Tropomodulins Control the Balance between Protrusive and Contractile Structures by Stabilizing Actin-Tropomyosin Filaments

Kumari, Reena; Jiu, Yaming; Carman, Peter J.; Tojkander, Sari; Kogan, Konstantin; Varjosalo, Markku; Gunning, Peter W.; Domínguez, Roberto; Lappalainen, Pekka

doi:10.1016/j.cub.2019.12.049

Cited by 29 publications

(41 citation statements)

References 58 publications

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“…Ventral stress fibers were originally defined as contractile actomyosin bundles, which attach to focal adhesions at their both ends ( Small et al, 1998 ; Hotulainen and Lappalainen, 2006 ). However, migrating mesenchymal cells harbor ventral stress fibers of various length, orientation, and thickness, and these can either locate entirely at the ventral surface of cells or rise toward the dorsal surface from their central regions ( Prager-Khoutorsky et al, 2011 ; Burnette et al, 2014 ; Elkhatib et al, 2014 ; Schulze et al, 2014 ; Baird et al, 2017 ; Lehtimäki et al, 2017b ; Kumari et al, 2020 ). To uncover the possible molecular differences between these diverse stress fibers, we utilized the 3D-structured illumination microscopy (SIM) on human osteosarcoma (U2OS) and mouse embryonic fibroblast (MEF) cells migrating on fibronectin.…”

Section: Resultsmentioning

confidence: 99%

Generation of stress fibers through myosin-driven reorganization of the actin cortex

Lehtimäki

Rajakylä

Tojkander

et al. 2021

eLife

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Contractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex, and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

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Section: Resultsmentioning

confidence: 99%

Generation of stress fibers through myosin-driven reorganization of the actin cortex

Lehtimäki

Rajakylä

Tojkander

et al. 2021

eLife

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“…Phalloidin staining was shown that wild-type cells contained prominent stress fibers, whereas both CAV-1 KO and RNA silencing induced CAV-1 knockdown (CAV-1 KD) cells contained a disorganized meshwork of actin filaments, characterized by thinner contractile stress fibers (Figure 3A and Supplementary Figures 3B,C). The quantification by using Ridge Detection plugin in ImageJ (Kumari et al, 2020;Zhao et al, 2020) confirmed that there was significant decrease in levels of thick actin filament bundles in CAV-1 KO/KD cells, whereas the total amount of filaments remained comparable (Figure 3B and Supplementary Figure 3C). To allow more precise analysis, cells were plated on crossbow shaped fibronectin micropatterns, where they obtain nearly identical shapes and display characteristic organization of stress-fiber network (Jiu et al, 2015).…”

Section: Phospho-deficient and Depletion Of Cav-1 Compromises The Assembly Of Contractile Stress Fibers By Deactivating Rhoa-dependent Mymentioning

confidence: 67%

Feedback-Driven Mechanisms Between Phosphorylated Caveolin-1 and Contractile Actin Assemblies Instruct Persistent Cell Migration

Shi

Wen

Wang

et al. 2021

Front. Cell Dev. Biol.

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The actin cytoskeleton and membrane-associated caveolae contribute to active processes, such as cell morphogenesis and motility. How these two systems interact and control directional cell migration is an outstanding question but remains understudied. Here we identified a negative feedback between contractile actin assemblies and phosphorylated caveolin-1 (CAV-1) in migrating cells. Cytoplasmic CAV-1 vesicles display actin-associated motilities by sliding along actin filaments or/and coupling to do retrograde flow with actomyosin bundles. Inhibition of contractile stress fibers, but not Arp2/3-dependent branched actin filaments, diminished the phosphorylation of CAV-1 on site Tyr14, and resulted in substantially increased size and decreased motility of cytoplasmic CAV-1 vesicles. Reciprocally, both the CAV-1 phospho-deficient mutation on site Tyr14 and CAV-1 knockout resulted in dramatic AMPK phosphorylation, further causing reduced active level of RhoA-myosin II and increased active level of Rac1-PAK1-Cofilin, consequently led to disordered contractile stress fibers and prominent lamellipodia. As a result, cells displayed depolarized morphology and compromised directional migration. Collectively, we propose a model in which feedback-driven regulation between actin and CAV-1 instructs persistent cell migration.

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“…Actomyosin contractility can also prevent lamellipodia formation by increasing membrane tension (Katsumi et al, 2002;Martinelli et al, 2013). Finally, actin nucleating mechanisms can compete for limiting actin monomers (Lomakin et al, 2015;Rotty et al, 2015;Suarez et al, 2015) and actin regulatory proteins (Kumari et al, 2020) to form contractile networks and prevent the generation of lamellipodia. Thus, it is not clear if RhoA activity is disrupting lamellipodia through inhibitory biochemical signaling, competition for actin monomers, or an NMII-dependent increase in cytoplasmic pressure and tension within the plasma membrane.…”

Section: Introductionmentioning

confidence: 99%

Myosin II and Arp2/3 cross-talk governs intracellular hydraulic pressure and lamellipodia formation

Patel

McKeon

Sao

et al. 2021

MBoC

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Human fibroblasts can switch between lamellipodia-dependent and -independent migration mechanisms on 2D surfaces and in 3D matrices. RhoA GTPase activity governs the switch from low-pressure lamellipodia to high-pressure lobopodia in response to the physical structure of the 3D matrix. Inhibiting actomyosin contractility in these cells reduces intracellular pressure and reverts lobopodia to lamellipodial protrusions via an unknown mechanism. To test the hypothesis that high pressure physically prevents lamellipodia formation, we manipulated pressure by activating RhoA or changing the osmolarity of the extracellular environment and imaged cell protrusions. We find RhoA activity inhibits Rac1-mediated lamellipodia formation through two distinct pathways. First, RhoA boosts intracellular pressure by increasing actomyosin contractility and water influx but acts upstream of Rac1 to inhibit lamellipodia formation. Increasing osmotic pressure revealed a second RhoA pathway which acts through non-muscle myosin II (NMII) to disrupt lamellipodia downstream of Rac1 and elevate pressure. Interestingly, Arp2/3 inhibition triggered a NMII-dependent increase in intracellular pressure, along with lamellipodia disruption. Together, these results suggest that actomyosin contractility and water influx are coordinated to increase intracellular pressure, and RhoA signaling can inhibit lamellipodia formation via two distinct pathways in high-pressure cells. [Media: see text] [Media: see text] [Media: see text]

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Tropomodulins Control the Balance between Protrusive and Contractile Structures by Stabilizing Actin-Tropomyosin Filaments

Cited by 29 publications

References 58 publications

Generation of stress fibers through myosin-driven reorganization of the actin cortex

Generation of stress fibers through myosin-driven reorganization of the actin cortex

Feedback-Driven Mechanisms Between Phosphorylated Caveolin-1 and Contractile Actin Assemblies Instruct Persistent Cell Migration

Myosin II and Arp2/3 cross-talk governs intracellular hydraulic pressure and lamellipodia formation

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