The Drosophila cell shape regulator c-Jun N-terminal kinase also functionsas a stress-activated protein kinase

Mammalian c-Jun N-terminal kinases (JNKs) are members of a group of stress- activated intracellular signalling molecules within the MAP kinase family. Molecular genetic analysis of a highly evolutionarily conserved Drosophila JNK homologue, DJNK, has demonstrated that this molecule plays an essential developmental role in cell shape regulation. However, it remains to be det ermined whether DJNK also responds to the broad range of cellular stresses and other stimuli that affect its mammalian counterpart. Here we demonstrat e that c-Jun, a substrate for mammalian JNKs. is a specific substrate for D JNK and that an antiserum that crossreacts with activated mammalian JNK at the conserved threonyl-prolyl-tyrosyl (TPY) motif within the activation loo p also specifically recognises the activated form of DJNK. Using these two assays, we show that DJNK activity is stimulated in cultured cells by sever al treatments that activate mammalian JNKs, including addition of arsenite, vanadate and ceramide derivatives. It is therefore concluded that in addit ion to its essential developmental functions. DJNK plays an important role in stress responses that mirrors its mammalian counterpart. (C) 2001 Elsevi er Science Ltd. All rights reserved.