INCREASED AMOUNT OF MEMBRANE TUBULIN IN ERYTHROCYTES FROM DIABETIC PATIENTS

RIVELLI, J; AMAIDEN, R; SANTANDER, V; MONESTEROLO, N; PREVITALI G; FERNANDEZ, A.; ARCE ,C; CASALE, C

Mar del Plata

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

SAIB

Part of tubulin in the cell associates with plasma membrane Na+,K+-ATPase forming a tubulin/ATPase complex that results in inhibition of enzyme activity. We previously demonstrated that treatment of cells with L-glutamate dissociates the complex and stimulates of enzyme activity, and re-formation of the complex requires the presence of glucose. It is known that in erythrocytes (RBC) of diabetics patients (DP), Na+,K+-ATPase activity is partially inhibited. We suspected that high glucose induced association of tubulin with Na+,K+-ATPase with resulting inhibition of the enzyme. Our preliminary studies showed that: a) Plasma membrane from DP’s RBC contains 120 % more tubulin than controls. b) DP`s RBC contain higher quantity of taxol-sedimentable tubulin. c) The characteristic marginal band of microtubules present in normal RBC seems to be absent in DP’s RBC. Results in a), b) and c) were similar to those obtained when normal RBC were treated with 20 mM glucose. A tentative conclusion is that high glucose induces displacement of tubulin to the membrane and interact with Na+,K+-ATPase. In agreement with this hypothesis, treatment of COS and CAD cells with high glucose increased the amount of microtubules and of membrane tubulin/ATPase complex. Our results support the idea that Na+,K+-ATPase is regulated by membrane tubulin which, in turn, is influenced by glucose levels.