosporine). I. Taxonomy and biological activity.","date":"1992","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/1556009","citation_count":35,"is_preprint":false},{"pmid":"25979333","id":"PMC_25979333","title":"Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25979333","citation_count":33,"is_preprint":false},{"pmid":"6371505","id":"PMC_6371505","title":"RK bacterial test for independently measuring chemical toxicity and mutagenicity: short-term forward selection assay.","date":"1984","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/6371505","citation_count":32,"is_preprint":false},{"pmid":"26450274","id":"PMC_26450274","title":"A major QTL corresponding to the Rk locus for resistance to root-knot nematodes in cowpea (Vigna unguiculata L. Walp.).","date":"2015","source":"TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik","url":"https://pubmed.ncbi.nlm.nih.gov/26450274","citation_count":32,"is_preprint":false},{"pmid":"12601058","id":"PMC_12601058","title":"Cone deactivation kinetics and GRK1/GRK7 expression in enhanced S cone syndrome caused by mutations in NR2E3.","date":"2003","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/12601058","citation_count":30,"is_preprint":false},{"pmid":"24496142","id":"PMC_24496142","title":"RK-1355A and B, novel quinomycin derivatives isolated from a microbial metabolites fraction library based on NPPlot screening.","date":"2014","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/24496142","citation_count":30,"is_preprint":false},{"pmid":"16039000","id":"PMC_16039000","title":"Vaccinia virus K1L protein mediates host-range function in RK-13 cells via ankyrin repeat and may interact with a cellular GTPase-activating protein.","date":"2005","source":"Virus research","url":"https://pubmed.ncbi.nlm.nih.gov/16039000","citation_count":30,"is_preprint":false},{"pmid":"2312404","id":"PMC_2312404","title":"A new inhibitor of protein kinase C, RK-286C (4'-demethylamino-4'-hydroxystaurosporine). I. Screening, taxonomy, fermentation and biological activity.","date":"1990","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/2312404","citation_count":30,"is_preprint":false},{"pmid":"36533897","id":"PMC_36533897","title":"A divergent RWP-RK transcription factor determines mating type in heterothallic Closterium.","date":"2023","source":"The New phytologist","url":"https://pubmed.ncbi.nlm.nih.gov/36533897","citation_count":29,"is_preprint":false},{"pmid":"17070587","id":"PMC_17070587","title":"A novel homozygous GRK1 mutation (P391H) in 2 siblings with Oguchi disease with markedly reduced cone responses.","date":"2006","source":"Ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/17070587","citation_count":26,"is_preprint":false},{"pmid":"12446833","id":"PMC_12446833","title":"Loci on chromosomes 14 and 2, distinct from ABCG5/ABCG8, regulate plasma plant sterol levels in a C57BL/6J x CASA/Rk intercross.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12446833","citation_count":26,"is_preprint":false},{"pmid":"16959285","id":"PMC_16959285","title":"Mutation of the Myxoma virus SERP2 P1-site to prevent proteinase inhibition causes apoptosis in cultured RK-13 cells and attenuates disease in rabbits, but mutation to alter specificity causes apoptosis without reducing virulence.","date":"2006","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/16959285","citation_count":26,"is_preprint":false},{"pmid":"18815734","id":"PMC_18815734","title":"Effect of dimerization of a beta-turn antimicrobial peptide, PST13-RK, on antimicrobial activity and mammalian cell toxicity.","date":"2008","source":"Biotechnology letters","url":"https://pubmed.ncbi.nlm.nih.gov/18815734","citation_count":25,"is_preprint":false},{"pmid":"8503893","id":"PMC_8503893","title":"Induction of metallothionein synthesis by cadmium and zinc in cultured rabbit kidney cells (RK-13).","date":"1993","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/8503893","citation_count":24,"is_preprint":false},{"pmid":"2312405","id":"PMC_2312405","title":"A new inhibitor of protein kinase C, RK-286C (4'-demethylamino-4'-hydroxystaurosporine). II. Isolation, physico-chemical properties and structure.","date":"1990","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/2312405","citation_count":24,"is_preprint":false},{"pmid":"16319817","id":"PMC_16319817","title":"A variant form of Oguchi disease mapped to 13q34 associated with partial deletion of GRK1 gene.","date":"2005","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/16319817","citation_count":22,"is_preprint":false},{"pmid":"15542637","id":"PMC_15542637","title":"Identification of Epstein-Barr virus RK-BARF0-interacting proteins and characterization of expression pattern.","date":"2004","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/15542637","citation_count":22,"is_preprint":false},{"pmid":"36090095","id":"PMC_36090095","title":"RK-33, a small molecule inhibitor of host RNA helicase DDX3, suppresses multiple variants of SARS-CoV-2.","date":"2022","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/36090095","citation_count":21,"is_preprint":false},{"pmid":"9573383","id":"PMC_9573383","title":"Two types of differentially photo-regulated nuclear genes that encode sigma factors for chloroplast RNA polymerase in the red alga Cyanidium caldarium strain RK-1.","date":"1998","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/9573383","citation_count":21,"is_preprint":false},{"pmid":"30845463","id":"PMC_30845463","title":"Mapping the Root-Knot Nematode Resistance Gene (Rk) in Tobacco with RAPD Markers.","date":"1998","source":"Plant disease","url":"https://pubmed.ncbi.nlm.nih.gov/30845463","citation_count":19,"is_preprint":false},{"pmid":"11217111","id":"PMC_11217111","title":"Asymmetric synthesis of a 3-acyltetronic acid derivative, RK-682, and formation of its calcium salt during silica gel column chromatography.","date":"2001","source":"Chemical & pharmaceutical bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/11217111","citation_count":19,"is_preprint":false},{"pmid":"12596853","id":"PMC_12596853","title":"Cloning of the maltose phosphorylase gene from Bacillus sp. strain RK-1 and efficient production of the cloned gene and the trehalose phosphorylase gene from Bacillus stearothermophilus SK-1 in Bacillus subtilis.","date":"2002","source":"Bioscience, biotechnology, and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12596853","citation_count":19,"is_preprint":false},{"pmid":"1556010","id":"PMC_1556010","title":"A new inhibitor of protein kinase C, RK-1409 (7-oxostaurosporine). II. Fermentation, isolation, physico-chemical properties and structure.","date":"1992","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/1556010","citation_count":19,"is_preprint":false},{"pmid":"7664758","id":"PMC_7664758","title":"Cytokinesis by a contractile ring in the primitive red alga Cyanidium caldarium RK-1.","date":"1995","source":"European journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/7664758","citation_count":18,"is_preprint":false},{"pmid":"20164334","id":"PMC_20164334","title":"Deletion of GRK1 causes retina degeneration through a transducin-independent mechanism.","date":"2010","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/20164334","citation_count":17,"is_preprint":false},{"pmid":"25870414","id":"PMC_25870414","title":"Functional interplay between the RK motif and linker segment dictates Oct4-DNA recognition.","date":"2015","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/25870414","citation_count":17,"is_preprint":false},{"pmid":"8082179","id":"PMC_8082179","title":"The trpA gene on the plastid genome of Cyanidium caldarium strain RK-1.","date":"1994","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8082179","citation_count":17,"is_preprint":false},{"pmid":"35605260","id":"PMC_35605260","title":"RWP-RK domain-containing transcription factors in the Viridiplantae: biology and phylogenetic relationships.","date":"2022","source":"Journal of experimental botany","url":"https://pubmed.ncbi.nlm.nih.gov/35605260","citation_count":16,"is_preprint":false},{"pmid":"19753316","id":"PMC_19753316","title":"A novel mutation in GRK1 causes Oguchi disease in a consanguineous Pakistani family.","date":"2009","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/19753316","citation_count":16,"is_preprint":false},{"pmid":"20688726","id":"PMC_20688726","title":"Neovascularization, enhanced inflammatory response, and age-related cone dystrophy in the Nrl-/-Grk1-/- mouse retina.","date":"2010","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/20688726","citation_count":15,"is_preprint":false},{"pmid":"1369312","id":"PMC_1369312","title":"New pyrrolobenzodiazepine antibiotics, RK-1441A and B. I. Biological properties.","date":"1990","source":"Agricultural and biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1369312","citation_count":15,"is_preprint":false},{"pmid":"12810823","id":"PMC_12810823","title":"Loci controlling plasma non-HDL and HDL cholesterol levels in a C57BL /6J x CASA /Rk intercross.","date":"2003","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/12810823","citation_count":15,"is_preprint":false},{"pmid":"16402022","id":"PMC_16402022","title":"Isolation and characterization of visual pigment kinase-related genes in carp retina: polyphyly in GRK1 subtypes, GRK1A and 1B.","date":"2005","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/16402022","citation_count":15,"is_preprint":false},{"pmid":"21504899","id":"PMC_21504899","title":"Phosphorylation of G protein-coupled receptor kinase 1 (GRK1) is regulated by light but independent of phototransduction in rod photoreceptors.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21504899","citation_count":15,"is_preprint":false},{"pmid":"33252155","id":"PMC_33252155","title":"New variants and in silico analyses in GRK1 associated Oguchi disease.","date":"2020","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/33252155","citation_count":13,"is_preprint":false},{"pmid":"1429228","id":"PMC_1429228","title":"A new inhibitor of protein kinase C, RK-1409B (4'-demethylamino-4'-hydroxy-3'-epistaurosporine).","date":"1992","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/1429228","citation_count":13,"is_preprint":false},{"pmid":"30521026","id":"PMC_30521026","title":"An RK/ST C-Terminal Motif is Required for Targeting of OEP7.2 and a Subset of Other Arabidopsis Tail-Anchored Proteins to the Plastid Outer Envelope Membrane.","date":"2019","source":"Plant & cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/30521026","citation_count":13,"is_preprint":false},{"pmid":"29901832","id":"PMC_29901832","title":"Autonomous and non-autonomous functions of the maize Shohai1 gene, encoding a RWP-RK putative transcription factor, in regulation of embryo and endosperm development.","date":"2018","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/29901832","citation_count":13,"is_preprint":false},{"pmid":"37813828","id":"PMC_37813828","title":"r/K selection of GC content in prokaryotes.","date":"2023","source":"Environmental microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/37813828","citation_count":12,"is_preprint":false},{"pmid":"16357827","id":"PMC_16357827","title":"Conserved structure and spatiotemporal function of the compact rhodopsin kinase (GRK1) enhancer/promoter.","date":"2005","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/16357827","citation_count":12,"is_preprint":false},{"pmid":"32435388","id":"PMC_32435388","title":"Drug Synergism: Studies of Combination of RK-52 and Curcumin against Rhodesain of Trypanosoma brucei rhodesiense.","date":"2020","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/32435388","citation_count":12,"is_preprint":false},{"pmid":"1671058","id":"PMC_1671058","title":"Evaluation of a new 2-nitroimidazole nucleoside analogue, RK-28 as a radiosensitizer for clinical use.","date":"1991","source":"International journal of radiation biology","url":"https://pubmed.ncbi.nlm.nih.gov/1671058","citation_count":12,"is_preprint":false},{"pmid":"17256472","id":"PMC_17256472","title":"RK-95113, a new angiogenesis inhibitor produced by Aspergillus fumigatus.","date":"2006","source":"The Journal of antibiotics","url":"https://pubmed.ncbi.nlm.nih.gov/17256472","citation_count":12,"is_preprint":false},{"pmid":"26330329","id":"PMC_26330329","title":"PLGA nanoparticle formulation of RK-33: an RNA helicase inhibitor against DDX3.","date":"2015","source":"Cancer chemotherapy and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26330329","citation_count":11,"is_preprint":false},{"pmid":"36273582","id":"PMC_36273582","title":"Grk7 but not Grk1 undergoes cAMP-dependent phosphorylation in zebrafish cone photoreceptors and mediates cone photoresponse recovery to elevated cAMP.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36273582","citation_count":11,"is_preprint":false},{"pmid":"26484505","id":"PMC_26484505","title":"TIMP-1 couples RhoK activation to IL-1β-induced astrocyte responses.","date":"2015","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/26484505","citation_count":11,"is_preprint":false},{"pmid":"32849368","id":"PMC_32849368","title":"Conserved Subgroups of the Plant-Specific RWP-RK Transcription Factor Family Are Present in Oomycete Pathogens.","date":"2020","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/32849368","citation_count":11,"is_preprint":false},{"pmid":"17765441","id":"PMC_17765441","title":"Novel mutations in the GRK1 gene in Japanese patients With Oguchi disease.","date":"2007","source":"American journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/17765441","citation_count":11,"is_preprint":false},{"pmid":"37076789","id":"PMC_37076789","title":"RWP-RK Domain 3 (OsRKD3) induces somatic embryogenesis in black rice.","date":"2023","source":"BMC plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/37076789","citation_count":11,"is_preprint":false},{"pmid":"16018718","id":"PMC_16018718","title":"Solution-phase and solid-phase syntheses of enzyme inhibitor RK-682 and antibiotic agglomerins.","date":"2005","source":"The Journal of organic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16018718","citation_count":11,"is_preprint":false},{"pmid":"27511724","id":"PMC_27511724","title":"A novel missense mutation of the GRK1 gene in Oguchi disease.","date":"2016","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/27511724","citation_count":10,"is_preprint":false},{"pmid":"19259435","id":"PMC_19259435","title":"Dynamics of Meloidogyne incognita Virulence to Resistance Genes Rk and Rk in Cowpea.","date":"2006","source":"Journal of nematology","url":"https://pubmed.ncbi.nlm.nih.gov/19259435","citation_count":10,"is_preprint":false},{"pmid":"32932820","id":"PMC_32932820","title":"Genome-Wide Identification, Characterization, and Regulation of RWP-RK Gene Family in the Nitrogen-Fixing Clade.","date":"2020","source":"Plants (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/32932820","citation_count":10,"is_preprint":false},{"pmid":"31908030","id":"PMC_31908030","title":"Phosphorylation at Serine 21 in G protein-coupled receptor kinase 1 (GRK1) is required for normal kinetics of dark adaption in rod but not cone photoreceptors.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31908030","citation_count":10,"is_preprint":false},{"pmid":"19834036","id":"PMC_19834036","title":"Effect of g protein-coupled receptor kinase 1 (Grk1) overexpression on rod photoreceptor cell viability.","date":"2009","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/19834036","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47474,"output_tokens":3498,"usd":0.097446},"stage2":{"model":"claude-opus-4-6","input_tokens":6902,"output_tokens":2945,"usd":0.162202},"total_usd":0.259648,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"Monomeric rhodopsin (in nanodiscs) is sufficient for normal GRK1 phosphorylation; GRK1 phosphorylates light-activated rhodopsin monomer as efficiently as rhodopsin in native disc membranes, and monomeric phosphorylated Rh* binds arrestin-1 with low nanomolar affinity and 1:1 stoichiometry.\",\n      \"method\": \"Reconstitution in nanodiscs, in vitro phosphorylation assay, fluorescence-based arrestin-binding affinity measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in defined lipid nanodiscs with quantitative binding measurements and multiple orthogonal methods\",\n      \"pmids\": [\"20966068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"GRK1 is required for light-dependent multi-site phosphorylation of both S and M cone opsins in mouse cone photoreceptors; without GRK1, light-activated cone opsins are neither phosphorylated nor bound by cone arrestin (mCAR).\",\n      \"method\": \"Genetic knockout (Nrl-/- and Nrl-/-Grk1-/- double-KO mice), in situ phosphorylation, isoelectric focusing, immunoprecipitation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean double-KO with multiple orthogonal biochemical readouts demonstrating GRK1 dependence of cone opsin phosphorylation\",\n      \"pmids\": [\"12853434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"cAMP-dependent protein kinase (PKA) phosphorylates GRK1 at Ser21, and this phosphorylation attenuates GRK1 enzymatic activity toward rhodopsin; rod outer segment preparations confirm GRK1 is a physiologically relevant PKA substrate.\",\n      \"method\": \"In vitro PKA phosphorylation assay, site-directed identification of Ser21, FLAG-tagged GRK1 expression in HEK-293 cells treated with forskolin, bovine rod outer segment phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis site identification, confirmed in cell-based and rod outer segment systems\",\n      \"pmids\": [\"15946941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The prenyl-binding protein PrBP/delta (encoded by Pde6d) is required for transport of farnesylated GRK1 to rod and cone photoreceptor outer segments; Pde6d-/- mice show partial mislocalization of GRK1 and a delay in dark-state recovery consistent with reduced outer-segment GRK1 levels.\",\n      \"method\": \"Pde6d knockout mouse, immunocytochemistry, single-cell electrophysiology, paired-flash ERG\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with direct localization data and corroborating physiological ERG phenotype\",\n      \"pmids\": [\"17496142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GRK1 is phosphorylated on Ser21 in a cAMP-dependent manner in dark-adapted retina (high cAMP) and dephosphorylated upon light exposure independently of phototransduction; adenylyl cyclase type 1 is required for dark-dependent GRK1 phosphorylation.\",\n      \"method\": \"Immunoblot with phospho-specific antibody, adenylyl cyclase 1 knockout mice, rod transducin α-subunit knockout mice, dark/light adaptation paradigms\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple KO models with quantitative phosphorylation measurements establishing cAMP pathway requirement and transducin independence\",\n      \"pmids\": [\"21504899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Phosphorylation of GRK1 at Ser21 by PKA is required for normal kinetics of rod dark adaptation but not cone dark adaptation; GRK1-S21A knock-in mice show delayed rod recovery after bleaching, consistent with increased rhodopsin phosphorylation slowing chromophore regeneration.\",\n      \"method\": \"GRK1-S21A knock-in mouse, ex vivo and in vivo ERG, dark adaptation assays, retinal morphology\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — precise knock-in mutation with physiological phenotype demonstrating cell-type-specific functional consequence\",\n      \"pmids\": [\"31908030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GRK1 deletion causes retinal degeneration through a transducin-independent, light-independent mechanism; Grk1-/-Gnat1-/- mice still degenerate, demonstrating that the protective role of GRK1 is not solely via quenching opsin/transducin signaling.\",\n      \"method\": \"Grk1-/-, Rpe65-/-Grk1-/-, and Grk1-/-Gnat1-/- multi-KO mice; histology, opsin phosphorylation assays, rod electrophysiology\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistatic triple-KO design with multiple orthogonal readouts identifying a second, non-signaling role for GRK1\",\n      \"pmids\": [\"20164334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Neuronal calcium sensor-1 (NCS-1) binds a GRK1-derived peptide at the hydrophobic C-lobe crevice; crystal structures show one GRK1 peptide copy binds versus two D2R peptide copies, with differential binding enabled by conformational flexibility of the NCS-1 C-terminal region (Ser178–Val190).\",\n      \"method\": \"Crystal structure of Ca2+/NCS-1 in complex with GRK1 peptide, ITC/biophysical binding measurements, C-terminal truncation mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional mutagenesis validation defining the GRK1-binding mode on NCS-1\",\n      \"pmids\": [\"25979333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human retina expresses GRK1 in both rod and cone photoreceptors; a splice variant GRK1b retains the last intron, produces mRNA exported to the cytosol, but the protein is expressed at low levels and has very low catalytic activity compared to GRK1a.\",\n      \"method\": \"Molecular cloning, RT-PCR, immunolocalization of GRK1 in rod and cone photoreceptors, catalytic activity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct cloning and localization with activity comparison, single lab\",\n      \"pmids\": [\"9478965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In zebrafish, GRK1A localizes to rod outer segments and GRK7-1 to cone outer segments; GRK7-1 has a 32-fold higher Vmax than GRK1A in phosphorylating light-activated rhodopsin, explaining the faster cone shutoff kinetics.\",\n      \"method\": \"In situ hybridization, immunohistochemistry, in vitro phosphorylation assay with recombinant GRK1A vs GRK7-1\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinetic reconstitution with direct localization data, multiple orthogonal methods\",\n      \"pmids\": [\"16787417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Species-specific differences exist in GRK1 and GRK7 cone expression: pigs and dogs express only GRK7 in cones; mice and rats express only GRK1 in cones; humans and monkeys co-express both, implying either GRK1 or GRK7 can mediate cone opsin desensitization depending on species.\",\n      \"method\": \"Immunocytochemistry with kinase-selective antibodies across multiple species retinas\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct localization across species by immunocytochemistry, single lab, no functional rescue\",\n      \"pmids\": [\"11717351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RP2 deletion in zebrafish reduces protein levels and causes abnormal retinal localization of GRK1 (and rod transducin subunits), linking RP2's role as an ARL3 GAP to the proper trafficking of farnesylated GRK1 in photoreceptors.\",\n      \"method\": \"TALEN-based RP2 knockout zebrafish, immunohistochemistry, immunoblot\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO with direct localization and protein quantification; single lab but mechanistic link via farnesylated protein trafficking established\",\n      \"pmids\": [\"26034134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GRK1 overexpression (~3-fold) in transgenic mice produces proportionally higher rhodopsin phosphorylation activity but does not protect against light-induced photoreceptor apoptosis; instead, excess opsin channeled through the GRK1 deactivation pathway increases susceptibility to stress-induced cell death.\",\n      \"method\": \"BAC transgenic mouse overexpressing GRK1, in vitro phosphorylation assay, ERG, morphometry, nucleosome release apoptosis assay\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic gain-of-function with enzymatic activity confirmation and multiple phenotypic readouts\",\n      \"pmids\": [\"19834036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In zebrafish, cone-expressed Grk1b does not undergo cAMP-dependent phosphorylation in vivo, whereas Grk7a does; PKA activity (via dominant-negative PKA transgene in cones) is required for Grk7a phosphorylation but not for Grk1b phosphorylation, revealing cell-type-specific regulation of GRK isoforms.\",\n      \"method\": \"Grk1a-/- and Grk1b-/- zebrafish, cone-specific dominant-negative PKA transgene, ERG with forskolin treatment, immunoblot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple KO and transgenic models with pharmacological intervention and electrophysiological readouts\",\n      \"pmids\": [\"36273582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The conserved ~0.2 kb enhancer/promoter immediately upstream of the GRK1 transcription start site is sufficient to drive expression specifically in rod photoreceptors, cone photoreceptors, and pinealocytes in transgenic mice, with developmental onset paralleling outer segment maturation.\",\n      \"method\": \"GFP reporter transgenic mice, fluorescence microscopy, RT-PCR, immunostaining during postnatal retinal development\",\n      \"journal\": \"Molecular vision\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo cis-regulatory mapping with spatiotemporal validation, single lab\",\n      \"pmids\": [\"16357827\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GRK1 (rhodopsin kinase) is a photoreceptor-specific serine/threonine kinase that phosphorylates light-activated rhodopsin and cone opsins at multiple C-terminal sites to initiate visual signal termination; its activity is negatively regulated by PKA-mediated phosphorylation at Ser21 in the dark (high cAMP), is modulated by NCS-1 binding, depends on PrBP/delta and RP2/ARL3 for farnesyl-dependent transport to outer segments, and operates on monomeric receptor with 1:1 stoichiometry, while also serving a second, light- and transducin-independent neuroprotective role in photoreceptor homeostasis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GRK1 (rhodopsin kinase) is a photoreceptor-specific serine/threonine kinase that phosphorylates light-activated rhodopsin and cone opsins at multiple C-terminal sites, initiating receptor deactivation and visual signal termination in both rod and cone photoreceptors [PMID:20966068, PMID:12853434]. GRK1 acts on monomeric rhodopsin with 1:1 stoichiometry and its catalytic activity is negatively regulated by PKA-mediated phosphorylation at Ser21 under dark-adapted (high cAMP) conditions, a modification required for normal rod dark adaptation kinetics [PMID:15946941, PMID:21504899, PMID:31908030]. Proper delivery of farnesylated GRK1 to photoreceptor outer segments depends on the prenyl-binding protein PrBP/δ and the RP2–ARL3 GTPase pathway [PMID:17496142, PMID:26034134]. Beyond its canonical role in signal quenching, GRK1 exerts a light- and transducin-independent neuroprotective function, as Grk1 deletion causes photoreceptor degeneration even when phototransduction is genetically abolished [PMID:20164334].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that GRK1 is expressed in both human rods and cones — and that a splice variant (GRK1b) exists but has minimal catalytic activity — defined the isoform landscape and implied GRK1a as the functionally dominant kinase in human photoreceptors.\",\n      \"evidence\": \"Molecular cloning, RT-PCR, immunolocalization and catalytic activity assays in human retina\",\n      \"pmids\": [\"9478965\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab characterization without independent replication\", \"Functional significance of GRK1b splice variant in vivo unresolved\", \"Whether GRK1 is the sole kinase for cone opsins in human cones was unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Cross-species immunolocalization revealed that cone GRK identity is species-dependent — mice use GRK1, pigs/dogs use GRK7, and primates co-express both — resolving confusion about cone opsin deactivation mechanisms.\",\n      \"evidence\": \"Immunocytochemistry with kinase-selective antibodies across mammalian retinas\",\n      \"pmids\": [\"11717351\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional rescue to confirm sufficiency of either kinase alone\", \"Relative contributions of GRK1 vs GRK7 in primate cones unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Genetic ablation of GRK1 in a cone-only mouse model proved that GRK1 is required for light-dependent phosphorylation of S and M cone opsins and for cone arrestin binding, establishing GRK1 as the essential cone opsin kinase in mice.\",\n      \"evidence\": \"Nrl−/− and Nrl−/−Grk1−/− double-KO mice with isoelectric focusing and immunoprecipitation\",\n      \"pmids\": [\"12853434\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GRK7 can substitute in species that express it in cones\", \"Downstream consequences of unphosphorylated cone opsin for cone survival\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of Ser21 as a PKA phosphorylation site that attenuates GRK1 activity answered how GRK1 is kept partially inhibited in the dark, providing a molecular mechanism for dark-state modulation of phototransduction deactivation.\",\n      \"evidence\": \"In vitro PKA phosphorylation, site-directed mutagenesis, confirmation in bovine rod outer segments and HEK-293 cells\",\n      \"pmids\": [\"15946941\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological consequence of Ser21 phosphorylation not yet tested\", \"Identity of the phosphatase that dephosphorylates Ser21 in light unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Kinetic comparison of zebrafish GRK1A and GRK7-1 showed a 32-fold higher Vmax for GRK7-1, explaining why cones that express GRK7 achieve faster signal shutoff than rods relying on GRK1.\",\n      \"evidence\": \"Recombinant kinase in vitro phosphorylation assays with in situ hybridization/immunohistochemistry in zebrafish retina\",\n      \"pmids\": [\"16787417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Vmax differences fully account for in vivo shutoff speed differences\", \"Structural basis for GRK7's higher activity unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrating that PrBP/δ is required for farnesylated GRK1 transport to outer segments identified the trafficking machinery for GRK1, linking prenyl-binding chaperone biology to phototransduction.\",\n      \"evidence\": \"Pde6d knockout mouse with immunocytochemistry and paired-flash ERG\",\n      \"pmids\": [\"17496142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether additional chaperones are needed for full GRK1 delivery\", \"How GRK1 is released from PrBP/δ at the outer segment\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Two key advances: (1) reconstitution in nanodiscs proved that monomeric rhodopsin is the functional GRK1 substrate with 1:1 stoichiometry, and (2) epistatic KO analysis revealed a transducin- and light-independent neuroprotective role for GRK1 distinct from signal quenching.\",\n      \"evidence\": \"Nanodisc reconstitution with fluorescence-based arrestin binding (PMID:20966068); Grk1−/−Gnat1−/− and Rpe65−/−Grk1−/− multi-KO mice with histology and electrophysiology (PMID:20164334)\",\n      \"pmids\": [\"20966068\", \"20164334\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the non-opsin GRK1 substrate mediating neuroprotection unknown\", \"Structural basis for GRK1 recognition of monomeric rhodopsin unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that dark-state GRK1-Ser21 phosphorylation requires adenylyl cyclase 1 but is independent of phototransduction (transducin) established that GRK1 regulation occurs via a parallel cAMP signaling axis.\",\n      \"evidence\": \"Phospho-specific immunoblotting in adenylyl cyclase 1 KO and rod transducin α-subunit KO mice under dark/light adaptation\",\n      \"pmids\": [\"21504899\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How light triggers Ser21 dephosphorylation independently of transducin not fully resolved\", \"Whether other cAMP effectors modulate GRK1 in parallel\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Two findings refined GRK1 regulation and trafficking: crystal structure of NCS-1 bound to a GRK1 peptide defined the interaction interface, and RP2 knockout in zebrafish linked ARL3 GTPase regulation to farnesylated GRK1 trafficking.\",\n      \"evidence\": \"Crystal structure of Ca²⁺/NCS-1–GRK1 peptide complex with ITC (PMID:25979333); TALEN-based RP2 KO zebrafish with immunolocalization (PMID:26034134)\",\n      \"pmids\": [\"25979333\", \"26034134\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of NCS-1–GRK1 interaction on kinase activity in photoreceptors unknown\", \"Whether RP2/ARL3 acts directly on PrBP/δ-GRK1 complexes not confirmed in mammalian retina\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"GRK1-S21A knock-in mice demonstrated that Ser21 phosphorylation is physiologically required for normal rod — but not cone — dark adaptation, establishing cell-type-specific PKA regulation of GRK1.\",\n      \"evidence\": \"GRK1-S21A knock-in mouse with ex vivo and in vivo ERG dark adaptation assays\",\n      \"pmids\": [\"31908030\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which excess rhodopsin phosphorylation slows chromophore regeneration not molecularly defined\", \"Whether cone-expressed GRK1 is regulated by alternative post-translational modifications\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Zebrafish genetic dissection showed that cone-expressed Grk1b escapes cAMP/PKA-dependent phosphorylation, unlike Grk7a, revealing isoform-specific regulatory logic in cones.\",\n      \"evidence\": \"Grk1a−/−, Grk1b−/− zebrafish with cone-specific dominant-negative PKA transgene, ERG and immunoblotting\",\n      \"pmids\": [\"36273582\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for differential PKA sensitivity among GRK isoforms unknown\", \"Relevance to mammalian cone biology where GRK1 is the cone kinase remains to be tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular identity of the non-opsin GRK1 substrate(s) mediating its transducin-independent neuroprotective function, the structural basis for GRK1 recognition of activated rhodopsin, and the mechanism coupling light to Ser21 dephosphorylation remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No substrate beyond opsins identified for the neuroprotective function\", \"No full-length GRK1–rhodopsin complex structure available\", \"Phosphatase responsible for light-dependent Ser21 dephosphorylation not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 5, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 8, 11]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [0, 1, 2, 4, 5, 6]},\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [0, 1, 5, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RHO\",\n      \"OPN1SW\",\n      \"OPN1MW\",\n      \"ARR1\",\n      \"NCS1\",\n      \"PDE6D\",\n      \"RP2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}