Abstract
Hippocalcin is a member of the neuronal calcium sensors (NCS) family predominantly expressed in the hippocampal pyramidal cells. We have found that hippocalcin binds to C-terminal region of Mixed Lineage Kinase (MLK) 3. Here we analyzed activity of MLK3 in hippocalcin deficient mice. Immunoblot analysis using substrate specific anti-phospho-antibodies revealed that MKK3, one of the substrate of MLK3, in hippocalcin deficient mice was higher phosphorylated than that in wild type. Kinase activity of immunoprecipitated MLK3 was examined using bacterially expressed MKK4 as a substrate. The resting MLK3 activity in hippocalcin deficient mice was higher than that in wild type. By adding recombinant hippocalcin (100ng) to the assay condition, the activity of MLK3, which was immunoprecipitated from wild type mice, was inhibited. These results indicate that the binding of hippocalcin to C-terminal domain of MLK3 directly inhibits MLK3 kinase activity. [J Physiol Sci. 2006;56 Suppl:S119]
