Optimized filopodia formation requires myosin tail domain cooperation

Abstract

Filopodia are actin-filled protrusions employed by cells to interact with their environment. Filopodia formation in Amoebozoa and Metazoa requires the phylogenetically diverse MyTH4-FERM (MF) myosins DdMyo7 and Myo10, respectively. While Myo10 is known to form antiparallel dimers, DdMyo7 lacks a coiled-coil domain in its proximal tail region, raising the question of how such divergent motors perform the same function. Here, it is shown that the DdMyo7 lever arm plays a role in both autoinhibition and function while the proximal tail region can mediate weak dimerization, and is proposed to be working in cooperation with the C-terminal MF domain to promote partner-mediated dimerization. Additionally, a forced dimer of the DdMyo7 motor is found to weakly rescue filopodia formation, further highlighting the importance of the C-terminal MF domain. Thus, weak dimerization activity of the DdMyo7 proximal tail allows for sensitive regulation of myosin activity to prevent inappropriate activation of filopodia formation. The results reveal that the principles of MF myosin-based filopodia formation are conserved via divergent mechanisms for dimerization.

Myosin-X and talin modulate integrin activity at filopodia tips

“…Yet, remarkably, swapping MYO10-FERM with talin-FERM fully supported filopodia function and integrin activation at filopodia tips, suggesting an unanticipated interchangeability between these FERM domains in spatially regulating integrin activation in filopodia. As other FERM domain-containing myosins, including MYO7 and MYO15, also localize to filopodia tips (Jacquemet et al, 2019;Arthur et al, 2019) , where their roles are mostly unknown, future work will examine the contribution of these unconventional myosins to filopodia functions. (D ) The number of MYO10-positive filopodia per cell was quantified (EGP-MYO10 WT , n = 93 cells; EGFP-MYO10 TF , n = 74 cells; three biological repeats).…”

VASP mediated actin dynamics activate and recruit a filopodia myosin

“…MF myosins are thought to act during initiation by cross-linking actin filaments, perhaps zipping them together as the motors walk up the filament towards the cortex (Ropars et al, 2016). Support for this model comes from the observation that forced dimers of motors can induce filopodia or filopodia-like protrusions in cells (Tokuo et al, 2007; Arthur et al, 2019; Masters and Buss, 2017; Liu et al, 2021). Myo10 has also been implicated in elongation by transporting VASP towards the tip of the growing filopodium to promote continued growth (Tokuo and Ikebe, 2004).…”

“…These myosins are regulated by head-tail autoinhibition, with the myosin folded into a compact conformation whereby binding of the C-terminal MF domain to the motor domain inhibits its activity. Opening up of the myosin followed by dimerization is required for activation of the myosin (Umeki et al, 2011; Sakai et al, 2011; Yang et al, 2006; Arthur et al, 2019). Partner binding mediated by their MF domains can typically stabilize the open, activated form of these myosins as well as promote dimerization (Sakai et al, 2011; Arthur et al, 2019; Liu et al, 2021).…”

“…Opening up of the myosin followed by dimerization is required for activation of the myosin (Umeki et al, 2011; Sakai et al, 2011; Yang et al, 2006; Arthur et al, 2019). Partner binding mediated by their MF domains can typically stabilize the open, activated form of these myosins as well as promote dimerization (Sakai et al, 2011; Arthur et al, 2019; Liu et al, 2021). The MyTH4-FERM (MF) domains in these myosins can indeed mediate interaction with partner proteins such as microtubules (Weber et al, 2004; Toyoshima and Nishida, 2007; Planelles-Herrero et al, 2016) and the cytoplasmic tails of adhesion and signaling receptors (Hirao et al, 1996; Hamada, 2000; Zhang et al, 2004; Zhu et al, 2007).…”

“…MF myosin and the actin regulators VASP and formin have been observed to coalesce into punctae during the initiation step that precedes extension (Young et al, 2018; Arthur et al, 2019; Cheng and Mullins, 2020). The mechanism by which Myo7s are targeted to such sites is unknown, but the first step of this process is likely to be regulated via relief of autoinhibition.…”