Myosin 1E localizes to actin polymerization sites in lamellipodia, affecting actin dynamics and adhesion formation

Abstract

SummaryBecause the actin network in active lamellipodia is continuously assembling at the edge, moving inward and disassembling, there is a question as to how actin-binding proteins and other components are transported to the leading edge and how nascent adhesions are stabilized. Active transport could play a significant role in these functions but the components involved are unknown. We show here that Myosin 1E (a long tailed Myosin 1 isoform) rapidly moves to the tips of active lamellipodia and to actin-rich early adhesions, unlike Myosin 1G, 1B or 1C (short tailed isoforms). Myosin 1E co-localizes with CARMIL, FHOD1, Arp3 and β3-integrin in those early adhesions. But these structures precede stable paxillin-rich adhesions. Myosin 1E movement depends upon actin-binding domains and the presence of an SH3 oligomerization domain. Overexpression of a Myosin 1E deletion mutant without the extreme C-terminal interacting (SH3) domain (Myosin 1EΔSH3) increases edge fluctuations and decreases stable adhesion lifetimes. In contrast, overexpression of Myosin 1E full tail domain (TH1+TH2+TH3/SH3) decreases edge fluctuation. In Myosin 1E knockdown cells, and more prominently in cells treated with Myosin 1 inhibitor, cell–matrix adhesions are also short-lived and fail to mature. We suggest that, by moving to actin polymerization sites and early adhesion sites in active lamellipodia, Myosin 1E might play important roles in transporting not only important polymerizing proteins but also proteins involved in adhesion stabilization.

Control of the Initiation and Termination of Kinesin-1-Driven Transport by Myosin-Ic and Nonmuscle Tropomyosin

“…Myosin-I proteins are single-headed, non-processive molecular motors that facilitate a variety of dynamic actin-membrane interactions [1, 2, 4, 20–22]. The widely expressed isoform, myosin-Ic (Myo1c), participates in exocytic trafficking [1], recycling of lipid raft cargos [1], and the final stages of GLUT4 transport beneath the plasma membrane [2, 3, 7], consistent with a possible role in cargo sorting to specific destinations [1, 3].…”

“…Myosin-I motors participate in a variety of membrane-actin interactions, including dynamic membrane transformations [4, 7, 20–22, 37]. For example, Myo1c has been hypothesized to participate in the recycling of lipid raft cargo toward the plasma membrane from peri-nuclear recycling tubes [1], and the last steps of GLUT4 trafficking toward the plasma membrane [2, 3, 7, 37].…”

Regulation of focal adhesion formation by a vinculin-Arp2/3 hybrid complex

“…Thus, formins create and elongate new linear actin filaments 27 . Specifically, the formins mDia1 and 2 and Formin 1 isoform IV have been shown to be required for the formation of FAs and have the capacity to modulate their characteristics, whereas FHOD1 has been shown to localize into early adhesion sites 26,[28][29][30] . In contrast, the Arp2/3 complex is mostly known for its ability to drive a branching polymerization of actin filaments 31 .…”

Myosin-I molecular motors at a glance

“…Myo1c, Myo1d and Myo1e have been found to contribute to the stability of cell-cell adhesion at adherens junctions, and Myo1e has been found at focal adhesions (Bi et al, 2013;Gupta et al, 2013;Hegan et al, 2015;Oh et al, 2013;Petzoldt et al, 2012;Spéder et al, 2006;Stöffler and Bähler, 1998;Stöffler et al, 1995;Tokuo and Coluccio, 2013). Myo1c localizes to E-cadherin-rich areas in cell-cell contacts between Madin-Darby canine kidney epithelial (MDCK) cells and contributes to the stability of these junctions, although it is unclear how Myo1c functionally establishes and/or maintains this stability (Tokuo and Coluccio, 2013).…”

“…In rats, Myo1d function at adherens junctions influences the establishment and/or maintenance of rotational planar cell polarity in ciliated tracheal and ependymal epithelial cells, but does not do so in all tissues that exhibit planar cell polarity (Hegan et al, 2015). Myo1e localizes to sites of actin polymerization and adhesion in lamellipodia, thereby influencing adhesion formation and actin dynamics through localization of its binding partners (Gupta et al, 2013;Stöffler et al, 1995). Myo1e also localizes to and regulates slit junctions, the highly specialized cell-cell contacts found in the glomerulus of kidney podocyte cells, suggesting why its absence results in kidney disease (Bi et al, 2013;Mele et al, 2011).…”