Autophagy has recently elicited significant attention as a mechanism that either protects or promotes cell death, although different autophagy pathways, and the cellular context in which they occur, remain to be elucidated. We report a thorough cellular and biochemical characterization of a novel selective autophagy that works as a protective cell response. This new selective autophagy is activated in pancreatic acinar cells during pancreatitis-induced vesicular transport alteration to sequester and degrade potentially deleterious activated zymogen granules. We have coined the term "zymophagy" to refer to this process. The autophagy-related protein VMP1, the ubiquitin-protease USP9x, and the ubiquitin-binding protein p62 mediate zymophagy. Moreover, VMP1 interacts with USP9x, indicating that there is a close cooperation between the autophagy pathway and the ubiquitin recognition machinery required for selective autophagosome formation. Zymophagy is activated by experimental pancreatitis in genetically engineered mice and cultured pancreatic acinar cells and by acute pancreatitis in humans. Furthermore, zymophagy has pathophysiological relevance by controlling pancreatitis-induced intracellular zymogen activation and helping to prevent cell death. Together, these data reveal a novel selective form of autophagy mediated by the VMP1-USP9x-p62 pathway, as a cellular protective response.Autophagy is an evolutionarily preserved cellular process that is responsible for the degradation of long lived proteins and entire organelles to maintain intracellular homeostasis and to contribute to starvation and stress responses. Macroautophagy involves the formation of double-membrane autophagosomes around cargoes, including larger structures such as organelles and protein aggregates. Autophagosomes then fuse with lysosomes, where the degradation of the cargoes takes place. Both nonselective "bulk" autophagy and selective autophagy of specific proteins and organelles have been described (1). Genetic analyses in yeast identified more than 30 conserved components that are required for different steps of autophagy (termed Atg1 to Atg32) (2). Several lines of evidence suggest the existence of different types of selective autophagic degradation pathways. Single proteins and cellular structures such as protein aggregates, peroxisomes, ribosomes, and mitochondria can be specifically engulfed by autophagosomes (3), but the mechanism of cargo recognition is not well understood. However, there is emerging evidence suggesting the involvement of ubiquitin in this process. For example, aggregate clearance by autophagy requires ubiquitylation and ubiquitin-binding receptors such as p62 (also known as SQSTM1) (4). Ubiquitylated artificial substrates are recognized by the autophagy machinery and are specifically degraded in lysosomes by a p62-dependent mechanism (5). Moreover, the selective degradation of excess ribosomes during starvation depends on the deubiquitylation activity of Ubp3/Bre5 (6). However, the repertoire of proteins that partic...

The Vacuole Membrane Protein 1 -VMP1- is a pancreatitis-associated transmembrane protein whose expression triggers autophagy in several human diseases. In the current study, we unveil the mechanism through which this protein induces autophagosome formation in mammalian cells. We show that VMP1 autophagy-related function requires its 20-aminoacid C-terminus hydrophilic domain (VMP1-AtgD). This is achieved through its direct binding to the BH3 motif of Beclin 1 leading to the formation of a complex with the Class III phosphatidylinositol-3 kinase (PI3K) hVps34, a key positive regulator of autophagy, at the site where autophagosomes are generated. This interaction also concomitantly promotes the dissociation of Bcl-2, an autophagy inhibitor, from Beclin 1. Moreover, we show that the VMP1-Beclin 1-hVps34 complex favors the association of Atg16L1 and LC3 with the autophagosomal membranes. Collectively, these findings reveal that VMP1 expression recruits and activates the Class III PI3K complex at the site of autophagosome formation during mammalian autophagy.

Pancreatic ductal adenocarcinoma (PDAC) has the lowest survival rate of all cancers and shows remarkable resistance to cell stress. Nuclear protein 1 (Nupr1), which mediates stress response in the pancreas, is frequently upregulated in pancreatic cancer. Here, we report that Nupr1 plays an essential role in pancreatic tumorigenesis. In a mouse model of pancreatic cancer with constitutively expressed oncogenic Kras G12D , we found that loss of Nupr1 protected from the development of pancreatic intraepithelial neoplasias (PanINs). Further, in cultured pancreatic cells, nutrient deprivation activated Nupr1 expression, which we found to be required for cell survival. We found that Nupr1 protected cells from stress-induced death by inhibiting apoptosis through a pathway dependent on transcription factor RelB and immediate early response 3 (IER3). NUPR1, RELB, and IER3 proteins were coexpressed in mouse PanINs from Kras G12D -expressing pancreas. Moreover, pancreasspecific deletion of Relb in a Kras G12D background resulted in delayed in PanIN development associated with a lack of IER3 expression. Thus, efficient PanIN formation was dependent on the expression of Nupr1 and Relb, with likely involvement of IER3. Finally, in patients with PDAC, expression of NUPR1, RELB, and IER3 was significantly correlated with a poor prognosis. Cumulatively, these results reveal a NUPR1/RELB/IER3 stressrelated pathway that is required for oncogenic Kras G12D -dependent transformation of the pancreas. IntroductionPancreatic ductal adenocarcinoma (PDAC) has the highest mortality rate and the lowest overall survival of all cancers (less than 3%-4% at 5 years). The incidence of PDAC almost equals its mortality rate and is increasing every year, with more than 38,000 predicted new cases in the United States and 65,000 in Europe. Surgery is the most effective treatment, but the mean life expectancy of the 15%-20% of patients who present with a resectable tumor is only 15-18 months (1). Even for patients eligible for surgery, aggressive metastasis often appears after operation, and survival of patients with metastatic disease is only 3-6 months (2). Chemotherapy and radiotherapy offer limited benefit for patients undergoing surgery in metastatic disease (3). Most strategies tested so far for the treatment of PDAC have consisted of using therapies that show some efficacy in other carcinomas, but none of them improved significantly the overall survival of PDAC patients. Hence, in order to develop new, efficient therapies against PDAC, future research must take into account PDAC specificities such as its remarkable resistance to cell stress, notably to the stress induced by chemotherapy and radiotherapy (4), and the preponderant presence of a fibrotic stroma, which favors tumor progression by creating a barrier against drug delivery and

Pancreatic ductal adenocarcinoma (PDAC) offers an optimal model for discovering “druggable” molecular pathways that participate in inflammation-associated cancer development. Chronic pancreatitis, a common prolonged inflammatory disease, behaves as a well-known premalignant condition that contributes to PDAC development. Although the mechanisms underlying the pancreatitis-to-cancer transition remain to be fully elucidated, emerging evidence supports the hypothesis that the actions of proinflammatory mediators on cells harboring Kras mutations promote neoplastic transformation. Recent elegant studies demonstrated that the IL-17 pathway mediates this phenomenon and can be targeted with antibodies, but the downstream mechanisms by which IL-17 functions during this transition are currently unclear. In this study, we demonstrate that IL-17 induces the expression of REG3β, a well-known mediator of pancreatitis, during acinar-to-ductal metaplasia and in early PanIN lesions. Furthermore, we found that REG3β promotes cell growth and decreases sensitivity to cell death through activation of the gp130-JAK2-STAT3-dependent pathway. Genetic inactivation of REG3β in the context of oncogenic Kras-driven PDAC resulted in reduced PanIN formation, an effect that could be rescued by administration of exogenous REG3β. Taken together, our findings provide mechanistic insight into the pathways underlying inflammation-associated pancreatic cancer, revealing a dual and contextual pathophysiological role for REG3β during pancreatitis and PDAC initiation.