p38JNK

p38JNK is not a single enzyme but a way to refer to two closely related branches of the mitogen-activated protein kinase (MAPK) signaling system: the p38 MAP kinases and the c-Jun N-terminal kinases (JNKs). These families respond to cellular stress and inflammatory signals and regulate diverse cellular outcomes, including gene expression, differentiation, proliferation, and apoptosis. There is no official kinase named “p38JNK”; the term is sometimes used informally to discuss the two MAPK subfamilies together.

p38 MAP kinases comprise four isoforms: p38α (MAPK14), p38β (MAPK11), p38γ (MAPK12), and p38δ (MAPK13). They are activated by upstream MAPK kinases MKK3 and MKK6 in response to stressors such as inflammatory cytokines, ultraviolet irradiation, and osmotic shock. Once activated, p38 kinases phosphorylate a variety of substrates, including transcription factors such as ATF2 and MEF2 family members, as well as other kinases, leading to changes in gene expression, cytokine production, cell cycle control, differentiation, and apoptosis in a context-dependent manner.

JNKs include JNK1, JNK2, and JNK3 (MAPK8, MAPK9, MAPK10). They are activated predominantly by MKK4 and MKK7 in response to stress signals such as UV, reactive oxygen species, and inflammatory cytokines. JNKs phosphorylate transcription factors such as c-Jun, contributing to AP-1–mediated gene expression. JNK signaling has roles in apoptosis, neuronal development and plasticity, metabolism, and, in some contexts, cell survival, reflecting pathway complexity and tissue specificity.

Both p38 and JNK pathways are subject to cross-talk with other signaling networks and are common targets in research and pharmacology, with several inhibitors used to study their functions.