ADP-ribosylation Factor 1 Protein Regulates Trypsinogen Activation via Organellar Trafficking of Procathepsin B Protein and Autophagic Maturation in Acute Pancreatitis

Several studies have suggested that autophagy might play a deleterious role in acute pancreatitis via intra-acinar activation of digestive enzymes. The prototype for this phenomenon is cathepsin B-mediated trypsin generation. To determine the organellar basis of this process, we investigated the subcellular distribution of the cathepsin B precursor, procathepsin B. We found that procathepsin B is enriched in Golgi-containing microsomes, suggesting a role for the ADP-ribosylation (ARF)-dependent trafficking of cathepsin B. Indeed, caerulein treatment increased processing of procathepsin B, whereas a known ARF inhibitor brefeldin A (BFA) prevented this. Similar treatment did not affect processing of procathepsin L. BFA-mediated ARF1 inhibition resulted in reduced cathepsin B activity and consequently reduced trypsinogen activation. However, formation of light chain 3 (LC3-II) was not affected, suggesting that BFA did not prevent autophagy induction. Instead, sucrose density gradient centrifugation and electron microscopy showed that BFA arrested caerulein-induced autophagosomal maturation. Therefore, ARF1-dependent trafficking of procathepsin B and the maturation of autophagosomes results in cathepsin B-mediated trypsinogen activation induced by caerulein. Background: Autophagy and cathepsin B-mediated trypsin generation may be deleterious in acute pancreatitis. The role of ARF1 in the process is unknown. Results: BFA-mediated ARF1 inhibition prevents caerulein-induced processing of procathepsin B and perturbs autophagic maturation. Conclusion: ARF1-dependent trafficking of procathepsin B and autophagic maturation result in trypsinogen activation. Significance: ARF1 plays a significant role in acute pancreatitis.