Interaction of Cholera Toxin B Subunit with Rat Intestinal Epithelial Cells

摘要

We prepared I-125-labeled cholera toxin B subunit (I-125-labeled CT-B, specific activity 98 Ci/mmol) and found that its binding to rat IEC-6 intestinal epithelial cells was high-affinity (K-d 1.9 nM). The binding of labeled protein was completely inhibited by unlabeled thymosin-alpha(1) (TM-alpha(1)), interferon-alpha(2) (IFN-alpha(2)), and synthetic peptide LKEKK, which corresponds to residues 16-20 in TM-alpha(1) and 131-135 in IFN-alpha(2) (K (i) 1.2, 0.9, and 1.6 nM, respectively), but was not inhibited by synthetic peptide KKEKL with inverted amino acid sequence (K (i) 10 mu M). Thus, TM-alpha(1), IFN-alpha(2), and the LKEKK peptide bind with high affinity and specificity to CT-B receptor on rIEC-6 cells. It was found that CT-B and the LKEKK peptide at concentrations of 10-1000 nM increased nitric oxide production and soluble guanylate cyclase activity in the cells in a dose-dependent manner.