Drosophila neurexin and neuroligin 1 display genetic and biochemical interactions. Dnrx and Dnlg1 are required for subcellular localization of Dlg at the synapse. Dnrx and Dnlg1 are required for the localization and stability of BMP receptor Wit. Dnrx and Dnlg1 regulate levels of BMP co-receptor Tkv and downstream effector Mad. Proper trans-synaptic adhesion is crucial for BMP receptor stability and signaling.