Hendershot: The cellular response to imbalances in protein folding in the ER and its role in normal cellular differentiation and disease

The ER chaperones are constitutively expressed and coordinately up-regulated at the level of transcription via shared promoter elements. Agents or conditions that negatively affect protein folding in the ER, the expression of mutant proteins that cannot fold, or even dramatic increases in protein synthesis in this organelle generate an ER stress signal that is transduced to the nucleus. This signal transduction pathway is referred to as the unfolded protein response (UPR) and many of the signal transducers and downstream effectors and targets have been identified.  In the absence of ER stress, BiP binds to the transmembrane proteins that “sense” and keeps them in an inactive state.  When unfolded proteins begin to accumulate, BiP is released from the transducers allowing them to be activated and initiate downstream signaling events.  In addition to imbalances in the normal ER environment, it is increasingly clear that the UPR plays an essential role in the differentiation in some tissues like plasma cells, in the normal homeostasis of tissues like pancreas and liver, and in a number of disease states including neurodegenerative diseases, viral infections and cancer. We are interested in 1) determining the mechanism of UPR activation and control during plasma cell differentiation, 2) understanding the significance of UPR activation in tumors, 3) establishing the role of the UPR in angiogenesis, and 4) identifying components of the UPR that affect the sensitivity of cancer cells to chemotherapeutic treatments.