title: Keratin overexpression levels correlate with the extent of spontaneous pancreatic injury.
abstract: Mutation of the adult hepatocyte keratins K8 and K18 predisposes to liver disease. In contrast, exocrine pancreas K8 and K18 are dispensable and are co-expressed with limited levels of membrane-proximal K19 and K20. Overexpression of mutant K18 or genetic ablation of K8 in mouse pancreas is well tolerated whereas overexpression of K8 causes spontaneous chronic pancreatitis. To better understand the effect of exocrine pancreatic keratin overexpression, we compared transgenic mice that overexpress K18, K8, or K8/K18, associated with minimal, modest, or large increases in keratin expression, respectively, with nontransgenic wild-type (WT) mice. Overexpression of the type-II keratin K8 up-regulated type-I keratins K18, K19, and K20 and generated K19/K20-containing neocytoplasmic typical or short filaments; however, overexpression of K18 had no effect on K8 levels. K8- and K18-overexpressing pancreata were histologically similar to WT, whereas K8/K18 pancreata displayed age-enhanced vacuolization and atrophy of the exocrine pancreas and exhibited keratin hyperphosphorylation. Zymogen granules in K8/K18 pancreata were 50% smaller and more dispersed than their normal apical concentration but were twice as numerous as in WT controls. Therefore, modest keratin overexpression has minor effects on the exocrine pancreas whereas significant keratin overexpression alters zymogen granule organization and causes aging-associated exocrine atrophy. Keratin absence or mutation is well tolerated after pancreatic but not liver injury, whereas excessive overexpression is toxic to the pancreas but not the liver when induced under basal conditions.
authors: Department of Medicine, Veterans Administration Palo Alto Health Care System, Palo Alto, CA, USA. dtoivola@abo.fi
authors: Diana M
authors: DM
authors: Toivola
authors: Ikuo
authors: I
authors: Nakamichi
authors: Pavel
authors: P
authors: Strnad
authors: Sara A
authors: SA
authors: Michie
authors: Nafisa
authors: N
authors: Ghori
authors: Masaru
authors: M
authors: Harada
authors: Karin
authors: K
authors: Zeh
authors: Robert G
authors: RG
authors: Oshima
authors: Helene
authors: H
authors: Baribault
authors: M Bishr
authors: MB
authors: Omary
mesh_terms: D000681:Amylases / Q000378:metabolism; D000818:Animals; D001284:Atrophy; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism; D053538:Keratin-18 / Q000235:genetics / Q000378:metabolism; D053539:Keratin-19 / Q000235:genetics / Q000378:metabolism; D053533:Keratin-8 / Q000235:genetics / Q000378:metabolism; D007633:Keratins / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D046790:Pancreas, Exocrine / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D010182:Pancreatic Diseases / Q000378:metabolism* / Q000473:pathology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D053538:Keratin-18; D053539:Keratin-19; D053533:Keratin-8; D012333:RNA, Messenger; D007633:Keratins; D000681:Amylases