Expression of the Na+/H+ exchanger-1 (NHE1) in rat heart mitochondria

VILLA-ABRILLE MC; CINGOLANI HE; ALVAREZ BV

Buenos Aires

Congreso; XVII Meeting ISHR Latin American Section; 2009

Federación Argentina de Cardiología

EXPRESSION OF THE Na+/H+ EXCHANGER (NHE1) IN RAT HEART MITOCHONDRIA Villa-Abrille MC, Cingolani HE, Alvarez BV. Centro de Invest. Cardiovasculares, Fac. Ciencias Médicas, La Plata, Argentina. Alvarez BV. Centro de Invest. Cardiovasculares, Fac. Ciencias Médicas, La Plata, Argentina. Electroneutral Na+/H+ exchange activity by NHE is a key component of mitochondrial volume and Ca2+ homeostasis. The molecular identity of the NHE expressed at the inner membrane of the mitochondrion is still controversial. To date, 10 mammalian NHE isoforms (NHE1 to NHE10) have been identified, displaying considerable differences in their primary structures, tissue distribution, membrane localization, biochemical and pharmacological properties, and responsiveness to different stimuli. We characterized the expression of the sarcolemmal NHE1 in mitochondria isolated from adult rat hearts, by immunoblot. A ~88 kDa band, corresponding to fully-glycosylated NHE1 protein, was detected by a goat polyclonal antibody in mitochondrial lysates obtained from adult rat left ventricles. NHE1 was also identified, and immunoprecipitated, with a rabbit polyclonal antibody, using rat heart mitochondrial lysates. Confocal microscopy studies conducted in freshly isolated rat heart cardiomyocytes showed localization of NHE1 in the intercalated disc regions, with additional staining of the nuclei and cell periphery. Interestingly, NHE1 co-localized with cytochrome C oxidase complex 1 protein, a marker of mitochondrial inner membrane, suggesting localization of NHE1 in the mitochondria. We proposed that NHE1 may be the Na+/H+ exchanger involved in the regulation of intramitochondrial Na+ and H+ levels