{"gene":"CDK5R1","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2001,"finding":"Crystal structure of the CDK5-p25 (p35 fragment) complex revealed that p25 activates CDK5 by tethering the unphosphorylated T-loop in the active conformation, an unprecedented mechanism distinct from phospho-CDK2-cyclin A activation. Residue Ser159 (equivalent to Thr160 on CDK2) contributes to CDK5-p35 binding specificity; substitution with threonine prevents p35 binding, while alanine substitution affects neither binding nor kinase activity.","method":"X-ray crystallography of CDK5-p25 complex combined with site-directed mutagenesis (Ser159 substitutions) and kinase activity assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis validation and kinase activity assays in a single rigorous study","pmids":["11583627"],"is_preprint":false},{"year":2001,"finding":"The nuclear protein SET binds the N-terminal region of p35(nck5a) and forms a complex with Cdk5/p35(nck5a). This interaction enhances the activity of the Cdk5/p35(nck5a) complex (but not Cdk5/p25). The acidic tail region of SET is required for the stimulatory effect. SET and p35(nck5a) co-localize in the nucleus when co-transfected, and endogenous SET and Cdk5/p35(nck5a) co-localize in cortical neurons.","method":"Affinity isolation from rat brain homogenates, mass spectrometry identification, Co-IP, co-transfection in COS-7 cells, immunostaining of cortical neurons, kinase activity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal affinity isolation + Co-IP + immunostaining + kinase assay, multiple orthogonal methods in one study","pmids":["11741927"],"is_preprint":false},{"year":2000,"finding":"Cdk5/p25(nck5a) exists in large multimeric complexes in bovine brain: a ~400 kDa complex associated with amphiphysin (which acts as a Cdk5/p25 substrate in this complex) and a >400 kDa complex associated with synapsin I. Separate Cdk5-containing complexes (200 to >400 kDa) exist that are free of p25(nck5a).","method":"Chromatographic fractionation (Mono-S, gel filtration), sequential immunoprecipitation, Western blotting of bovine brain extracts","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple chromatographic and immunochemical methods in one study, single lab","pmids":["10797574"],"is_preprint":false},{"year":1996,"finding":"p35nck5a is a neuron-specific protein expressed in postmitotic neurons (not glial cells) throughout rat brain development. Its temporal expression pattern correlates with Cdk5-associated kinase activity during brain development. In adult brain, p35nck5a is enriched in cell bodies and dendrites, with very low levels in axons; in fetal/neonatal brain it is also detectable in axonal pathways.","method":"Northern blot, immunohistochemistry, in situ hybridization in developing rat brain","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Northern blot, IHC, ISH) with kinase activity correlation, single lab","pmids":["8865202"],"is_preprint":false},{"year":1996,"finding":"In developing rat cerebellum, p35nck5a is always expressed in the cell body throughout development, while Cdk5 translocates from cell body to axon during maturation. Cdk5 kinase activity correlates with p35nck5a expression levels rather than Cdk5 expression levels, indicating p35nck5a is the physiological determinant of Cdk5 activity in immature neurons.","method":"Immunolocalization and kinase activity assays in developing rat cerebellum","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional (kinase activity) correlation, single lab, two methods","pmids":["8896840"],"is_preprint":false},{"year":1996,"finding":"In developing rat cerebellum, Cdk5 is phosphorylated on tyrosine in proliferative stages but not in post-mitotic stages. Cdk5 and p35nck5a are associated even in proliferative stages, but Cdk5-p35 kinase activity is barely detectable in proliferating cells and increases up to 6-fold during neuronal differentiation, suggesting post-translational regulation (tyrosine dephosphorylation of Cdk5) controls kinase activity rather than expression levels.","method":"Immunoprecipitation, kinase activity assays, phosphotyrosine immunoblotting in rat cerebellum","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical assays with phosphorylation state analysis, single lab, multiple methods","pmids":["8939471"],"is_preprint":false},{"year":1997,"finding":"p35nck5a co-localizes with Cdk5 in Lewy bodies in substantia nigra, locus ceruleus, and neocortex of Parkinson's disease brains, supporting involvement of the Cdk5/p35nck5a complex in neurofilament phosphorylation and Lewy body formation.","method":"Immunohistochemistry of postmortem PD brain tissue with co-localization analysis","journal":"Acta neuropathologica","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — immunohistochemical co-localization, multiple brain regions, single lab","pmids":["9255390"],"is_preprint":false},{"year":2000,"finding":"During kindling progression in rat hippocampus, Cdk5/p35(nck5a) kinase activity increases and correlates with p35(nck5a) expression (not Cdk5 expression). Cdk5 translocates from axon to soma when kinase activity is high. Tau phosphorylation levels correlate with Cdk5 kinase activity during kindling, implicating Cdk5/p35 in synaptic reorganization.","method":"Kinase activity assays, Western blot, immunohistochemical subcellular localization, tau phosphorylation analysis in kindling rat hippocampus","journal":"The Japanese journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assays, localization, and phosphorylation correlated in one study, single lab","pmids":["11120919"],"is_preprint":false},{"year":2001,"finding":"p35Nck5a forms a complex with Cdk5 in monocytic cells that has protein kinase activity. Ectopic co-expression of Cdk5 and p35Nck5a in undifferentiated HL60 cells induces expression of CD14 and non-specific esterase, markers of monocytic phenotype, demonstrating a functional role for the Cdk5/p35Nck5a complex in monocytic differentiation.","method":"Co-immunoprecipitation, kinase assays, ectopic co-expression in HL60 cells, monocytic differentiation marker assays","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP kinase assay plus gain-of-function with defined cellular phenotype, single lab","pmids":["11389014"],"is_preprint":false},{"year":2011,"finding":"miR-103 and miR-107 directly interact with a specific target site in the CDK5R1 3'-UTR (validated by luciferase assay), reducing CDK5R1 mRNA and p35 protein levels. miR-107 shifts CDK5R1 transcript from polysomal to subpolysomal fractions, indicating direct suppression of translation efficiency. Overexpression of miR-103/107 or CDK5R1 silencing reduces neuroblastoma cell migration, placing CDK5R1 downstream of these miRNAs in neuronal migration.","method":"Luciferase reporter assay, transfection of miRNA precursors/antagonists, Western blot, polysome profiling, migration assay in SK-N-BE cells","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Moderate — luciferase validation, polysome profiling, and functional migration assay with multiple orthogonal methods in one study","pmids":["21625387"],"is_preprint":false},{"year":2014,"finding":"nELAV and hnRNPA2/B1 RNA-binding proteins bind to the same U-rich element within the C2.1 region of the CDK5R1 3'-UTR and oppositely regulate CDK5R1 mRNA stability and p35 protein levels. nELAV has a positive regulatory effect; hnRNPA2/B1 has a negative/destabilizing effect. hnRNPA2/B1 can downregulate nELAV protein content, and in co-expression, the overall effect is decreased p35.","method":"UV-crosslinking/CLIP, pull-down with mass spectrometry, mRNA stability assays, Western blot, co-expression experiments in neuronal cells","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 / Strong — UV-CLIP + MS identification + functional mRNA stability and protein level assays, multiple orthogonal methods","pmids":["24792867"],"is_preprint":false},{"year":2015,"finding":"The CDK5R1 p.A108V mutation identified in intellectual disability patients impairs p35 cleavage by the calcium-dependent protease calpain, as demonstrated by functional assay. CDK5R1 3'-UTR mutations alter gene expression levels in luciferase reporter assays.","method":"Calpain cleavage assay with mutant p35 (A108V), luciferase reporter assays with 3'-UTR mutations","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical cleavage assay plus luciferase functional assay, single lab, two methods","pmids":["26657932"],"is_preprint":false},{"year":2015,"finding":"Overexpression of Cdk5r1 in primary rat β-cells is sufficient to induce proliferation while maintaining glucose-stimulated insulin secretion, and confers protection against apoptosis induced by etoposide and thapsigargin. Cdk5r1-induced proliferation requires kinase activity (blocked by roscovitine) and results in pRb phosphorylation.","method":"Cdk5r1 overexpression in primary rat β-cells, proliferation assays, kinase inhibitor (roscovitine), pRb phosphorylation Western blot, apoptosis assays, glucose-stimulated insulin secretion assay","journal":"Journal of diabetes research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with defined cellular phenotype and pharmacological inhibition confirming kinase dependence, multiple readouts, single lab","pmids":["26788519"],"is_preprint":false},{"year":2016,"finding":"Multiple members of the miR-15/107 family regulate p35 (CDK5R1) protein levels. Their overexpression reduces APP phosphorylation at Thr668, a CDK5-specific site, linking miR-15/107 family-mediated CDK5R1 regulation to CDK5 substrate phosphorylation. miR-15/107 family members are downregulated in AD hippocampus and temporal cortex, while CDK5R1 mRNA levels are increased in AD hippocampus.","method":"miRNA transfection, Western blot for p35 and phospho-APP (Thr668), qRT-PCR in cell lines and human AD brain tissue","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional overexpression assays with downstream substrate phosphorylation readout, replicated across multiple miRNA family members","pmids":["27343180"],"is_preprint":false},{"year":2023,"finding":"Overexpression of CDK5R1 in Schwann cells promotes proliferation, migration, inhibits apoptosis, and upregulates BDNF and TrkB expression via CDK5. In a rat sciatic nerve crush model, CDK5R1 overexpression promotes functional recovery. The mechanism involves CDK5-mediated activation of BDNF/TrkB signaling.","method":"CDK5R1 overexpression (pcDNA3.1) in Schwann cells, CCK-8, EdU, scratch, flow cytometry assays; Western blot for CDK5/BDNF/TrkB; sciatic nerve injury rat model","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with multiple cellular phenotypes and in vivo model, single lab","pmids":["37848102"],"is_preprint":false},{"year":2023,"finding":"CDK5R1 overexpression in Ewing's sarcoma cells activates CDK5, leading to retinoblastoma protein (Rb) phosphorylation and persistent overexpression of cyclin E (CCNE), driving cell proliferation. miR-152, which directly targets CDK5R1, suppresses this proliferative pathway.","method":"Microarray, CDK5R1 overexpression in ES cell lines, Western blot for CDK5 activity/pRb/CCNE, miR-152 overexpression with tumor xenograft assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with defined molecular mechanism (pRb, CCNE), in vitro and in vivo validation, single lab","pmids":["37899376"],"is_preprint":false}],"current_model":"CDK5R1 encodes p35, the primary activator of CDK5 kinase, which binds CDK5 and tethers its unphosphorylated T-loop in the active conformation (via the p25 fragment); in neurons p35 is localized to cell bodies and its expression level is the principal determinant of CDK5 activity, enabling phosphorylation of substrates such as tau, neurofilament proteins, pRb, and APP-Thr668. p35 levels are tightly regulated post-transcriptionally by RNA-binding proteins (nELAV, hnRNPA2/B1) and multiple miRNAs (miR-103/107, miR-15/107 family, miR-152) acting on its large 3'-UTR, and p35 can be proteolytically cleaved by calpain (a process disrupted by the A108V mutation). The Cdk5/p35 complex also interacts with the nuclear protein SET (which enhances its activity) and exists in high-molecular-weight complexes with amphiphysin and synapsin I at synapses, and functions beyond neurons to drive monocytic differentiation, β-cell proliferation, and Schwann cell growth via a CDK5-BDNF/TrkB axis."},"narrative":{"mechanistic_narrative":"CDK5R1 encodes p35 (p35nck5a), the neuron-specific activating subunit of CDK5 kinase, and is the principal physiological determinant of CDK5 activity: kinase activity tracks p35 expression levels rather than CDK5 levels during neuronal development and in plastic states such as kindling [PMID:8865202, PMID:8896840, PMID:11120919]. Structurally, the p35-derived p25 fragment activates CDK5 by tethering its unphosphorylated T-loop in the active conformation, an activation mechanism distinct from phospho-cyclin/CDK pairs, with residue Ser159 conferring binding specificity [PMID:11583627]. The Cdk5/p35 complex assembles into high-molecular-weight multimeric complexes with amphiphysin (a substrate) and synapsin I in brain, and is further stimulated by the nuclear protein SET, which binds the N-terminal region of p35 via its acidic tail [PMID:11741927, PMID:10797574]. p35 abundance is set post-transcriptionally through its long 3'-UTR, which is bound by competing RNA-binding proteins nELAV (stabilizing) and hnRNPA2/B1 (destabilizing) at a shared U-rich element, and is targeted by multiple miRNAs including miR-103/107, the miR-15/107 family, and miR-152 [PMID:21625387, PMID:24792867, PMID:27343180]. Through CDK5 activation, p35 drives substrate phosphorylation including pRb, APP-Thr668, and tau, coupling its levels to neuronal migration, proliferation, and disease states [PMID:21625387, PMID:27343180, PMID:37899376]. Beyond neurons, CDK5R1 gain-of-function drives monocytic differentiation, β-cell proliferation with apoptosis protection, and Schwann cell proliferation via a CDK5-BDNF/TrkB axis [PMID:11389014, PMID:26788519, PMID:37848102]. A CDK5R1 p.A108V mutation in intellectual disability impairs calpain-dependent cleavage of p35 [PMID:26657932].","teleology":[{"year":1996,"claim":"Established that p35 is a neuron-specific protein whose expression, not CDK5 expression, sets CDK5 kinase activity, defining CDK5R1 as the physiological rate-limiting activator in neurons.","evidence":"Northern blot, IHC, in situ hybridization, immunolocalization and kinase assays in developing rat brain and cerebellum","pmids":["8865202","8896840"],"confidence":"Medium","gaps":["Did not resolve the structural basis of activation","Correlation between p35 level and activity does not establish exclusivity over other regulatory inputs"]},{"year":1996,"claim":"Identified an additional post-translational layer of regulation: tyrosine phosphorylation state of CDK5 gates kinase activity of the assembled Cdk5/p35 complex even when the two proteins are bound.","evidence":"Immunoprecipitation, kinase assays, phosphotyrosine immunoblotting in rat cerebellum","pmids":["8939471"],"confidence":"Medium","gaps":["Identity of the tyrosine kinase/phosphatase not established","Relationship between this regulation and developmental p35 level changes unclear"]},{"year":2000,"claim":"Showed the Cdk5/p35 complex is not free but embedded in large multimeric assemblies with synaptic proteins, linking it to synaptic machinery.","evidence":"Chromatographic fractionation, sequential immunoprecipitation, Western blotting of bovine brain extracts","pmids":["10797574"],"confidence":"Medium","gaps":["Stoichiometry and functional consequence of amphiphysin/synapsin association not defined","Whether p35-free Cdk5 complexes have distinct functions unknown"]},{"year":2001,"claim":"Defined the structural mechanism of CDK5 activation by p35, showing p25 tethers the unphosphorylated T-loop active and identifying Ser159 as a specificity determinant.","evidence":"X-ray crystallography of CDK5-p25 with site-directed mutagenesis and kinase assays","pmids":["11583627"],"confidence":"High","gaps":["Structure used the p25 fragment, not full-length p35","Does not address regulation by accessory proteins or phosphorylation in cells"]},{"year":2001,"claim":"Identified SET as a direct N-terminal binding partner that enhances Cdk5/p35 activity, revealing a positive protein regulator specific to the p35 (not p25) complex.","evidence":"Affinity isolation, MS, Co-IP, co-transfection in COS-7, neuronal immunostaining, kinase assays","pmids":["11741927"],"confidence":"High","gaps":["Mechanism by which SET's acidic tail stimulates activity not resolved","Physiological contexts requiring SET unclear"]},{"year":2001,"claim":"Extended CDK5R1 function beyond neurons by showing the Cdk5/p35 complex is sufficient to drive monocytic differentiation.","evidence":"Co-IP, kinase assays, ectopic co-expression in HL60 cells with differentiation marker readouts","pmids":["11389014"],"confidence":"Medium","gaps":["Endogenous role in monocyte biology not established","Relevant CDK5 substrates in differentiation not identified"]},{"year":2011,"claim":"Established direct miRNA control of p35 via the 3'-UTR, with miR-103/107 suppressing translation and CDK5R1 acting downstream to control neuronal migration.","evidence":"Luciferase reporter, miRNA precursor/antagonist transfection, polysome profiling, migration assay in SK-N-BE cells","pmids":["21625387"],"confidence":"High","gaps":["In vivo relevance to brain development not tested","Whether migration effect is fully CDK5-dependent not formally isolated"]},{"year":2014,"claim":"Defined a competing RNA-binding protein switch (nELAV stabilizing, hnRNPA2/B1 destabilizing) acting on a shared U-rich 3'-UTR element to set p35 levels.","evidence":"UV-CLIP, pull-down/MS, mRNA stability assays, Western blot, co-expression in neuronal cells","pmids":["24792867"],"confidence":"High","gaps":["Signals controlling the nELAV/hnRNPA2/B1 balance unknown","Interplay with miRNA regulation on the same UTR not resolved"]},{"year":2015,"claim":"Linked CDK5R1 directly to human disease, showing a p.A108V mutation in intellectual disability impairs calpain cleavage of p35 and 3'-UTR variants alter expression.","evidence":"Calpain cleavage assay with mutant p35, luciferase reporter assays with 3'-UTR mutations","pmids":["26657932"],"confidence":"Medium","gaps":["Consequence of impaired cleavage for CDK5 activity in neurons not measured","Causality at the patient level not established by these biochemical assays alone"]},{"year":2016,"claim":"Connected miR-15/107 family regulation of p35 to a specific CDK5 substrate event (APP-Thr668) and to Alzheimer's disease, where these miRNAs fall and CDK5R1 mRNA rises.","evidence":"miRNA transfection, Western blot for p35 and phospho-APP-Thr668, qRT-PCR in cell lines and human AD brain","pmids":["27343180"],"confidence":"Medium","gaps":["Causal contribution to AD pathology not demonstrated","Whether UTR-level changes drive the observed AD mRNA increase unknown"]},{"year":2023,"claim":"Demonstrated CDK5R1 drives proliferative programs in non-neuronal cells, via CDK5-mediated pRb phosphorylation/cyclin E in sarcoma and a BDNF/TrkB axis in Schwann cells, with miR-152 as a direct upstream suppressor.","evidence":"CDK5R1 overexpression in Ewing's sarcoma and Schwann cells, Western blot for CDK5/pRb/CCNE/BDNF/TrkB, miR-152 overexpression, xenograft and sciatic nerve crush models","pmids":["37899376","37848102"],"confidence":"Medium","gaps":["Endogenous requirement (loss-of-function) not tested in these contexts","Direct CDK5 substrates mediating BDNF/TrkB upregulation not identified"]},{"year":null,"claim":"How the converging post-transcriptional inputs (competing RBPs, multiple miRNA families) and post-translational events (calpain cleavage, CDK5 tyrosine phosphorylation) are integrated in vivo to set p35 levels and direct substrate selection remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No in vivo loss-of-function dissection of the UTR regulatory network","Substrate selectivity rules of activated CDK5 across tissues not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3,4]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,8,12,15]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,4]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,4,7,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[8,9,14]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[9,10,13]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[12,15]}],"complexes":["Cdk5/p35 kinase complex"],"partners":["CDK5","SET","AMPHIPHYSIN","SYNAPSIN I","HNRNPA2B1","ELAVL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q15078","full_name":"Cyclin-dependent kinase 5 activator 1","aliases":["Cyclin-dependent kinase 5 regulatory subunit 1","TPKII regulatory subunit"],"length_aa":307,"mass_kda":34.1,"function":"p35 is a neuron specific activator of CDK5. The complex p35/CDK5 is required for neurite outgrowth and cortical lamination. Involved in dendritic spine morphogenesis by mediating the EFNA1-EPHA4 signaling. Activator of TPKII. The complex p35/CDK5 participates in the regulation of the circadian clock by modulating the function of CLOCK protein: phosphorylates CLOCK at 'Thr-451' and 'Thr-461' and regulates the transcriptional activity of the CLOCK-BMAL1 heterodimer in association with altered stability and subcellular distribution","subcellular_location":"Nucleus; Cytoplasm, perinuclear region; Perikaryon","url":"https://www.uniprot.org/uniprotkb/Q15078/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CDK5R1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CDK5R1","total_profiled":1310},"omim":[{"mim_id":"621025","title":"RAB3A-INTERACTING PROTEIN-LIKE 1; RAB3IL1","url":"https://www.omim.org/entry/621025"},{"mim_id":"619771","title":"VRK SERINE/THREONINE KINASE 3; VRK3","url":"https://www.omim.org/entry/619771"},{"mim_id":"613675","title":"CHROMOSOME 17q11.2 DELETION SYNDROME, 1.4-MB","url":"https://www.omim.org/entry/613675"},{"mim_id":"610004","title":"COLLAGEN, TYPE XXV, ALPHA-1; COL25A1","url":"https://www.omim.org/entry/610004"},{"mim_id":"609194","title":"CDK5 AND ABL ENZYME SUBSTRATE 1; CABLES1","url":"https://www.omim.org/entry/609194"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":71.3}],"url":"https://www.proteinatlas.org/search/CDK5R1"},"hgnc":{"alias_symbol":["p35nck5a","Nck5a","p35"],"prev_symbol":[]},"alphafold":{"accession":"Q15078","domains":[{"cath_id":"1.10.472.10","chopping":"147-303","consensus_level":"high","plddt":95.4513,"start":147,"end":303}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15078","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15078-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15078-F1-predicted_aligned_error_v6.png","plddt_mean":72.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CDK5R1","jax_strain_url":"https://www.jax.org/strain/search?query=CDK5R1"},"sequence":{"accession":"Q15078","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15078.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15078/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15078"}},"corpus_meta":[{"pmid":"11583627","id":"PMC_11583627","title":"Structure and regulation of the CDK5-p25(nck5a) complex.","date":"2001","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11583627","citation_count":232,"is_preprint":false},{"pmid":"21625387","id":"PMC_21625387","title":"The role of miR-103 and miR-107 in regulation of CDK5R1 expression and in cellular migration.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21625387","citation_count":87,"is_preprint":false},{"pmid":"27343180","id":"PMC_27343180","title":"The miR-15/107 Family of microRNA Genes Regulates CDK5R1/p35 with Implications for Alzheimer's Disease Pathogenesis.","date":"2016","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/27343180","citation_count":79,"is_preprint":false},{"pmid":"9255390","id":"PMC_9255390","title":"p35nck5a and cyclin-dependent kinase 5 colocalize in Lewy bodies of brains with Parkinson's disease.","date":"1997","source":"Acta neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/9255390","citation_count":71,"is_preprint":false},{"pmid":"29997370","id":"PMC_29997370","title":"Multiple Layers of CDK5R1 Regulation in Alzheimer's Disease Implicate Long Non-Coding RNAs.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29997370","citation_count":68,"is_preprint":false},{"pmid":"11741927","id":"PMC_11741927","title":"The protein SET binds the neuronal Cdk5 activator p35nck5a and modulates Cdk5/p35nck5a activity.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11741927","citation_count":56,"is_preprint":false},{"pmid":"10797574","id":"PMC_10797574","title":"Cdk5/p25(nck5a) interaction with synaptic proteins in bovine brain.","date":"2000","source":"Journal of cellular 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letters","url":"https://pubmed.ncbi.nlm.nih.gov/37848102","citation_count":4,"is_preprint":false},{"pmid":"30733659","id":"PMC_30733659","title":"An Interstitial 17q11.2 de novo Deletion Involving the CDK5R1 Gene in a High-Functioning Autistic Patient.","date":"2018","source":"Molecular syndromology","url":"https://pubmed.ncbi.nlm.nih.gov/30733659","citation_count":4,"is_preprint":false},{"pmid":"36847717","id":"PMC_36847717","title":"LncRNA HAGLR promotes the proliferation, migration, and neurotrophic factor production of Schwann cells via miR-204/CDK5R1 after sciatic nerve injury.","date":"2023","source":"Journal of neuropathology and experimental neurology","url":"https://pubmed.ncbi.nlm.nih.gov/36847717","citation_count":3,"is_preprint":false},{"pmid":"19544209","id":"PMC_19544209","title":"Cloning and spatio-temporal expression of porcine CDK5 and CDK5R1(p35) genes.","date":"2009","source":"Animal 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Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/11055117","citation_count":0,"is_preprint":false},{"pmid":"40932634","id":"PMC_40932634","title":"Precision Targeting in Gastric Cancer: AI-Driven Discovery of MET, ADORA2A, CDK5R1, and ADORA1.","date":"2025","source":"Assay and drug development technologies","url":"https://pubmed.ncbi.nlm.nih.gov/40932634","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.03.24309763","title":"Analysis of variants in untranslated and promoter regions and breast cancer risk using whole genome sequencing data","date":"2024-07-05","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.03.24309763","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17653,"output_tokens":4369,"usd":0.059247,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12134,"output_tokens":3838,"usd":0.07831,"stage2_stop_reason":"end_turn"},"total_usd":0.137557,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"Crystal structure of the CDK5-p25 (p35 fragment) complex revealed that p25 activates CDK5 by tethering the unphosphorylated T-loop in the active conformation, an unprecedented mechanism distinct from phospho-CDK2-cyclin A activation. Residue Ser159 (equivalent to Thr160 on CDK2) contributes to CDK5-p35 binding specificity; substitution with threonine prevents p35 binding, while alanine substitution affects neither binding nor kinase activity.\",\n      \"method\": \"X-ray crystallography of CDK5-p25 complex combined with site-directed mutagenesis (Ser159 substitutions) and kinase activity assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis validation and kinase activity assays in a single rigorous study\",\n      \"pmids\": [\"11583627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The nuclear protein SET binds the N-terminal region of p35(nck5a) and forms a complex with Cdk5/p35(nck5a). This interaction enhances the activity of the Cdk5/p35(nck5a) complex (but not Cdk5/p25). The acidic tail region of SET is required for the stimulatory effect. SET and p35(nck5a) co-localize in the nucleus when co-transfected, and endogenous SET and Cdk5/p35(nck5a) co-localize in cortical neurons.\",\n      \"method\": \"Affinity isolation from rat brain homogenates, mass spectrometry identification, Co-IP, co-transfection in COS-7 cells, immunostaining of cortical neurons, kinase activity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal affinity isolation + Co-IP + immunostaining + kinase assay, multiple orthogonal methods in one study\",\n      \"pmids\": [\"11741927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Cdk5/p25(nck5a) exists in large multimeric complexes in bovine brain: a ~400 kDa complex associated with amphiphysin (which acts as a Cdk5/p25 substrate in this complex) and a >400 kDa complex associated with synapsin I. Separate Cdk5-containing complexes (200 to >400 kDa) exist that are free of p25(nck5a).\",\n      \"method\": \"Chromatographic fractionation (Mono-S, gel filtration), sequential immunoprecipitation, Western blotting of bovine brain extracts\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple chromatographic and immunochemical methods in one study, single lab\",\n      \"pmids\": [\"10797574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"p35nck5a is a neuron-specific protein expressed in postmitotic neurons (not glial cells) throughout rat brain development. Its temporal expression pattern correlates with Cdk5-associated kinase activity during brain development. In adult brain, p35nck5a is enriched in cell bodies and dendrites, with very low levels in axons; in fetal/neonatal brain it is also detectable in axonal pathways.\",\n      \"method\": \"Northern blot, immunohistochemistry, in situ hybridization in developing rat brain\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Northern blot, IHC, ISH) with kinase activity correlation, single lab\",\n      \"pmids\": [\"8865202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"In developing rat cerebellum, p35nck5a is always expressed in the cell body throughout development, while Cdk5 translocates from cell body to axon during maturation. Cdk5 kinase activity correlates with p35nck5a expression levels rather than Cdk5 expression levels, indicating p35nck5a is the physiological determinant of Cdk5 activity in immature neurons.\",\n      \"method\": \"Immunolocalization and kinase activity assays in developing rat cerebellum\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional (kinase activity) correlation, single lab, two methods\",\n      \"pmids\": [\"8896840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"In developing rat cerebellum, Cdk5 is phosphorylated on tyrosine in proliferative stages but not in post-mitotic stages. Cdk5 and p35nck5a are associated even in proliferative stages, but Cdk5-p35 kinase activity is barely detectable in proliferating cells and increases up to 6-fold during neuronal differentiation, suggesting post-translational regulation (tyrosine dephosphorylation of Cdk5) controls kinase activity rather than expression levels.\",\n      \"method\": \"Immunoprecipitation, kinase activity assays, phosphotyrosine immunoblotting in rat cerebellum\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical assays with phosphorylation state analysis, single lab, multiple methods\",\n      \"pmids\": [\"8939471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"p35nck5a co-localizes with Cdk5 in Lewy bodies in substantia nigra, locus ceruleus, and neocortex of Parkinson's disease brains, supporting involvement of the Cdk5/p35nck5a complex in neurofilament phosphorylation and Lewy body formation.\",\n      \"method\": \"Immunohistochemistry of postmortem PD brain tissue with co-localization analysis\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — immunohistochemical co-localization, multiple brain regions, single lab\",\n      \"pmids\": [\"9255390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"During kindling progression in rat hippocampus, Cdk5/p35(nck5a) kinase activity increases and correlates with p35(nck5a) expression (not Cdk5 expression). Cdk5 translocates from axon to soma when kinase activity is high. Tau phosphorylation levels correlate with Cdk5 kinase activity during kindling, implicating Cdk5/p35 in synaptic reorganization.\",\n      \"method\": \"Kinase activity assays, Western blot, immunohistochemical subcellular localization, tau phosphorylation analysis in kindling rat hippocampus\",\n      \"journal\": \"The Japanese journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assays, localization, and phosphorylation correlated in one study, single lab\",\n      \"pmids\": [\"11120919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"p35Nck5a forms a complex with Cdk5 in monocytic cells that has protein kinase activity. Ectopic co-expression of Cdk5 and p35Nck5a in undifferentiated HL60 cells induces expression of CD14 and non-specific esterase, markers of monocytic phenotype, demonstrating a functional role for the Cdk5/p35Nck5a complex in monocytic differentiation.\",\n      \"method\": \"Co-immunoprecipitation, kinase assays, ectopic co-expression in HL60 cells, monocytic differentiation marker assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP kinase assay plus gain-of-function with defined cellular phenotype, single lab\",\n      \"pmids\": [\"11389014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"miR-103 and miR-107 directly interact with a specific target site in the CDK5R1 3'-UTR (validated by luciferase assay), reducing CDK5R1 mRNA and p35 protein levels. miR-107 shifts CDK5R1 transcript from polysomal to subpolysomal fractions, indicating direct suppression of translation efficiency. Overexpression of miR-103/107 or CDK5R1 silencing reduces neuroblastoma cell migration, placing CDK5R1 downstream of these miRNAs in neuronal migration.\",\n      \"method\": \"Luciferase reporter assay, transfection of miRNA precursors/antagonists, Western blot, polysome profiling, migration assay in SK-N-BE cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase validation, polysome profiling, and functional migration assay with multiple orthogonal methods in one study\",\n      \"pmids\": [\"21625387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"nELAV and hnRNPA2/B1 RNA-binding proteins bind to the same U-rich element within the C2.1 region of the CDK5R1 3'-UTR and oppositely regulate CDK5R1 mRNA stability and p35 protein levels. nELAV has a positive regulatory effect; hnRNPA2/B1 has a negative/destabilizing effect. hnRNPA2/B1 can downregulate nELAV protein content, and in co-expression, the overall effect is decreased p35.\",\n      \"method\": \"UV-crosslinking/CLIP, pull-down with mass spectrometry, mRNA stability assays, Western blot, co-expression experiments in neuronal cells\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — UV-CLIP + MS identification + functional mRNA stability and protein level assays, multiple orthogonal methods\",\n      \"pmids\": [\"24792867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The CDK5R1 p.A108V mutation identified in intellectual disability patients impairs p35 cleavage by the calcium-dependent protease calpain, as demonstrated by functional assay. CDK5R1 3'-UTR mutations alter gene expression levels in luciferase reporter assays.\",\n      \"method\": \"Calpain cleavage assay with mutant p35 (A108V), luciferase reporter assays with 3'-UTR mutations\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical cleavage assay plus luciferase functional assay, single lab, two methods\",\n      \"pmids\": [\"26657932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Overexpression of Cdk5r1 in primary rat β-cells is sufficient to induce proliferation while maintaining glucose-stimulated insulin secretion, and confers protection against apoptosis induced by etoposide and thapsigargin. Cdk5r1-induced proliferation requires kinase activity (blocked by roscovitine) and results in pRb phosphorylation.\",\n      \"method\": \"Cdk5r1 overexpression in primary rat β-cells, proliferation assays, kinase inhibitor (roscovitine), pRb phosphorylation Western blot, apoptosis assays, glucose-stimulated insulin secretion assay\",\n      \"journal\": \"Journal of diabetes research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with defined cellular phenotype and pharmacological inhibition confirming kinase dependence, multiple readouts, single lab\",\n      \"pmids\": [\"26788519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Multiple members of the miR-15/107 family regulate p35 (CDK5R1) protein levels. Their overexpression reduces APP phosphorylation at Thr668, a CDK5-specific site, linking miR-15/107 family-mediated CDK5R1 regulation to CDK5 substrate phosphorylation. miR-15/107 family members are downregulated in AD hippocampus and temporal cortex, while CDK5R1 mRNA levels are increased in AD hippocampus.\",\n      \"method\": \"miRNA transfection, Western blot for p35 and phospho-APP (Thr668), qRT-PCR in cell lines and human AD brain tissue\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional overexpression assays with downstream substrate phosphorylation readout, replicated across multiple miRNA family members\",\n      \"pmids\": [\"27343180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Overexpression of CDK5R1 in Schwann cells promotes proliferation, migration, inhibits apoptosis, and upregulates BDNF and TrkB expression via CDK5. In a rat sciatic nerve crush model, CDK5R1 overexpression promotes functional recovery. The mechanism involves CDK5-mediated activation of BDNF/TrkB signaling.\",\n      \"method\": \"CDK5R1 overexpression (pcDNA3.1) in Schwann cells, CCK-8, EdU, scratch, flow cytometry assays; Western blot for CDK5/BDNF/TrkB; sciatic nerve injury rat model\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with multiple cellular phenotypes and in vivo model, single lab\",\n      \"pmids\": [\"37848102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CDK5R1 overexpression in Ewing's sarcoma cells activates CDK5, leading to retinoblastoma protein (Rb) phosphorylation and persistent overexpression of cyclin E (CCNE), driving cell proliferation. miR-152, which directly targets CDK5R1, suppresses this proliferative pathway.\",\n      \"method\": \"Microarray, CDK5R1 overexpression in ES cell lines, Western blot for CDK5 activity/pRb/CCNE, miR-152 overexpression with tumor xenograft assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with defined molecular mechanism (pRb, CCNE), in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"37899376\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CDK5R1 encodes p35, the primary activator of CDK5 kinase, which binds CDK5 and tethers its unphosphorylated T-loop in the active conformation (via the p25 fragment); in neurons p35 is localized to cell bodies and its expression level is the principal determinant of CDK5 activity, enabling phosphorylation of substrates such as tau, neurofilament proteins, pRb, and APP-Thr668. p35 levels are tightly regulated post-transcriptionally by RNA-binding proteins (nELAV, hnRNPA2/B1) and multiple miRNAs (miR-103/107, miR-15/107 family, miR-152) acting on its large 3'-UTR, and p35 can be proteolytically cleaved by calpain (a process disrupted by the A108V mutation). The Cdk5/p35 complex also interacts with the nuclear protein SET (which enhances its activity) and exists in high-molecular-weight complexes with amphiphysin and synapsin I at synapses, and functions beyond neurons to drive monocytic differentiation, β-cell proliferation, and Schwann cell growth via a CDK5-BDNF/TrkB axis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CDK5R1 encodes p35 (p35nck5a), the neuron-specific activating subunit of CDK5 kinase, and is the principal physiological determinant of CDK5 activity: kinase activity tracks p35 expression levels rather than CDK5 levels during neuronal development and in plastic states such as kindling [#3, #4, #7]. Structurally, the p35-derived p25 fragment activates CDK5 by tethering its unphosphorylated T-loop in the active conformation, an activation mechanism distinct from phospho-cyclin/CDK pairs, with residue Ser159 conferring binding specificity [#0]. The Cdk5/p35 complex assembles into high-molecular-weight multimeric complexes with amphiphysin (a substrate) and synapsin I in brain, and is further stimulated by the nuclear protein SET, which binds the N-terminal region of p35 via its acidic tail [#1, #2]. p35 abundance is set post-transcriptionally through its long 3'-UTR, which is bound by competing RNA-binding proteins nELAV (stabilizing) and hnRNPA2/B1 (destabilizing) at a shared U-rich element, and is targeted by multiple miRNAs including miR-103/107, the miR-15/107 family, and miR-152 [#9, #10, #13]. Through CDK5 activation, p35 drives substrate phosphorylation including pRb, APP-Thr668, and tau, coupling its levels to neuronal migration, proliferation, and disease states [#9, #13, #15]. Beyond neurons, CDK5R1 gain-of-function drives monocytic differentiation, \\u03b2-cell proliferation with apoptosis protection, and Schwann cell proliferation via a CDK5-BDNF/TrkB axis [#8, #12, #14]. A CDK5R1 p.A108V mutation in intellectual disability impairs calpain-dependent cleavage of p35 [#11].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that p35 is a neuron-specific protein whose expression, not CDK5 expression, sets CDK5 kinase activity, defining CDK5R1 as the physiological rate-limiting activator in neurons.\",\n      \"evidence\": \"Northern blot, IHC, in situ hybridization, immunolocalization and kinase assays in developing rat brain and cerebellum\",\n      \"pmids\": [\"8865202\", \"8896840\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not resolve the structural basis of activation\", \"Correlation between p35 level and activity does not establish exclusivity over other regulatory inputs\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Identified an additional post-translational layer of regulation: tyrosine phosphorylation state of CDK5 gates kinase activity of the assembled Cdk5/p35 complex even when the two proteins are bound.\",\n      \"evidence\": \"Immunoprecipitation, kinase assays, phosphotyrosine immunoblotting in rat cerebellum\",\n      \"pmids\": [\"8939471\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the tyrosine kinase/phosphatase not established\", \"Relationship between this regulation and developmental p35 level changes unclear\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed the Cdk5/p35 complex is not free but embedded in large multimeric assemblies with synaptic proteins, linking it to synaptic machinery.\",\n      \"evidence\": \"Chromatographic fractionation, sequential immunoprecipitation, Western blotting of bovine brain extracts\",\n      \"pmids\": [\"10797574\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and functional consequence of amphiphysin/synapsin association not defined\", \"Whether p35-free Cdk5 complexes have distinct functions unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the structural mechanism of CDK5 activation by p35, showing p25 tethers the unphosphorylated T-loop active and identifying Ser159 as a specificity determinant.\",\n      \"evidence\": \"X-ray crystallography of CDK5-p25 with site-directed mutagenesis and kinase assays\",\n      \"pmids\": [\"11583627\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure used the p25 fragment, not full-length p35\", \"Does not address regulation by accessory proteins or phosphorylation in cells\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified SET as a direct N-terminal binding partner that enhances Cdk5/p35 activity, revealing a positive protein regulator specific to the p35 (not p25) complex.\",\n      \"evidence\": \"Affinity isolation, MS, Co-IP, co-transfection in COS-7, neuronal immunostaining, kinase assays\",\n      \"pmids\": [\"11741927\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which SET's acidic tail stimulates activity not resolved\", \"Physiological contexts requiring SET unclear\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Extended CDK5R1 function beyond neurons by showing the Cdk5/p35 complex is sufficient to drive monocytic differentiation.\",\n      \"evidence\": \"Co-IP, kinase assays, ectopic co-expression in HL60 cells with differentiation marker readouts\",\n      \"pmids\": [\"11389014\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous role in monocyte biology not established\", \"Relevant CDK5 substrates in differentiation not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established direct miRNA control of p35 via the 3'-UTR, with miR-103/107 suppressing translation and CDK5R1 acting downstream to control neuronal migration.\",\n      \"evidence\": \"Luciferase reporter, miRNA precursor/antagonist transfection, polysome profiling, migration assay in SK-N-BE cells\",\n      \"pmids\": [\"21625387\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance to brain development not tested\", \"Whether migration effect is fully CDK5-dependent not formally isolated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined a competing RNA-binding protein switch (nELAV stabilizing, hnRNPA2/B1 destabilizing) acting on a shared U-rich 3'-UTR element to set p35 levels.\",\n      \"evidence\": \"UV-CLIP, pull-down/MS, mRNA stability assays, Western blot, co-expression in neuronal cells\",\n      \"pmids\": [\"24792867\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals controlling the nELAV/hnRNPA2/B1 balance unknown\", \"Interplay with miRNA regulation on the same UTR not resolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked CDK5R1 directly to human disease, showing a p.A108V mutation in intellectual disability impairs calpain cleavage of p35 and 3'-UTR variants alter expression.\",\n      \"evidence\": \"Calpain cleavage assay with mutant p35, luciferase reporter assays with 3'-UTR mutations\",\n      \"pmids\": [\"26657932\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Consequence of impaired cleavage for CDK5 activity in neurons not measured\", \"Causality at the patient level not established by these biochemical assays alone\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected miR-15/107 family regulation of p35 to a specific CDK5 substrate event (APP-Thr668) and to Alzheimer's disease, where these miRNAs fall and CDK5R1 mRNA rises.\",\n      \"evidence\": \"miRNA transfection, Western blot for p35 and phospho-APP-Thr668, qRT-PCR in cell lines and human AD brain\",\n      \"pmids\": [\"27343180\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution to AD pathology not demonstrated\", \"Whether UTR-level changes drive the observed AD mRNA increase unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated CDK5R1 drives proliferative programs in non-neuronal cells, via CDK5-mediated pRb phosphorylation/cyclin E in sarcoma and a BDNF/TrkB axis in Schwann cells, with miR-152 as a direct upstream suppressor.\",\n      \"evidence\": \"CDK5R1 overexpression in Ewing's sarcoma and Schwann cells, Western blot for CDK5/pRb/CCNE/BDNF/TrkB, miR-152 overexpression, xenograft and sciatic nerve crush models\",\n      \"pmids\": [\"37899376\", \"37848102\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous requirement (loss-of-function) not tested in these contexts\", \"Direct CDK5 substrates mediating BDNF/TrkB upregulation not identified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the converging post-transcriptional inputs (competing RBPs, multiple miRNA families) and post-translational events (calpain cleavage, CDK5 tyrosine phosphorylation) are integrated in vivo to set p35 levels and direct substrate selection remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo loss-of-function dissection of the UTR regulatory network\", \"Substrate selectivity rules of activated CDK5 across tissues not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3, 4]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 8, 12, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 4, 7, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [8, 9, 14]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [9, 10, 13]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [12, 15]}\n    ],\n    \"complexes\": [\"Cdk5/p35 kinase complex\"],\n    \"partners\": [\"CDK5\", \"SET\", \"amphiphysin\", \"synapsin I\", \"hnRNPA2B1\", \"ELAVL\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}