title: Hepatocystin is not secreted in cyst fluid of hepatocystin mutant polycystic liver patients.
abstract: Autosomal dominant polycystic liver disease (PCLD) is characterized by multiple liver cysts and is caused by mutations in PRKCSH (hepatocystin). Mechanisms of cystogenesis are unknown, but previous studies have shown that hepatocystin is secreted in vitro. The goal of this study was to determine the fate of hepatocystin in vivo. Using immunoprecipitation, we determined that mutant hepatocystin is secreted from both apical and basolateral cell surface of MDCK cells stably transfected with mutant hepatocystin. Analysis of 60 cyst fluid samples from polycystic livers using Western blot, MALDI-TOF MS or nLC-MS/MS did not detect hepatocystin in liver cyst fluid. We did identify 163 ubiquitous serum proteins. No paracrine or autocrine factors were recognized. Although cyst fluids vary greatly in protein concentration, a PCLD specific protein pattern was not established. In conclusion, hepatocystin is not secreted in PCLD liver cyst fluid, suggesting that mutant hepatocystin is either not produced or degraded intracellularly. PCLD cysts develop from intralobular bile ductules and cyst fluid mainly contains common serum proteins comparable to that of other polycystic diseases.
authors.affiliation: Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. e.waanders@mdl.umcn.nl
authors.forename: Esmé
authors.initials: E
authors.lastname: Waanders
authors.forename: Anke L L
authors.initials: AL
authors.lastname: Lameris
authors.forename: Huub J M
authors.initials: HJ
authors.lastname: Op den Camp
authors.forename: Wendy
authors.initials: W
authors.lastname: Pluk
authors.forename: Jolein
authors.initials: J
authors.lastname: Gloerich
authors.forename: Simon P
authors.initials: SP
authors.lastname: Strijk
authors.forename: Joost P H
authors.initials: JP
authors.lastname: Drenth
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000032:analysis / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002460:Cell Line; D020420:Cyst Fluid / Q000737:chemistry / Q000378:metabolism*; D003560:Cysts / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005959:Glucosidases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008107:Liver Diseases / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009154:Mutation; D012709:Serum Albumin / Q000032:analysis / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry; D014162:Transfection
chemical_list: D001798:Blood Proteins; D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D012709:Serum Albumin; D005959:Glucosidases; C070368:PRKCSH protein, human