RGD Reference Report - Expression and localization of aquaporin water channels in rat hepatocytes. Evidence for a role in canalicular bile secretion. - Rat Genome Database

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Expression and localization of aquaporin water channels in rat hepatocytes. Evidence for a role in canalicular bile secretion.

Authors: Huebert, RC  Splinter, PL  Garcia, F  Marinelli, RA  LaRusso, NF 
Citation: Huebert RC, etal., J Biol Chem 2002 Jun 21;277(25):22710-7.
RGD ID: 625402
Pubmed: PMID:11932260   (View Abstract at PubMed)
DOI: DOI:10.1074/jbc.M202394200   (Journal Full-text)

Although bile formation requires that large volumes of water be rapidly transported across liver epithelia, including hepatocytes, the molecular mechanisms by which water is secreted into bile are obscure. The aquaporins are a family of 10 channel-forming, integral membrane proteins of approximately 28 kDa numbered 0-9 that allow water to rapidly traverse epithelial barriers in several organs including kidney, eye, and brain. We found transcripts of three of 10 aquaporins in hepatocytes (aquaporin 8 aquaporin 9 > aquaporin 0) by reverse transcription-polymerase chain reaction and quantitative ribonuclease protection assays; immunohistochemistry confirmed the presence of these three proteins in liver. Immunoblots of subcellular fractions of hepatocytes showed enrichment of aquaporins 0 and 8 in microsomes and canalicular plasma membranes; aquaporin 9 was enriched only in basolateral plasma membranes. Immunofluorescence of hepatocyte couplets confirmed the intracellular/canalicular localization of aquaporins 0 and 8 and the basolateral localization of aquaporin 9. Upon exposure of couplets to a choleretic stimulus (i.e. dibutyryl cAMP), aquaporin 8 redistributed to the canalicular plasma membrane; the subcellular distributions of aquaporins 0 and 9 were unaffected. In addition, exposure of couplets to dibutyryl cAMP caused an increase in canalicular water transport in the presence and absence of an osmotic gradient, an effect that was blocked by aquaporin inhibitors. These results provide evidence that aquaporins are present in hepatocytes and that aquaporins are involved in agonist-stimulated canalicular bile secretion.



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Aqp8Ratcanalicular bile acid transport  IDA  RGD 
Aqp9Ratcanalicular bile acid transport  IDA  RGD 
MipRatcanalicular bile acid transport  IDA  RGD 
Aqp8Ratwater transport  IDA  RGD 
Aqp9Ratwater transport  IDA  RGD 
MipRatwater transport  IDA  RGD 

Cellular Component

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Aqp9Ratbasolateral plasma membrane  IDA  RGD 
Aqp8Ratintracellular canaliculus  IDA  RGD 
MipRatintracellular canaliculus  IDA  RGD 

Molecular Function

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Aqp8Ratwater channel activity  IDA  RGD 
Aqp9Ratwater channel activity  IDA  RGD 
MipRatwater channel activity  IDA  RGD 

Objects Annotated

Genes (Rattus norvegicus)
Aqp8  (aquaporin 8)
Aqp9  (aquaporin 9)
Mip  (major intrinsic protein of lens fiber)


Additional Information