Jun N-terminal Kinase 2, also known as JNK2, is a member of the mitogen-activated protein kinase (MAPK) family, specifically belonging to the subgroup of stress-activated protein kinases (SAPKs). JNK2 plays a pivotal role in the regulation of cell survival, apoptosis, proliferation, differentiation, and inflammatory responses. Upon activation by upstream signaling molecules, JNK2 phosphorylates various transcription factors, particularly members of the c-Jun family (including c-Jun itself), as well as ATF2, p53, and others. This phosphorylation event modulates the transcriptional activity of these factors, ultimately influencing the expression of genes involved in the aforementioned cellular processes. The activation of JNK2 is a complex process that involves the phosphorylation of specific threonine and tyrosine residues within its activation loop by MAPK kinases (MKKs), primarily MKK4 and MKK7. This phosphorylation event triggers a conformational change in JNK2, allowing it to become fully active and capable of phosphorylating its downstream substrates. The upstream signaling pathways that lead to JNK2 activation are diverse and include pathways activated by TNF-α, IL-1, and other inflammatory cytokines, as well as pathways activated by environmental stresses such as UV radiation and oxidative stress.
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