RESUMO
Teneurins are ancient metazoan cell adhesion receptors that control brain development and neuronal wiring in higher animals. The extracellular C terminus binds the adhesion GPCR Latrophilin, forming a trans-cellular complex with synaptogenic functions. However, Teneurins, Latrophilins, and FLRT proteins are also expressed during murine cortical cell migration at earlier developmental stages. Here, we present crystal structures of Teneurin-Latrophilin complexes that reveal how the lectin and olfactomedin domains of Latrophilin bind across a spiraling beta-barrel domain of Teneurin, the YD shell. We couple structure-based protein engineering to biophysical analysis, cell migration assays, and in utero electroporation experiments to probe the importance of the interaction in cortical neuron migration. We show that binding of Latrophilins to Teneurins and FLRTs directs the migration of neurons using a contact repulsion-dependent mechanism. The effect is observed with cell bodies and small neurites rather than their processes. The results exemplify how a structure-encoded synaptogenic protein complex is also used for repulsive cell guidance.
Assuntos
Proteínas do Tecido Nervoso/ultraestrutura , Receptores de Peptídeos/metabolismo , Tenascina/metabolismo , Animais , Adesão Celular/fisiologia , Cristalografia por Raios X/métodos , Células HEK293 , Humanos , Células K562 , Proteínas de Repetições Ricas em Leucina , Glicoproteínas de Membrana/metabolismo , Glicoproteínas de Membrana/ultraestrutura , Proteínas de Membrana/metabolismo , Proteínas de Membrana/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL/embriologia , Proteínas do Tecido Nervoso/metabolismo , Neuritos/metabolismo , Neurogênese/fisiologia , Neurônios/metabolismo , Complexo Glicoproteico GPIb-IX de Plaquetas/metabolismo , Complexo Glicoproteico GPIb-IX de Plaquetas/ultraestrutura , Ligação Proteica/fisiologia , Proteínas/metabolismo , Proteínas/ultraestrutura , Receptores de Superfície Celular/metabolismo , Receptores de Peptídeos/ultraestrutura , Sinapses/metabolismo , Tenascina/ultraestruturaRESUMO
Latrophilin adhesion-GPCRs (Lphn1-3 or ADGRL1-3) and Unc5 cell guidance receptors (Unc5A-D) interact with FLRT proteins (FLRT1-3), thereby promoting cell adhesion and repulsion, respectively. How the three proteins interact and function simultaneously is poorly understood. We show that Unc5D interacts with FLRT2 in cis, controlling cell adhesion in response to externally presented Lphn3. The ectodomains of the three proteins bind cooperatively. Crystal structures of the ternary complex formed by the extracellular domains reveal that Lphn3 dimerizes when bound to FLRT2:Unc5, resulting in a stoichiometry of 1:1:2 (FLRT2:Unc5D:Lphn3). This 1:1:2 complex further dimerizes to form a larger 'super-complex' (2:2:4), using a previously undescribed binding motif in the Unc5D TSP1 domain. Molecular dynamics simulations, point-directed mutagenesis and mass spectrometry demonstrate the stability and molecular properties of these complexes. Our data exemplify how receptors increase their functional repertoire by forming different context-dependent higher-order complexes.
