Effects of Genistein and Curcumin on Non ATP-Hydrolytic CFTR Mutants

The Cystic Fibrosis Transmembrane conductance Regulator (CFTR) chloride channel plays an important role in salt and water transport across epithelia and defective function due to mutations in the CFTR gene cause cystic fibrosis (CF). Numerous small molecules have been shown to increase the activity of CFTR mutants presumably by binding to the CFTR protein. Among the many CFTR potentiators, genistein is perhaps the most extensively studied. Recently a component of the spice turmeric, curcumin was reported to strongly activate wild type and mutated CFTR including F508del and G551D mutations. Recently we found that genistein and curcumin have a synergistic effect in the potentiation of G551D-CFTR (Yu, Miki et al. J Cystic Fibrosis 10: 243 - 252, 2011). However, the mechanism through which these compounds increase the CFTR activity is still unclear.To study the mechanisms of genistein and curcumin, we investigated the effects of genistein and curcumin on the non ATP-hydrolytic CFTR mutants, K1250A- and E1371S- CFTR, expressed in CHO cells using whole-cell clamp technique. The reflect to the single channel currents. Because of their open probability close to 1, the whole-cell currents are thought to reflect the amplitude of their single channel currents.Curcumin did not significantly affect the whole-cell currents obtained from CHO cells expressing K1250A- or E1371 S-CFTR whereas genistein induced a voltage-dependent block on them. Interestingly a combined application of genistein and curcumin induced a voltage-independent reversible reduction in K1250A- or E1371A-CFTR whole-cell currents. This current reduction seemed to be mainly induced by the genistein and curcumin accessing to CFTR proteins from the external side.