pS2/TFF1 interacts directly with the VWFC cysteine-rich domains of mucins

Background & Aims: Trefoil factors (TFFs) are secreted gastrointestinal pro teins that have been shown to protect and promote healing of the gastrointe stinal tract. Moreover, pS2/TFF1 is essential for normal differentiation of the gastric mucosa because deficient mice develop antropyloric adenomas, T o date, it is unclear how TFFs mediate their functions. Methods: Using the yeast 2-hybrid system, we attempted to identify murine TFF1 interacting pro teins by screening a stomach and duodenum complementary DNA (cDNA) expressi on library. Results: Four positive clones were isolated. Sequence and expre ssion studies showed that they corresponded to the murine counterpart of hu man cDNA sequences encoding carboxy-terminal fragments of mMuc2 (489 residu es) and mMuc5AC (427, 430, and 894 residues) mucin proteins, Mutagenesis ex periments showed that TFF1 interacts with the 2 mucins through binding with their VWFC1 and WVFC2 (von Willebrand factor C) cysteine-rich domains. Con clusions: These results show that the gastrointestinal protective effect of TFF1, and presumably of the other TFFs, is caused at least partially by th eir participation, via mucin binding, in the correct organization of the mu cous layer that protects the apical side of the mucosa from deleterious lum inal agents.