Nap1 Regulates Dictyostelium Cell Motility and Adhesion through SCAR-Dependent and -Independent Pathways

Ibarra, Neysi; Blagg, Simone L.; Vázquez, Francisca; Insall, Robert H.

doi:10.1016/j.cub.2006.02.068

Cited by 79 publications

(90 citation statements)

References 24 publications

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“…In none of these cases (migration of the AVE, endoderm and mesoderm) does loss of Nap1 completely block cell migration in vivo. This finding is similar to that seen with mutations in Dictyostelium NapA, PirA and Scar, which encode the homologs of Nap1, Sra1 and WAVE (Blagg et al, 2003;Ibarra et al, 2006). NapA, PirA and Scar mutant cells are motile and can move towards a chemoattractant, but they move more slowly and fail to orient efficiently towards the chemoattractant.…”

Section: Discussionsupporting

confidence: 78%

“…The WAVE complex is crucial for diverse aspects of morphogenesis during development, including chemotactic movement of Dictyostelium amoebae (Blagg et al, 2003;Ibarra et al, 2006), axon pathfinding in Drosophila (Hummel et al, 2000) and spreading of the surface ectoderm in C. elegans (Soto et al, 2002). However, the roles of the WAVE complex in the morphogenetic events required for early vertebrate development have not been studied.…”

Section: Introductionmentioning

confidence: 99%

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Axis specification and morphogenesis in the mouse embryo requireNap1, a regulator of WAVE-mediated actin branching

2006

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Dynamic cell movements and rearrangements are essential for the generation of the mammalian body plan, although relatively little is known about the genes that coordinate cell movement and cell fate. WAVE complexes are regulators of the actin cytoskeleton that couple extracellular signals to polarized cell movement. Here, we show that mouse embryos that lack Nap1, a regulatory component of the WAVE complex, arrest at midgestation and have defects in morphogenesis of all three embryonic germ layers. WAVE protein is not detectable in Nap1 mutants, and other components of the WAVE complex fail to localize to the surface of Nap1 mutant cells; thus loss of Nap1 appears to inactivate the WAVE complex in vivo. Nap1 mutants show specific morphogenetic defects: they fail to close the neural tube, fail to form a single heart tube (cardia bifida), and show delayed migration of endoderm and mesoderm. Other morphogenetic processes appear to proceed normally in the absence of Nap1/WAVE activity: the notochord, the layers of the heart, and the epithelial-to-mesenchymal transition (EMT) at gastrulation appear normal. A striking phenotype seen in approximately one quarter of Nap1 mutants is the duplication of the anteroposterior body axis. The axis duplications arise because Nap1 is required for the normal polarization and migration of cells of the Anterior Visceral Endoderm (AVE), an early extraembryonic organizer tissue. Thus, the Nap1 mutant phenotypes define the crucial roles of Nap1/WAVE-mediated actin regulation in tissue organization and establishment of the body plan of the mammalian embryo.

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Section: Discussionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Axis specification and morphogenesis in the mouse embryo requireNap1, a regulator of WAVE-mediated actin branching

2006

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“…Multicellular development requires multiple aspects of cell movement, adhesion and contractility (Ibarra et al, 2006). To investigate the involvement of MEGAP in multicellular development we developed wild-type AX3 and all mgp-null strains on nitrocellulose membranes (Fig.…”

Section: Phototaxis and Developmentmentioning

confidence: 99%

Dictyostelium MEGAPs: F-BAR domain proteins that regulate motility and membrane tubulation in contractile vacuoles

Heath

Insall

2008

Journal of Cell Science

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PCH family proteins are fundamentally important proteins, linking membrane curvature events with cytoskeletal reorganisation. One group, the MEGAPs (also called srGAPs and WRPs) contain RhoGAP domains in addition to the F-BAR domain. We disrupted MEGAP1 and MEGAP2 in Dictyostelium both singly and in combination. We found a strong cytoskeletal phenotype in MEGAP1– cells and a subtle phototaxis defect in MEGAP2– slugs. MEGAP1–/2– cells have an overabundance of filopodia and slug motility and function are affected. The most dramatic changes, however, are on contractile vacuoles. MEGAP1–/2– cells empty their contractile vacuoles less efficiently than normal and consequently have three times the usual number. GFP-tagged MEGAP1 localises to tubules of the contractile vacuole network and when vacuoles start to empty they recruit cytosolic GFP-MEGAP1. Mutants in the Saccharomyces homologues RGD1 and RGD2 also show abnormal vacuoles, implying that this role is conserved. Thus, MEGAP is an important regulator of the contractile vacuole network, and we propose that tubulation of the contractile vacuole by MEGAP1 represents a novel mechanism for driving vacuole emptying.

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“…Similarly, the SCAR/WAVE complex requires multiple upstream activators such as plasma-membrane-associated phosphoinositides and Rac (Miki et al, 1998;Steffen et al, 2004;Oikawa et al, 2004;Lebensohn and Kirschner, 2009;Chen et al, 2010). Proteins in the SCAR/WAVE family are essential for actin polymerization and movement in many different cell contexts (Bear et al, 1998;Miki et al, 1998;Zallen et al, 2002;Yan et al, 2003;Rogers et al, 2003;Weiner et al, 2006;Ibarra et al, 2006;Patel et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Diffusion, capture and recycling of SCAR/WAVE and Arp2/3 complexes observed in cells by single-molecule imaging

Millius

Watanabe

Weiner

2012

Journal of Cell Science

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SummaryThe SCAR/WAVE complex drives lamellipodium formation by enhancing actin nucleation by the Arp2/3 complex. Phosphoinositides and Rac activate the SCAR/WAVE complex, but how SCAR/WAVE and Arp2/3 complexes converge at sites of nucleation is unknown. We analyzed the single-molecule dynamics of WAVE2 and p40 (subunits of the SCAR/WAVE and Arp2/3 complexes, respectively) in XTC cells. We observed lateral diffusion of both proteins and captured the transition of p40 from diffusion to network incorporation. These results suggest that a diffusive 2D search facilitates binding of the Arp2/3 complex to actin filaments necessary for nucleation. After nucleation, the Arp2/3 complex integrates into the actin network and undergoes retrograde flow, which results in its broad distribution throughout the lamellipodium. By contrast, the SCAR/WAVE complex is more restricted to the cell periphery. However, with single-molecule imaging, we also observed WAVE2 molecules undergoing retrograde motion. WAVE2 and p40 have nearly identical speeds, lifetimes and sites of network incorporation. Inhibition of actin retrograde flow does not prevent WAVE2 association and disassociation with the membrane but does inhibit WAVE2 removal from the actin cortex. Our results suggest that membrane binding and diffusion expedites the recruitment of nucleation factors to a nucleation site independent of actin assembly, but after network incorporation, ongoing actin polymerization facilitates recycling of SCAR/WAVE and Arp2/3 complexes.

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Nap1 Regulates Dictyostelium Cell Motility and Adhesion through SCAR-Dependent and -Independent Pathways

Cited by 79 publications

References 24 publications

Axis specification and morphogenesis in the mouse embryo requireNap1, a regulator of WAVE-mediated actin branching

Axis specification and morphogenesis in the mouse embryo requireNap1, a regulator of WAVE-mediated actin branching

Dictyostelium MEGAPs: F-BAR domain proteins that regulate motility and membrane tubulation in contractile vacuoles

Diffusion, capture and recycling of SCAR/WAVE and Arp2/3 complexes observed in cells by single-molecule imaging

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