The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The requested target is unambiguous. Human MAP3K2 is the approved gene encoding mitogen-activated protein kinase kinase kinase 2 (MEKK2), UniProt Q9Y2U5. It is not MAP3K3/MEKK3 or MAP3K20. Its 619-residue architecture—an N-terminal PB1 interaction domain, intervening regulatory region, and C-terminal STE-family protein-kinase domain—matches the supplied UniProt/InterPro description. The strongest functional assignment is an intracellular serine/threonine MAP3K that activates MAP2Ks, particularly MEK5/MAP2K5 and MKK6/MAP2K6, thereby connecting upstream stimuli to ERK5 and p38 signaling. Direct evidence for every historically proposed substrate is not equally strong. (vish2025structuralbasisfor pages 1-2, ibrahim2025thefunctionalrole pages 31-34, vish2025structuralbasisfor pages 2-3)
| Feature | Best-supported annotation | Evidence type/model | Confidence and limitations |
|---|---|---|---|
| Identity and synonyms | Human MAP3K2 encodes mitogen-activated protein kinase kinase kinase 2, also called MEKK2; UniProt Q9Y2U5. It is a STE11-family Ser/Thr MAP3K. MAP3K3/MEKK3 and MAP3K20 are distinct proteins. | Concordant human protein annotation and peer-reviewed literature (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3) | High. Symbol, protein name, organism, and family are concordant. |
| Architecture | The canonical protein is 619 aa and contains an N-terminal PB1 interaction domain, an intervening regulatory region, and a C-terminal STE-family protein-kinase domain. | Sequence/domain annotation plus structural and biochemical studies (vish2025structuralbasisfor pages 1-2, ibrahim2025thefunctionalrole pages 31-34) | High for length and PB1–kinase architecture. Exact regulatory-region boundaries may vary among resources or isoforms. |
| Catalytic function | ATP-dependent protein kinase that transfers the γ-phosphate of ATP to Ser/Thr residues on protein substrates: ATP + protein-OH → ADP + phosphoprotein. | Kinase-family annotation supported by purified-protein and human-cell phosphorylation assays (vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 10-11) | High. Robust catalytic constants were not available in the retrieved evidence. |
| Direct substrate: MEK5/MAP2K5 | MEKK2 binds and phosphorylates MEK5, activating the MEK5–ERK5 signaling module. | PB1 mutagenesis, co-immunoprecipitation, pathway inhibition, and human HEK293T phosphorylation assays (vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 2-3) | High. MEK5 is one of the best-established physiological MAP2K substrates. |
| Direct substrate: MKK6/MAP2K6 | MEKK2 directly phosphorylates MKK6, including activation-loop Ser207, supporting downstream p38 signaling. | Purified-protein kinase assays and HEK293T experiments; assays used 10 nM MEKK2, 500 nM MKK6, 1 mM ATP, and a 10-minute incubation at 30 °C (vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 10-11) | High for biochemical and cellular phosphorylation. Its physiological importance is likely context dependent. |
| Substrate recognition | MEK5 recruitment is PB1–PB1 dependent. MKK6 lacks a PB1 domain and relies more strongly on the kinase-domain αG-helix interface. Both substrates require αG-mediated productive engagement. | Domain deletion and point-mutant studies, split-luciferase interaction assays, phosphorylation assays, and structural analysis (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 2-3) | High. MKK6 phosphorylation experiments used N=5 and gave ANOVA p≤0.0001; interaction assays used N=25 and gave p≤0.0001 (vish2025structuralbasisfor pages 7-8). |
| Activation mechanism | Kinase-domain dimerization promotes trans-autophosphorylation and activation. The αG helix and C-terminal activation segment contribute to the dimerization interface. | Human HEK293T mutagenesis and trans-phosphorylation experiments plus structural and biochemical analysis (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3) | High. Activation-loop numbering is reported as Ser519 or Ser520 in different sources, so sequence and isoform conventions must be checked. |
| SMYD3 regulation | SMYD3-mediated methylation of Lys260 can enhance oncogenic MAP3K2 signaling, reportedly by opposing PP2A-mediated negative control in Ras-driven cancer models. | Cancer-cell and animal-model findings summarized in recent mechanistic sources (corridore2024roleofmekk2 pages 23-28, corridore2024roleofmekk2a pages 23-28) | Moderate to high mechanistic confidence. Disease dependence and therapeutic generalizability remain preclinical. |
| 14-3-3 regulation | Phosphorylated Thr283 recruits 14-3-3, restricting MEKK2 homodimerization and activation-loop phosphorylation. T283A disrupts binding and alters JNK, IL-6, ERK, and proliferation outputs. | Site-directed mutagenesis and cellular-signaling studies summarized in mechanistic literature (corridore2024roleofmekk2 pages 23-28, corridore2024roleofmekk2a pages 23-28) | Moderate. Effects are context dependent and do not establish uniform inhibition of every downstream branch. |
| Ubiquitin-dependent turnover | NEDD4L directly binds, polyubiquitinates, and promotes degradation of MEKK2. This supplies negative feedback following IL-17-induced activation-loop phosphorylation and limits p38 and NF-κB inflammatory signaling. | Cell-based assays and Nedd4l-deficient mouse inflammation and EAE models (li2022e3ubiquitinligase pages 17-17) | High for pathway regulation. Much of the organism-level evidence is murine rather than human clinical evidence. |
| Localization | MAP3K2 is predominantly described as a cytoplasmic intracellular signaling kinase. Activation-dependent redistribution or nuclear access has been reported, but localization appears dynamic and context dependent. | Cellular annotation and secondary synthesis rather than definitive endogenous spatial mapping (ibrahim2025thefunctionalrole pages 31-34, thiriet2013mitogenactivatedproteinkinase pages 14-17) | Moderate to low. An exclusive compartment should not be assigned without stronger endogenous imaging or fractionation evidence. |
| Principal signaling pathways | The best-supported axis is MEKK2 → MEK5 → ERK5. Direct MKK6 phosphorylation supports p38 signaling. Context-dependent evidence also connects MEKK2 to MKK7/JNK and inflammatory NF-κB outputs. | Direct substrate assays for ERK5 and p38 branches; older biochemical, genetic, and inflammatory models for JNK and NF-κB (vish2025structuralbasisfor pages 7-8, thiriet2013mitogenactivatedproteinkinase pages 25-29, li2022e3ubiquitinligase pages 17-17) | High for MEK5–ERK5 and direct MKK6 phosphorylation; moderate and context dependent for JNK and NF-κB. Other proposed substrates are not equally established. |
| Translational status | MAP3K2 is an experimental target in cancer, inflammation, cardiovascular stress, and immune signaling. A 2.4 Å ponatinib-bound kinase-domain structure demonstrates inhibitor-binding feasibility, but no validated MAP3K2-selective clinical therapy was identified. | Preclinical cell and animal studies, structural pharmacology, and target–disease database evidence (OpenTargets Search: -MAP3K2, vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3) | Preclinical. Ponatinib is not MAP3K2-selective; database associations are hypothesis-generating and do not establish clinical efficacy or causality. |
Table: Evidence-tiered annotation of human MAP3K2/MEKK2, covering its catalytic activity, substrates, regulation, localization, pathways, and translational status while identifying context-dependent or weakly supported conclusions.
Literature consistently equates MAP3K2 with MEKK2 and classifies it in the STE11 subfamily of serine/threonine MAP3Ks. Recent structural work describes a 619-amino-acid protein with an N-terminal PB1 domain and C-terminal catalytic domain separated by roughly 200 residues, fully concordant with Q9Y2U5 and the supplied PB1/kinase-domain annotations. MAP3K3/MEKK3 is a close paralogue, but it is a different gene and was not treated as the target here. (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3)
Some secondary sources report inconsistent apparent molecular masses, including approximately 69.7 or 94 kDa. Sequence-defined length and accession are therefore safer identifiers than apparent gel mobility or older tabular mass estimates. (ibrahim2025thefunctionalrole pages 31-34, keshet2010themapkinase pages 5-7)
MAP3K2 is an ATP-dependent protein serine/threonine kinase. Its generic reaction is:
ATP + protein–OH → ADP + protein–O–phosphate
As a MAP3K, its physiologically relevant acceptors are principally activation-loop serine/threonine residues in downstream MAP2Ks. The best-supported direct substrates in the retrieved evidence are MEK5 and MKK6. In purified-protein assays, 10 nM MEKK2 phosphorylated 500 nM MKK6 at Ser207 in the presence of 1 mM ATP during a 10-minute reaction at 30 °C; a D483N kinase-inactive mutant served as a catalytic control. Human HEK293T experiments independently detected MEKK2-dependent MEK5 Ser311/Thr315 and MKK6 Ser207 phosphorylation. (vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 10-11)
Older literature also assigns MKK4/MKK7, MEK1/2, IKK and other proteins to MAP3K2-dependent signaling. These should not all be annotated as equally established direct physiological substrates: some relationships derive from overexpression, in-vitro assays, pathway readouts, or secondary reviews rather than endogenous substrate validation. The most defensible core annotation is therefore MEK5 and MKK6 kinase, with context-dependent participation in JNK and NF-κB branches. (ibrahim2025thefunctionalrole pages 31-34, thiriet2013mitogenactivatedproteinkinase pages 25-29)
MAP3K2 specificity depends substantially on docking and assembly rather than solely on catalytic-site peptide preference.
Thus, PB1-mediated recruitment confers particularly strong pathway specificity for MEK5–ERK5, whereas αG-mediated contacts support catalytic engagement of both MEK5 and MKK6.
Kinase-domain dimerization promotes MAP3K2 trans-autophosphorylation. Mutations affecting the αG-helix/activation-segment interface eliminate phosphorylation-dependent mobility shifts in HEK293T cells, while co-expression experiments support phosphorylation in trans. Recent structural analysis identified a conserved dimerization surface centered on the αG helix and C-terminal activation segment. Activation-loop numbering appears as Ser519 or Ser520 among sources, probably reflecting sequence/isoform conventions; annotations should preserve the source-specific numbering. (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3)
In Ras-driven cancer models, the methyltransferase SMYD3 methylates MAP3K2 Lys260. This modification has been proposed to prevent PP2A-mediated negative regulation, sustaining MAP3K2-to-MEK1/2 signaling. The mechanism is experimentally important but remains context dependent rather than a universal basal function of MAP3K2. (corridore2024roleofmekk2 pages 23-28, corridore2024roleofmekk2a pages 23-28)
Phosphorylated Thr283 recruits 14-3-3 proteins. Binding limits MAP3K2 homodimerization and activation-loop phosphorylation. A T283A substitution disrupts 14-3-3 interaction and changes JNK, IL-6, ERK and proliferation outputs, indicating that the site regulates pathway allocation as well as overall activity. (corridore2024roleofmekk2 pages 23-28, corridore2024roleofmekk2a pages 23-28)
A 2022 EMBO Reports study identified NEDD4L as a negative regulator that directly binds, polyubiquitinates and promotes degradation of MEKK2. In IL-17 receptor signaling, activation-loop phosphorylation was required both for downstream p38/NF-κB activation and NEDD4L-dependent signal termination. Nedd4l deficiency enhanced inflammatory signaling and aggravated experimental autoimmune encephalomyelitis in mice. This is strong mechanistic evidence, although organism-level disease evidence is predominantly murine. Publication: September 2022; DOI: https://doi.org/10.15252/embr.202254603. (li2022e3ubiquitinligase pages 17-17)
MAP3K2 is best described as a predominantly cytoplasmic intracellular signaling kinase rather than a secreted, membrane-spanning, or structural protein. Its PB1-dependent complexes and kinase cascades are assembled in the cytoplasmic signaling compartment. Secondary synthesis also reports activation-dependent nuclear entry, but the retrieved literature did not provide equally strong endogenous imaging or fractionation evidence. Accordingly, “cytoplasm, with potentially dynamic stimulus-dependent redistribution” is more defensible than an exclusive nuclear or organellar assignment. (ibrahim2025thefunctionalrole pages 31-34, thiriet2013mitogenactivatedproteinkinase pages 14-17)
The highest-confidence signaling route is:
MAP3K2/MEKK2 → MAP2K5/MEK5 → MAPK7/ERK5
PB1-domain assembly makes this a particularly coherent module. ERK5 signaling responds to mitogens and stressors such as cytokines, shear stress, hyperosmolarity and oxidative stress and contributes to survival, differentiation and mechanoadaptation. However, MEKK3 and other upstream kinases can also activate MEK5; downstream ERK5 activity should not automatically be attributed exclusively to MAP3K2. (vish2025structuralbasisfor pages 1-2, thiriet2013mitogenactivatedproteinkinase pages 25-29)
Direct phosphorylation of MKK6 provides a mechanistic route from MAP3K2 to p38 MAPKs. This branch is prominent in inflammatory and stress responses, including IL-17 signaling, where MAP3K2 contributes to p38 and NF-κB activation before NEDD4L-dependent termination. (vish2025structuralbasisfor pages 7-8, vish2025structuralbasisfor pages 10-11, li2022e3ubiquitinligase pages 17-17)
MAP3K2 has context-dependent links to MKK7/JNK and IKK/NF-κB signaling, including cytokine, immune-cell and stress models. Evidence supports biological participation, but direct-substrate and pathway dominance vary by cell type. These branches should therefore be annotated as supported secondary pathways, not as invariant outputs. (ibrahim2025thefunctionalrole pages 31-34, thiriet2013mitogenactivatedproteinkinase pages 25-29, li2022e3ubiquitinligase pages 17-17)
Recent work has focused less on redefining catalytic function and more on regulatory RNAs, cancer dependencies and inflammatory control. Studies reported MAP3K2-associated regulatory axes in hypoxic human AC16 cardiomyocytes and esophageal squamous-cell carcinoma, while ovarian-cancer work used MAP3K2 knockdown as part of investigating MEK5–ERK5 pathway dependence. These are preclinical model systems, not evidence of an approved biomarker or therapy.
A 2023 review emphasized MAP3K-family control of interferon and NF-κB signaling in antiviral immunity, but family-level conclusions should not be converted automatically into MAP3K2-specific mechanisms. A 2024 study of SMYD3 phosphorylation/methylation regulation further explored Thr263, Thr283 and Lys260, although the retrieved source was a thesis-like document with incomplete journal metadata and should be weighted below fully peer-reviewed primary studies. (corridore2024roleofmekk2a pages 106-109, corridore2024roleofmekk2 pages 23-28)
The most consequential recent mechanistic advance actually retrieved was later structural work: a 2.4 Å ponatinib-bound MAP3K2 kinase-domain structure and direct dissection of MEK5/MKK6 recognition. It was accepted in November 2025 and therefore lies outside the requested 2023–2024 priority window, but it materially updates current understanding. PDB 9P6A; DOI: https://doi.org/10.1038/s41467-025-66884-5. (vish2025structuralbasisfor pages 1-2, vish2025structuralbasisfor pages 2-3, vish2025structuralbasisfor pages 10-11)
MAP3K2 currently has three principal research applications:
No validated MAP3K2-selective clinical therapy or established diagnostic use was identified. Open Targets lists comparatively modest associations with venous thromboembolism (score 0.322), neurodegenerative disease (0.303), deep-vein thrombosis (0.271), thrombophilia (0.253) and cutaneous lupus erythematosus (0.229). These are evidence-aggregation scores—not effect sizes, prevalence estimates, or proof of causality—and are best treated as hypothesis-generating. (OpenTargets Search: -MAP3K2)
The evidence supports the following conservative functional statement:
MAP3K2/MEKK2 is a predominantly cytoplasmic STE-family serine/threonine MAP kinase kinase kinase that undergoes dimerization-dependent autophosphorylation and phosphorylates MAP2Ks. Its best-established substrates are MEK5, recruited through PB1-domain interactions to activate ERK5, and MKK6, engaged through kinase-domain αG surfaces to activate p38. Its activity is tuned by phosphorylation, 14-3-3 binding, SMYD3-mediated Lys260 methylation and ubiquitin-dependent turnover, enabling context-dependent ERK5, p38, JNK and NF-κB signaling.
Confidence is high for identity, domain architecture, kinase activity, MEK5/MKK6 phosphorylation, PB1-dependent MEK5 assembly and dimerization/autophosphorylation. Confidence is moderate and context dependent for broad substrate lists, nuclear localization, pathway dominance in specific diseases and therapeutic tractability. Most disease applications remain preclinical, and the absence of selective clinical inhibitors limits causal pharmacological validation.
References
(vish2025structuralbasisfor pages 1-2): Kimberly J. Vish, Clotilde Huet-Calderwood, Byung Hak Ha, David A. Calderwood, and Titus J. Boggon. Structural basis for mekk2 dimerization and substrate recognition. Nature Communications, Nov 2025. URL: https://doi.org/10.1038/s41467-025-66884-5, doi:10.1038/s41467-025-66884-5. This article has 3 citations and is from a highest quality peer-reviewed journal.
(ibrahim2025thefunctionalrole pages 31-34): A Ibrahim. The functional role of map3k2 in pancreatic ductal adenocarcinoma. Unknown journal, 2025.
(vish2025structuralbasisfor pages 2-3): Kimberly J. Vish, Clotilde Huet-Calderwood, Byung Hak Ha, David A. Calderwood, and Titus J. Boggon. Structural basis for mekk2 dimerization and substrate recognition. Nature Communications, Nov 2025. URL: https://doi.org/10.1038/s41467-025-66884-5, doi:10.1038/s41467-025-66884-5. This article has 3 citations and is from a highest quality peer-reviewed journal.
(vish2025structuralbasisfor pages 7-8): Kimberly J. Vish, Clotilde Huet-Calderwood, Byung Hak Ha, David A. Calderwood, and Titus J. Boggon. Structural basis for mekk2 dimerization and substrate recognition. Nature Communications, Nov 2025. URL: https://doi.org/10.1038/s41467-025-66884-5, doi:10.1038/s41467-025-66884-5. This article has 3 citations and is from a highest quality peer-reviewed journal.
(vish2025structuralbasisfor pages 10-11): Kimberly J. Vish, Clotilde Huet-Calderwood, Byung Hak Ha, David A. Calderwood, and Titus J. Boggon. Structural basis for mekk2 dimerization and substrate recognition. Nature Communications, Nov 2025. URL: https://doi.org/10.1038/s41467-025-66884-5, doi:10.1038/s41467-025-66884-5. This article has 3 citations and is from a highest quality peer-reviewed journal.
(corridore2024roleofmekk2 pages 23-28): RN Corridore. Role of mekk2 phosphorylation at threonine 263 on smyd3-mediated methylation of lysine 260. Unknown journal, 2024.
(corridore2024roleofmekk2a pages 23-28): RN Corridore. Role of mekk2 phosphorylation at threonine 263 on smyd3-mediated methylation of lysine 260. Unknown journal, 2024.
(li2022e3ubiquitinligase pages 17-17): Hui Li, Ning Wang, Yu Jiang, Haofei Wang, Zengfeng Xin, Huazhang An, Hao Pan, Wangqian Ma, Ting Zhang, Xiaojian Wang, and Wenlong Lin. E3 ubiquitin ligase nedd4l negatively regulates inflammation by promoting ubiquitination of mekk2. EMBO Reports, Sep 2022. URL: https://doi.org/10.15252/embr.202254603, doi:10.15252/embr.202254603. This article has 34 citations and is from a highest quality peer-reviewed journal.
(thiriet2013mitogenactivatedproteinkinase pages 14-17): M. Thiriet. Mitogen-activated protein kinase module. ArXiv, pages 311-378, 2013. URL: https://doi.org/10.1007/978-1-4614-4370-4_6, doi:10.1007/978-1-4614-4370-4_6. This article has 6 citations.
(thiriet2013mitogenactivatedproteinkinase pages 25-29): M. Thiriet. Mitogen-activated protein kinase module. ArXiv, pages 311-378, 2013. URL: https://doi.org/10.1007/978-1-4614-4370-4_6, doi:10.1007/978-1-4614-4370-4_6. This article has 6 citations.
(OpenTargets Search: -MAP3K2): Open Targets Query (-MAP3K2, 6 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(keshet2010themapkinase pages 5-7): Yonat Keshet and Rony Seger. The map kinase signaling cascades: a system of hundreds of components regulates a diverse array of physiological functions. Methods in molecular biology, 661:3-38, Jan 2010. URL: https://doi.org/10.1007/978-1-60761-795-2_1, doi:10.1007/978-1-60761-795-2_1. This article has 867 citations and is from a peer-reviewed journal.
(corridore2024roleofmekk2a pages 106-109): RN Corridore. Role of mekk2 phosphorylation at threonine 263 on smyd3-mediated methylation of lysine 260. Unknown journal, 2024.