Trans-induced cis interaction in the tripartite NGL-1, netrin-G1 and LAR adhesion complex promotes development of excitatory synapses.

The initial contact between axons and dendrites at early neuronal synapses is mediated by surface adhesion molecules and is thought to induce synaptic maturation through the recruitment of additional synaptic proteins. The initiation of synaptic maturation should be tightly regulated to ensure that synaptic maturation occurs selectively at subcellular sites of axo-dendritic adhesion. However, the underlying mechanism is poorly understood. Here, we report that the initial trans-synaptic adhesion mediated by presynaptic netrin-G1 and postsynaptic NGL-1 (netrin-G1 ligand-1) induces a cis interaction between netrin-G1 and the receptor protein tyrosine phosphatase LAR (leukocyte antigen-related), and that this promotes presynaptic differentiation. We propose that trans-synaptic adhesions at early neuronal synapses trigger recruitment of neighboring adhesion molecules in a cis manner in order to couple initial axo-dendritic adhesion with synaptic differentiation.