The ER chaperone and signaling regulator GRP78/BiP as a monitor of endoplasmic reticulum stress.

The multiple implications of ER stress and the unfolded protein response in health and disease highlight the importance of identifying convenient monitoring systems for its onset under various experimental or physiological settings. A large volume of studies establish that induction of GRP78 is a marker for ER stress. GRP78, also referred to as BiP, is a central regulator for ER stress due to its role as a major ER chaperone with anti-apoptotic properties as well as its ability to control the activation of transmembrane ER stress sensors (IRE1, PERK, and ATF6) through a binding-release mechanism. In the following report, we present several methods to measure GRP78 induction. This can be achieved by measuring the Grp78 promoter activity or by measuring the level of Grp78 transcripts or GRP78 protein. These techniques can be applied to tissue culture cells as well as tissues and organs.