title: Proteoglycans support proper granule formation in pancreatic acinar cells.
abstract: Zymogen granules (ZG) are specialized organelles in the exocrine pancreas which allow digestive enzyme storage and regulated secretion. The molecular mechanisms of their biogenesis and the sorting of zymogens are still incompletely understood. Here, we investigated the role of proteoglycans in granule formation and secretion of zymogens in pancreatic AR42J cells, an acinar model system. Cupromeronic Blue cytochemistry and biochemical studies revealed an association of proteoglycans primarily with the granule membrane. Removal of proteoglycans by carbonate treatment led to a loss of membrane curvature indicating a supportive role in the maintenance of membrane shape and stability. Chemical inhibition of proteoglycan synthesis impaired the formation of normal electron-dense granules in AR42J cells and resulted in the formation of unusually small granule structures. These structures still contained the zymogen carboxypeptidase, a cargo molecule of secretory granules, but migrated to lighter fractions after density gradient centrifugation. Furthermore, the basal secretion of amylase was increased in AR42J cells after inhibitor treatment. In addition, irregular-shaped granules appeared in pancreatic lobules. We conclude that the assembly of a proteoglycan scaffold at the ZG membrane is supporting efficient packaging of zymogens and the proper formation of stimulus-competent storage granules in acinar cells of the pancreas.
authors.affiliation: Centre for Cell Biology and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Aroso
authors.affiliation: Department of Cell Biology and Cell Pathology, University of Marburg, 35037, Marburg, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Agricola
authors.affiliation: College of Life and Environmental Sciences, Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Hacker
authors.affiliation: Centre for Cell Biology and Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal. m.schrader@exeter.ac.uk.|College of Life and Environmental Sciences, Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK. m.schrader@exeter.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Schrader
mesh_terms: D061354:Acinar Cells / Q000187:drug effects / Q000378:metabolism*; D000681:Amylases / Q000378:metabolism; D000818:Animals; D002268:Carboxypeptidases / Q000378:metabolism; D002460:Cell Line; D004792:Enzyme Precursors / Q000378:metabolism; D006027:Glycosides / Q000494:pharmacology; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D046790:Pancreas, Exocrine / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011509:Proteoglycans / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D004792:Enzyme Precursors; D006027:Glycosides; D011509:Proteoglycans; C010807:xylosides; D000681:Amylases; D002268:Carboxypeptidases
keywords: Exocrine secretion; Granule membrane proteins; Organelle biogenesis; Pancreas; Pancreatic AR42J cells; Proteoglycan; Secretory granule; Zymogen granules