Cell migration-promoting and apoptosis-inhibiting activities of Bm-TFF2 require distinct structure basis

Human trefoil factors (TFFs) play an important role in wound healing, epithelial restitution and anti-inflammatory effects in the gastrointestinal tract by stimulating cell migration and inhibiting cell apoptosis. In our previous study, Bm-TFF2, an amphibian trefoil factor, which is isolated from the skin secretions of frog Bombina maxima, has much stronger activities than human TFFs. We believe that the expression of the recombinant Bm-TFF2 in vitro is useful to decipher its role in amphibian skin repair. Bm-TFF2 contains 12 cysteine residues and has two TFF-domains. In this study, we expressed full-length of Bm-TFF2 and its single-domain truncations (Bm-TFF2-D1 and Bm-TFF2-D2, each contains a single TFF-domain of Bm-TFF2). The recombinant proteins, including full-length and its single-domain truncations of Bm-TFF2, can promote the migration of human epithelial AGS cells and wound healing of rat intestinal epithelial IEC-6 cells. However, only the full-length of Bm-TFF2, but not its single-domain truncations, can inhibit ceramide-induced apoptosis in AGS cells. In summary, it is the first time to use the recombinant Bm-TFF2 and its truncations to investigate its structure–function relationship. And we report that full-length and each domain of Bm-TFF2 can induce cell migration but only the full-length of Bm-TFF2 can suppress apoptosis, indicating that cell migration-promoting and apoptosis-inhibiting activities of Bm-TFF2 require distinct structure basis.

Research highlights
► The recombinant full-length and single-domain truncations of Bm-TFF2 were expressed in vitro, facilitating the structure–function investigation of Bm-TFF2.
► Each TFF-domain was beneficial to the migration-promoting activity of Bm-TFF2.
► The apoptosis-suppressing activity of Bm-TFF2 required the intact two TFF-domains.