Affinage

CDK4

Cyclin-dependent kinase 4 · UniProt P11802

Round 2 corrected
Length
303 aa
Mass
33.7 kDa
Annotated
2026-04-28
130 papers in source corpus 43 papers cited in narrative 43 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CDK4 is a D-type cyclin-dependent serine/threonine kinase that functions as a master regulator of the G1-to-S phase cell cycle transition and integrates mitogenic, metabolic, and immune-regulatory signals. Upon binding D-type cyclins (assembled with the aid of CIP/KIP scaffold proteins p21/p27), CDK4 is activated by CAK/Cdk7-mediated phosphorylation of Thr172 and sequentially phosphorylates Rb to displace HDAC, relieve E2F-mediated transcriptional repression, and commit cells to S-phase entry; this activation is negatively regulated by INK4 family inhibitors (p16, p15, p18, p19) that compete with D-cyclins for CDK4 binding, modulated by Hsp90/Cdc37 chaperoning and Fkbp5-mediated prolyl isomerization of the T-loop (PMID:8449399, PMID:7935441, PMID:10499802, PMID:23622515, PMID:30485818). Beyond Rb, CDK4 directly phosphorylates GCN5 to suppress hepatic gluconeogenesis, AMPKα2 to inhibit fatty acid oxidation, FLCN to regulate lysosomal mTORC1 recruitment, SPOP to stabilize PD-L1, EZH2 to activate STAT3-driven inflammatory gene expression, and CDC25A to generate a G1/S negative-feedback loop (PMID:24870244, PMID:29053957, PMID:31395606, PMID:29160310, PMID:32701505, PMID:28192398). Germline CDK4 R24C mutations that abolish p16 binding cause familial melanoma susceptibility (PMID:8528263, PMID:7652577).

Mechanistic history

Synthesis pass · year-by-year structured walk · 16 steps
  1. 1993 High

    The identification of p16INK4a as a direct CDK4 inhibitor and the reconstitution of CDK4/cyclin D-dependent Rb phosphorylation established the core p16–CDK4/cyclin D–Rb–E2F pathway governing G1/S progression.

    Evidence In vitro kinase inhibition assays, baculovirus/Sf9 reconstitution of CDK4/cyclin D complexes, E2F release assays, co-IP in normal vs. SV40-transformed fibroblasts

    PMID:8101826 PMID:8259215 PMID:8449399

    Open questions at the time
    • Mechanism of CDK4 enzymatic activation (activating kinase) unknown at this stage
    • Stoichiometry and competition between p16 and cyclins for CDK4 binding not yet defined
  2. 1994 High

    Discovery that CAK (Cdk7/cyclin H) phosphorylates CDK4 on Thr172 for activation, and that CIP/KIP proteins promote CDK4/cyclin D assembly and nuclear targeting, resolved how CDK4 is activated and how its complexes are assembled in a regulated manner.

    Evidence In vitro reconstitution with p39MO15/cyclin H, immune-depletion, quantitative assembly kinetics, subcellular fractionation

    PMID:7935441 PMID:9106657

    Open questions at the time
    • Whether Cdk7 is the sole CDK4-activating kinase in vivo was not established
    • CIP/KIP titration model (assembly vs. inhibition) not fully resolved
  3. 1994 High

    The expansion of the INK4 family (p15INK4B, p18INK4C, p19INK4D) revealed that CDK4/6 activity is controlled by a family of structurally related competitive inhibitors, some induced by extracellular signals like TGF-β.

    Evidence cDNA isolation, yeast two-hybrid, kinase inhibition assays, TGF-β induction in keratinocytes, retroviral overexpression and cell cycle analysis

    PMID:7739547 PMID:8001816 PMID:8078588 PMID:8741839

    Open questions at the time
    • Relative contribution of individual INK4 members in specific tissues not yet determined
    • Structural basis for INK4–CDK4 competition with cyclins not resolved
  4. 1995 High

    The CDK4 R24C mutation in melanoma and its confirmation as a familial melanoma susceptibility allele demonstrated that p16-CDK4 binding is a critical tumor-suppressor axis in human cancer.

    Evidence Mutation sequencing from melanoma tissue and familial kindreds, p16/p21/p27 binding assays, CTL recognition assay

    PMID:7652577 PMID:8528263

    Open questions at the time
    • Whether R24C alters CDK4 kinase activity per se or only p16 binding was not fully dissected
    • Tissue specificity of melanoma susceptibility not mechanistically explained
  5. 1999 High

    Mechanistic dissection of ordered Rb inactivation showed that CDK4/6 first phosphorylates the Rb C-terminus to displace HDAC, while CDK2 subsequently disrupts the pocket domain to release E2F, establishing a two-step Rb inactivation model.

    Evidence In vitro phosphorylation with defined Rb mutants, HDAC binding assays, co-immunoprecipitation

    PMID:10499802

    Open questions at the time
    • Whether this ordered phosphorylation sequence operates identically in all cell types was untested
    • Full complement of CDK4-specific Rb phosphorylation sites not mapped
  6. 2000 High

    The discovery that c-MYC transcriptionally activates CDK4 placed CDK4 downstream of a major oncogenic transcription factor, integrating mitogenic signaling with cell cycle kinase expression.

    Evidence SAGE, promoter binding assay, ectopic CDK4 rescue of c-MYC-deficient RAT1 cells

    PMID:10688915

    Open questions at the time
    • Whether MYC-dependent CDK4 induction is rate-limiting for proliferation in most contexts was unclear
  7. 2001 High

    CDK4 R24C knock-in mice confirmed that INK4-insensitive CDK4 is sufficient to initiate melanoma in vivo, and genetic epistasis established a hierarchy among INK4 family members (p18 > p15) in melanocyte tumor suppression.

    Evidence Knock-in mouse model, carcinogen treatment, tumor sequencing, genetic crosses with INK4 knockouts

    PMID:11606789

    Open questions at the time
    • Molecular mechanism of melanocyte-specific CDK4 dependency not resolved
    • Contribution of CDK6 in this tissue not assessed
  8. 2006 High

    Structural and genetic studies revealed that Hsp90/Cdc37 chaperone CDK4 as a ternary complex, and that combined CDK4/CDK2 loss causes embryonic lethality due to Rb hypo-phosphorylation, confirming CDK4 cooperates with CDK2 to inactivate Rb in vivo.

    Evidence Single-particle EM of Hsp90-Cdc37-Cdk4, double knockout mice, HPV-E7 rescue experiments

    PMID:16678773 PMID:16949366

    Open questions at the time
    • How Cdc37 specifically recognizes CDK4 over other kinases remained unclear
    • Tissue-specific requirements for CDK4 vs. CDK2 not fully delineated
  9. 2013 High

    Chemical genetic proof that Cdk7 is the physiological CDK4-activating kinase, required to maintain (not just establish) CDK4 activity during G1 exit, defined the upstream CDK activation cascade.

    Evidence Analog-sensitive Cdk7 allele, in vitro Cdk4 activation, cell quiescence/exit phosphorylation time course

    PMID:23622515

    Open questions at the time
    • Whether Cdk7 regulation of CDK4 vs. CDK6 differs quantitatively was not resolved
  10. 2014 High

    CDK4 was shown to directly phosphorylate GCN5, suppressing hepatic gluconeogenesis independently of cell cycle control, establishing CDK4 as a metabolic kinase linking insulin/amino acid signaling to glucose homeostasis.

    Evidence In vitro CDK4 kinase assay on GCN5, PGC-1α acetylation, Cdk4−/− mouse metabolic phenotype, CDK4 inhibitor treatment

    PMID:24870244

    Open questions at the time
    • Full spectrum of CDK4 metabolic substrates not catalogued
    • Relative contributions of CDK4 vs. CDK6 to hepatic metabolism unclear
  11. 2017 High

    A burst of discoveries identified multiple non-Rb CDK4 substrates (AMPKα2, SPOP, CDC25A) and revealed CDK4/6 inhibitors stimulate anti-tumor immunity by activating endogenous retroviruses, linking CDK4 kinase activity to fatty acid oxidation, PD-L1 stability, G1/S feedback, and immune surveillance.

    Evidence In vitro kinase assays on AMPKα2/SPOP/CDC25A, Cdk4−/− mouse exercise phenotype, AMPK epistasis, ubiquitination reconstitution, tumor-infiltrating lymphocyte analysis, dsRNA/IFN measurement in preclinical models and clinical biopsies

    PMID:28192398 PMID:28813415 PMID:29053957 PMID:29160310

    Open questions at the time
    • Structural basis for CDK4 recognition of diverse non-Rb substrates unknown
    • Whether SPOP phosphorylation occurs at physiological CDK4 activity levels in all tumor types not established
  12. 2018 High

    Fkbp5 was identified as a CDK4-specific regulator that both sequesters CDK4 within Hsp90 complexes and inhibits Thr172 phosphorylation through prolyl isomerization, providing a novel conformational gating mechanism for CDK4 activation during myogenic differentiation.

    Evidence Prolyl isomerase assay, Thr172 phosphorylation analysis, Fkbp5−/− mouse muscle regeneration

    PMID:30485818

    Open questions at the time
    • Whether other prolyl isomerases similarly regulate CDK4 is unknown
    • Generalizability beyond muscle differentiation not tested
  13. 2019 High

    CDK4 was shown to phosphorylate FLCN to regulate lysosomal mTORC1 recruitment in response to amino acids, extending CDK4's metabolic functions to nutrient-sensing and lysosomal biology, while chemo-proteomics revealed that high p16/CDKN2A levels prevent palbociclib engagement of CDK4.

    Evidence In vitro CDK4 kinase assay on FLCN, lysosomal function assays, mTORC1 imaging, chemo-proteomics target engagement in isogenic CDKN2A cell lines

    PMID:30837298 PMID:31395606

    Open questions at the time
    • Whether CDK4-FLCN axis operates independently of Rb phosphorylation in all contexts unclear
    • No crystal structure of CDK4-FLCN complex
  14. 2020 High

    Live single-cell imaging established that CDK4/6 activity rises before CDK2 activity during cell cycle entry and that stress signals can rapidly inactivate CDK4/6 to return cells to quiescence, positioning CDK4/6 as the primary G1 activity sensor determining quiescence exit.

    Evidence Single-cell CDK4/6 and CDK2 live-cell activity reporters, stress perturbation experiments

    PMID:32255427

    Open questions at the time
    • Molecular identity of stress signals that inactivate CDK4/6 not fully defined
    • Whether CDK4 and CDK6 contribute equally in this reporter system is unresolved
  15. 2021 High

    CDK6 upregulation was shown to confer CDK4/6 inhibitor resistance through formation of p18INK4C-cyclin D-CDK6 ternary complexes that occlude drug binding while retaining kinase activity, explaining a major clinical resistance mechanism and motivating selective CDK4 inhibitor development.

    Evidence In vitro binding/kinase assays, chemo-proteomics, physical modeling, PROTAC degrader validation in vivo

    PMID:34544752

    Open questions at the time
    • Whether resistance-conferring ternary complexes form in all tumor contexts untested
    • Structural details of drug occlusion at atomic resolution lacking
  16. 2025 High

    Selective CDK4 inhibition demonstrated that CDK4 is dispensable for hematopoiesis (CDK6-dependent) while essential for HR+ breast cancer cell proliferation, establishing a therapeutic window for selective CDK4 targeting with reduced neutropenia.

    Evidence Selective CDK4 inhibitor profiling, neutrophil toxicity assays, CDK4 vs. CDK6 selectivity, HR+ breast cancer models

    PMID:40068598

    Open questions at the time
    • Long-term resistance mechanisms to selective CDK4 inhibitors not characterized
    • Whether selective CDK4 inhibition preserves the immune-stimulatory effects of dual CDK4/6 inhibition is unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • Outstanding questions include the structural basis for CDK4 substrate recognition across its diverse non-Rb targets, the extent to which CDK4 metabolic and immune functions are Rb-independent, and how CDK4 and CDK6 are differentially deployed across tissues and tumor types.
  • No high-resolution structure of CDK4 bound to non-Rb substrates
  • Rb-independent vs. Rb-dependent contributions of CDK4 not systematically dissected
  • Tissue-specific CDK4 vs. CDK6 functional partitioning incompletely mapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 9 GO:0016740 transferase activity 8
Localization
GO:0005634 nucleus 2 GO:0005829 cytosol 2
Pathway
R-HSA-1640170 Cell Cycle 9 R-HSA-162582 Signal Transduction 5 R-HSA-1643685 Disease 5 R-HSA-1430728 Metabolism 2 R-HSA-168256 Immune System 2
Partners
CCND1CCND2CCND3CDC37CDKN1ACDKN1BCDKN2AFKBP5
Complex memberships
Cyclin D1-CDK4Cyclin D2-CDK4Cyclin D3-CDK4Hsp90-Cdc37-CDK4

Evidence

Reading pass · 43 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1993 p16 (INK4a) binds directly to CDK4 and inhibits the catalytic activity of CDK4/cyclin D complexes, acting in a regulatory feedback circuit with CDK4, D-type cyclins, and retinoblastoma protein. Biochemical binding assays, kinase inhibition assays, cDNA isolation Nature High 8259215
1993 CDK4 in complex with D-type cyclins phosphorylates the retinoblastoma protein (pRb) at sites identical to those phosphorylated in human T cells; only D-type cyclins activate CDK4 enzyme activity; cyclin D2/D3 (but not D1) bind pRb directly; CDK4/cyclin D complexes phosphorylate pRb and release E2F-1. Baculovirus/Sf9 reconstitution, in vitro kinase assay, co-immunoprecipitation, pRb fusion protein phosphorylation Genes & development High 8449399
1993 In SV40-transformed cells, CDK4 dissociates from cyclin D, PCNA, and p21 and instead associates exclusively with a 16 kDa protein (p16), demonstrating subunit rearrangement of CDK4 complexes is associated with cellular transformation. Co-immunoprecipitation, biochemical fractionation of normal vs. transformed fibroblasts Genes & development High 8101826
1994 CDK4/cyclin D complexes require phosphorylation on Thr-172 for enzymatic activation; this step is catalyzed by CAK (cdk-activating kinase, p39MO15/cyclin H complex), which can phosphorylate and activate both cdk2 and cdk4 in their respective cyclin complexes. In vitro kinase assay, immune-depletion, baculovirus reconstitution with p39MO15 and cyclin H Molecular and cellular biology High 7935441
1994 p21(CIP), p27(KIP), and p57(KIP2) promote the assembly of CDK4 with D-type cyclins; at low concentrations p21 promotes active CDK4/cyclin D complex formation, and most cellular CDK4/cyclin D kinase activity co-associates with p21; CIP/KIP proteins also target CDK4 and cyclin D1 to the nucleus. In vitro assembly assays, kinetic analyses (K_a, K_off measurements), immunodepletion, subcellular fractionation Genes & development High 9106657
1994 p15INK4B, a new member of the p16 family induced ~30-fold by TGF-β in human keratinocytes, inhibits CDK4 and CDK6, identifying it as a potential effector of TGF-β-mediated G1 cell cycle arrest. cDNA isolation, TGF-β induction assay, CDK4/6 kinase inhibition assay Nature High 8078588
1994 CDK6 (PLSTIRE gene product) is activated by D-type cyclins and phosphorylates pRb during mid-G1, analogous to CDK4. Sf9 baculovirus co-expression, in vitro kinase assay, co-immunoprecipitation Molecular and cellular biology High 8114739
1994 p18 (INK4C) interacts strongly with CDK6 and weakly with CDK4, inhibits cyclin D-CDK6 kinase activity, and forms binary (not ternary) complexes with CDK4/CDK6, competing with cyclin binding; growth suppression by p18 correlates with wild-type pRb function. Yeast two-hybrid, in vitro binding, kinase inhibition assay, growth suppression in NIH 3T3 cells Genes & development High 8001816
1994 A 15-kDa CDK-binding protein (p15cdk-BP) specifically binds CDK4/cyclin D and CDK5, but not CDC2 or CDK2, identifying a distinct CDK4-selective binding partner. Affinity chromatography (p15cdk-BP-Sepharose), anti-CDK antibody Western blotting, phosphopeptide mapping The Journal of biological chemistry Medium 8175758
1995 A CDK4 R24C point mutation (arginine-to-cysteine at residue 24) found in human melanoma prevents binding of p16INK4a (but not p21 or p27KIP1), rendering CDK4 insensitive to this tumor suppressor; the mutant peptide is recognized as a tumor-specific antigen by cytolytic T lymphocytes. Mutant CDK4 sequencing from melanoma tissue, p16/p21/p27 binding assay, CTL recognition assay Science High 7652577
1995 Mouse p19 (INK4D) and p18 (INK4C) specifically inhibit CDK4 and CDK6 kinase activities but not CDK2, CDC2; they bind CDK4/CDK6 directly (in or out of cyclin D complexes) and can displace cyclin D from CDK4/6 in vivo, inducing G1 arrest. In vitro kinase inhibition assay, co-immunoprecipitation, retroviral overexpression, cell cycle analysis Molecular and cellular biology High 7739547
1996 p19INK4D is a specific inhibitor of CDK4 and CDK6; it interacts with both kinases (independently of cyclins) and inhibits their activity; interaction with CDK4/CDK6 is hindered by the cyclin subunit, and binary cyclin D–p19 or cyclin D–CDK6 complexes are mutually exclusive, suggesting INK4 proteins and D cyclins compete for CDK4/6 binding. Yeast two-hybrid, co-immunoprecipitation, kinase inhibition assay, chromosome mapping Molecular biology of the cell High 8741839
1996 During myogenic differentiation, p18INK4C protein increases 50-fold and sequentially associates first with CDK6 then with CDK4, with all CDK6 and half of CDK4 complexed with p18 in terminally differentiated muscle; CDK4 kinase activity decreases during differentiation, supporting p18 as critical for maintaining permanent cell cycle arrest in muscle. Co-immunoprecipitation, Western blot, kinase activity assay in C2C12 cells and adult mouse muscle Molecular biology of the cell High 8898364
1996 Random mutagenesis of p16INK4a reveals that multiple residues throughout the entire gene are important for binding to CDK4, with no single mutational hot spot; mutations reducing binding also severely affect kinase-inhibitory activity. Random mutagenesis, yeast two-hybrid binding assay, kinase inhibition assay Biochemical and biophysical research communications Medium 8573142
1996 Germline CDK4 R24C (and R24H) mutations in the p16INK4a-binding domain cause familial melanoma susceptibility. Germline mutation sequencing in familial melanoma kindreds Nature genetics High 8528263
1997 ARF (p19ARF) binds to MDM2 and promotes its degradation, stabilizing p53; deletion of the INK4a-ARF locus simultaneously impairs both the p16INK4a-cyclin D/CDK4-Rb and ARF-MDM2-p53 tumor suppression pathways. Co-immunoprecipitation, MDM2 degradation assay, G1 arrest rescue experiment Cell High 9529249
1999 CDK4 T172 phosphorylation in the T-loop is a critical activating modification; the novel CDK4-binding protein p34(SEI-1) antagonizes p16INK4a by rendering cyclin D1-CDK4 resistant to p16INK4a inhibition, and SEI-1 expression is induced by serum stimulation, facilitating cyclin D-CDK complex formation. In vitro kinase assay, p16 competition binding assay, serum induction experiment, ectopic expression in fibroblasts Genes & development High 10580009
1999 Sequential CDK4/6-dependent phosphorylation of the Rb C-terminal region initiates intramolecular interactions that displace histone deacetylase from the Rb pocket, blocking active transcriptional repression; subsequent CDK2-mediated pocket phosphorylation disrupts pocket structure and releases E2F, providing a molecular basis for ordered Rb inactivation during G1. In vitro phosphorylation assays, mutant Rb constructs, co-immunoprecipitation, HDAC binding assays Cell High 10499802
2000 c-MYC transcriptionally activates CDK4 via four conserved MYC binding sites in the CDK4 promoter; c-MYC-deficient RAT1 cells show delayed cell cycle progression associated with defective CDK4 induction, and ectopic CDK4 expression partially rescues this growth defect. Serial analysis of gene expression (SAGE), promoter binding/transcription assay, c-MYC-deficient cell rescue experiment PNAS High 10688915
2001 Knock-in mice expressing the CDK4 R24C allele (insensitive to INK4 inhibition) are highly susceptible to melanoma development; these tumors lack p19ARF/p53 mutations, indicating the p16INK4a/CDK4/Rb pathway is specifically involved in melanoma. Deletion of p18INK4C (but not p15INK4B) confers additional proliferative advantage, establishing a functional hierarchy of INK4 proteins on CDK4 in melanocytes. Knock-in mouse model, carcinogen treatment, tumor sequencing, genetic epistasis with INK4 knockouts PNAS High 11606789
2006 Single-particle electron microscopy of a reconstituted Hsp90-Cdc37-Cdk4 complex defines its 3D structure and stoichiometry; Cdc37 acts as a scaffold simultaneously binding Cdk4 and Hsp90, and conformational changes in Cdk4 are coupled to the Hsp90 ATPase cycle. Reconstitution and purification of ternary complex, single-particle EM, stoichiometry determination, comparison with Hsp90 crystal structure Molecular cell High 16949366
2006 Combined loss of Cdk2 and Cdk4 in mice causes embryonic lethality (~E15) with heart defects, progressive decline in Rb phosphorylation, reduced E2F-target gene expression, and premature senescence in MEFs; HPV-E7 inactivation of Rb rescues these defects, demonstrating Cdk2 and Cdk4 cooperate to phosphorylate Rb in vivo and couple G1/S transition to mitosis via E2F. Double knockout mice, Rb phosphorylation assay, E2F target gene expression, HPV-E7 rescue, p27 knockout epistasis Developmental cell High 16678773
2006 T-loop phosphorylation of CDK4 (but not CDK6) at Thr172 is a determining target for cell cycle control by extracellular factors; CDK4's subcellular location and association with D-type cyclins are regulated by mitogenic/antimitogenic signals. Biochemical analysis of CDK4 T172 phosphorylation in response to extracellular signals, subcellular fractionation, comparison with CDK6 Cell division Medium 17092340
2009 The CDK4-pRB-E2F1 pathway controls insulin secretion in pancreatic β-cells by regulating expression of Kir6.2 (a K-ATP channel component); glucose activates CDK4 via the insulin/GSK-3β pathway, leading to E2F1 activation and increased Kir6.2 expression; CDK4 inhibition or E2F1 knockout impairs insulin secretion and causes glucose intolerance in mice. Chromatin immunoprecipitation from tissues, CDK4 inhibitor treatment, E2f1−/− mouse phenotype, Kir6.2 rescue experiment Nature cell biology High 19597485
2010 STAT1 directly interacts with the cyclin D1/CDK4 complex; IFN-γ activates STAT1 (via Ser727 phosphorylation), which interacts with cyclin D1 to promote its proteasomal degradation, reducing Rb phosphorylation and inducing G1 arrest independently of STAT1 transcriptional activity. Co-immunoprecipitation, STAT1 point mutant analysis, proteasome inhibitor treatment, STAT1-deficient cell comparison Cell cycle Medium 21084836
2013 Cdk7 is a Cdk4- and Cdk6-activating kinase in human cells, required to maintain (not just establish) Cdk4 activity; Cdk7 activating phosphorylation rises concurrently with Cdk4 activating phosphorylation as cells exit quiescence, and Cdk7 accelerates Cdk4 activation in vitro, establishing a CDK-activation cascade during G1 progression. Chemical genetics (analog-sensitive Cdk7), in vitro Cdk4 activation assay, cell quiescence/exit experiments, phosphorylation time course Molecular cell High 23622515
2013 Cdk4 loss abrogates centrosome amplification and binucleation in HER2+ breast cancer cells; Nek2 protein levels decrease upon Cdk4 knockdown and vice versa, indicating a molecular connection whereby Cdk4 signals centrosome amplification through Nek2, and defective cytokinesis (normalized by Cdk4 downregulation) is the source of binucleation. shRNA knockdown, Nek2 overexpression, centrosome/cell cycle analysis in HER2+ cell lines PloS one Medium 23776583
2014 Cyclin D1-CDK4 phosphorylates and activates GCN5 acetyltransferase, which then acetylates and inhibits PGC-1α activity on gluconeogenic genes, thereby suppressing hepatic glucose production independently of cell cycle progression; insulin/GSK-3β signaling stabilizes nuclear cyclin D1, and dietary amino acids increase hepatic cyclin D1 mRNA. Cell-based high-throughput chemical screen, in vitro kinase assay (CDK4 phosphorylating GCN5), PGC-1α acetylation assay, Cdk4−/− mouse metabolic phenotype, Cdk4 inhibitor treatment Nature High 24870244
2014 PD0332991 (palbociclib) inhibits CDK4/6 activity but paradoxically stabilizes activated cyclin D3-CDK4/6 complexes that are devoid of p21/p27; the inhibitor has opposite effects on p21-bound versus p21-free CDK4/6 complexes, and stabilized activated complexes persist for ≥24 h after drug removal, causing paradoxical cell cycle entry without mitogenic stimulation. CDK4/6 complex purification, phosphorylation state analysis, cell cycle assay after drug washout Cell cycle Medium 25486476
2017 CDK4 directly phosphorylates AMPKα2 to inhibit its activity, thereby repressing fatty acid oxidation and promoting anaerobic glycolysis; Cdk4−/− mice have increased oxidative metabolism and exercise capacity, and CDK4 inhibition mimics this metabolic shift in an AMPK-dependent manner in skeletal muscle. In vitro kinase assay (CDK4 phosphorylating AMPKα2), non-phosphorylatable AMPKα2 mutants, CDK4 inhibitor treatment, Cdk4−/− mouse exercise phenotype, AMPK-deficient muscle epistasis Molecular cell High 29053957
2017 Cyclin D-CDK4 phosphorylates SPOP (speckle-type POZ protein), promoting SPOP degradation via FZR1/APC; this stabilizes PD-L1 protein. When CDK4/6 is inhibited, SPOP degradation is prevented, enabling SPOP to ubiquitinate PD-L1 via cullin 3 for proteasomal degradation, thus reducing PD-L1 levels and increasing tumor-infiltrating lymphocytes. In vitro CDK4 kinase assay on SPOP, co-immunoprecipitation, ubiquitination assay, CDK4/6 inhibitor treatment in vivo, SPOP loss-of-function mutations in tumors Nature High 29160310
2017 CDK4/6 inhibitors activate tumor cell expression of endogenous retroviral elements, increasing intracellular double-stranded RNA and stimulating type III interferon production; CDK4/6 inhibitors also markedly suppress regulatory T cell proliferation; both effects involve reduced activity of the E2F target DNMT1, promoting anti-tumor immunity. Mouse tumor models, transcriptomic analysis of clinical trial biopsies, regulatory T cell proliferation assay, dsRNA/IFN measurement Nature High 28813415
2017 CyclinD/Cdk4 phosphorylates TSC1/2 in Drosophila wing disc cells at the G1/S transition, activating TORC1; this reveals a conserved mechanism linking cell cycle progression to nutrient sensing via Cdk4. In situ TORC1 activity readout (anti-phospho-dRpS6 antibody), genetic epistasis in Drosophila wing disc, CycD/Cdk4 overexpression Developmental cell Medium 28829945
2017 CyclinD1-CDK4 directly phosphorylates CDC25A on Ser40 during G1, promoting CDC25A degradation in a βTrCP-dependent manner, thus generating a negative feedback loop controlling the G1/S transition. In vitro kinase assay (cyclin D1-CDK4 on CDC25A), phosphorylation mapping (Ser40), βTrCP-dependent stability assay, cell cycle synchrony Oncogene High 28192398
2018 CDK4/6 phosphorylates EZH2 in keratinocytes, triggering EZH2-mediated methylation-induced STAT3 activation; active STAT3 induces IκBζ, a proinflammatory transcription factor required for cytokine synthesis in psoriasis; pharmacological or genetic inhibition of CDK4/6 or EZH2 suppresses IκBζ and psoriatic gene expression. In vitro CDK4/6 kinase assay on EZH2, STAT3 methylation/activation assay, CDK4/6i and EZH2i treatment in keratinocytes and mouse psoriasis models The Journal of clinical investigation High 32701505
2018 Fkbp5 promotes myoblast differentiation through two CDK4-specific mechanisms: (1) it sequesters CDK4 within the Hsp90 storage complex, preventing cyclin D1-CDK4 complex formation; (2) it promotes cis-trans isomerization of the Thr172-Pro173 peptide bond in CDK4, inhibiting Thr172 phosphorylation (required for CDK4 activation). Fkbp5−/− mice show delayed muscle regeneration. Co-immunoprecipitation, peptidyl prolyl isomerization assay, Thr172 phosphorylation assay, Fkbp5−/− mouse muscle regeneration, comparison with Fkbp4 Cell reports High 30485818
2019 CDK4 phosphorylates folliculin (FLCN), regulating mTORC1 recruitment to the lysosomal surface in response to amino acids; CDK4 also directly regulates lysosomal function and is essential for lysosomal degradation, thereby regulating mTORC1 activity; CDK4 loss leads to lysosomal dysfunction, impaired autophagic flux, and cancer cell senescence. In vitro CDK4 kinase assay on FLCN, lysosomal function assays, mTORC1 recruitment imaging, CDK4 inhibitor and genetic inactivation in xenograft models Cancer research High 31395606
2019 CDK4 interaction with CDKN2A (p16INK4a family proteins) in cells prevents palbociclib from engaging CDK4; high CDKN2A causes drug insensitivity by occupying CDK4 before the inhibitor can bind, as shown by chemo-proteomics target engagement profiling in isogenic cells. Chemo-proteomics (activity-based protein profiling), isogenic cell lines with engineered CDKN2A levels, CDK4 target engagement assay Molecular cancer therapeutics High 30837298
2020 CDK4/6 activity increases rapidly before CDK2 activity during cell cycle entry; stress signals in G1 can rapidly inactivate CDK4/6 to return cells to quiescence with decreasing probability as cells approach S phase, revealing CDK4/6 as the primary G1 activity determining quiescence exit timing and G1 length. Single-cell CDK4/6 and CDK2 activity reporter system (live imaging), stress signal perturbations eLife High 32255427
2021 CDK4-dependent activation of p38 MAPK determines cell size homeostasis; CDK4 activity sets the target size threshold at which p38 is inactivated to permit cell cycle progression, functioning analogously to a thermostat dial for cell size. CDK4 inhibition/activation experiments, p38 activity assays, cell size measurements, genetic perturbations Developmental cell Medium 34022133
2021 CDK6 upregulation confers resistance to CDK4/6 inhibitors by inducing and binding INK4 proteins (e.g., p18INK4C); the p18INK4C-cyclin D-CDK6 ternary complex occludes CDK4/6 inhibitor (palbociclib) binding while only weakly suppressing ATP binding, as shown by in vitro binding and kinase assays with physical modeling. In vitro binding assay, kinase assay, chemo-proteomics, physical modeling, PROTAC degrader development Cancer discovery High 34544752
2023 SETDB1 protects CDK4/6-phosphorylated RB (p-RB) from degradation; TRIM28 binds and promotes ubiquitination and proteasomal degradation of CDK4/6-phosphorylated RB; SETDB1 (via its Tudor domain binding to methylated RB, independent of methyltransferase activity) opposes TRIM28 to stabilize p-RB, identifying a CDK4/6-dependent, TRIM28-mediated RB inactivation mechanism. Co-immunoprecipitation, ubiquitination assay, SETDB1 Tudor domain mutant analysis, antisense oligonucleotide, palbociclib combination in vivo Cancer research High 36637424
2025 Selective CDK4 inhibition (atirmociclib/PF-07220060) shows reduced neutropenia compared to dual CDK4/6 inhibitors because CDK4 is dispensable for hematopoiesis (where CDK6 dominates), while HR+ breast cancer cells are highly CDK4-dependent; greater CDK4 target coverage leads to deeper anti-tumor responses. Selective CDK4 inhibitor development, neutrophil toxicity assays, CDK4 vs. CDK6 selectivity profiling, HR+ breast cancer cell line sensitivity, in vivo tumor models Cancer cell High 40068598

Source papers

Stage 0 corpus · 130 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1993 A new regulatory motif in cell-cycle control causing specific inhibition of cyclin D/CDK4. Nature 3482 8259215
2005 Towards a proteome-scale map of the human protein-protein interaction network. Nature 2090 16189514
1994 p15INK4B is a potential effector of TGF-beta-induced cell cycle arrest. Nature 1966 8078588
2013 Genetics of rheumatoid arthritis contributes to biology and drug discovery. Nature 1778 24390342
2005 A human protein-protein interaction network: a resource for annotating the proteome. Cell 1704 16169070
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
1998 ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus deletion impairs both the Rb and p53 tumor suppression pathways. Cell 1365 9529249
1997 New functional activities for the p21 family of CDK inhibitors. Genes & development 1269 9106657
1993 Direct binding of cyclin D to the retinoblastoma gene product (pRb) and pRb phosphorylation by the cyclin D-dependent kinase CDK4. Genes & development 1214 8449399
2017 CDK4/6 inhibition triggers anti-tumour immunity. Nature 1165 28813415
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2005 The bromodomain protein Brd4 is a positive regulatory component of P-TEFb and stimulates RNA polymerase II-dependent transcription. Molecular cell 1075 16109376
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
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