Assembling actin filaments for protrusion

Rottner, Klemens; Schaks, Matthias

doi:10.1016/j.ceb.2018.09.004

Cited by 84 publications

(86 citation statements)

References 101 publications

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“…This could work in a fashion similar to what has recently been suggested for the Rac binding protein FAM49B [29][30][31]. Such a scenario would also fit the observation that certain missense mutations in Rac1 leading to ID cause its loss of function [22], as well as the model that RhoA signalling is typically upregulated and Rac signalling suppressed in ID [32].…”

Section: Discussionsupporting

confidence: 59%

“…Two studies found mutations in the NCKAP1 gene, encoding for Nap1, with unknown functions [19,20]. While loss-of-function mutations have been described for the WASF1 gene [21], encoding the protein WAVE1, another recent study found mutations in the RAC1 gene and suggested these mutations to either generate dominant negative or constitutively active alleles [22]. Other studies found mutations in CYFIP2, which were accused to cause gain-of-function with respect to WRC activation [23,24], but experimental evidence for this assumption was hitherto missing.…”

Section: Introductionmentioning

confidence: 99%

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Molecular dissection of neurodevelopmental disorder-causing mutations in CYFIP2

Schaks

Rottner

2020

Preprint

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Actin remodelling is frequently regulated by antagonistic activities driving protrusion and contraction downstream of Rac and Rho small GTPases, respectively. WAVE regulatory complex (WRC), which primarily operates downstream of Rac, plays pivotal roles in neuronal morphogenesis. Recently, two independent studies described de novo mutations in the CYFIP2 subunit of WRC, which caused intellectual disability (ID) in humans. Although mutations had been proposed to effect WRC activation, no experimental evidence for this was provided. Here, we made use of CRISPR/Cas9-engineered B16-F1 cell lines that were reconstituted with ID-causing CYFIP variants in the context of compromised WRC activation with or without reduced Rac activities, which established that the majority of CYFIP2 mutations (5 out of 8) indeed cause constitutive WRC activation. Strikingly, activating mutations are positioned in a conserved WAVE-binding region mediating WRC transinhibition. As opposed to such gain-of-function mutations, a truncating mutant represented a loss-of-function variant, because it failed to interact with WRC components, and two mutants displayed no or at best a moderate increase of WRC activation. Collectively, our data show that CYFIP2 mutations frequently but not always coincide with WRC activation and suggest that normal brain development requires a delicate and precisely tuned balance of neuronal WRC activity.

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Section: Discussionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Molecular dissection of neurodevelopmental disorder-causing mutations in CYFIP2

Schaks

Rottner

2020

Preprint

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“…Since both CD44 and CD9 were required for CLEC-2-induced protrusion formation, we examined Arp2/3 + protrusions in CD44 KO and CD9 KO FRCs as a functional readout of actively protruding membrane. Rac1 nucleates the Arp2/3 complex, which drives formation of new actin filaments, branching from pre-existing filaments in the cortical actin network, at the leading edge of lamellipodia (51). Both CD44 KO and CD9 KO FRCs show increased membrane Arp2/3 + (ARPC2) localisation in cell protrusions compared to control FRCs (Fig.…”

Section: Cd9 Controls Frc-frc Interactionsmentioning

confidence: 96%

“…CLEC-2 binding to podoplanin results in loss of RhoA activity and an increase in Rac1 activity (24). Rac1 nucleates Arp2/3, which drives formation of new actin filaments, branching from pre-existing filaments in the cortical actin network, at the leading edge of lamellipodia (50). We examined Arp2/3 + protrusions in CD44 KO and CD9 KO FRCs.…”

Section: Podoplanin Ligand Function Is Independent Of Cd44 or Cd9mentioning

confidence: 99%

Fibroblastic Reticular Cell Response to Dendritic Cells Requires Coordinated Activity of Podoplanin, CD44 and CD9

Winde

Makris

Millward

et al. 2019

Preprint

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Lymph node expansion is pivotal during immune activation. It is controlled by interactions between CLEC-2 hi migratory dendritic cells and podoplanin + fibroblastic reticular cells (FRCs) resulting in rapid loss of actomyosin contractility permitting FRC spreading. Podoplanin is an inflammatory marker in many pathologies, reported to facilitate both contractility and cell protrusions. However, how podoplanin expression is regulated, and how this one membrane protein can elicit these opposing phenotypes is unknown. We report that CLEC-2 binding to FRCs induces transcriptional upregulation of podoplanin, increasing surface protein expression. Further, we find that tetraspanin CD82 is required for trafficking of podoplanin to the plasma membrane. At the cell surface, podoplanin elicits multiple functions, balanced by its membrane binding partners hyaluronan receptor CD44 and tetraspanin CD9. FRCs lacking expression of both CD44 and CD9 are hypercontractile, and upon binding to CLEC-2 hi dendritic cells, both CD44 KO and CD9 KO FRCs exhibit defective protrusion formation and fail to spread. Podoplanin co-localises with CD44 or CD9 in distinct membrane domains, and both CD44 and CD9 are required for FRCs to spread in response to dendritic cells, however they control formation of cell protrusions via different and complimentary mechanisms. In vivo, surface expression levels of podoplanin, CD44 and CD9 are upregulated on T-cell zone FRCs in the early phase of lymph node expansion. Our data support a model whereby podoplanin resides in distinct plasma membrane domains, and that CLEC-2 binding serves as a molecular switch to change podoplanin function. Podoplanin | CD44 | CD9 | CD82 | Tetraspanins | Fibroblastic reticular cell | Lymph node Correspondence: s.acton@ucl.ac.uk de Winde et al. | bioRχiv | October 3, 2019 | 1-2

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“…Many such factors are members of the W iskott - A ldrich S yndrome P rotein (WASP) family, and are integral in activating the complex at different cellular locations [4]. Most WASP-family proteins promote actin assembly during membrane protrusion and cell motility [5], but how the different factors collaborate during these processes is not well understood.…”

Section: Introductionmentioning

confidence: 99%

WHIMP links the actin nucleation machinery to Src-family kinase signaling during protrusion and motility

Kabrawala

Zimmer

Campellone

2020

Preprint

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17Cell motility is governed by cooperation between the Arp2/3 complex and nucleation factors 18 from the Wiskott-Aldrich Syndrome Protein (WASP) family, which together assemble actin 19 filament networks to drive membrane protrusion. Here we identify WHIMP (WAVE Homology In 20Membrane Protrusions) as a new member of the WASP family. The Whimp gene is encoded on 21 the X-chromosome of multiple animals, including mice. Murine WHIMP promotes Arp2/3-22 dependent actin assembly, but is less potent than other nucleation factors. Nevertheless, 23 WHIMP-mediated Arp2/3 activation enhances both plasma membrane ruffling and wound 24 healing migration, whereas WHIMP depletion impairs protrusion and slows motility. WHIMP 25 expression also increases Src-family kinase activity, and WHIMP-induced ruffles contain the 26 additional nucleation factors WAVE1, WAVE2, and N-WASP, but not JMY or WASH. Perturbing 27 the function of Src-family kinases, WAVE proteins, or Arp2/3 complex inhibits WHIMP-driven 28 ruffling. These results suggest that WHIMP-mediated actin assembly plays a direct role in 29 membrane protrusion, but also results in feedback control of tyrosine kinase signaling to 30 modulate the activation of multiple WASP-family proteins. 31 32 33 3 AUTHOR SUMMARY 34The actin cytoskeleton is a collection of protein polymers that assemble and disassemble within 35 cells at specific times and locations. Sophisticated cytoskeletal regulators called nucleation 36 factors ensure that actin polymerizes when and where it is needed, and most nucleation factors 37 are members of the Wiskott-Aldrich Syndrome Protein (WASP) family. Several of the 8 known 38WASP-family proteins function in cell motility, but how the different factors collaborate with one 39 another is not well understood. In this study, we identified WHIMP, a new WASP-family 40 member which is encoded on the X chromosome of a variety of animals. In mouse cells, 41 WHIMP enhances cell motility by assembling actin filaments that push the cell membrane 42 forward. Unexpectedly, WHIMP also activates tyrosine kinase enzymes, proteins that stimulate 43 multiple WASP-family members during motility. Our results open new avenues of research into 44 how nucleation factors cooperate during movement and how the molecular activities that 45 underlie motility differ in distinct cell types and organisms. 46 47 48 the recruitment and activation of a 7-subunit macromolecule named the Arp2/3 complex [2], 52 which acts in concert with binding partners called nucleation-promoting factors [3]. Many such 53 factors are members of the Wiskott-Aldrich Syndrome Protein (WASP) family, and are integral in 54 activating the complex at different cellular locations [4]. Most WASP-family proteins promote 55 actin assembly during membrane protrusion and cell motility [5], but how the different factors 56 collaborate during these processes is not well understood. 57 WASP-family members are defined by the presence of a WH2-Connector-Acidic (WCA) 58 domain in which one or more WH2 motifs bind actin monome...

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Assembling actin filaments for protrusion

Cited by 84 publications

References 101 publications

Molecular dissection of neurodevelopmental disorder-causing mutations in CYFIP2

Molecular dissection of neurodevelopmental disorder-causing mutations in CYFIP2

Fibroblastic Reticular Cell Response to Dendritic Cells Requires Coordinated Activity of Podoplanin, CD44 and CD9

WHIMP links the actin nucleation machinery to Src-family kinase signaling during protrusion and motility

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