LOW-CONDUCTANCE HIGH SELECTIVE INOSITOL (1,4,5)-TRIPHOSPHATE ACTIVATED CA2-MEMBRANE OF A431 CARCINOMA-CELLS( CHANNELS IN PLASMA)

In many cells, activation of receptors coupled to PIP2 turnover result s in Ca2+ release from the intracellular stores accompanied by Ca2+ in flux across the PM. It is not well established yet whether Ca2+ influx is activated by IP3 or by an unknown signal generated upon Ca2+ store depletion. We report here a single-channel study of low-conductance I P3-activated channels of very high selectivity for Ca2+ in the PM of A 431 carcinoma cells. The channels are strongly potential dependent and sensitive to [Ca2+](i) within the physiological range. The data obtai ned argues for IP3 acting directly on plasma membrane Ca2+ channels. ( C) 1997 Federation of European Biochemical Societies.