Distribution of ZAKI-4 in neurons of mouse cerebral cortex

ZAKI-4 was identified as a product of thyroid hormone responsive gene cloned from cultured human skin fibroblasts. A recent in vitro study revealed that ZAKI-4 belongs to a family of proteins that inhibit calcineurin function. Though ZAKI-4 mRNA is known to be expressed abundantly in brain, the subcellular distribution of ZAKI-4 protein is still not known. Here we investigated the localization of ZAKI-4 in the mouse brain using immunohistochemistry. It was revealed that ZAKI-4 was distributed in neurons of the brain. Immunoelectron microscopy showed that ZAKI-4 was mainly localized in the cytoplasm of soma, but not in nuclei nor organella such as mitochondria or endoplasmic reticulum. Since the cellular localization of ZAKI-4 in neurons overlaps with that of calcineurin, it is postulated that ZAKI-4 exerts a calcineurin- inhibitory effect in neurons of the mouse brain in vivo.