Eps8 controls actin-based motility by capping the barbed ends of actin filaments

Abstract

Actin filament barbed-end capping proteins are essential for cell motility, as they regulate the growth of actin filaments to generate propulsive force. One family of capping proteins, whose prototype is gelsolin, shares modular architecture, mechanism of action, and regulation through signalling-dependent mechanisms, such as Ca(2+) or phosphatidylinositol-4,5-phosphate binding. Here we show that proteins of another family, the Eps8 family, also show barbed-end capping activity, which resides in their conserved carboxy-terminal effector domain. The isolated effector domain of Eps8 caps barbed ends with an affinity in the nanomolar range. Conversely, full-length Eps8 is auto-inhibited in vitro, and interaction with the Abi1 protein relieves this inhibition. In vivo, Eps8 is recruited to actin dynamic sites, and its removal impairs actin-based propulsion. Eps8-family proteins do not show any similarity to gelsolin-like proteins. Thus, our results identify a new family of actin cappers, and unveil novel modalities of regulation of capping through protein-protein interactions. One established function of the Eps8-Abi1 complex is to participate in the activation of the small GTPase Rac, suggesting a multifaceted role for this complex in actin dynamics, possibly through the participation in alternative larger complexes.

The actin-binding protein EPS8 binds VE-cadherin and modulates YAP localization and signaling

“…EPS8 also directly binds to actin filaments controlling the rate of polymerization/depolymerization by capping the fast-growing ends of filaments Disanza et al, 2004Disanza et al, , 2006Hertzog et al, 2010). Consistently, EPS8, in vivo, is required for optimal actin-based motility impacting migratory properties of different cells (Frittoli et al, 2011).…”

Restricted Arp3 expression in the testis prevents blood–testis barrier disruption during junction restructuring at spermatogenesis

“…Remarkably, inhibition of N-WASP by wiskostatin in the testis in vivo did not lead to germ cell detachment or BTB damage, unlike Eps8, which is an actin-regulating protein with multiple functions, whose knockdown by RNAi would lead to germ cell loss and BTB damage in vivo (17). Although the Arp2/3 complex can serve as a downstream effector of Eps8 through the activation of Rac and WASP family verprolin-homologous protein (WAVE) (5,18), Eps8 has more diverse effects on the actin cytoskeleton that are not mediated through Arp2/3 complex, such as actin capping and bundling (19,20). Thus, the activation of Arp2/3 complex by N-WASP can be limited to actin cytoskeletal restructuring via actin branching, instead of maintaining junction integrity in the testis.…”

Progressive hearing loss and gradual deterioration of sensory hair bundles in the ears of mice lacking the actin-binding protein Eps8L2

“…Depending on their association with other signal transducers, they act directly on actin by binding to it and by modulating actin bundling and/or actin barbed-end capping activities (32)(33)(34). Notably, Eps8L2 lacks IRSp53 binding, which is essential in Eps8 for relieving inhibition of actin-bundling activity (33).…”