VAMP8 is the v-SNARE that mediates basolateral exocytosis in a mouse model of alcoholic pancreatitis.
In rodents and humans, alcohol exposure has been shown to predispose the pancreas to cholinergic or viral induction of pancreatitis. We previously developed a rodent model in which exposure to an ethanol (EtOH) diet, followed by carbachol (Cch) stimulation, redirects exocytosis from the apical to the basolateral plasma membrane of acinar cells, resulting in ectopic zymogen enzyme activation and pancreatitis. This redirection of exocytosis involves a soluble NSF attachment receptor (SNARE) complex consisting of syntaxin-4 and synapse-associated protein of 23 kDa (SNAP-23). Here, we investigated the role of the zymogen granule (ZG) SNARE vesicle-associated membrane protein 8 (VAMP8) in mediating basolateral exocytosis. In WT mice, in vitro EtOH exposure or EtOH diet reduced Cch-stimulated amylase release by redirecting apical exocytosis to the basolateral membrane, leading to alcoholic pancreatitis. Further reduction of zymogen secretion, caused by blockade of both apical and basolateral exocytosis and resulting in a more mild induction of alcoholic pancreatitis, was observed in Vamp8(-/-) mice in response to these treatments. In addition, although ZGs accumulated in Vamp8(-/-) acinar cells, ZG-ZG fusions were reduced compared with those in WT acinar cells, as visualized by electron microscopy. This reduction in ZG fusion may account for reduced efficiency of apical exocytosis in Vamp8(-/-) acini. These findings indicate that VAMP8 is the ZG-SNARE that mediates basolateral exocytosis in alcoholic pancreatitis and that VAMP8 is critical for ZG-ZG homotypic fusion.
Department of Medicine, University of Toronto and University Health Network, Toronto, Ontario, Canada.
Laura I
LI
Cosen-Binker
Marcelo G
MG
Binker
Cheng-Chun
CC
Wang
Wanjin
W
Hong
Herbert Y
HY
Gaisano
D000681:Amylases / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics; D002217:Carbachol / Q000494:pharmacology; D016207:Cytokines / Q000097:blood; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D015227:Lipid Peroxidation / Q000187:drug effects / Q000235:genetics; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008854:Microscopy, Electron; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D046790:Pancreas, Exocrine / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D019512:Pancreatitis, Alcoholic / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D009195:Peroxidase / Q000378:metabolism; D050766:Qb-SNARE Proteins / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D050683:R-SNARE Proteins / Q000235:genetics / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D022142:Secretory Vesicles / Q000187:drug effects / Q000502:physiology; D016704:Synapsins / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
D016207:Cytokines; D016328:NF-kappa B; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; C107017:Snap23 protein, mouse; D016704:Synapsins; C491831:Vamp8 protein, mouse; D002217:Carbachol; D009195:Peroxidase; D000681:Amylases; D014357:Trypsin