Affinage

STK16

Serine/threonine-protein kinase 16 · UniProt O75716

Length
305 aa
Mass
34.7 kDa
Annotated
2026-04-28
10 papers in source corpus 10 papers cited in narrative 10 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

STK16 is a constitutively active, Golgi-resident serine/threonine kinase that couples membrane trafficking and actin dynamics to cell cycle progression. It undergoes myristoylation and palmitoylation and autophosphorylates at Tyr198 within its activation segment, a modification essential for both catalytic activity and correct Golgi/membrane localization (PMID:31574902). STK16 directly binds and regulates actin polymerization in a kinase-activity-dependent manner, and its loss or inhibition causes Golgi fragmentation, mitotic delay, and cytokinesis failure (PMID:28294156, PMID:27082499). STK16 also phosphorylates c-MYC at Ser452 to protect it from proteasomal degradation, promoting colorectal cancer cell proliferation (PMID:38622518).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1998 High

    Establishing STK16 as an active kinase resolved the fundamental question of whether the predicted ORF encodes a catalytically competent enzyme, showing it autophosphorylates and phosphorylates exogenous substrates in vitro.

    Evidence In vitro kinase assay with bacterially purified STK16 (PKL12) protein

    PMID:9712705

    Open questions at the time
    • No endogenous substrate identified
    • No cellular context for kinase function
    • Regulation of activity unknown
  2. 2001 High

    Identification of GlcNAcK as a physical interactor that modulates STK16 activity without being a substrate established the first regulatory mechanism for STK16 kinase output.

    Evidence Yeast two-hybrid, reciprocal co-immunoprecipitation in vitro and in vivo, and in vitro kinase assays

    PMID:11741987

    Open questions at the time
    • Mechanism by which GlcNAcK modulates STK16 activity unknown
    • In vivo physiological relevance of the interaction not tested
    • Downstream substrates still unidentified
  3. 2005 High

    Demonstration that STK16 resides at the Golgi and can translocate to the nucleus upon Golgi disruption or overexpression defined its subcellular context and linked it to VEGF secretion, establishing a functional connection to secretory pathway biology.

    Evidence Immunofluorescence, subcellular fractionation, kinase-dead E202A mutant, VEGF secretion assay, and xenograft model

    PMID:16310770

    Open questions at the time
    • Mechanism of Golgi retention not determined
    • Whether nuclear translocation has a transcriptional role unclear
    • VEGF regulation could be indirect
  4. 2016 High

    Development of a selective inhibitor (STK16-IN-1) and orthogonal RNAi validation revealed that STK16 kinase activity is required for normal cell division, with its loss causing binucleation/cytokinesis defects.

    Evidence Selective ATP-competitive inhibitor validated by KinomeScan, RNAi knockdown in MCF-7 cells, cell proliferation and binucleation assays

    PMID:27082499

    Open questions at the time
    • Cytokinesis substrate(s) unknown
    • Whether binucleation phenotype reflects actin dysfunction not yet tested
    • Limited to one cell line
  5. 2017 High

    Direct binding of STK16 to actin and kinase-activity-dependent regulation of actin dynamics mechanistically connected STK16's Golgi residence to Golgi structural maintenance and mitotic progression.

    Evidence In vitro actin-binding and polymerization assays, STK16 knockdown, kinase inhibitor, live-cell imaging

    PMID:28294156

    Open questions at the time
    • Whether STK16 phosphorylates actin or an actin-regulatory protein is unknown
    • Structural basis for the actin interaction not resolved
    • Golgi-to-mitotic spindle transition mechanism unclear
  6. 2019 High

    Identification of Tyr198 autophosphorylation as the critical event for both kinase activity and Golgi/membrane targeting unified the catalytic and localization functions into a single regulatory switch.

    Evidence Site-directed mutagenesis of Thr185, Ser197, and Tyr198; in vitro kinase assays; live-cell imaging and cell cycle analysis

    PMID:31574902

    Open questions at the time
    • How Tyr198 phosphorylation controls membrane binding mechanistically (lipid vs. protein interaction) is unknown
    • Whether other kinases also phosphorylate Tyr198 not addressed
    • Crystal structure of the activation segment not available
  7. 2019 Medium

    Pharmacological evidence extended STK16's physiological role beyond cell-autonomous proliferation, showing it mediates non-adrenergic smooth muscle contraction in prostate and detrusor tissues.

    Evidence Organ bath contractility assay with STK16-IN-1 in human prostate and detrusor tissue strips

    PMID:31867686

    Open questions at the time
    • No genetic validation (knockout or knockdown) in smooth muscle
    • Downstream contractile substrate of STK16 unknown
    • Single pharmacological tool compound used
  8. 2024 Medium

    Identification of c-MYC Ser452 as a direct STK16 phosphorylation site that prevents ubiquitin-proteasomal degradation provided the first defined in vivo substrate linking STK16 to oncogenic signaling.

    Evidence In vitro and in vivo phosphorylation assays, STK16 knockout and pharmacological inhibition, colorectal cancer xenograft model

    PMID:38622518

    Open questions at the time
    • Single-lab finding not yet independently replicated
    • Whether Ser452 phosphorylation occurs in non-cancer contexts unknown
    • Relationship between Golgi-localized STK16 and nuclear c-MYC phosphorylation spatially unexplained

Open questions

Synthesis pass · forward-looking unresolved questions
  • The full substrate repertoire of STK16, the structural basis of its actin regulation and Golgi retention, and whether its nuclear translocation has a direct transcriptional function remain unresolved.
  • No unbiased phosphoproteomics screen for STK16 substrates published
  • No crystal or cryo-EM structure available
  • Nuclear function beyond VEGF overexpression correlation not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0008092 cytoskeletal protein binding 1
Localization
GO:0005794 Golgi apparatus 3 GO:0005634 nucleus 1 GO:0005886 plasma membrane 1
Pathway
R-HSA-1640170 Cell Cycle 3 R-HSA-1643685 Disease 2
Partners
ACTBDRG1MYCNAGKWDR1

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 STK16 (PKL12) encodes a serine/threonine protein kinase capable of autophosphorylation and phosphorylating exogenous substrates (e.g., enolase) in vitro, establishing its intrinsic catalytic activity. In vitro kinase assay with E. coli-purified protein Biochemical and biophysical research communications High 9712705
2001 STK16 (PKL12) physically interacts with N-acetylglucosamine kinase (GlcNAcK); GlcNAcK is not a substrate of STK16 but potently modulates STK16 kinase activity on defined substrate proteins in vitro, suggesting a regulatory role for GlcNAcK in PKL12-mediated phosphorylation. Yeast two-hybrid, in vitro and in vivo co-immunoprecipitation, in vitro kinase assay, subcellular colocalization The Journal of biological chemistry High 11741987
2005 STK16 localizes to the Golgi complex under basal conditions; treatment with brefeldin A or nocodazole, or constitutive overexpression, causes STK16 to translocate to the nuclear compartment. A kinase-dead mutant (E202A) retains both Golgi association and nuclear translocation capability, indicating kinase activity is not required for these localizations. STK16 overexpression enhances VEGF production and secretion. Indirect immunofluorescence, subcellular fractionation, kinase-dead mutant (E202A), retroviral overexpression, VEGF secretion assay, in vivo xenograft Experimental cell research High 16310770
2016 STK16 inhibition by the selective ATP-competitive inhibitor STK16-IN-1 (IC50 = 0.295 μM) reduces cell number and causes accumulation of binucleated cells in MCF-7 cells, a phenotype recapitulated by RNAi knockdown of STK16, establishing a role for STK16 kinase activity in cell cycle/cytokinesis. Kinase inhibitor (STK16-IN-1), KinomeScan selectivity profiling, RNAi knockdown, cell proliferation and binucleation assays ACS chemical biology High 27082499
2017 STK16 localizes to the Golgi throughout the cell cycle, directly binds actin, and regulates actin dynamics in a concentration- and kinase activity-dependent manner in vitro. STK16 knockdown or kinase inhibition disrupts actin polymerization, causes Golgi fragmentation, delays mitotic entry, prolongs mitosis, and causes prometaphase and cytokinesis arrest. In vitro actin-binding and actin dynamics assays, STK16 knockdown, kinase inhibitor, live-cell imaging, immunofluorescence Scientific reports High 28294156
2019 STK16 autophosphorylates at Tyr198 (as well as Thr185 and Ser197) within its activation segment; mutation of Tyr198 alone significantly reduces kinase activity, abolishes Golgi and membrane localization, and impairs cell cycle progression, identifying Tyr198 autophosphorylation as essential for STK16 activity and correct subcellular targeting. Site-directed mutagenesis of autophosphorylation sites, in vitro kinase assays, live-cell imaging/immunofluorescence for localization, cell cycle analysis International journal of molecular sciences High 31574902
2019 STK16 interacts with binding partners GlcNAcK, DRG1, MAL2, actin, and WDR1, participates in TGF-β signaling, TGN protein secretion and sorting, cell cycle regulation, and Golgi assembly, and undergoes fatty acylation (myristoylation and palmitoylation) as post-translational modifications. Review integrating Co-IP, genetic, and biochemical data from multiple studies International journal of molecular sciences Medium 30974739
2024 STK16 directly phosphorylates c-MYC at serine 452, which protects c-MYC from degradation via the ubiquitin-proteasome pathway, thereby promoting colorectal cancer cell proliferation; STK16 knockout or pharmacological inhibition reduces c-MYC levels and curtails tumor growth in vivo. Immunoprecipitation, immunoblot, in vitro/in vivo phosphorylation assay, STK16 knockout, pharmacological inhibition, xenograft animal model Molecular medicine (Cambridge, Mass.) Medium 38622518
2022 ETS1 transcriptionally regulates STK16 expression; miR-181a-5p (delivered via M1 macrophage exosomes) targets ETS1 and STK16, reducing STK16 levels and promoting apoptosis via the AKT1 pathway in lung adenocarcinoma cells. Luciferase reporter assay, ChIP assay, miRNA mimic/inhibitor transfection, siRNA knockdown, CCK-8, apoptosis assay, xenograft Cancer science Medium 35092121
2019 STK16 kinase activity mediates non-adrenergic, non-neurogenic smooth muscle contractions in human prostate (endothelin-1 and U46619-induced) and male detrusor (carbachol, metacholine, and U46619-induced), as the selective inhibitor STK16-IN-1 specifically suppresses these contractions while leaving adrenergic and neurogenic contractions unaffected. Organ bath contractility assay, Western blot, immunofluorescence, pharmacological inhibition with STK16-IN-1 Naunyn-Schmiedeberg's archives of pharmacology Medium 31867686

Source papers

Stage 0 corpus · 10 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2022 Exosomes from M1-polarized macrophages promote apoptosis in lung adenocarcinoma via the miR-181a-5p/ETS1/STK16 axis. Cancer science 38 35092121
2001 Functional interaction between the Ser/Thr kinase PKL12 and N-acetylglucosamine kinase, a prominent enzyme implicated in the salvage pathway for GlcNAc recycling. The Journal of biological chemistry 26 11741987
2005 Nucleocytoplasmic shuttling of STK16 (PKL12), a Golgi-resident serine/threonine kinase involved in VEGF expression regulation. Experimental cell research 22 16310770
2017 STK16 regulates actin dynamics to control Golgi organization and cell cycle. Scientific reports 20 28294156
1998 Cloning, expression analysis, and functional characterization of PKL12, a member of a new subfamily of ser/thr kinases. Biochemical and biophysical research communications 20 9712705
2016 Discovery of a Highly Selective STK16 Kinase Inhibitor. ACS chemical biology 19 27082499
2019 Serine/Threonine Protein Kinase STK16. International journal of molecular sciences 16 30974739
2019 The STK16 inhibitor STK16-IN-1 inhibits non-adrenergic and non-neurogenic smooth muscle contractions in the human prostate and the human male detrusor. Naunyn-Schmiedeberg's archives of pharmacology 8 31867686
2019 Tyr198 is the Essential Autophosphorylation Site for STK16 Localization and Kinase Activity. International journal of molecular sciences 5 31574902
2024 STK16 promoted colorectal cancer progress in a c-MYC signaling-dependent manner. Molecular medicine (Cambridge, Mass.) 3 38622518