Expression of the bile acid transport protein during liver development and in hepatoma cells.
The expression of the hepatocyte Na(+)-dependent bile acid transport protein during liver development and in hepatoma cells has been characterized using a monoclonal antibody (mAb 25D-1) which specifically recognizes this 49-kDa carrier system. mAb binding studies demonstrated a greatly reduced concentration of this transport protein on the surface of hepatoma tissue culture (HTC) cells, a result consistent with the greater than 95% reduction in bile acid transport capacity when compared with normal adult hepatocytes. Immunoprecipitation procedures with 25D-1 were utilized to quantitate the presence of this transport protein in HTC cells as well as in adult hepatocytes that had been labeled with [35S]methionine or Na125I. These studies indicate that the 49-kDa transport protein is not expressed either on the surface or in any intracellular compartment in HTC cells. mAb binding to fetal cells (day 17) also indicated a greatly decreased number of transport molecules in the plasma membrane. Total cell content of this carrier protein during the next 7 weeks of liver development, as measured by immunoprecipitation, increased in a linear fashion reaching 92% of the adult level at 4 weeks after birth, which parallels the increase in transport function. These results demonstrate that bile acid transport capacity is directly related to the level of expression of this 49-kDa membrane protein.
von Dippe
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Department of Biochemistry, University of Southern California School of Medicine, Los Angeles 90033.
Levy
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D000375:Aging; D000818:Animals; D000911:Antibodies, Monoclonal; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D002478:Cells, Cultured; D005333:Fetus; D006913:Hydroxysteroid Dehydrogenases; D008099:Liver / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008562:Membrane Glycoproteins; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains; D013656:Taurocholic Acid / Q000378:metabolism*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D006913:Hydroxysteroid Dehydrogenases; D008562:Membrane Glycoproteins; D013656:Taurocholic Acid; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)