MEMBRANE TUBULIN AND NA+,K+-ATPASE ACTIVITY OF HYPERTENSIVE PATIENTS ERYTHROCYTES

AMAIDEN, R; RIVELLI-ANTONELLI, J. F; SANTANDER, V; MONESTEROLO NE; PREVITALI G; PIE-JUSTE, J; ARCE, C; CASALE CH

Mar del Plata

Congreso; SAIB-Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2007

SAIB

We previously showed that, in several cell types, acetylated tubulin associates with plasma membrane Na+,K+-ATPase and inhibits the enzyme activity. This also occurs in normal human erythrocytes. Since Na+ accumulates in erythrocytes of hypertensive patients due to an inhibited state of Na+,K+-ATPase, we considered the possibility that Na+,K+-ATPase was inhibited by interaction with tubulin. We analyzed the amount of tubulin and Na+,K+-ATPase activity in erythrocytes membranes from hypertensive patients (HP) as compared with normal individuals. Our results show that: 1) The amount of total tubulin in membranes of HP erythrocytes is higher than those of controls; 2) Na+,K+-ATPase activity in HP erythrocytes is 50% lower than in controls; 3) The relative proportions of the different isotypes of tubulin (tyrosinated, detyrosinated and acetylated) were the same in membranes erythrocytes of HP and controls; 4) Tubulin coprecipitates with a 110 kDa protein when detergent-solubilized HP’s erythrocyte membranes were treated with antibody to total tubulin linked to Sepharose beads; 5) HP`s erythrocytes contain higher quantity of taxol-sedimentable tubulin. According with these results, it seems that the sodium pump in erythrocytes from hypertensive patients is forming part of a complex with a 110KD protein, presumably Na+,K+-ATPase, resulting in inhibition of its enzyme activity.