delta-Catenin, Presenilin, and the Synaptic-Adherens Junction Complex

摘要

delta -Catenin was first cloned in a yeast two-hybrid system as an interactor with the loop region of presenilin 1. delta-Catenin is a mammalian brain protein in the Arma-dillo(Arm) repeat superfamily with sequence similarity to the adherens junction protein p120~(ctn). delta-Catenin can be immunoprecipitated as a complex with other components of the adherens junction, including cadherin and beta-catenin, from transfected cells and brain. The ectopic expression of delta-catenin in MDCK cells altered their morphology, induced the elaboration of lamellipodia, interfered with monolayer formation, and increased scattering in response to hepatocyte growth factor treatment. Interestingly, delta-catenin can also be immunoprecipitated in a complex with certain synaptic proteins. Together these findings suggest that delta-catenin may serve as a linker that joins the synapse and the adherens junction. The interaction with cadherin involves direct contact between the highly conserved juxtamembrane region of the cadherin carboxy terminus and the Arm-repeat of delta-catenin. The interaction with synaptic elements may involve the PDZ binding domain. In developing mouse brain, staining with delta-catenin antibodies is prominent towards the apical boundary of the neuroepithelial cells in the ventricular zone. In mature brain, delta-catenin is localized to the dendrites. Staining is particularly prominent in the apical dendrites of pyramidal cells. Armadillo/beta catenin is also present in the presenilin 1 immunocomplex; however, this interaction is not direct. The interaction between Armadillo/beta-catenin and presenilin 1 requires a third protein, which may be delta-catenin. Presenilin may mediate the delivery of a multi-protein complex to the region of the adherens and synaptic junctions.