Filopodial protrusion driven by density-dependent Ena-TOCA-1 interactions.

Thomas C A Blake, Helen M Fox, Vasja Urbančič, Roshan Ravishankar, Adam Wolowczyk, Edward S Allgeyer, Julia Mason, Gaudenz Danuser, Jennifer L Gallop

Journal of cell science 2024 Mar 15

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Filopodia are narrow actin-rich protrusions with important roles in neuronal development where membrane-binding adaptor proteins, such as I-BAR- and F-BAR-domain-containing proteins, have emerged as upstream regulators that link membrane interactions to actin regulators such as formins and proteins of the Ena/VASP family. Both the adaptors and their binding partners are part of diverse and redundant protein networks that can functionally compensate for each other. To explore the significance of the F-BAR domain-containing neuronal membrane adaptor TOCA-1 (also known as FNBP1L) in filopodia we performed a quantitative analysis of TOCA-1 and filopodial dynamics in Xenopus retinal ganglion cells, where Ena/VASP proteins have a native role in filopodial extension. Increasing the density of TOCA-1 enhances Ena/VASP protein binding in vitro, and an accumulation of TOCA-1, as well as its coincidence with Ena, correlates with filopodial protrusion in vivo. Two-colour single-molecule localisation microscopy of TOCA-1 and Ena supports their nanoscale association. TOCA-1 clusters promote filopodial protrusion and this depends on a functional TOCA-1 SH3 domain and activation of Cdc42, which we perturbed using the small-molecule inhibitor CASIN. We propose that TOCA-1 clusters act independently of membrane curvature to recruit and promote Ena activity for filopodial protrusion. © 2024. Published by The Company of Biologists Ltd.

Citation

Thomas C A Blake, Helen M Fox, Vasja Urbančič, Roshan Ravishankar, Adam Wolowczyk, Edward S Allgeyer, Julia Mason, Gaudenz Danuser, Jennifer L Gallop. Filopodial protrusion driven by density-dependent Ena-TOCA-1 interactions. Journal of cell science. 2024 Mar 15;137(6)