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

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