Affinage

CAMKK1

Calcium/calmodulin-dependent protein kinase kinase 1 · UniProt Q8N5S9

Round 2 corrected
Length
505 aa
Mass
55.7 kDa
Annotated
2026-04-28
41 papers in source corpus 11 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CAMKK1 is a Ca²⁺/calmodulin-dependent serine/threonine kinase kinase that sits at the apex of a CaMK signaling cascade, phosphorylating and activating CaMKI and CaMKIV at their activation-loop threonines in a manner requiring Ca²⁺/CaM binding to both CAMKK1 and its substrates (PMID:7642608, PMID:7615569, PMID:8621423). Its activity is negatively regulated by PKA-mediated phosphorylation at Thr-108 and by a CaMKI-dependent feedback loop (PMID:10187789), and is selectively inhibited by 14-3-3γ, which forms a compact complex that blocks the active site and suppresses Ca²⁺/CaM association — a mechanism structurally distinct from the looser 14-3-3 interaction with paralog CAMKK2 (PMID:37817008). CAMKK1 also contributes to AMPK activation downstream of Ca²⁺ signals (PMID:19520843) and functions in axon regeneration, where its expression is controlled by the miR-132-5p axis, and in osteoclast differentiation, where it is de-repressed upon Nrf2 suppression (PMID:36936807, PMID:39674449).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 1995 High

    Identification of CAMKK1 as the upstream kinase kinase for CaMKI and CaMKIV established the existence of a multi-tier Ca²⁺/CaM-dependent kinase cascade and showed it could amplify CREB-dependent transcription.

    Evidence Cloning from rat brain, in vitro kinase assays with purified proteins, COS-7 co-expression with CaMKIV and CREB reporter

    PMID:7615569 PMID:7642608

    Open questions at the time
    • Endogenous tissue-level validation of cascade hierarchy not yet provided
    • Relative contributions of CAMKK1 vs CAMKK2 to CaMKIV activation not distinguished
  2. 1996 High

    Demonstration that Ca²⁺/CaM must bind both CAMKK1 and CaMKIV for productive phosphorylation resolved how Ca²⁺ signals gate two independent steps in the cascade and explained why a constitutively active CAMKK alone is insufficient for full substrate activation.

    Evidence Truncation and mutagenesis of both CAMKK and CaMKIV, in vitro reconstitution, ionomycin stimulation in COS-7 cells

    PMID:8621423

    Open questions at the time
    • Structural basis for CaM-gated substrate accessibility unknown
    • Whether CaMKI activation follows the same dual-CaM requirement not tested
  3. 1998 High

    Mapping the autoinhibitory domain of CaMKI and showing that CaM relief of autoinhibition is a prerequisite for CAMKK1-mediated activation-loop phosphorylation clarified the substrate-side gating mechanism.

    Evidence Systematic site-directed mutagenesis of CaMKI helix-loop-helix domain, in vitro kinase assays

    PMID:9705275

    Open questions at the time
    • Crystal structure of CAMKK1–CaMKI complex not available
    • In vivo relevance of individual CaMKI autoinhibitory residues not tested
  4. 1999 High

    Discovery that PKA phosphorylates CAMKK1 at Thr-108 to inhibit it, and that CaMKI performs the same phosphorylation, revealed cAMP–Ca²⁺ signal integration and a negative-feedback loop within the CaMK cascade.

    Evidence In vitro PKA and CaMKI phosphorylation, phosphopeptide mapping, forskolin treatment in PC12 cells and hippocampal slices

    PMID:10187789

    Open questions at the time
    • Physiological relevance of CaMKI feedback in specific neuronal circuits not established
    • Additional regulatory phosphosites may exist
  5. 2009 Medium

    Placing CaMKK upstream of AMPK in adiponectin signaling extended CAMKK1's functional scope beyond the CaMK cascade to metabolic energy sensing, though CAMKK1 was not distinguished from CAMKK2 in this context.

    Evidence Pharmacological PLC/Ca²⁺ inhibition and siRNA knockdown in muscle cells, AMPK activity assays

    PMID:19520843

    Open questions at the time
    • CAMKK1-specific contribution not isolated from CAMKK2
    • Tissue-specific isoform requirements for AMPK activation unclear
  6. 2018 High

    Crystal structures of CAMKK1 with ATP-competitive inhibitors revealed exploitable active-site differences between CAMKK1 and CAMKK2, enabling paralog-selective chemical probe development.

    Evidence X-ray crystallography, kinase inhibitor screening, isothermal titration calorimetry

    PMID:30287839

    Open questions at the time
    • No structure of CAMKK1 in its autoinhibited or CaM-bound state
    • Selectivity over broader kinome not fully profiled
  7. 2023 High

    Structural and biophysical characterization showed that 14-3-3γ inhibits CAMKK1 by plugging the active site with its C-terminal helices and blocking CaM binding, whereas CAMKK2 forms a looser complex — explaining paralog-selective regulation.

    Evidence SAXS, HDX-MS, fluorescence spectroscopy

    PMID:37817008

    Open questions at the time
    • Atomic-resolution co-crystal structure of CAMKK1:14-3-3γ complex not determined
    • Phosphorylation sites on CAMKK1 that create the 14-3-3 docking motif not fully mapped
  8. 2023 Medium

    Identification of CAMKK1 as a miR-132-5p target that promotes axon regeneration linked this kinase kinase to peripheral nerve repair and exosome-mediated intercellular signaling.

    Evidence Proteomics, miRNA target validation, antagomir injection in rat sciatic nerve injury model

    PMID:36936807

    Open questions at the time
    • Direct CAMKK1 substrates mediating axon extension not identified
    • Whether CaMKI or CaMKIV mediates the regenerative signal downstream unclear
  9. 2024 Medium

    Demonstration that Nrf2 directly binds and suppresses CAMKK1, whose de-repression drives osteoclast differentiation, placed CAMKK1 in bone remodeling downstream of oxidative-stress signaling.

    Evidence Co-IP, Nrf2 knockout mice, CAMKK1 silencing, Micro-CT and TRAP staining in infection-induced bone loss model

    PMID:39674449

    Open questions at the time
    • Mechanism by which Nrf2 suppresses CAMKK1 (transcriptional vs protein-level) not resolved
    • CAMKK1 substrates in osteoclastogenesis not identified
    • Generalizability beyond parasitic infection model untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the identity of CAMKK1-specific substrates outside the CaMK/AMPK axis, the structural basis of CaM-gated substrate recognition, the in vivo tissue-specific contributions of CAMKK1 versus CAMKK2, and the full repertoire of regulatory phosphosites and their upstream kinases.
  • No CAMKK1 knockout mouse phenotype reported
  • Full phosphosite map with validated upstream kinases lacking
  • No structure of CAMKK1 in complex with CaM or a substrate kinase

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 5 GO:0016740 transferase activity 4
Localization
GO:0005829 cytosol 2
Pathway
R-HSA-162582 Signal Transduction 5
Partners
CAMK1CAMK4NRF2PRKAB1PRKACAYWHAG

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 CAMKK1 (originally named CaM-kinase kinase) was cloned from rat brain as a 505-amino acid serine/threonine kinase that phosphorylates and activates CaM-kinase I and CaM-kinase IV but not CaM-kinase II in a Ca2+/calmodulin-dependent manner; co-expression with CaM-kinase IV gave 14-fold enhancement of CREB-dependent gene expression. Molecular cloning, COS-7 cell expression, in vitro kinase assay, co-expression with CaMKIV + reporter assay The Journal of biological chemistry High 7642608
1995 CaM-kinase Ia kinase (CAMKK1-equivalent) phosphorylates CaMKIV at Thr-196 in a Ca2+/CaM- and MgATP-dependent manner, and Thr-196 phosphorylation is essential for activation; T196A mutation abolishes both phosphorylation and activation of CaMKIV. In vitro kinase assay with purified pig brain CaMK kinase, site-directed mutagenesis (T196A), phosphorylation stoichiometry measurement The Journal of biological chemistry High 7615569
1996 Activation of CaMKIV by CAMKK1 requires Ca2+/CaM binding to BOTH enzymes: a constitutively active truncated CaMKK (CaMKK1-434) can phosphorylate a CaMKIV fragment lacking the autoinhibitory domain in a Ca2+/CaM-independent manner, but phosphorylation of full-length CaMKIV still requires Ca2+/CaM binding to CaMKIV itself. Ionomycin stimulation in COS-7 cells confirmed Ca2+-dependent cascade activation requiring intact Thr196. In vitro phosphorylation assays with truncated and mutant CaMKK and CaMKIV, intact cell ionomycin stimulation, COS-7 co-expression The Journal of biological chemistry High 8621423
1998 CAMKK1 phosphorylates and activates CaMKI; CaMKI autoinhibition is mediated by a C-terminal helix-loop-helix domain (Ile286–Met316) and Ca2+/CaM relieves this inhibition allowing CAMKK to access and phosphorylate the activation loop. Specific residues Phe298, Ile294, Ile286, Val290, Trp303, and Phe307 were identified as critical for autoinhibition and CaM-binding of CaMKI. In vitro kinase assay, site-directed mutagenesis of CaMKI regulatory domain residues, recombinant protein structure-function analysis The Journal of biological chemistry High 9705275
1999 cAMP-dependent protein kinase (PKA) phosphorylates CAMKK1 primarily at Thr-108 in vitro and in intact cells, inhibiting its kinase activity; CaMKI also phosphorylates CAMKK1 at the same sites suggesting a negative-feedback mechanism. Forskolin treatment in PC12 cells rapidly inhibits both CAMKK1 and CaMKI activity, and hippocampal slice PKA activation increases CAMKK1 phosphorylation. In vitro PKA phosphorylation assay, phosphopeptide mapping, intact PC12 cell and hippocampal slice pharmacology (forskolin), CaMKI in vitro phosphorylation of CaMKK The Journal of biological chemistry High 10187789
2009 Adiponectin activates AMPK in muscle cells via a minor pathway involving phospholipase C-induced Ca2+ release from the ER, which activates Ca2+/calmodulin-dependent protein kinase kinase (CaMKK, including CAMKK1), thereby phosphorylating AMPK; this is distinct from the major APPL1/LKB1-dependent pathway. Pharmacological inhibition of phospholipase C and Ca2+ chelation, AMPK activity assay in muscle cells, epistasis via siRNA knockdown The Journal of biological chemistry Medium 19520843
2018 Crystal structures of CAMKK1 bound to two ATP-competitive inhibitors were determined, revealing exploitable structural differences between CAMKK1 and CAMKK2 despite high sequence identity. Isothermal titration calorimetry showed the most potent inhibitors bind with thermodynamics dominated by favorable enthalpy. X-ray crystallography, kinase inhibitor library screening, isothermal titration calorimetry Scientific reports High 30287839
2023 14-3-3γ protein inhibits CAMKK1 by directly blocking the kinase active site with its last two C-terminal helices, forming a compact and rigid complex that also suppresses Ca2+/CaM binding to CAMKK1. In contrast, the CaMKK2:14-3-3 complex is looser and more flexible, explaining why 14-3-3 binding selectively inhibits CAMKK1 but not CAMKK2. Small-angle X-ray scattering (SAXS), hydrogen/deuterium exchange coupled to MS (HDX-MS), fluorescence spectroscopy Protein science High 37817008
2023 In peripheral nerve injury, CAMKK1 is a downstream substrate of miR-132-5p: TFAP2C (delivered via fibroblast exosomes) represses miR-132-5p expression in dorsal root ganglion neurons, relieving suppression of CAMKK1 and thereby promoting axon extension. miR-132-5p antagomir in rats stimulates CAMKK1 expression and improves sciatic nerve axon regeneration. Proteomics, exosome functional assays, miRNA target validation, antagomir injection in rat sciatic nerve injury model Bioactive materials Medium 36936807
2024 Nrf2 directly interacts with and negatively regulates CAMKK1; Echinococcus granulosus protoscolex infection suppresses Nrf2, leading to upregulation of CAMKK1 which drives osteoclast differentiation and bone loss. Nrf2 knockout mice show exacerbated CAMKK1-dependent bone loss, and silencing CAMKK1 alone inhibits osteoclast differentiation. Transcriptome sequencing, Western blot, Q-PCR, co-immunoprecipitation, Nrf2 knockout mouse model, Micro-CT imaging, TRAP staining, small-molecule inhibitor (Crenolani) in vivo International journal of biological macromolecules Medium 39674449
2025 Phosphoproteomic coregulation analysis identified RPS6KB1 (S6K1) as a novel upstream kinase of CAMKK1 at its predominant phosphosite S74 (outside the kinase domain). Predominant phosphosites of CAMKK1 are located outside the kinase domain, and their phosphomotifs are highly homologous to those of CAMKK2. Global phosphoproteome dataset analysis, coregulation analysis of phosphosites, kinase-substrate inference from phosphoproteomics Omics : a journal of integrative biology Low 40079160

Source papers

Stage 0 corpus · 41 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
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
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
2012 Quantitative analysis of HSP90-client interactions reveals principles of substrate recognition. Cell 708 22939624
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2004 Proteomic, functional, and domain-based analysis of in vivo 14-3-3 binding proteins involved in cytoskeletal regulation and cellular organization. Current biology : CB 386 15324660
2013 Protein interaction network of the mammalian Hippo pathway reveals mechanisms of kinase-phosphatase interactions. Science signaling 383 24255178
2008 CaM kinase I alpha-induced phosphorylation of Drp1 regulates mitochondrial morphology. The Journal of cell biology 377 18695047
1995 Characterization of a Ca2+/calmodulin-dependent protein kinase cascade. Molecular cloning and expression of calcium/calmodulin-dependent protein kinase kinase. The Journal of biological chemistry 208 7642608
2009 Genome-wide and candidate gene association study of cigarette smoking behaviors. PloS one 197 19247474
2009 Adiponectin activates AMP-activated protein kinase in muscle cells via APPL1/LKB1-dependent and phospholipase C/Ca2+/Ca2+/calmodulin-dependent protein kinase kinase-dependent pathways. The Journal of biological chemistry 178 19520843
2001 Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs. Genome research 151 11230166
1995 Phosphorylation and activation of Ca(2+)-calmodulin-dependent protein kinase IV by Ca(2+)-calmodulin-dependent protein kinase Ia kinase. Phosphorylation of threonine 196 is essential for activation. The Journal of biological chemistry 139 7615569
2011 Interactions of pathological hallmark proteins: tubulin polymerization promoting protein/p25, beta-amyloid, and alpha-synuclein. The Journal of biological chemistry 131 21832049
1996 Requirements for calcium and calmodulin in the calmodulin kinase activation cascade. The Journal of biological chemistry 113 8621423
2006 Variants in the GH-IGF axis confer susceptibility to lung cancer. Genome research 101 16741161
2020 Kinase Interaction Network Expands Functional and Disease Roles of Human Kinases. Molecular cell 88 32707033
2010 Ppm1E is an in cellulo AMP-activated protein kinase phosphatase. Cellular signalling 81 20801214
1998 Characterization of the mechanism of regulation of Ca2+/ calmodulin-dependent protein kinase I by calmodulin and by Ca2+/calmodulin-dependent protein kinase kinase. The Journal of biological chemistry 81 9705275
2020 Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains. Cell reports 79 32814053
1999 Inhibition of the Ca2+/calmodulin-dependent protein kinase I cascade by cAMP-dependent protein kinase. The Journal of biological chemistry 67 10187789
2021 Histone deacetylase inhibitors inhibit cervical cancer growth through Parkin acetylation-mediated mitophagy. Acta pharmaceutica Sinica. B 66 35256949
2023 A central chaperone-like role for 14-3-3 proteins in human cells. Molecular cell 54 36931259
2010 International Lung Cancer Consortium: coordinated association study of 10 potential lung cancer susceptibility variants. Carcinogenesis 47 20106900
2010 A Large-scale genetic association study of esophageal adenocarcinoma risk. Carcinogenesis 42 20453000
2020 Global proteomics of Ubqln2-based murine models of ALS. The Journal of biological chemistry 37 33277362
2013 14-3-3 proteins sequester a pool of soluble TRIM32 ubiquitin ligase to repress autoubiquitylation and cytoplasmic body formation. Journal of cell science 35 23444366
2023 Fibroblast exosomal TFAP2C induced by chitosan oligosaccharides promotes peripheral axon regeneration via the miR-132-5p/CAMKK1 axis. Bioactive materials 25 36936807
2025 Orchestrating Intracellular Calcium Signaling Cascades by Phosphosite-Centric Regulatory Network: A Comprehensive Analysis on Kinases CAMKK1 and CAMKK2. Omics : a journal of integrative biology 23 40079160
2018 Structural Analysis of Inhibitor Binding to CAMKK1 Identifies Features Necessary for Design of Specific Inhibitors. Scientific reports 12 30287839
2017 A Novel Role for CAMKK1 in the Regulation of the Mesenchymal Stem Cell Secretome. Stem cells translational medicine 10 28688176
2013 Polymorphism rs7214723 in CAMKK1 and lung cancer risk in Chinese population. Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine 10 23737288
2023 Identification of Small Molecule Inhibitors and Ligand Directed Degraders of Calcium/Calmodulin Dependent Protein Kinase Kinase 1 and 2 (CaMKK1/2). Journal of medicinal chemistry 9 38009718
2023 14-3-3 protein inhibits CaMKK1 by blocking the kinase active site with its last two C-terminal helices. Protein science : a publication of the Protein Society 8 37817008
2020 Discovery of potent Camkk1 kinase inhibitors through e-pharmacophore and molecular screening approaches. Journal of biomolecular structure & dynamics 5 33155526
2024 Mechanisms of Nrf2 suppression and Camkk1 upregulation in Echinococcus granulosus-induced bone loss. International journal of biological macromolecules 4 39674449
2021 Polymorphism rs7214723 in CAMKK1: a new genetic variant associated with cardiovascular diseases. Bioscience reports 3 34165505
2025 CAMKK1 in Obesity and Type 2 Diabetes Mellitus: Evidence of Interaction With Appetite-Regulating, Metabolic and Inflammatory Factors. Endocrinology, diabetes & metabolism 0 40965347