Role of Herp in the endoplasmic reticulum stress response.

Application of differential display to cultured rat astrocytes allowed cloning of Herp cDNA. Although Herp was strongly induced by endoplasmic reticulum (ER) stress, it decayed rapidly consequent to proteasome-mediated degradation. To investigate the role of this molecule in terms of the stress response, Herp knockout cells were developed using F9 embryonic carcinoma cells.

Transmission of cell stress from endoplasmic reticulum to mitochondria: enhanced expression of Lon protease.

The rat homologue of a mitochondrial ATP-dependent protease Lon was cloned from cultured astrocytes exposed to hypoxia. Expression of Lon was enhanced in vitro by hypoxia or ER stress, and in vivo by brain ischemia. These observations suggested that changes in nuclear gene expression (Lon) triggered by ER stress had the potential to impact important mitochondrial processes such as assembly and/or degradation of cytochrome c oxidase (COX).