| Research Abstract |
The carboxyl terminus-truncated cadherin (nonfunctional cadherin) loses its ability not only for the cell adhesion but also for the association with cytoplasmic proteins called alpha and beta cetenin. To rescue this nonfunctional cadherin as adhesion molecules, we constructed three cDNAs for fusion proteins between nonfunctional E-cadherin and alpha catenin, nEalpha, nEalphaN and nEalphaC, where intact, amino-terminal and carboxy-terminal half of alpha catenin, respectively, were directly linked to the nonfunctional E-cadherin, and introduced them into mouse L cells. The subcellular distribution and cell adhesion activity of nEalpha and nEalphaC molecules was the same as to those of intact E-cadherin transfectants : They were concentrated at cell-cell adhesion sites in a linear fashion and showed strong cell adhesion activity. nEalphaN molecules, which also bound to cytoskeletons, showed very poor cell adhesion activity. Taken together, we conclude that in the formation of the cadherin-catenin complex, the mechanical association of alpha caten, especially its carboxy-terminal half with E-cadherin is a key step for the cadherin-mediated cell adhesion. Considering that nEalpha was not associated with endogenous beta catenin in transfectants, there should be some difference in the nature of cell adhesion between nEalpha and intact E-cadherin transfectants.Close comparison revealed that the behavior of nEalpha molecules during cytokinesis was quite different from that of intact E-cadherin, and that the intercellular motility, i.e. the cell movement in a onfluent sheet, was significantly suppressed in nEalpha transfectants. The possible functions of beta cetenin are discussed with a special reference to its role as a negative regulator for the cadherin-mediated cell adhesion system.
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