Mitogen-activated protein kinase kinase 4-c-Jun N-terminal kinase signaling pathway (MKK4-JNK pathway)

The MKK4-JNK signaling pathway is a central component of the mitogen-activated protein kinase (MAPK) system, primarily responsible for transducing stress signals and pro-inflammatory stimuli into cellular responses [1, 14]. In immune cells, this pathway plays a pivotal role in the activation, proliferation, and differentiation of T and B lymphocytes, as well as the regulation of cytokine production, including IL-2 and TNF-α [1, 2, 5]. MKK4 (Mitogen-activated protein kinase kinase 4) serves as a dual-specificity kinase that activates JNK (c-Jun N-terminal kinase) by phosphorylating its Thr-Pro-Tyr motif [3, 15]. Once activated, JNK phosphorylates downstream transcription factors such as c-Jun, which then modulate the expression of genes involved in apoptosis, survival, and the immune response [14, 18]. Dysregulation of the MKK4-JNK axis is associated with a wide range of diseases, including rheumatoid arthritis, neurodegeneration, and various cancers, where it can act as either a tumor suppressor or an oncogene depending on the context [4, 11, 19]. Therapeutic strategies targeting this pathway involve small-molecule inhibitors designed to block MKK4 or JNK activity, offering potential treatments for inflammatory disorders and promoting tissue regeneration, such as in the liver [8, 12, 17]. Notable inhibitors include HRX215, which targets MKK4 for liver regeneration, and various JNK inhibitors like tanzisertib being investigated for inflammatory and fibrotic conditions [10, 12, 17]. However, the broad physiological roles of this pathway present challenges for drug development, particularly regarding off-target effects and the potential for systemic immunosuppression [3, 19].

Other names

MAP2K4-JNK pathwaySEK1-JNK pathwaySAPK/JNK signaling axisStress-activated protein kinase pathway

Small-molecule inhibition of MKK4 or JNK kinases, which blocks the phosphorylation cascade and prevents the activation of downstream transcription factors like c-Jun and ATF2, thereby suppressing the production of pro-inflammatory cytokines and modulating cell survival or death [3, 8, 19].