Fig. 1. Syntaxin 1A and CFTR physically and functionally interact in 16HBE14o- cells. (A) Syntaxin-1A-specific IgG (Naren et al., 2000) can coimmunoprecipitate CFTR from 16HBE14o- cells. (B) Representative whole-cell I_CFTR in 16HBE14o- cells maximally stimulated by addition of cAMP cocktail to the external bath with voltage steps ranging from -110 to +110 mV in increments of 10 mV in the absence and presence of 350 nM GST-Syn1AC. (C) Current-voltage relationship of I_CFTR from (B). The reversal potentials for the Cl^- current in control conditions and in the presence of GST-Syn1AC, GST-Munc18 and GST-Syn1AH3 were -18±1.5 mV (n=6), -15±2.7 mV (n=7), -10.2±1.2mV (n=5) and -14±1.5 mV (n=5), respectively. (D) The I_CFTR was similar irrespective of whether disruption of Syn1A-CFTR interaction was by GST-Syn1AC or by 300 nM GST-Munc18. Whole-cell I_CFTR in the presence of 350 nM GST-Syn1AH3 was not significantly different from the control currents. Current density for control I_CFTR was 29.6±10.0 pA/pF (n=6). Current densities in the presence of GST-Syn1AC and GST-Munc18 increased threefold to 85.0±12.3 pA/pF (n=7) and 88.4±17.9 pA/pF (n=5) respectively. When Syn1AH3 was included in the pipette solution, the current density was 26.9±7.4 pA/pF (n=5). Asterisk (^*) indicates p <0.05 when comparing the densities of either control currents or I_CFTR in the presence of GST-Syn1AH3 with currents in the presence of either GST-Syn1AC or GST-Munc 18.