Identification of Band 3-like Proteins and Cl/HCO Exchange in Isolated Cardiomyocytes

doi:10.1074/jbc.270.3.1315

Identification of Band 3-like Proteins and Cl/HCO Exchange in Isolated Cardiomyocytes (*)

From the Laboratoire de Physiopathologie Cardiovasculaire, INSERM U-390, Centre Hospitalier Universitaire Arnaud de Villeneuve, 34295 Montpellier, France and the,
(1)Institut Jacques Monod, CNRS Unité Mixte de Recherche 9922, Université Paris-7, 75251 Paris, France

^§ To whom correspondence should be addressed: Fax: 33-67-41-52-42.

Abstract

The identification of the protein that exerts the function of Cl/HCO₃ exchange is still unresolved in cardiac tissue. We have addressed this issue by using a multiple technical approach. Western blotting analysis with an antibody raised against human erythroid whole band 3 protein, the so-called protein that mediates the Cl/HCO₃ exchange in erythrocytes, showed that adult cardiomyocytes expressed two proteins immunologically related to the erythroid band 3. These proteins migrated in SDS-polyacrylamide gel electrophoresis with apparent molecular masses of 80 and 120 kDa. They were specifically found in the membrane but not in the cytosolic or the myofibril fractions of adult cardiomyocytes. Confocal microscopy further indicated that the immunostained proteins were mainly located at the sarcolemma and along T-tubules, typical membrane structures of adult cardiomyocytes. Using an antibody raised against a cardiac amino-terminal domain of rat AE3, we found that the 120-kDa protein is the translation product of the AE3 gene specifically expressed in heart and brain. Using an antiserum raised against a specific domain of mouse erythroid band 3 (AE1), which is not shared by AE3, we showed that the 80-kDa protein is likely to be a truncated translation product of the AE1 gene. Microinjection of the anti-human erythroid whole band 3 antibody into single isolated cardiac cells significantly inhibited the Cl/HCO₃ exchange activity. Furthermore, the anti-AE1 antibody strongly decreased the efficiency of 4,4′-diisothiocyanatostilbene-2,2′-disulfonate to inhibit the ionic exchange. We thus suggest that the 80-kDa or both the 80- and the 120-kDa proteins immunologically related to the erythroid band 3 protein perform the anionic exchange in rat cardiomyocytes.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

AE

anion exchanger

PBS

phosphate-buffered saline

BSA

bovine serum albumin

SNARF1/AM

seminaphthorhodafluor acetoxymethylester

BAPTA/AM

1,2-bis-(2-aminophenoxy)ethane-N-N-N[prime]-N′-tetraacetic acid acetoxymethylester

DIDS

4,4′-diisothiocyanatostilbene-2,2′-disulfonate

ECL

enhanced chemiluminescence

Pipes

1,4-piperazinediethanesulfonic acid.
↵²M. Pucéat, I. Korichneva, R. Cassoly, and G. Vassort, manuscript in preparation.
- Received June 9, 1994.
- Revision received October 21, 1994.