Enabled Negatively Regulates Diaphanous-Driven Actin Dynamics In Vitro and In Vivo

Abstract

Summary Actin regulators facilitate cell migration by controlling cell protrusion architecture and dynamics. As the behavior of individual actin regulators becomes clear, we must address why cells require multiple regulators with similar functions and how they cooperate to create diverse protrusions. We characterized Diaphanous and Enabled as a model, using complementary approaches: cell culture, biophysical analysis, and Drosophila morphogenesis. We found Dia and Ena have distinct biochemical properties that contribute to the different protrusion morphologies each induces. Dia is a more processive, faster elongator, paralleling the long, stable filopodia it induces in vivo, while Ena promotes filopodia with more dynamic changes in number, length and lifetime. Acting together, Ena and Dia induce protrusions distinct from those induced by either alone, with Ena reducing Dia-driven protrusion length and number. Consistent with this, EnaEVH1 binds Dia directly and inhibits DiaFH1FH2-mediated nucleation in vitro. Finally, Ena rescues hemocyte migration defects caused by activated Dia.

Profilin-1 Serves as a Gatekeeper for Actin Assembly by Arp2/3-Dependent and -Independent Pathways

“…The fact that formin inhibition did not affect the F-actin organization and content of the Arpc2−/− cells is surprising given the key role that formins play in compensating for the loss of Arp2/3 complex activity in fission yeast (Burke et al, 2014). However, yeast cells do not have proteins homologous to Ena/VASP and recent data in insect cells indicate that Ena/VASP proteins and formins do not merely substitute for each other functionally, but have a more complex interaction than previously suspected (Bilancia et al, 2014). Our data in mammalian cells indicate that Ena/VASP proteins play a major role in compensating for the loss of Arp2/3 complex when it comes to maintaining overall F-actin levels.…”

Loss of Gα12/13exacerbates apical area dependence of actomyosin contractility

“…, 2007). Dia, a member of the formin family, is both an actin nucleation and elongation factor (Goode and Eck, 2007; Bilancia et al. , 2014).…”

Self-organization of protrusions and polarity during eukaryotic chemotaxis

“…While a handful of studies have implicated some formins (particularly those of the Dia subgroup) in mediating migration [55,56], the exact mechanisms by which they do so are not completely clear, even in 2D migration. One in vitro study has proposed a mechanism where formins associate with the free barbed ends of filaments nucleated by Arp2/3 to create some of the longer filaments seen at the leading edge of migrating cells [57]; and later work found that the formin Dia and Enabled (a member Ena/VASP family of actin assembly factors) directly interact to modulate the migration speed of Drosophila hematocytes [58]. It will thus be important to address how different mechanisms of actin assembly (e.g., WRC-, WASP-, and formin-mediated), which produce filament networks with distinct architectures, collaborate to drive cell migration under varying environmental conditions.…”