The role of Ca2+ signalling in the physiology and pathophysiology of exocrine pancreas

Deletion of the WD40 domain of ATG16L1 exacerbates acute pancreatitis, abolishes LAP-like non-canonical autophagy and slows trypsin degradation

The WD40 domain (WDD) of ATG16L1 plays a pivotal role in non-canonical autophagy. This study examined the role of recently identified LAP-like non-canonical autophagy (LNCA) in acute pancreatitis. LNCA involves rapid single-membrane LC3 conjugation to endocytic vacuoles in pancreatic acinar cells. The rationale for this study was the previously observed presence of trypsin in the organelles undergoing LNCA; aberrant trypsin formation is an important factor in pancreatitis development. Here we report that the deletion of WDD (attained in ATG16L1[E230] mice) eliminated LNCA, aggravated caerulein-induced acute pancreatitis and suppressed the fast trypsin degradation observed in both a rapid caerulein-induced disease model and in caerulein-treated isolated pancreatic acinar cells. These experiments indicate that LNCA is a WDD-dependent mechanism and suggest that it plays not an activating but a protective role in acute pancreatitis. Furthermore, palmitoleic acid, another inducer of experimental acute pancreatitis, strongly inhibited LNCA, suggesting a novel mechanism of pancreatic lipotoxicity.Abbreviation: AMY: amylase; AP: acute pancreatitis; CASM: conjugation of Atg8 to single membranes; CCK: cholecystokinin; FAEE model: fatty acid and ethanol model; IL6: interleukin 6; LA: linoleic acid; LAP: LC3-associated phagocytosis; LMPO: lung myeloperoxidase; LNCA: LAP-like non-canonical autophagy; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MPO: myeloperoxidase; PMPO: pancreatic myeloperoxidase; POA: palmitoleic acid; WDD: WD40 domain; WT: wild type.

Autophagy, Acute Pancreatitis and the Metamorphoses of a Trypsinogen-Activating Organelle

Recent studies have highlighted the importance of autophagy and particularly non-canonical autophagy in the development and progression of acute pancreatitis (a frequent disease with considerable morbidity and significant mortality). An important early event in the development of acute pancreatitis is the intrapancreatic activation of trypsinogen, (i.e., formation of trypsin) leading to the autodigestion of the organ. Another prominent phenomenon associated with the initiation of this disease is vacuolisation and specifically the formation of giant endocytic vacuoles in pancreatic acinar cells. These organelles develop in acinar cells exposed to several inducers of acute pancreatitis (including taurolithocholic acid and high concentrations of secretagogues cholecystokinin and acetylcholine). Notably, early trypsinogen activation occurs in the endocytic vacuoles. These trypsinogen-activating organelles undergo activation, long-distance trafficking, and non-canonical autophagy. In this review, we will discuss the role of autophagy in acute pancreatitis and particularly focus on the recently discovered LAP-like non-canonical autophagy (LNCA) of endocytic vacuoles.