Alternative splicing of the rat sodium/bile acid transporter changes its cellular localization and transport properties

Konstantinos N Lazaridis, Pam Tietz, Ting Wu, Sertac Kip, Paul A. Dawson, Nicholas F La Russo

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96 Citations (Scopus)

Abstract

Bile secretion involves the structural and functional interplay of hepatocytes and cholangiocytes, the cells lining the intrahepatic bile ducts. Hepatocytes actively secrete bile acids into the canalicular space and cholangiocytes then transport bile acids in a vectorial manner across their apical and basolateral plasma membranes. The initial step in the transepithelial transport of bile acids across rat cholangiocytes is apical uptake by a Na+-dependent bile acid transporter (ASBT). To date, the molecular basis of the obligate efflux mechanism for extrusion of bile acids across the cholangiocyte basolateral membrane remains unknown. We have identified an exon-2 skipped, alternatively spliced form of ASBT, designated t-ASBT, expressed in rat cholangiocytes, ileum, and kidney. Alternative splicing causes a frameshift that produces a 154-aa protein. Antipeptide antibodies detected the ≃19 kDa t-ASBT polypeptide in rat cholangiocytes, ileum, and kidney. The t-ASBT was specifically localized to the basolateral domain of cholangiocytes. Transport studies in Xenopus oocytes revealed that t-ASBT can function as a bile acid efflux protein. Thus, alternative splicing changes the cellular targeting of ASBT, alters its functional properties, and provides a mechanism for rat cholangiocytes and other bile acid-transporting epithelia to extrude bile acids. Our work represents an example in which a single gene appears to encode via alternative splicing both uptake and obligate efflux carriers in a bile acid-transporting epithelial cell.

Original languageEnglish (US)
Pages (from-to)11092-11097
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue number20
StatePublished - Sep 26 2000

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Alternative Splicing
Bile Acids and Salts
Sodium
Ileum
Hepatocytes
Kidney
Intrahepatic Bile Ducts
bile acid binding proteins
Xenopus
Bile
Oocytes
Exons
Proteins
Epithelium
Epithelial Cells
Cell Membrane
Peptides
Membranes
Antibodies
Genes

ASJC Scopus subject areas

  • General
  • Genetics

Cite this

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title = "Alternative splicing of the rat sodium/bile acid transporter changes its cellular localization and transport properties",
abstract = "Bile secretion involves the structural and functional interplay of hepatocytes and cholangiocytes, the cells lining the intrahepatic bile ducts. Hepatocytes actively secrete bile acids into the canalicular space and cholangiocytes then transport bile acids in a vectorial manner across their apical and basolateral plasma membranes. The initial step in the transepithelial transport of bile acids across rat cholangiocytes is apical uptake by a Na+-dependent bile acid transporter (ASBT). To date, the molecular basis of the obligate efflux mechanism for extrusion of bile acids across the cholangiocyte basolateral membrane remains unknown. We have identified an exon-2 skipped, alternatively spliced form of ASBT, designated t-ASBT, expressed in rat cholangiocytes, ileum, and kidney. Alternative splicing causes a frameshift that produces a 154-aa protein. Antipeptide antibodies detected the ≃19 kDa t-ASBT polypeptide in rat cholangiocytes, ileum, and kidney. The t-ASBT was specifically localized to the basolateral domain of cholangiocytes. Transport studies in Xenopus oocytes revealed that t-ASBT can function as a bile acid efflux protein. Thus, alternative splicing changes the cellular targeting of ASBT, alters its functional properties, and provides a mechanism for rat cholangiocytes and other bile acid-transporting epithelia to extrude bile acids. Our work represents an example in which a single gene appears to encode via alternative splicing both uptake and obligate efflux carriers in a bile acid-transporting epithelial cell.",
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T1 - Alternative splicing of the rat sodium/bile acid transporter changes its cellular localization and transport properties

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AU - Tietz, Pam

AU - Wu, Ting

AU - Kip, Sertac

AU - Dawson, Paul A.

AU - La Russo, Nicholas F

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