Cryptdins are
antimicrobial peptides secreted by Paneth cells located at the base of intestinal crypts. In addition to their antimicrobial function, cryptdins may also regulate
salt and water secretion by intestinal epithelial cells. Recent work with short-circuit current measurements indicated that at least one
cryptdin peptide,
cryptdin 3, induces apical conductance(s) in Cl(-) secretory, including
cystic fibrosis, epithelia. In the present study, we characterized the
cryptdin 3-induced
anion channel activity in human embryonic kidney (HEK) cells with single-channel patch-clamp techniques. The patch pipette was filled with
solution containing different concentrations of
cryptdin 3, and, after gigaseal formation, the channel activity was recorded with either cell-attached or inside-out patch modes. We found an
anion selective channel with a conductance of 15 pS and open probability of 0.19, regardless of
cryptdin 3 concentration. The mean open and closed times varied with the
cryptdin 3 concentration. For
cryptdin 3 concentrations of 10, 4, 1, and 0.5 microg/ml in the pipette, the corresponding mean open times were 1.2, 7.0, 9.0, and 17.4 ms and the corresponding mean closed times were 1.1, 1.6, 4.2, and 12.5 ms. These results suggest that
cryptdin 3 forms
anion-selective channels on the cytoplasmic membrane of HEK cells and that the kinetics of one such channel are affected by its interaction with other such channels.