GRP78/BiP is a novel downstream target of IGF-1 receptor mediated signaling.

Glucose regulated protein 78/immunoglobulin binding protein (GRP78/BiP) is an endoplasmic reticulum (ER) chaperone protein and master regulator of the unfolded protein response (UPR). The response of GRP78 to overt pharmacologically induced ER stress is well established, whereas the modulation of GRP78 to physiologic changes is less characterized. In this study, we examined the regulation of GRP78 in response to reduced IGF-1 growth factor signaling, a common consequence of calorie restriction (CR).