Phosphatidyl inositol-4,5-bisphosphate bound to bovine cardiac Na1/Ca21 exchanger displays a MgATP regulation similar to that of the exchange fluxes

CARLA ASTEGGIANO, GRACIELA BERBERIAN AND LUIS BEAUGE

EUROPEAN JOURNAL OF BIOCHEMISTRY

Oxford : Blackwell

Año: 2001 vol. 268 p. 437 - 442

0014-2956

This work shows the existence of a phosphatidylinositol 4,5-bisphosphate (PtdIns-4,5-P2) bound form of the cardiac sarcolemmal Na1/Ca21 exchanger. That was demonstrated in Western blots and cross-immunoprecipitation by using specific antibodies against the NCX1 exchanger (NCX1) and against PtdIns-4,5-P2. In addition, PtdIns-4,5-P2 bound to the Na1/Ca21 exchanger and the Na1/Ca21 exchange fluxes displayed a similar MgATP regulation: (a) both increase by 100±130% when membrane vesicles are incubated (15±20 s at 37 8C) with 1 mm MgATP and 1 mm Ca21 (b) in the presence of 100 mm Ca21, MgATP fails to stimulate the exchange fluxes and does not modify the levels of PtdIns-4,5-P2 bound to the exchanger. In addition, in the absence of Ca21, the net synthesis of total membrane PtdIns-4,5-P2 is greatly reduced compared with that in the presence of 1 mm Ca21. Furthermore, in the absence of Ca21 there is no effect of MgATP on the levels of PtdIns-4,5-P2 bound to the exchanger. These results indicate that, in bovine heart, MgATP-stimulation of Na1/Ca21 exchange is associated with intracellular Ca21-dependent levels of PtdIns-4,5-P2 bound to the exchanger molecule.