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Ectonucleotidases, purine nucleoside transporter, and function of the bile canalicular plasma membrane of the hepatocyte
Author(s) -
Che Mingxin,
Gatmaitan Zenaida,
Arias Irwin M.
Publication year - 1997
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.11.2.9039951
Subject(s) - apyrase , adenosine , purinergic receptor , biochemistry , nucleoside , nucleoside transporter , extracellular , atpase , purinergic signalling , purine , 5' nucleotidase , transporter , nucleotide , nucleotidase , biology , adenosine a2b receptor , chemistry , microbiology and biotechnology , adenosine receptor , receptor , enzyme , gene , agonist
Ectonucleotidases are enzymes that degrade extracellular nucleotides. Extracellular nucleotides (especially ATP) and their degradation products (particularly adenosine) have multiple effects on cell functions by acting through purinergic receptors. Adenosine nucleotides are present in bile, which suggests that hepatocytes may release nucleotides into the canaliculus where they are promptly degraded into adenosine by ecto‐ATPase and 5'‐nucleotidase, which have been identified in the canalicular plasma membrane. Adenosine is then transported into hepatocytes by a Na + ‐depen‐dent nucleoside transporter that is present in the canalicular plasma membrane. Purification and molecular cloning of ecto‐ATPase and other canalicular proteins are complicated by an abundant canalicular plasma membrane protein, cCAM 105. However, the recent cloning of an ecto‐ATPase (apyrase) from potato tubers provides a new oppor‐tunity to identify the canalicular ecto‐ATPase. The canalicular Na + ‐dependent purine nucleoside transporter has been cloned from rat liver. Study of its expression during development and other physio‐logical circumstances suggests that the transporter may play an important role in maintaining hepatic purine levels that are essential for the liver to serve as a major source of purines for tissues (i.e., brain, muscle) that lack pathways for de novo purine biosynthesis.—Che, M., Gatmaitan, Z., Arias, I. M. Ectonucleotidases, purine nucleoside transporter, and function of the bile canalicular plasma membrane of the hepatocyte. FASEB J. 11, 101‐108 (1997)