A novel C-type lectin regulating cell growth, cell adhesion and cell differentiation of the multipotent epithelium in budding tunicates

We have isolated two Ca2+-dependent, galactose-binding polypeptides from th e budding tunicate, Polyandrocarpa misakiensis. Based on their partial amin o acid sequences, full-length cDNAs were cloned. One of them was identical with a tunicate C-type lectin (TC14-2) reported previously. The other was a novel C-type lectin, referred to as TC14-3. In living animals, they appear ed to be coupled. This complex of lectins, when applied in vitro to tunicat e multipotent cells of epithelial origin, blocked cell proliferation and in duced cell aggregation. The aggregates expressed a homolog of the integrin a-chain and other differentiation markers specific for epithelial cells. Re combinant TC14-3 could reproduce all the activities of native lectins by it self, which was accelerated by recombinant TC14-2. The inhibitory activity of TC14-3 on cell growth was completely abolished by the addition of 50 muM D-galactose. Anti-TC14-3 monoclonal antibody showed that the antigen was e xpressed constitutively by the multipotent epithelial and mesenchymal cells . These results provide evidence that in P. misakiensis a C-type lectin pla ys a novel, cytostatic role in regulating cell growth, cell adhesion and ce ll differentiation during asexual reproduction.