Two papers in this issue of Neuron add a new dimension to our understanding of liprin and LAR RPTP function during synapse formation. Kaufmann et al. (2002) present evidence that Dliprin-α interacts with Dlar to regulate presynaptic morphogenesis of the Drosophila neuromuscular junction. Wyszynski et al. (2002) demonstrate that mammalian liprin-α1 forms a complex with the PDZ protein GRIP and LAR in both pre- and postsynaptic compartments of hippocampal neurons and is required for the clustering of the GluR2 glutamate receptor in dendritic spines.