Anti-SLC26A6 (aa 613-662) polyclonal antibody

Bicarbonate facilitate more than 50% of pH recovery in the acidotic myocardium, and have roles in cardiac hypertrophy and steady-state pH regulation. To determine which bicarbonate transporters are responsible for this activity, we measured the expression levels of all known HCO3--anion exchange proteins in mouse heart, by quantitative real time RT-PCR. Bicarbonate-anion exchangers are members of either the SLC4A or the SLC26A gene families. In neonatal and adult myocardium, AE1 (Slc4a1), AE2 (Slc4a2), AE3 (Slc4a3) (AE3fl and AE3c variants), Slc26a3 and Slc26a6 were expressed. Adult hearts expressed Slc26a3 and Slc4a1-3 mRNAs at similar levels, while Slc26a6 mRNA was about seven-fold higher than AE3, which was more abundant than any other. Immunohistochemistry revealed that Slc26a6 and AE3 are present in the plasma membrane of ventricular myocytes. Slc26a6 expression levels were higher in ventricle than atrium, whereas AE3 was detected only in ventricle. Cl--HCO3- and Cl--OH- exchange activity of SLC26A6 and AE3 were investigated in transfected HEK293 cells, using intracellular fluorescence measurements of 2',7'-bis (2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), to monitor intracellular pH (pH(i)). Rates of pHi change were measured under HCO3--containing (Cl--HCO3-) or nominally HCnO(3)(-)-free (Cl--OH-) conditions. HCO3- fluxes were similar for cells expressing AE3fl, SLC26A6 or Slc26a3, suggesting that they have similar transport activity. However, only SLC26A6 and Slc26a3 functioned as Cl--OH- exchangers. Activation of a-adrenergic receptors, which stimulates protein kinase C, inhibited SLC26A6 Cl--HCO3- exchange activity. We conclude that Slc26a6 is the predominant Cl--HCO3- and Cl--OH- exchanger of the myocardium and that Slc26a6 is negatively regulated upon alpha-adrenergic stimulation.

IRBIT (also called AHCYL1) was originally identified as a binding protein of the intracellular Ca2+ channel inositol 1,4,5-trisphosphate (IP3) receptor and functions as an inhibitory regulator of this receptor. Unexpectedly, many functions have subsequently been identified for IRBIT including the activation of multiple ion channels and ion transporters, such as the Na+/HCO3- co-transporter NBCe1-B, the Na+/H+ exchanger NHE3, the Cl- channel cystic fibrosis transmembrane conductance regulator (CFTR), and the Cl-/HCO3- exchanger Slc26a6. The characteristic serine-rich region in IRBIT plays a critical role in the functions of this protein. In this review, we describe the evolution, domain structure, expression pattern, and physiological roles of IRBIT and discuss the potential molecular mechanisms underlying the coordinated regulation of these diverse ion channels/transporters through IRBIT. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau. (C) 2014 Elsevier B.V. All rights reserved.