Structural Basis of Latrophilin-FLRT Interaction

Latrophilins, receptors for spider venom α-latrotoxin, are adhesion type G-protein-coupled receptors with emerging functions in synapse development. The N-terminal region binds the endogenous cell adhesion molecule FLRT, a major regulator of cortical and synapse development. We present crystallographic data for the mouse Latrophilin3 lectin and olfactomedin-like (Olf) domains, thereby revealing the Olf β-propeller fold and conserved calcium-binding site. We locate the FLRT-Latrophilin binding surfaces by a combination of sequence conservation analysis, point mutagenesis, and surface plasmon resonance experiments. In stripe assays, we show that wild-type Latrophilin3 and its high-affinity interactor FLRT2, but not the binding-impaired mutants we generated, promote HeLa cell adhesion. In contrast, cortical neurons expressing endogenous FLRTs are repelled by wild-type Latrophilin3 and not by the binding-impaired mutant. Taken together, we present molecular level insights into Latrophilin structure, its FLRT-binding mechanism, and a role for Latrophilin and FLRT that goes beyond a simply adhesive interaction. [Display omitted] •The LPHN olfactomedin-like domain forms a five-bladed β propeller•A conserved calcium-binding site is located at the center of the protein•Latrophilin-FLRT binding depends on a conserved binding site•Mutations in the binding site inhibit Latrophilin-FLRT signaling Jackson et al. describe a crystal structure of mLPHN3 lectin and olfactomedin-like (Olf) domains, revealing the Olf β-propeller fold and calcium-binding site. Assays using HeLa cells and cortical neurons reveal a bi-functional role for Olf and its ligand FLRT, leading to HeLa cell adhesion and neuron repulsion.