The Integrin/Kindlin/Talin adhesome axis regulates mechanosensory neuron development in C. elegans

Abstract

Evolutionarily conserved, integrin receptors mediate cell-extracellular matrix interactions as part of an expansive adhesion network known as the integrin adhesome. Integrins functions bi-directionally: outside-in signaling is initiated by the binding of extracellular matrix molecules, and inside-out signaling occurs via intracellular activators like Kindlin and Talin. In neurons, integrin signaling has broad roles in cell migration, axon development, and synapse formation. However, much less is known about the effects of Talin and Kindlin on neuron development in vivo and whether they affect behavior is unknown. After curating the conserved C. elegans adhesome, our proteomic studies in C. elegans identified physical associations between a prominent player in nervous system development, RPM-1/MYCBP2, and numerous adhesome components including PAT-3 (β-integrin), TLN-1 (Talin), and UNC-112 (Kindlin). Utilizing a neuron-specific, CRISPR-based strategy to selectively degrade PAT-3, UNC-112, and TLN-1, we demonstrate that this Integrin/Kindlin/Talin axis functions in C. elegans mechanosensory neurons to regulate axon termination and synapse formation. Using super-resolution microscopy, we show that TLN-1 and RPM-1 co-localize at axon termination sites. Genetic interaction, developmental time-course, and pharmacological results suggest TLN-1 inhibits RPM-1 to influence microtubule dynamics and growth cone collapse. Conversely, results on chemical synapse formation suggest TLN-1 functions coordinately with RPM-1 to shape both presynaptic bouton assembly and maintenance. Our results also indicate that TLN-1 influences synapse formation via inside-out signaling. Consistent with our synaptic findings, we demonstrate that TLN-1 regulates behavioral habituation to repeated mechanosensory stimulation. Finally, the RPM-1 human ortholog, MYCBP2, was recently associated with a neurodevelopmental disorder and we note that the adhesome subnetwork physically associated with RPM-1 has extensive links to human neurobehavioral abnormalities. Thus, our findings have identified an Integrin/Kindlin/Talin axis that interacts with RPM-1 to affect mechanosensory neuron development and highlights important new links between the integrin adhesome and neurodevelopmental disorders.