Selective activation of JNK/SAPK by interleukin‐1 in rabbit liver is mediated by MKK7

Abstract
Activation of jun N‐terminal kinase (JNK)/stress‐activated protein kinase (SAPK) by interleukin‐1 (IL‐1) has been reported in many cells and in rabbit liver. Here we report selective activation of JNK/SAPK, without activation of p38 or p42 mitogen‐activated protein kinases (MAPKs), by IL‐1 in rabbit liver. We identified an IL‐1 regulated JNK/SAPK activator present in rabbit liver using S Sepharose chromatography. It was purified and immunoprecipitated by two antisera to MAP kinase kinase 7 (MKK7). It was not recognised by an antibody to MKK4. We conclude that MKK7 is the activator of JNK/SAPK activated by IL‐1 in liver and that JNK/SAPK is the only MAPK activated by IL‐1 in liver.