DOK3

DOK3 is a hematopoietic adaptor protein that functions as a broad inhibitory signaling hub downstream of immunoreceptors, Toll-like receptors, and cytokine receptors in B cells, macrophages, neutrophils, T cells, osteoclasts, and platelets. Upon tyrosine phosphorylation by Src-family kinases (principally Lyn) or Btk, DOK3 recruits distinct effectors to suppress specific signaling branches: SHIP-1 to inhibit JNK (PMID:14993273); Grb2 to sequester the Sos/Shc complex and block Ras-ERK activation (PMID:16436051, PMID:17290227); PP1 to dephosphorylate CARD9 and dampen NF-κB/JNK in antifungal immunity (PMID:31180338); PP4C to dephosphorylate CARD11 and attenuate TCR signaling (PMID:37906628); and SHP-2 to dephosphorylate MyD88-Y257 and suppress JAK2-STAT3 in neutrophils (PMID:36172386). DOK3 also promotes type I interferon production by scaffolding a TRAF3–TBK1 complex for IRF3 activation (PMID:24929003), and its protein levels are controlled by TRAF6-mediated K48-linked polyubiquitination at Lys-27 (PMID:26548852) and by PRDX1-dependent autophagy-lysosomal degradation (PMID:40893682), while its mRNA is stabilized by IGF2BP2-mediated m6A recognition (PMID:41999269).

1. 2000 High

   Establishing DOK3 as an inhibitory adaptor: the first study showed that Src-family-kinase-dependent tyrosine phosphorylation of DOK3 recruits SHIP and Csk to suppress NFAT activation and cytokine release in B cells, defining it as a negative regulator of immunoreceptor signaling.

   Evidence Co-immunoprecipitation, mutagenesis, and NFAT reporter assays in B-cell lines

   PMID:10733577

   Open questions at the time

   • Relative contributions of SHIP vs. Csk to inhibition were unclear
   • In vivo role not yet tested
2. 2004 High

   Resolving which effector mediates JNK suppression: SHIP-1, not Csk, was identified as the DOK3 partner responsible for selectively inhibiting BCR-evoked JNK, with SHIP-1-deficient B cells phenocopying DOK3 loss for this pathway.

   Evidence Co-immunoprecipitation and kinase assays in SHIP-1 knockout mouse B cells

   PMID:14993273

   Open questions at the time

   • How DOK3 activates SHIP-1 catalytic activity was not resolved
3. 2006 High

   Identifying the Grb2-sequestration mechanism for Ras-ERK inhibition: DOK3 was shown to bind Grb2 via phosphotyrosine-SH2 interaction, sequestering Grb2-Sos away from Shc and thereby blocking Ras-ERK, establishing a second distinct inhibitory pathway through the same adaptor.

   Evidence Site-directed mutagenesis (Dok-3-FF) with Ras/ERK activation and Grb2-Sos-Shc recruitment assays

   PMID:16436051

   Open questions at the time

   • Whether Grb2-sequestration and SHIP-1 recruitment operate simultaneously or in distinct contexts was unknown
4. 2007 High

   Defining the membrane-proximal spatial mechanism and in vivo requirement: DOK3 was localized to the plasma membrane inner leaflet as a major Lyn substrate, where phosphorylated DOK3 recruits Grb2 to inhibit Btk-PLCγ2-Ca²⁺ signaling; Dok3-knockout mice confirmed hyperproliferation and hyperactivation of NF-κB, JNK, and p38 in B cells.

   Evidence Subcellular fractionation, live-cell imaging, Dok-3⁻/⁻ mice with Ca²⁺ flux, proliferation, and kinase assays

   PMID:17290227 PMID:17363732

   Open questions at the time

   • Which PH/PTB domain determinants drive membrane association was not fully mapped
   • Redundancy with DOK1/DOK2 in vivo was not assessed
5. 2011 High

   Revealing a non-inhibitory scaffolding function: DOK3, together with Grb2 and Cbl, was found to couple BCR microclusters to dynein-dependent directed movement on microtubules, showing DOK3 also organizes spatial signaling architecture beyond simple inhibition.

   Evidence High-resolution live imaging, quantitative MS, and Dok-3-deficient B cells

   PMID:21703542

   Open questions at the time

   • Direct DOK3-dynein interaction not demonstrated
   • Whether this function operates in non-B hematopoietic cells was unknown
6. 2012 High

   Extending DOK3 function to innate immunity: DOK3 was shown to negatively regulate TLR4/LPS-induced ERK and cytokine production in macrophages and to stabilize negative regulators (SHIP1, IRAK-M, SOCS1) during endotoxin tolerance.

   Evidence Dok3⁻/⁻ macrophages and mice, ERK/ubiquitination assays, cytokine ELISA

   PMID:22761938

   Open questions at the time

   • Mechanism by which DOK3 stabilizes IRAK-M and SOCS1 was not defined
7. 2013 High

   Identifying the DAP12 ITAM–PTB domain interaction: DOK3 was shown to bind the DAP12 ITAM through its PTB domain, providing the molecular basis for its recruitment and Src-dependent phosphorylation at the membrane during TLR4 signaling in macrophages.

   Evidence Co-immunoprecipitation, domain mapping, Dok3⁻/⁻ macrophages with in vivo LPS challenge

   PMID:23962980

   Open questions at the time

   • Structural basis of PTB-ITAM recognition not resolved
8. 2014 High

   Uncovering a positive signaling role in type I IFN production: DOK3 was found to scaffold TRAF3–TBK1 complex formation via its C-terminal tyrosine-rich domain, enabling TBK1 activation and IRF3-dependent IFN-β expression, with Btk identified as a DOK3 kinase. Separately, DOK3-mediated Ca²⁺ attenuation was shown to sustain PDL1/PDL2 expression required for plasma cell differentiation.

   Evidence Dok3⁻/⁻ macrophages, co-IP, IFN-β reporter, bone marrow reconstitution, genetic epistasis with BTK and PLCγ2 KO mice

   PMID:24929003 PMID:25053811

   Open questions at the time

   • Whether the IFN-β-promoting and ERK-inhibitory functions are cell-type-specific was not resolved
   • Btk phosphorylation sites on DOK3 not mapped
9. 2015 High

   Defining how DOK3 protein levels are controlled: TRAF6 was identified as the E3 ligase that K48-polyubiquitinates DOK3 at Lys-27, targeting it for degradation during TLR9 stimulation; a K27R mutant resists degradation and suppresses cytokine output.

   Evidence Ubiquitination assays, K27R mutagenesis, lentiviral reconstitution in Dok3⁻/⁻ macrophages, cytokine ELISA

   PMID:26548852

   Open questions at the time

   • Whether other E3 ligases also target DOK3 was unknown
   • Half-life measurements under basal conditions not reported
10. 2017 High

    Extending DOK3's inhibitory role to osteoclast biology: DOK3 was shown to limit osteoclastogenesis by inhibiting Syk and ERK downstream of RANKL/M-CSF, with DAP12/DOK3 double-KO epistasis revealing DOK3 also restrains DAP12-independent osteoclast formation.

    Evidence DOK3⁻/⁻ and DKO mice, osteoclast differentiation assays, bone histomorphometry

    PMID:28650106

    Open questions at the time

    • The DAP12-independent DOK3 activation mechanism in osteoclasts was not identified
11. 2019 High

    Identifying phosphatase recruitment as a DOK3 inhibitory mechanism: DOK3 was shown to recruit PP1 to dephosphorylate CARD9, dampening NF-κB and JNK and attenuating antifungal neutrophil responses, demonstrating DOK3 inhibits signaling not only by effector sequestration but also by direct phosphatase delivery.

    Evidence Co-IP of DOK3-PP1-CARD9 complex, Dok3⁻/⁻ mice challenged with Candida albicans, signaling and functional assays

    PMID:31180338

    Open questions at the time

    • How DOK3 selects PP1 over other phosphatases was not determined
12. 2021 High

    Establishing DOK3 as a JAK2-STAT3 suppressor in neutrophils: DOK3 was found to limit JAK2/STAT3 activation and calprotectin production in colonic neutrophils, maintaining gut microbial homeostasis; separately, ULK1 was placed upstream of DOK3 in osteoclast differentiation.

    Evidence Dok3⁻/⁻ mice with DSS colitis model, microbiota transfer rescue; ULK1/DOK3 co-knockdown with Syk/JNK assays

    PMID:34743196 PMID:34820053

    Open questions at the time

    • Direct ULK1-DOK3 interaction not biochemically demonstrated
    • Mechanism linking DOK3 to JAK2 inhibition was not fully delineated
13. 2022 Medium

    Delineating the SHP-2/MyD88 axis: DOK3 was shown to recruit SHP-2 to dephosphorylate MyD88 at Y257, providing the molecular mechanism for JAK2-STAT3 suppression downstream of TLR4.

    Evidence Co-IP, MyD88-Y257 phosphorylation assays, DOK3⁻/⁻ neutrophils, TLR4/JAK2/STAT3 inhibitor epistasis

    PMID:36172386

    Open questions at the time

    • Single study; independent replication needed
    • Whether SHP-2 recruitment is direct or bridged by another adaptor was not resolved
14. 2023 High

    Extending the phosphatase-recruitment paradigm to T cells: DOK3 was shown to recruit PP4C to dephosphorylate CARD11, dampening TCR signaling and modulating Th cell differentiation, with hypomorphic CARD11 variants in atopic dermatitis patients exhibiting increased DOK3 binding.

    Evidence Co-IP, CARD11 phosphorylation assays, Dok3⁻/⁻ mice with experimental atopic dermatitis, patient variant binding analysis

    PMID:37906628

    Open questions at the time

    • Whether DOK3-PP4C and DOK3-PP1 complexes are mutually exclusive was not tested
    • Functional impact of enhanced CARD11 variant-DOK3 binding on patient phenotype not fully resolved
15. 2025 Medium

    Identifying a second degradation pathway: PRDX1 was shown to physically interact with DOK3 and promote its autophagy-lysosomal degradation, with the molecular glue Salvianolic acid B enhancing this interaction to suppress plasma cell differentiation and arthritis.

    Evidence Co-IP, autophagy-lysosome inhibition, collagen-induced arthritis mouse model, small molecule treatment

    PMID:40893682

    Open questions at the time

    • PRDX1-DOK3 binding site not mapped
    • Relationship between TRAF6-mediated and PRDX1-mediated degradation pathways not examined
16. 2026 Medium

    Revealing post-transcriptional regulation of DOK3 levels: IGF2BP2 was found to bind and stabilize DOK3 mRNA via m6A modifications at specific sites, with DOK3 reconstitution rescuing hyper-inflammatory NF-κB activation in IGF2BP2-deficient cells.

    Evidence m6A site mapping, RNA immunoprecipitation, IGF2BP2 KD/OE, DOK3 reconstitution, NF-κB and cytokine assays

    PMID:41999269

    Open questions at the time

    • Which methyltransferase deposits these m6A marks was not identified
    • Whether m6A regulation of DOK3 is cell-type-specific is unknown

• Unresolved: the structural basis for DOK3's selective recruitment of different phosphatases (PP1, PP4C, SHP-2) and effectors (SHIP-1, Grb2, TRAF3) in different cell types and signaling contexts, and whether DOK3 post-translational modifications (specific phosphotyrosine sites, ubiquitination patterns) encode effector selectivity.
• No structural data (crystal/cryo-EM) for DOK3 or its complexes
• Phosphosite-to-effector mapping is incomplete
• Functional redundancy with DOK1/DOK2 across hematopoietic lineages not systematically addressed