C-Jun N-terminal kinases
C -Jun N -terminal kinases ( JNK ), and phospho - stress -activated kinases ( SAPK ) are for the cellular transmission of stimuli (signal transduction ), in particular stress signals, important enzymes. Your name is derived from the ability to phosphorylate the N- terminal amino acid residues of c-Jun. Biochemically JNKs belong to the protein kinases of the MAP kinase family.
JNKs are involved in a signaling cascade. At the beginning of this signaling cascade are, inter alia, Stress factors such as UV irradiation, interleukins or chemokines, as well as numerous others. This also explains the term " stress kinases ". Meanwhile, research has shown, however, that JNKs play an important role in a variety of physiological processes.
There are three types of JNKs, JNK1 and JNK2, which are further subdivided by alternative splicing in a 46- kDa variant and a 54 - kDa variant. Thus, a total of ten known isoforms. The individual isoforms phosphorylate other proteins. To exert this function is often a scaffold protein such as JIP ( JNK -interacting protein ) is required.
Cellular targets for JNKs are believed to proteins in the cell nucleus (in particular the phosphorylation of c -Jun that regulates the gene expression of the AP-1 ), proteins of the cytoskeleton of the cell, as well as proteins with BH3 motif. Of the latter, the anti -apoptotic Bcl -2 is inactivated by phosphorylation, pro-apoptotic factors such as Bax are activated.