The major portion of our research is aimed at elucidating fundamental mechanisms that regulate protein folding and the cellular responses to the accumulation of unfolded protein within the endoplasmic reticulum (ER). Research into the fundamental processes that regulate protein synthesis and folding within the ER should have impact on the understanding of genetic diseases that result from protein folding defects.

Accumulation of unfolded proteins within the ER induces an adaptive stress response known as the unfolded protein response (UPR). The UPR is transduced from the ER lumen to the nucleus by three transmembrane proteins IRE1, ATF6, and PERK. Activation of the UPR induces the production of a family of basic leucine zipper-containing transcription factors that activate transcription of genes encoding functions to reduce the protein-folding load and increase the protein folding capacity of the ER. IRE1 is a serine/threonine protein kinase and endoribonuclease that signals transcriptional activation by initiating a novel splicing reaction on the mRNA encoding the transcription factor XBP1. UPR activation promotes trafficking of ATF6 from the ER to the Golgi where it is processed to yield a cytosolic fragment that is a potent transcriptional activator. Finally, the protein kinase PERK signals translational attenuation through phosphorylation of the alpha subunit of the eukaryotic translation initiation factor 2 (eIF2a) on serine residue 51. This phosphorylation also induces translation of the transcription factor ATF4. We have demonstrated that PERK/eIF2a signaling is essential for glucose-regulated insulin production by pancreatic beta cells, where defects in this pathway result in beta cell dysfunction and diabetes. The findings demonstrate an unprecedented link between glucose metabolism, protein translation, and protein folding and have implication in the treatment of diabetes. Future studies directed to elucidate the molecular logic for the UPR adaptive response will provide fundamental insight into numerous pathological conditions such as viral infection, cancer, inflammation, metabolic disease and atherosclerosis, and protein folding diseases such as Parkinson's disease and Alzheimer's disease.