Novel mechanisms of regulating endoplasmic reticulum homeostasis in alcoholic pancreatitis

项目总结

Project Summary Alcohol abuse is a major risk factor in initiating pancreatitis in humans and in rodents. However, only less than 10% of heavy drinkers develop alcoholic pancreatitis whereas most heavy drinkers have mild and autolimited pathological changes, suggesting that a refined adaptation in pancreatic cells to protect against the detrimental effects of alcohol. Pancreatic exocrine acinar cells possess high protein synthetic rates to produce and secrete large amounts of digestive enzymes. To meet the high demand of protein synthesis, acinar cells are exceptionally enriched with endoplasmic reticulum (ER). Dysregulation of ER homeostasis can lead to ER stress and acinar cell damage resulting in the onset of pancreatitis. Cells use protective mechanisms such as autophagy to balance the homeostasis of organelles such as ER to adapt and protect themselves from ER stress. Defective basal autophagy in mouse pancreas disrupts ER homoeostasis resulting in ER stress and spontaneous pancreatitis. We recently demonstrated that transcription factor EB (TFEB) directly regulates lysosomal biogenesis and, indirectly, autophagy, which is impaired by alcohol causing alcoholic hepatitis and pancreatitis. Our preliminary studies showed that alcohol feeding decreased VMP1 (vacuole membrane protein 1), an ER-resident multispanning transmembrane protein, at both mRNA and protein levels in an experimental alcohol pancreatitis mouse model. More importantly, acinar cell-specific deletion of VMP1 in mice leads to increased ER stress and spontaneous pancreatitis. Damaged and excess ER can be removed via selective autophagy, termed as ER-phagy, which helps to maintain ER homeostasis and relieve ER stress. Our long- term goal of this proposal is to understand the molecular mechanisms for how alcohol decreases VMP1 in acinar cells and how VMP1-mediated autophagy protects against alcohol-induced pancreatitis. The objective of this proposal is to understand how VMP1-mediated ER-phagy is impaired by alcohol in acinar cells and how to pharmacologically maintain acinar cell ER homeostasis to protect against alcohol-induced pancreatitis. We will determine how genetic and pharmacological activation of TFEB-VMP1-mediated ER-phagy regulates ER homeostasis and protects against alcohol-induced pancreatitis. This proposal will establish a foundation for the development of novel therapeutics for treating alcoholic pancreatitis through modulation of VMP1-mediated ER-phagy to maintain acinar cell organelle homeostasis.