Sucrase-isomaltase is and adenosine 3′, 5′-cyclic monophosphate-dependent epithelial chloride channel

Arthur L. Finn, Eldo V. Kuzhikandathil, Gerry S. Oxford, Yoshi Itoh-Lindstrom

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Background and Aims: We previously isolated a monoclonal antibody against a Necturus gallbladder epitope that blocks native adenosine 3′, 5′-cyclic monophosphate (cAMP)-dependent chloride channels in intestine, gallbladder, urinary bladder, and airway epithelia in various animals. Methods: Using this antibody, we purified a 200-kilodalton protein that, when reconstituted in lipid bilayers, forms 9-pS chloride channels that are blocked by the antibody. Results: Amino acid sequencing of the purified protein showed strong homology to rabbit sucrase-isomaltase, an abundant intestinal enzyme. Western blot analysis of the in vitro-translated sucrase-isomaltase was indistinguishable from that of the protein used in the lipid bilayer studies. Expression of this protein in Chinese hamster ovary cells and in Xenopus laevis oocytes yielded cAMP-dependent chloride currents that in the latter system were blocked by the antibody. Conclusions: Because the monoclonal antibody blocks cAMP-dependent currents in epithelia as well as those produced both by the reconstituted and by the heterologously expressed protein, sucrase-isomaltase is a cAMP-dependent epithelial chloride channel. Thus an enzyme that can also function as an ion channel has been described for the first time.

Original languageEnglish (US)
Pages (from-to)117-125
Number of pages9
JournalGastroenterology
Volume120
Issue number1
DOIs
StatePublished - Jan 2001

Keywords

  • Chinese hamster ovary
  • Cystic fibrosis transmembrane conductance regulator
  • Polymerase chain reaction
  • Reverse transcription
  • Sucrase-isomaltase

ASJC Scopus subject areas

  • Hepatology
  • Gastroenterology

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