The functional and physical relationship between the DRA bicarbonate transporter and carbonic anhydrase II.

Abstract

COOH-terminal cytoplasmic tails of chloride/bicarbonate anion exchangers (AE) bind cytosolic carbonic anhydrase II (CAII) to form a bicarbonate transport metabolon, a membrane protein complex that accelerates transmembrane bicarbonate flux. To determine whether interaction with CAII affects the downregulated in adenoma (DRA) chloride/bicarbonate exchanger, anion exchange activity of DRA-transfected HEK-293 cells was monitored by following changes in intracellular pH associated with bicarbonate transport. DRA-mediated bicarbonate transport activity of 18 +/- 1 mM H+ equivalents/min was inhibited 53 +/- 2% by 100 mM of the CAII inhibitor, acetazolamide, but was unaffected by the membrane-impermeant carbonic anhydrase inhibitor, 1-[5-sulfamoyl-1,3,4-thiadiazol-2-yl-(aminosulfonyl-4-phenyl)]-2,6-dimethyl-4-phenyl-pyridinium perchlorate. Compared with AE1, the COOH-terminal tail of DRA interacted weakly with CAII. Overexpression of a functionally inactive CAII mutant, V143Y, reduced AE1 transport activity by 61 +/- 4% without effect on DRA transport activity (105 +/- 7% transport activity relative to DRA alone). We conclude that cytosolic CAII is required for full DRA-mediated bicarbonate transport. However, DRA differs from other bicarbonate transport proteins because its transport activity is not stimulated by direct interaction with CAII.

• Authors: Deborah Sterling, Nathan J D Brown, Claudiu T Supuran, Joseph R Casey
• Journal: American journal of physiology. Cell physiology (Am J Physiol Cell Physiol) Vol. 283 Issue 5 Pg. C1522-9 (Nov 2002) ISSN: 0363-6143 [Print] United States
• PMID: 12372813 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antiporters
• Bicarbonates
• Carbonic Anhydrase Inhibitors
• Carrier Proteins
• Chloride-Bicarbonate Antiporters
• Chlorides
• Membrane Proteins
• SLC26A3 protein, human
• Sulfate Transporters
• Carbonic Anhydrase II
• Acetazolamide

Topics

• Acetazolamide (pharmacology)
• Adenoma (metabolism)
• Antiporters
• Bicarbonates (metabolism)
• Carbonic Anhydrase II (antagonists & inhibitors, metabolism)
• Carbonic Anhydrase Inhibitors (pharmacology)
• Carrier Proteins (genetics, metabolism)
• Cell Line
• Cell Membrane (metabolism)
• Chloride-Bicarbonate Antiporters
• Chlorides (metabolism)
• Down-Regulation
• Humans
• Membrane Proteins (genetics, metabolism)
• Protein Binding (physiology)
• Sulfate Transporters
• Transfection