The c-Jun N-terminal protein kinase family of mitogen-activated protein kinases (JNK MAPKs)

The c-Jun N-terminal protein kinase mitogen-activated protein kinases (JNK MAPKs) are an evolutionarily-conserved family of serine/threonine protein k inases. First identified in 1990 when intraperitoneal injection of the prot ein synthesis inhibitor cycloheximide activated a 54 kDa protein kinase, th e JNK MAPKs have now taken on a prominent role in signal transduction. This research has revealed a number of levels of complexity. Alternative gene s plicing is now recognised to result in ten different JNK MAPK isoforms of 4 6-55 kDa, and these isoforms differ in their substrate affinities. Furtherm ore, although originally classified as stress-activated protein kinases (SA PKs), or SAPKs, the JNK MAPKs are also critical mediators of signal transdu ction in response to stimulation by cytokines and some growth factors, JNK MAPKs have been shown to be critical mediators in dorsal closure in develop ing Drosophila embryos, and targeted knockout of murine JNK MAPKs has sugge sted a critical involvement of these kinases in mammalian embryonic develop ment. Recent work has also highlighted their importance in programmed cell death. Thus, the JNK MAPKs may provide a critical target for regulation in both normal and diseased states. (C) 2001 Elsevier Science Ltd. All rights reserved.