TY - JOUR TI - Noncanonical binding of BiP ATPase domain to Ire1 and Perk is dissociated by unfolded protein CH1 to initiate ER stress signaling AU - Carrara, Marta AU - Prischi, Filippo AU - Nowak, Piotr R AU - Kopp, Megan C AU - Ali, Maruf MU A2 - Harrison, Stephen C VL - 4 PY - 2015 DA - 2015/02/18 SP - e03522 C1 - eLife 2015;4:e03522 DO - 10.7554/eLife.03522 UR - https://doi.org/10.7554/eLife.03522 AB - The unfolded protein response (UPR) is an essential cell signaling system that detects the accumulation of misfolded proteins within the endoplasmic reticulum (ER) and initiates a cellular response in order to maintain homeostasis. How cells detect the accumulation of misfolded proteins remains unclear. In this study, we identify a noncanonical interaction between the ATPase domain of the ER chaperone BiP and the luminal domains of the UPR sensors Ire1 and Perk that dissociates when authentic ER unfolded protein CH1 binds to the canonical substrate binding domain of BiP. Unlike the interaction between chaperone and substrates, we found that the interaction between BiP and UPR sensors was unaffected by nucleotides. Thus, we discover that BiP is dual functional UPR sensor, sensing unfolded proteins by canonical binding to substrates and transducing this event to noncanonical, signaling interaction to Ire1 and Perk. Our observations implicate BiP as the key component for detecting ER stress and suggest an allosteric mechanism for UPR induction. KW - UPR KW - ER stress KW - Ire1 KW - perk KW - unfolded protein JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -