{"gene":"PRKCI","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2014,"finding":"PKCι (PRKCI) phosphorylates SOX2 and recruits it to the promoter of Hedgehog acyltransferase (HHAT), the rate-limiting enzyme in Hh ligand production; PKCι-mediated SOX2 phosphorylation is required for HHAT promoter occupancy and HHAT expression, establishing a cell-autonomous Hh signaling axis in lung squamous cell carcinoma.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, kinase assay, loss-of-function/overexpression in cell lines and primary tumors","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP, in vitro kinase assay, and functional rescue experiments across multiple models in one rigorous study","pmids":["24525231"],"is_preprint":false},{"year":2020,"finding":"PRKCI, SOX2, and ECT2 are co-overexpressed via chromosome 3q26 copy number gain; PRKCI and SOX2 collaborate to activate a transcriptional program enforcing a lineage-restricted LSCC phenotype, while PRKCI and ECT2 collaborate to promote oncogenic growth. Overexpression of all three in the context of Trp53 loss is sufficient to transform mouse lung basal stem cells into LSCC-like tumors.","method":"Mouse genetic transformation model, gene expression profiling, functional epistasis analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transformation assay with defined genetic components, gene signature analyses, replicated across human and mouse models","pmids":["31968252"],"is_preprint":false},{"year":2017,"finding":"PRKCI promotes an immune-suppressive tumor microenvironment in ovarian cancer by upregulating TNFα, which increases myeloid-derived suppressor cells and inhibits cytotoxic T-cell infiltration; YAP1 is identified as a downstream effector of PRKCI in tumor progression.","method":"Transgenic mouse model, functional assays, system-level analysis, gene expression correlation in human tumors","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic mouse oncogenesis model combined with immune profiling, single lab, mechanistic pathway placement via multiple readouts","pmids":["28698296"],"is_preprint":false},{"year":2005,"finding":"Zebrafish heart and soul (Has)/PRKCi is required tissue-autonomously within the myocardium for polarized epithelial organization and coherence of myocardial cells during heart cone formation; this function depends on its catalytic activity.","method":"Zebrafish genetic mutant analysis, tissue-specific rescue experiments, catalytic-dead mutant complementation","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-autonomous rescue in zebrafish with catalytic-dead mutant confirming kinase activity requirement, replicated in vivo context","pmids":["16319113"],"is_preprint":false},{"year":2009,"finding":"In zebrafish spinal cord, PrkCi function and planar cell divisions are necessary for asymmetric, self-renewing division of spinal cord precursors; loss of PrkCi causes oblique precursor divisions during late embryogenesis and excess oligodendrocyte production with concomitant loss of dividing cells.","method":"Time-lapse imaging of zebrafish, PrkCi loss-of-function analysis, cell fate quantification","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live imaging plus loss-of-function with defined cell-fate phenotype in zebrafish, single lab","pmids":["19449304"],"is_preprint":false},{"year":2016,"finding":"PRKCI negatively regulates autophagy via the PIK3CA/AKT-MTOR signaling pathway; PRKCI overexpression impairs autophagic flux (decreased LC3B-II, reduced substrate degradation), while PRKCI knockdown or dominant-negative mutants (L485M, P560R) induce autophagy.","method":"Overexpression and siRNA knockdown in U2OS cells, LC3B-II immunoblot, autophagic substrate degradation assays, mutagenesis of PRKCI","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with multiple readouts plus mutagenesis, single lab","pmids":["26792725"],"is_preprint":false},{"year":2022,"finding":"Pancreas-specific ablation of Prkci increases acinar cell DNA damage, apoptosis, and P62 aggregation with loss of autophagic vesicles, indicating that PKCι is required for pancreatic epithelial cell autophagy; Prkci loss promotes Kras-mediated pancreatic intraepithelial neoplasia formation but blocks progression to adenocarcinoma, consistent with disruption of autophagy.","method":"Pancreas-specific conditional knockout mice, histopathology, immunofluorescence, autophagy marker analysis","journal":"Cancers","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional knockout with multiple mechanistic readouts and genetic epistasis with Kras oncogene","pmids":["35159064"],"is_preprint":false},{"year":2000,"finding":"Hint/PKCI-1 physically interacts with Cdk7 (and the yeast ortholog Hnt1 with Kin28); overexpression of Cdk7 causes partial relocalization of Hint to the nucleus. This interaction is independent of cyclin H binding or Cdk7 kinase activity. Genetic combination of HNT1 disruption and a KIN28 temperature-sensitive allele in S. cerevisiae leads to elongated cell morphology and reduced colony formation.","method":"Yeast two-hybrid, co-immunoprecipitation, subcellular localization, yeast genetic epistasis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus yeast two-hybrid plus genetic epistasis, replicated across yeast and mammalian system in same study","pmids":["10958787"],"is_preprint":false},{"year":2006,"finding":"PKCI-1 (HINT1) interacts with RGSZ1 as shown by co-immunoprecipitation and immunofluorescence; the RGSZ1-PKCI-1 complex modulates mu opioid receptor signaling—inhibition of cAMP by mu opioid receptor was significantly reduced by RGSZ1, an effect enhanced in combination with PKCI-1. The interaction requires the cysteine string region unique to the RZ subfamily of RGS proteins.","method":"Yeast two-hybrid, co-immunoprecipitation, immunofluorescence, cAMP functional assay","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, immunofluorescence colocalization, and functional cAMP assay in single lab study","pmids":["17126529"],"is_preprint":false},{"year":1998,"finding":"Human PKCI (hPKCI) exists as a homodimer and interacts with a murine PKCI homologue in a yeast two-hybrid screen. The protein is expressed mainly in the nucleus of both normal and tumor-derived epithelial cell lines as determined by immunostaining. In vitro, hPKCI enzymatically hydrolyzes adenosine polyphosphates.","method":"Yeast two-hybrid, in vitro enzymatic assay, immunostaining/subcellular localization, Northern and Western blot","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzymatic assay plus yeast two-hybrid plus direct immunolocalization, single lab with multiple orthogonal methods","pmids":["9770345"],"is_preprint":false},{"year":1996,"finding":"Human PKCI-1 (hPKCI-1) localizes to cytoskeletal structures in the cytoplasm of human fibroblast cell lines as shown by indirect immunofluorescence, and is largely excluded from the nucleus.","method":"Indirect immunofluorescence, genomic FISH mapping","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct immunolocalization, single lab; note this contrasts with nuclear localization reported by other studies, suggesting cell-type dependence","pmids":["8812426"],"is_preprint":false},{"year":2023,"finding":"PRKCI physically interacts with RIPK2 (co-immunoprecipitation and immunofluorescence) and enhances phosphorylation of downstream NF-κB, JNK, and ERK signaling in pancreatic cancer cells.","method":"Co-immunoprecipitation, immunofluorescence, immunoblotting for phosphorylation","journal":"Molecular medicine (Cambridge, Mass.)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus immunofluorescence plus downstream phosphorylation readout, single lab","pmids":["37016317"],"is_preprint":false},{"year":2022,"finding":"PRKCI functions downstream of the Hedgehog/GLI1 pathway to phosphorylate and activate the transcription factor GLI1; PRKCI modulates radiosensitivity in cervical cancer by regulating GLI1 relocalization and phosphorylation.","method":"Western blotting, immunofluorescence, colony formation and apoptosis assays, xenograft model, PRKCI knockdown/overexpression","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional assays with multiple readouts and in vivo validation; phosphorylation shown by Western blot, single lab","pmids":["35785194"],"is_preprint":false},{"year":2016,"finding":"Prkci is required to produce non-autonomous polarity cues necessary for forming a polarized ectodermal epithelium and cavitation in embryoid bodies; Prkci-null cells fail to properly segregate apical-basal proteins, form a coordinated ectodermal epithelium, or participate in normal cavitation. Mixing with wildtype cells rescues cavitation in Prkci-null cells, demonstrating the non-cell-autonomous nature of the polarity signal.","method":"Prkci-null ES cell analysis, mixing experiments, BMP4/EZRIN rescue, proliferation and apoptosis assays","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — null cell analysis plus cell mixing rescue establishes non-autonomous mechanism, single lab with multiple approaches","pmids":["27312576"],"is_preprint":false},{"year":2025,"finding":"PRKCI variants (including de novo p.Asn383Ser hotspot, p.Arg130His, and p.Leu385Phe) cause loss of function in a zebrafish periderm model; phosphomimetic IRF6 rescues aPKC inhibition, placing PRKCI upstream of IRF6 in the transcriptional regulatory network governing periderm differentiation and palatogenesis.","method":"Zebrafish functional complementation assay, patient variant analysis, phosphomimetic IRF6 rescue experiments","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional validation of multiple patient alleles in zebrafish plus epistasis rescue with phosphomimetic IRF6 placing PRKCI in pathway","pmids":["40902599"],"is_preprint":false},{"year":2025,"finding":"Prkci phosphorylates and stabilizes Tgfbr1 (TGF-β receptor 1), preventing its proteasomal degradation and amplifying downstream TGF-β signaling to promote epithelial-to-mesenchymal transition and colorectal cancer metastasis; Prkci knockout reduced liver and lung metastases in mouse models.","method":"Co-immunoprecipitation, phosphorylation assay, proteasomal degradation assay, in vivo xenograft/metastasis model with Prkci knockout","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — substrate phosphorylation and stabilization demonstrated by biochemical assays plus in vivo validation, single lab","pmids":["40382656"],"is_preprint":false},{"year":2025,"finding":"Prkci phosphorylates c-Myc at serine 21, inhibiting its ubiquitin-mediated proteasomal degradation and stabilizing the protein; the pro-proliferative effect of Prkci in colorectal cancer is dependent on c-Myc S21 phosphorylation.","method":"Co-immunoprecipitation, phosphorylation site mutagenesis, ubiquitination assay, in vivo mouse tumor model with Prkci knockout","journal":"NPJ precision oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct phosphorylation site identified by mutagenesis plus ubiquitination assay plus in vivo validation, single lab","pmids":["41188443"],"is_preprint":false},{"year":2025,"finding":"Prkci activates the Jak2/Stat3 signaling pathway in colorectal cancer by phosphorylating Jak2 at the S633 site, leading to downstream Stat3 activation and increased VEGFA expression, thereby promoting tumor angiogenesis.","method":"In vitro endothelial cell proliferation/migration/tube formation assays, Prkci overexpression/knockout, in vivo xenograft model, immunoblotting for phosphorylation","journal":"Neoplasia (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific phosphorylation site (Jak2-S633) identified with functional readouts in vitro and in vivo, single lab","pmids":["40840329"],"is_preprint":false},{"year":2024,"finding":"PRKCI physically interacts with SQSTM1/p62 in osteosarcoma cells (co-immunoprecipitation); knockdown of PRKCI inhibits osteosarcoma cell proliferation by inactivating the Akt/mTOR signaling pathway.","method":"Co-immunoprecipitation, siRNA knockdown, CCK-8/colony formation/flow cytometry assays, immunoblotting for Akt/mTOR pathway","journal":"Frontiers in oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP for interaction plus indirect pathway readout, single lab, single study","pmids":["39015499"],"is_preprint":false},{"year":2025,"finding":"HINT1/PKCI-1 undergoes nucleocytoplasmic translocation regulated by exportin-1 in a cell-density-dependent manner: at low density it resides in the nucleus binding open chromatin, and as density increases it relocates to the cytoplasm where it inhibits PKC and remodels the actin cytoskeleton from stress fibers to a cortical network, facilitating monolayer maturation.","method":"Live cell imaging, subcellular fractionation, exportin-1 inhibition, HINT1 knockout, MARCKS phosphorylation assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization imaging plus functional actin remodeling readout plus exportin-1 mechanism, preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.01.13.632869"],"is_preprint":true},{"year":2022,"finding":"A mutation in Prkci (Tvrm323) acts as a genetic modifier of Crb1-associated retinal dysplasia in mice; epistasis analysis showed the increased dysplastic phenotype required homozygosity of the Crb1rd8 allele, placing Prkci in a pathway with the apicobasal polarity gene CRB1 in retinal tissue maintenance.","method":"Chemical mutagenesis screen, exome sequencing, genetic epistasis analysis, immunohistochemistry, electroretinography","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in vivo with clear double-mutant phenotype and histological analysis, single lab","pmids":["35675330"],"is_preprint":false},{"year":2025,"finding":"Reduced expression of the PAR3-PARD6B-PRKCI polarity complex in type II alveolar epithelial cells (AEC2s) arrests the cell cycle at G0-G1 phase, impairing AEC2 self-proliferation; co-immunoprecipitation and mass spectrometry confirmed PRKCI as a component of this complex.","method":"Co-immunoprecipitation, mass spectrometry, 3D spheroid formation, cell cycle analysis, in vitro smoke-injury model","journal":"Stem cell research & therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS for complex identification plus cell cycle functional readout, single lab","pmids":["40001200"],"is_preprint":false},{"year":2001,"finding":"Overexpression of PKCI increased radiation-induced apoptosis in normal LM cells and repressed c-fos transcription in a Ras-dependent manner; this effect was not observed in ATM-mutated AT cells, suggesting PKCI functions in the Ras-dependent signal transduction pathway regulating c-fos transcription.","method":"Transfection/overexpression, TUNEL apoptosis assay, CAT reporter assay for c-fos transcription, Western blot for Ras","journal":"International journal of radiation oncology, biology, physics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — overexpression reporter assay, single lab, single method per readout, indirect pathway inference","pmids":["11173133"],"is_preprint":false}],"current_model":"PRKCI (PKCι) is an atypical serine/threonine protein kinase that functions as an oncogene and cell polarity regulator: it phosphorylates substrates including SOX2 (driving Hedgehog/HHAT transcription), GLI1 (activating Hh signaling), Jak2-S633 (activating Jak2/Stat3/VEGFA angiogenic signaling), Tgfbr1 (preventing its proteasomal degradation to amplify TGF-β signaling), and c-Myc-S21 (blocking ubiquitin-mediated degradation); it participates in the PAR3-PAR6-PKCι apical polarity complex required for epithelial organization, cavitation, and organ morphogenesis across vertebrate species; it negatively regulates autophagy via the PIK3CA/AKT-MTOR axis; it interacts with RGSZ1 to modulate mu opioid receptor signaling; and it undergoes density-dependent nucleocytoplasmic shuttling (via exportin-1) to inhibit cytoplasmic PKC and remodel the actin cytoskeleton."},"narrative":{"mechanistic_narrative":"PRKCI (PKCι) is an atypical serine/threonine protein kinase that operates at the intersection of epithelial polarity control and oncogenic signaling [PMID:16319113, PMID:24525231]. As the catalytic core of the PAR3–PAR6(PARD6B)–PKCι apical polarity complex, it is required tissue-autonomously for polarized epithelial organization, with kinase activity essential for myocardial coherence during heart morphogenesis [PMID:16319113] and for asymmetric self-renewing divisions of neural precursors [PMID:19449304]; it supplies non-cell-autonomous polarity cues for ectodermal epithelialization and cavitation [PMID:27312576] and supports AEC2 stem-cell self-proliferation through the same complex [PMID:40001200]. In human disease, PRKCI loss-of-function variants impair periderm differentiation upstream of IRF6, causing a palatogenesis defect [PMID:40902599], and a Prkci allele acts as a genetic modifier of CRB1-associated retinal dysplasia, integrating it into the apicobasal polarity network [PMID:35675330]. As an oncogene, PRKCI is co-amplified with SOX2 and ECT2 at chromosome 3q26 and drives lung squamous carcinoma by phosphorylating SOX2 to activate HHAT-dependent cell-autonomous Hedgehog signaling [PMID:24525231, PMID:31968252], and it phosphorylates and activates GLI1 downstream of Hedgehog [PMID:35785194]. Across colorectal cancer it phosphorylates substrates to stabilize oncogenic effectors and amplify signaling—Tgfbr1 (blocking proteasomal degradation to drive EMT and metastasis) [PMID:40382656], c-Myc at Ser21 (blocking ubiquitin-mediated degradation to promote proliferation) [PMID:41188443], and Jak2 at Ser633 (activating Jak2/Stat3/VEGFA angiogenic signaling) [PMID:40840329]—and it shapes an immunosuppressive microenvironment via TNFα and YAP1 [PMID:28698296]. PRKCI also negatively regulates autophagy through the PIK3CA/AKT–mTOR axis, a function required for pancreatic acinar cell homeostasis [PMID:26792725, PMID:35159064]. A distinct set of findings describe a nuclear, adenosine-polyphosphate-hydrolyzing PKCI/HINT1 protein that homodimerizes, binds RGSZ1 to modulate mu-opioid receptor signaling, and undergoes density-dependent nucleocytoplasmic shuttling [PMID:9770345, PMID:17126529]; these belong to the HINT1 gene product and are noted here for completeness.","teleology":[{"year":1998,"claim":"Early characterization sought to define the basic biochemistry and localization of the PKCI protein, establishing a nuclear homodimer with enzymatic activity against adenosine polyphosphates.","evidence":"Yeast two-hybrid, in vitro enzymatic assay, and immunostaining in epithelial cell lines","pmids":["9770345","8812426"],"confidence":"Medium","gaps":["These findings describe the HINT1/PKCI-1 hydrolase, not the PRKCI kinase, reflecting symbol ambiguity in the corpus","Conflicting nuclear vs cytoskeletal localization across cell types unresolved"]},{"year":2000,"claim":"Whether PKCI-1/HINT1 had protein partners controlling localization was addressed by identifying a Cdk7 interaction independent of kinase activity, with a functional genetic interaction in yeast.","evidence":"Yeast two-hybrid, co-IP, and HNT1/KIN28 genetic epistasis in S. cerevisiae","pmids":["10958787"],"confidence":"Medium","gaps":["Pertains to HINT1, not the PRKCI kinase","Biochemical consequence of the interaction undefined"]},{"year":2005,"claim":"The in vivo developmental requirement for PKCι catalytic activity in epithelial polarity was established by showing tissue-autonomous, kinase-dependent rescue of myocardial coherence in zebrafish.","evidence":"Zebrafish heart and soul mutant with catalytic-dead complementation","pmids":["16319113"],"confidence":"High","gaps":["Direct polarity substrates in myocardium not identified","Relationship to PAR complex assembly not biochemically resolved"]},{"year":2009,"claim":"The role of PKCι in cell-fate decisions was extended by showing its requirement for planar, asymmetric self-renewing divisions of spinal cord precursors.","evidence":"Time-lapse imaging and loss-of-function with cell-fate quantification in zebrafish","pmids":["19449304"],"confidence":"Medium","gaps":["Molecular mechanism linking PKCι to division-plane orientation unknown","Substrates in precursor cells unidentified"]},{"year":2014,"claim":"A cell-autonomous oncogenic Hedgehog axis was uncovered: PKCι phosphorylates SOX2 to drive HHAT-dependent Hh ligand production in lung squamous carcinoma.","evidence":"Co-IP, ChIP, in vitro kinase assay, and functional rescue across cell and tumor models","pmids":["24525231"],"confidence":"High","gaps":["SOX2 phosphosite mapping not detailed","Generality of the axis beyond LSCC untested"]},{"year":2016,"claim":"Two distinct PKCι functions were defined—negative regulation of autophagy via PIK3CA/AKT-mTOR, and provision of non-cell-autonomous polarity cues for epithelialization and cavitation.","evidence":"Gain/loss-of-function with autophagy flux readouts in U2OS cells; Prkci-null ES cell mixing and rescue experiments","pmids":["26792725","27312576"],"confidence":"Medium","gaps":["Identity of the secreted/non-autonomous polarity cue undefined","Direct kinase link to mTOR pathway not established"]},{"year":2017,"claim":"PKCι's oncogenic role was shown to extend to the tumor microenvironment, promoting immune suppression via TNFα and acting through YAP1.","evidence":"Transgenic ovarian cancer mouse model with immune profiling and human tumor correlation","pmids":["28698296"],"confidence":"Medium","gaps":["Direct kinase-substrate link to TNFα/YAP1 not shown","Single lab"]},{"year":2020,"claim":"The genetic basis of PRKCI oncogenicity in LSCC was placed in context: 3q26 co-amplification with SOX2 and ECT2 cooperatively transforms lung basal stem cells.","evidence":"Mouse genetic transformation model with epistasis and gene-signature analysis","pmids":["31968252"],"confidence":"High","gaps":["Mechanistic separation of SOX2 vs ECT2 collaboration partially defined","Contribution of kinase activity per se not isolated"]},{"year":2022,"claim":"The autophagy function was validated in vivo and shown to constrain pancreatic tumorigenesis, while GLI1 was added as a direct activating substrate downstream of Hedgehog.","evidence":"Pancreas-specific Prkci knockout with autophagy markers and Kras epistasis; GLI1 phosphorylation/relocalization assays with xenografts","pmids":["35159064","35785194"],"confidence":"High","gaps":["GLI1 phosphosite not mapped","Mechanism connecting PKCι to autophagic machinery still indirect"]},{"year":2024,"claim":"Additional partners and signaling contexts were reported, including SQSTM1/p62 binding in osteosarcoma linked to Akt/mTOR.","evidence":"Co-IP and knockdown with Akt/mTOR readout in osteosarcoma cells","pmids":["39015499"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation; interaction not independently confirmed","Functional significance of p62 binding unclear"]},{"year":2025,"claim":"A burst of substrate-level studies defined how PKCι amplifies oncogenic signaling—stabilizing Tgfbr1, c-Myc(S21), and activating Jak2(S633)/Stat3/VEGFA—while a human-genetics study placed it upstream of IRF6 in palatogenesis and density-dependent shuttling was characterized.","evidence":"Co-IP/phosphosite mutagenesis/ubiquitination assays with in vivo CRC metastasis models; zebrafish patient-variant complementation with IRF6 rescue; live imaging and exportin-1 inhibition (preprint)","pmids":["40382656","41188443","40840329","40902599","40001200","35675330"],"confidence":"High","gaps":["Whether the multiple CRC substrates are engaged simultaneously or context-dependently is unresolved","The density-dependent shuttling result is from a preprint describing HINT1, distinct from the PRKCI kinase"]},{"year":null,"claim":"A unified model reconciling PKCι's polarity-complex scaffolding function with its diverse oncogenic substrate repertoire, and clarifying which findings belong to PRKCI versus the co-symbolic HINT1 protein, remains to be established.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model integrating PAR-complex binding with substrate selection","Substrate prioritization across tissues unknown","Corpus mixes PRKCI kinase and HINT1 hydrolase findings"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,12,15,16,17]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,3,16,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,13,21]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[10,19]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[9,19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,12,15,17]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[3,4,13,14]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[5,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,2,15,16]}],"complexes":["PAR3-PAR6(PARD6B)-PKCι apical polarity complex"],"partners":["PARD6B","PAR3","RIPK2","SQSTM1","RGSZ1","TGFBR1","JAK2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P41743","full_name":"Protein kinase C iota type","aliases":["Atypical protein kinase C-lambda/iota","PRKC-lambda/iota","aPKC-lambda/iota","nPKC-iota"],"length_aa":596,"mass_kda":68.3,"function":"Calcium- and diacylglycerol-independent serine/ threonine-protein kinase that plays a general protective role against apoptotic stimuli, is involved in NF-kappa-B activation, cell survival, differentiation and polarity, and contributes to the regulation of microtubule dynamics in the early secretory pathway. Is necessary for BCR-ABL oncogene-mediated resistance to apoptotic drug in leukemia cells, protecting leukemia cells against drug-induced apoptosis. In cultured neurons, prevents amyloid beta protein-induced apoptosis by interrupting cell death process at a very early step. In glioblastoma cells, may function downstream of phosphatidylinositol 3-kinase (PI(3)K) and PDPK1 in the promotion of cell survival by phosphorylating and inhibiting the pro-apoptotic factor BAD. Can form a protein complex in non-small cell lung cancer (NSCLC) cells with PARD6A and ECT2 and regulate ECT2 oncogenic activity by phosphorylation, which in turn promotes transformed growth and invasion. In response to nerve growth factor (NGF), acts downstream of SRC to phosphorylate and activate IRAK1, allowing the subsequent activation of NF-kappa-B and neuronal cell survival. Functions in the organization of the apical domain in epithelial cells by phosphorylating EZR. This step is crucial for activation and normal distribution of EZR at the early stages of intestinal epithelial cell differentiation. Forms a protein complex with LLGL1 and PARD6B independently of PARD3 to regulate epithelial cell polarity. Plays a role in microtubule dynamics in the early secretory pathway through interaction with RAB2A and GAPDH and recruitment to vesicular tubular clusters (VTCs). In human coronary artery endothelial cells (HCAEC), is activated by saturated fatty acids and mediates lipid-induced apoptosis. Involved in early synaptic long term potentiation phase in CA1 hippocampal cells and short term memory formation (By similarity)","subcellular_location":"Cytoplasm; Membrane; Endosome; Nucleus","url":"https://www.uniprot.org/uniprotkb/P41743/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PRKCI","classification":"Not Classified","n_dependent_lines":72,"n_total_lines":1208,"dependency_fraction":0.059602649006622516},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000163558","cell_line_id":"CID001247","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"PARD6B","stoichiometry":10.0},{"gene":"LLGL1","stoichiometry":10.0},{"gene":"LLGL2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001247","total_profiled":1310},"omim":[{"mim_id":"616850","title":"WD REPEAT-CONTAINING PROTEIN 83; WDR83","url":"https://www.omim.org/entry/616850"},{"mim_id":"609737","title":"CRUMBS CELL POLARITY COMPLEX COMPONENT 3; CRB3","url":"https://www.omim.org/entry/609737"},{"mim_id":"607484","title":"PAR6 FAMILY CELL POLARITY REGULATOR ALPHA; PARD6A","url":"https://www.omim.org/entry/607484"},{"mim_id":"607032","title":"SMG1 NONSENSE-MEDIATED mRNA DECAY-ASSOCIATED PI3K-RELATED KINASE; SMG1","url":"https://www.omim.org/entry/607032"},{"mim_id":"600539","title":"PROTEIN KINASE C, IOTA FORM; PRKCI","url":"https://www.omim.org/entry/600539"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Microtubules","reliability":"Additional"},{"location":"Cytokinetic bridge","reliability":"Additional"},{"location":"Primary cilium","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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    \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, kinase assay, loss-of-function/overexpression in cell lines and primary tumors\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP, in vitro kinase assay, and functional rescue experiments across multiple models in one rigorous study\",\n      \"pmids\": [\"24525231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRKCI, SOX2, and ECT2 are co-overexpressed via chromosome 3q26 copy number gain; PRKCI and SOX2 collaborate to activate a transcriptional program enforcing a lineage-restricted LSCC phenotype, while PRKCI and ECT2 collaborate to promote oncogenic growth. Overexpression of all three in the context of Trp53 loss is sufficient to transform mouse lung basal stem cells into LSCC-like tumors.\",\n      \"method\": \"Mouse genetic transformation model, gene expression profiling, functional epistasis analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transformation assay with defined genetic components, gene signature analyses, replicated across human and mouse models\",\n      \"pmids\": [\"31968252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PRKCI promotes an immune-suppressive tumor microenvironment in ovarian cancer by upregulating TNFα, which increases myeloid-derived suppressor cells and inhibits cytotoxic T-cell infiltration; YAP1 is identified as a downstream effector of PRKCI in tumor progression.\",\n      \"method\": \"Transgenic mouse model, functional assays, system-level analysis, gene expression correlation in human tumors\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic mouse oncogenesis model combined with immune profiling, single lab, mechanistic pathway placement via multiple readouts\",\n      \"pmids\": [\"28698296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Zebrafish heart and soul (Has)/PRKCi is required tissue-autonomously within the myocardium for polarized epithelial organization and coherence of myocardial cells during heart cone formation; this function depends on its catalytic activity.\",\n      \"method\": \"Zebrafish genetic mutant analysis, tissue-specific rescue experiments, catalytic-dead mutant complementation\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-autonomous rescue in zebrafish with catalytic-dead mutant confirming kinase activity requirement, replicated in vivo context\",\n      \"pmids\": [\"16319113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In zebrafish spinal cord, PrkCi function and planar cell divisions are necessary for asymmetric, self-renewing division of spinal cord precursors; loss of PrkCi causes oblique precursor divisions during late embryogenesis and excess oligodendrocyte production with concomitant loss of dividing cells.\",\n      \"method\": \"Time-lapse imaging of zebrafish, PrkCi loss-of-function analysis, cell fate quantification\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live imaging plus loss-of-function with defined cell-fate phenotype in zebrafish, single lab\",\n      \"pmids\": [\"19449304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PRKCI negatively regulates autophagy via the PIK3CA/AKT-MTOR signaling pathway; PRKCI overexpression impairs autophagic flux (decreased LC3B-II, reduced substrate degradation), while PRKCI knockdown or dominant-negative mutants (L485M, P560R) induce autophagy.\",\n      \"method\": \"Overexpression and siRNA knockdown in U2OS cells, LC3B-II immunoblot, autophagic substrate degradation assays, mutagenesis of PRKCI\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with multiple readouts plus mutagenesis, single lab\",\n      \"pmids\": [\"26792725\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Pancreas-specific ablation of Prkci increases acinar cell DNA damage, apoptosis, and P62 aggregation with loss of autophagic vesicles, indicating that PKCι is required for pancreatic epithelial cell autophagy; Prkci loss promotes Kras-mediated pancreatic intraepithelial neoplasia formation but blocks progression to adenocarcinoma, consistent with disruption of autophagy.\",\n      \"method\": \"Pancreas-specific conditional knockout mice, histopathology, immunofluorescence, autophagy marker analysis\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional knockout with multiple mechanistic readouts and genetic epistasis with Kras oncogene\",\n      \"pmids\": [\"35159064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Hint/PKCI-1 physically interacts with Cdk7 (and the yeast ortholog Hnt1 with Kin28); overexpression of Cdk7 causes partial relocalization of Hint to the nucleus. This interaction is independent of cyclin H binding or Cdk7 kinase activity. Genetic combination of HNT1 disruption and a KIN28 temperature-sensitive allele in S. cerevisiae leads to elongated cell morphology and reduced colony formation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, subcellular localization, yeast genetic epistasis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus yeast two-hybrid plus genetic epistasis, replicated across yeast and mammalian system in same study\",\n      \"pmids\": [\"10958787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PKCI-1 (HINT1) interacts with RGSZ1 as shown by co-immunoprecipitation and immunofluorescence; the RGSZ1-PKCI-1 complex modulates mu opioid receptor signaling—inhibition of cAMP by mu opioid receptor was significantly reduced by RGSZ1, an effect enhanced in combination with PKCI-1. The interaction requires the cysteine string region unique to the RZ subfamily of RGS proteins.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, immunofluorescence, cAMP functional assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, immunofluorescence colocalization, and functional cAMP assay in single lab study\",\n      \"pmids\": [\"17126529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human PKCI (hPKCI) exists as a homodimer and interacts with a murine PKCI homologue in a yeast two-hybrid screen. The protein is expressed mainly in the nucleus of both normal and tumor-derived epithelial cell lines as determined by immunostaining. In vitro, hPKCI enzymatically hydrolyzes adenosine polyphosphates.\",\n      \"method\": \"Yeast two-hybrid, in vitro enzymatic assay, immunostaining/subcellular localization, Northern and Western blot\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzymatic assay plus yeast two-hybrid plus direct immunolocalization, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"9770345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Human PKCI-1 (hPKCI-1) localizes to cytoskeletal structures in the cytoplasm of human fibroblast cell lines as shown by indirect immunofluorescence, and is largely excluded from the nucleus.\",\n      \"method\": \"Indirect immunofluorescence, genomic FISH mapping\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct immunolocalization, single lab; note this contrasts with nuclear localization reported by other studies, suggesting cell-type dependence\",\n      \"pmids\": [\"8812426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PRKCI physically interacts with RIPK2 (co-immunoprecipitation and immunofluorescence) and enhances phosphorylation of downstream NF-κB, JNK, and ERK signaling in pancreatic cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, immunoblotting for phosphorylation\",\n      \"journal\": \"Molecular medicine (Cambridge, Mass.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus immunofluorescence plus downstream phosphorylation readout, single lab\",\n      \"pmids\": [\"37016317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PRKCI functions downstream of the Hedgehog/GLI1 pathway to phosphorylate and activate the transcription factor GLI1; PRKCI modulates radiosensitivity in cervical cancer by regulating GLI1 relocalization and phosphorylation.\",\n      \"method\": \"Western blotting, immunofluorescence, colony formation and apoptosis assays, xenograft model, PRKCI knockdown/overexpression\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional assays with multiple readouts and in vivo validation; phosphorylation shown by Western blot, single lab\",\n      \"pmids\": [\"35785194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Prkci is required to produce non-autonomous polarity cues necessary for forming a polarized ectodermal epithelium and cavitation in embryoid bodies; Prkci-null cells fail to properly segregate apical-basal proteins, form a coordinated ectodermal epithelium, or participate in normal cavitation. Mixing with wildtype cells rescues cavitation in Prkci-null cells, demonstrating the non-cell-autonomous nature of the polarity signal.\",\n      \"method\": \"Prkci-null ES cell analysis, mixing experiments, BMP4/EZRIN rescue, proliferation and apoptosis assays\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null cell analysis plus cell mixing rescue establishes non-autonomous mechanism, single lab with multiple approaches\",\n      \"pmids\": [\"27312576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRKCI variants (including de novo p.Asn383Ser hotspot, p.Arg130His, and p.Leu385Phe) cause loss of function in a zebrafish periderm model; phosphomimetic IRF6 rescues aPKC inhibition, placing PRKCI upstream of IRF6 in the transcriptional regulatory network governing periderm differentiation and palatogenesis.\",\n      \"method\": \"Zebrafish functional complementation assay, patient variant analysis, phosphomimetic IRF6 rescue experiments\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional validation of multiple patient alleles in zebrafish plus epistasis rescue with phosphomimetic IRF6 placing PRKCI in pathway\",\n      \"pmids\": [\"40902599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Prkci phosphorylates and stabilizes Tgfbr1 (TGF-β receptor 1), preventing its proteasomal degradation and amplifying downstream TGF-β signaling to promote epithelial-to-mesenchymal transition and colorectal cancer metastasis; Prkci knockout reduced liver and lung metastases in mouse models.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation assay, proteasomal degradation assay, in vivo xenograft/metastasis model with Prkci knockout\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate phosphorylation and stabilization demonstrated by biochemical assays plus in vivo validation, single lab\",\n      \"pmids\": [\"40382656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Prkci phosphorylates c-Myc at serine 21, inhibiting its ubiquitin-mediated proteasomal degradation and stabilizing the protein; the pro-proliferative effect of Prkci in colorectal cancer is dependent on c-Myc S21 phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation site mutagenesis, ubiquitination assay, in vivo mouse tumor model with Prkci knockout\",\n      \"journal\": \"NPJ precision oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct phosphorylation site identified by mutagenesis plus ubiquitination assay plus in vivo validation, single lab\",\n      \"pmids\": [\"41188443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Prkci activates the Jak2/Stat3 signaling pathway in colorectal cancer by phosphorylating Jak2 at the S633 site, leading to downstream Stat3 activation and increased VEGFA expression, thereby promoting tumor angiogenesis.\",\n      \"method\": \"In vitro endothelial cell proliferation/migration/tube formation assays, Prkci overexpression/knockout, in vivo xenograft model, immunoblotting for phosphorylation\",\n      \"journal\": \"Neoplasia (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific phosphorylation site (Jak2-S633) identified with functional readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"40840329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PRKCI physically interacts with SQSTM1/p62 in osteosarcoma cells (co-immunoprecipitation); knockdown of PRKCI inhibits osteosarcoma cell proliferation by inactivating the Akt/mTOR signaling pathway.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, CCK-8/colony formation/flow cytometry assays, immunoblotting for Akt/mTOR pathway\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP for interaction plus indirect pathway readout, single lab, single study\",\n      \"pmids\": [\"39015499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HINT1/PKCI-1 undergoes nucleocytoplasmic translocation regulated by exportin-1 in a cell-density-dependent manner: at low density it resides in the nucleus binding open chromatin, and as density increases it relocates to the cytoplasm where it inhibits PKC and remodels the actin cytoskeleton from stress fibers to a cortical network, facilitating monolayer maturation.\",\n      \"method\": \"Live cell imaging, subcellular fractionation, exportin-1 inhibition, HINT1 knockout, MARCKS phosphorylation assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization imaging plus functional actin remodeling readout plus exportin-1 mechanism, preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.01.13.632869\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A mutation in Prkci (Tvrm323) acts as a genetic modifier of Crb1-associated retinal dysplasia in mice; epistasis analysis showed the increased dysplastic phenotype required homozygosity of the Crb1rd8 allele, placing Prkci in a pathway with the apicobasal polarity gene CRB1 in retinal tissue maintenance.\",\n      \"method\": \"Chemical mutagenesis screen, exome sequencing, genetic epistasis analysis, immunohistochemistry, electroretinography\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in vivo with clear double-mutant phenotype and histological analysis, single lab\",\n      \"pmids\": [\"35675330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Reduced expression of the PAR3-PARD6B-PRKCI polarity complex in type II alveolar epithelial cells (AEC2s) arrests the cell cycle at G0-G1 phase, impairing AEC2 self-proliferation; co-immunoprecipitation and mass spectrometry confirmed PRKCI as a component of this complex.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, 3D spheroid formation, cell cycle analysis, in vitro smoke-injury model\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS for complex identification plus cell cycle functional readout, single lab\",\n      \"pmids\": [\"40001200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Overexpression of PKCI increased radiation-induced apoptosis in normal LM cells and repressed c-fos transcription in a Ras-dependent manner; this effect was not observed in ATM-mutated AT cells, suggesting PKCI functions in the Ras-dependent signal transduction pathway regulating c-fos transcription.\",\n      \"method\": \"Transfection/overexpression, TUNEL apoptosis assay, CAT reporter assay for c-fos transcription, Western blot for Ras\",\n      \"journal\": \"International journal of radiation oncology, biology, physics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — overexpression reporter assay, single lab, single method per readout, indirect pathway inference\",\n      \"pmids\": [\"11173133\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PRKCI (PKCι) is an atypical serine/threonine protein kinase that functions as an oncogene and cell polarity regulator: it phosphorylates substrates including SOX2 (driving Hedgehog/HHAT transcription), GLI1 (activating Hh signaling), Jak2-S633 (activating Jak2/Stat3/VEGFA angiogenic signaling), Tgfbr1 (preventing its proteasomal degradation to amplify TGF-β signaling), and c-Myc-S21 (blocking ubiquitin-mediated degradation); it participates in the PAR3-PAR6-PKCι apical polarity complex required for epithelial organization, cavitation, and organ morphogenesis across vertebrate species; it negatively regulates autophagy via the PIK3CA/AKT-MTOR axis; it interacts with RGSZ1 to modulate mu opioid receptor signaling; and it undergoes density-dependent nucleocytoplasmic shuttling (via exportin-1) to inhibit cytoplasmic PKC and remodel the actin cytoskeleton.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PRKCI (PKCι) is an atypical serine/threonine protein kinase that operates at the intersection of epithelial polarity control and oncogenic signaling [#3, #0]. As the catalytic core of the PAR3–PAR6(PARD6B)–PKCι apical polarity complex, it is required tissue-autonomously for polarized epithelial organization, with kinase activity essential for myocardial coherence during heart morphogenesis [#3] and for asymmetric self-renewing divisions of neural precursors [#4]; it supplies non-cell-autonomous polarity cues for ectodermal epithelialization and cavitation [#13] and supports AEC2 stem-cell self-proliferation through the same complex [#21]. In human disease, PRKCI loss-of-function variants impair periderm differentiation upstream of IRF6, causing a palatogenesis defect [#14], and a Prkci allele acts as a genetic modifier of CRB1-associated retinal dysplasia, integrating it into the apicobasal polarity network [#20]. As an oncogene, PRKCI is co-amplified with SOX2 and ECT2 at chromosome 3q26 and drives lung squamous carcinoma by phosphorylating SOX2 to activate HHAT-dependent cell-autonomous Hedgehog signaling [#0, #1], and it phosphorylates and activates GLI1 downstream of Hedgehog [#12]. Across colorectal cancer it phosphorylates substrates to stabilize oncogenic effectors and amplify signaling—Tgfbr1 (blocking proteasomal degradation to drive EMT and metastasis) [#15], c-Myc at Ser21 (blocking ubiquitin-mediated degradation to promote proliferation) [#16], and Jak2 at Ser633 (activating Jak2/Stat3/VEGFA angiogenic signaling) [#17]—and it shapes an immunosuppressive microenvironment via TNFα and YAP1 [#2]. PRKCI also negatively regulates autophagy through the PIK3CA/AKT–mTOR axis, a function required for pancreatic acinar cell homeostasis [#5, #6]. A distinct set of findings describe a nuclear, adenosine-polyphosphate-hydrolyzing PKCI/HINT1 protein that homodimerizes, binds RGSZ1 to modulate mu-opioid receptor signaling, and undergoes density-dependent nucleocytoplasmic shuttling [#9, #8]; these belong to the HINT1 gene product and are noted here for completeness.\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Early characterization sought to define the basic biochemistry and localization of the PKCI protein, establishing a nuclear homodimer with enzymatic activity against adenosine polyphosphates.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro enzymatic assay, and immunostaining in epithelial cell lines\",\n      \"pmids\": [\"9770345\", \"8812426\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"These findings describe the HINT1/PKCI-1 hydrolase, not the PRKCI kinase, reflecting symbol ambiguity in the corpus\", \"Conflicting nuclear vs cytoskeletal localization across cell types unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Whether PKCI-1/HINT1 had protein partners controlling localization was addressed by identifying a Cdk7 interaction independent of kinase activity, with a functional genetic interaction in yeast.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, and HNT1/KIN28 genetic epistasis in S. cerevisiae\",\n      \"pmids\": [\"10958787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pertains to HINT1, not the PRKCI kinase\", \"Biochemical consequence of the interaction undefined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The in vivo developmental requirement for PKCι catalytic activity in epithelial polarity was established by showing tissue-autonomous, kinase-dependent rescue of myocardial coherence in zebrafish.\",\n      \"evidence\": \"Zebrafish heart and soul mutant with catalytic-dead complementation\",\n      \"pmids\": [\"16319113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct polarity substrates in myocardium not identified\", \"Relationship to PAR complex assembly not biochemically resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The role of PKCι in cell-fate decisions was extended by showing its requirement for planar, asymmetric self-renewing divisions of spinal cord precursors.\",\n      \"evidence\": \"Time-lapse imaging and loss-of-function with cell-fate quantification in zebrafish\",\n      \"pmids\": [\"19449304\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking PKCι to division-plane orientation unknown\", \"Substrates in precursor cells unidentified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A cell-autonomous oncogenic Hedgehog axis was uncovered: PKCι phosphorylates SOX2 to drive HHAT-dependent Hh ligand production in lung squamous carcinoma.\",\n      \"evidence\": \"Co-IP, ChIP, in vitro kinase assay, and functional rescue across cell and tumor models\",\n      \"pmids\": [\"24525231\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SOX2 phosphosite mapping not detailed\", \"Generality of the axis beyond LSCC untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Two distinct PKCι functions were defined—negative regulation of autophagy via PIK3CA/AKT-mTOR, and provision of non-cell-autonomous polarity cues for epithelialization and cavitation.\",\n      \"evidence\": \"Gain/loss-of-function with autophagy flux readouts in U2OS cells; Prkci-null ES cell mixing and rescue experiments\",\n      \"pmids\": [\"26792725\", \"27312576\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the secreted/non-autonomous polarity cue undefined\", \"Direct kinase link to mTOR pathway not established\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"PKCι's oncogenic role was shown to extend to the tumor microenvironment, promoting immune suppression via TNFα and acting through YAP1.\",\n      \"evidence\": \"Transgenic ovarian cancer mouse model with immune profiling and human tumor correlation\",\n      \"pmids\": [\"28698296\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct kinase-substrate link to TNFα/YAP1 not shown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The genetic basis of PRKCI oncogenicity in LSCC was placed in context: 3q26 co-amplification with SOX2 and ECT2 cooperatively transforms lung basal stem cells.\",\n      \"evidence\": \"Mouse genetic transformation model with epistasis and gene-signature analysis\",\n      \"pmids\": [\"31968252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic separation of SOX2 vs ECT2 collaboration partially defined\", \"Contribution of kinase activity per se not isolated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The autophagy function was validated in vivo and shown to constrain pancreatic tumorigenesis, while GLI1 was added as a direct activating substrate downstream of Hedgehog.\",\n      \"evidence\": \"Pancreas-specific Prkci knockout with autophagy markers and Kras epistasis; GLI1 phosphorylation/relocalization assays with xenografts\",\n      \"pmids\": [\"35159064\", \"35785194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GLI1 phosphosite not mapped\", \"Mechanism connecting PKCι to autophagic machinery still indirect\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Additional partners and signaling contexts were reported, including SQSTM1/p62 binding in osteosarcoma linked to Akt/mTOR.\",\n      \"evidence\": \"Co-IP and knockdown with Akt/mTOR readout in osteosarcoma cells\",\n      \"pmids\": [\"39015499\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation; interaction not independently confirmed\", \"Functional significance of p62 binding unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A burst of substrate-level studies defined how PKCι amplifies oncogenic signaling—stabilizing Tgfbr1, c-Myc(S21), and activating Jak2(S633)/Stat3/VEGFA—while a human-genetics study placed it upstream of IRF6 in palatogenesis and density-dependent shuttling was characterized.\",\n      \"evidence\": \"Co-IP/phosphosite mutagenesis/ubiquitination assays with in vivo CRC metastasis models; zebrafish patient-variant complementation with IRF6 rescue; live imaging and exportin-1 inhibition (preprint)\",\n      \"pmids\": [\"40382656\", \"41188443\", \"40840329\", \"40902599\", \"40001200\", \"35675330\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the multiple CRC substrates are engaged simultaneously or context-dependently is unresolved\", \"The density-dependent shuttling result is from a preprint describing HINT1, distinct from the PRKCI kinase\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified model reconciling PKCι's polarity-complex scaffolding function with its diverse oncogenic substrate repertoire, and clarifying which findings belong to PRKCI versus the co-symbolic HINT1 protein, remains to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model integrating PAR-complex binding with substrate selection\", \"Substrate prioritization across tissues unknown\", \"Corpus mixes PRKCI kinase and HINT1 hydrolase findings\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 12, 15, 16, 17]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 3, 16, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 13, 21]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [10, 19]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [9, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 12, 15, 17]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [3, 4, 13, 14]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 15, 16]}\n    ],\n    \"complexes\": [\"PAR3-PAR6(PARD6B)-PKCι apical polarity complex\"],\n    \"partners\": [\"PARD6B\", \"PAR3\", \"RIPK2\", \"SQSTM1\", \"RGSZ1\", \"TGFBR1\", \"JAK2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}