Crystal structure of Lamellipodin implicates diverse functions in actin polymerization and Ras signaling

Chang, Yu-Chung; Zhang, Hao; Brennan, Mark L.; Wu, Jiangxue

doi:10.1007/s13238-012-2082-x

Cited by 9 publications

(19 citation statements)

References 26 publications

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“…The overall structure of the complex is shown in Figure 1A. As first observed in the Grb10 RA-PH structure [12], and more recently in the RIAM [17] and lamellipodin [19] RA-PH structures, the RA and PH domains of Grb14, together with the intervening linker of ~40 residues, share an extensive interaction interface, which creates an integrated two-domain structural unit. The four copies of Grb14 RA-PH -Ras in the asymmetric unit are highly similar and superimpose on one another with a root-mean-square deviation (rmsd) of <1 Å (410 Cα atoms).…”

Section: Resultsmentioning

confidence: 74%

“…The PH domain adopts the canonical PH-domain fold [21], comprising a seven-stranded β sheet and a C-terminal α helix. An additional helix follows on the C-terminal end, which is also present in the Grb10 [12], RIAM [17], and lamellipodin [22] RA-PH structures. In the Grb10 RA-PH structure, this extra helix mediates RA-PH dimerization [12], but it is not observed to do so in the Grb14 RA-PH structure, although that does not necessarily preclude a dimerization role for this helix in vivo .…”

Section: Resultsmentioning

confidence: 99%

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Structural Basis for the Interaction of the Adaptor Protein Grb14 with Activated Ras

Qamra

Hubbard

2013

PLoS ONE

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Grb14, a member of the Grb7-10-14 family of cytoplasmic adaptor proteins, is a tissue-specific negative regulator of insulin signaling. Grb7-10-14 contain several signaling modules, including a Ras-associating (RA) domain, a pleckstrin-homology (PH) domain, a family-specific BPS (between PH and SH2) region, and a C-terminal Src-homology-2 (SH2) domain. We showed previously that the RA and PH domains, along with the BPS region and SH2 domain, are necessary for downregulation of insulin signaling. Here, we report the crystal structure at 2.4-Å resolution of the Grb14 RA and PH domains in complex with GTP-loaded H-Ras (G12V). The structure reveals that the Grb14 RA and PH domains form an integrated structural unit capable of binding simultaneously to small GTPases and phosphoinositide lipids. The overall mode of binding of the Grb14 RA domain to activated H-Ras is similar to that of the RA domains of RalGDS and Raf1 but with important distinctions. The integrated RA-PH structural unit in Grb7-10-14 is also found in a second adaptor family that includes Rap1-interacting adaptor molecule (RIAM) and lamellipodin, proteins involved in actin-cytoskeleton rearrangement. The structure of Grb14 RA-PH in complex with H-Ras represents the first detailed molecular characterization of tandem RA-PH domains bound to a small GTPase and provides insights into the molecular basis for specificity.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Structural Basis for the Interaction of the Adaptor Protein Grb14 with Activated Ras

Qamra

Hubbard

2013

PLoS ONE

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“…This observation reveals that small lamellipodin puncta are precursors to larger VASP/lamellipodin clusters that concentrate at the tips of nascent filopodia bundles and raises the question of how small lamellipodin puncta form in the first place. Two possibilities are: (i) lamellipodin can independently form small homo-oligomers, which is supported by a structural study that identified two dimerization motifs at its N-terminal RAPH domain (Chang et al 2013) and (ii) lamellipodin foci mark the position of larger complexes that contain other, as yet unidentified proteins.…”

Section: Discussionmentioning

confidence: 97%

“…The Ena/VASP Homology-1 (EVH1) domain of VASP helps determine its subcellular localization by binding proteins that contain an FPPPP (or less commonly LPPPP) motif, such as zyxin, vinculin, Abi1, RIAM, and lamellipodin (Ball et al 2000;Lafuente et al 2004;Brindle et al 1996;Reinhard et al 1996;Gertler et al 1996;Prehoda et al 1999; Krause et al 2004;Bear et al 2000;Niebuhr et al 1997) . Using purified proteins and in vitro assays we previously found that lamellipodin, which contains six F/LPPPP motifs and forms membrane-associated dimers (Chang et al 2013) , can co-cluster with VASP on actin filaments (Hansen and Mullins 2015) . We also found that clusters of purified lamellipodin recruit VASP and dramatically increase the processivity of its actin polymerase activity.…”

Section: Introductionmentioning

confidence: 99%

Leading-edge VASP clusters assemble at sites containing lamellipodin and exhibit size-dependent instability

Cheng

Mullins

2020

Preprint

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The shape of many eukaryotic cells depends on the actin cytoskeleton; and localized changes in actin assembly dynamics underlie many changes in cell shape. Polymerases of the Ena/VASP family modulate cell shape by locally accelerating actin filament assembly and slowing filament capping. When concentrated into discrete foci at the leading edge, VASP promotes formation of filopodia, but the mechanisms that drive VASP clustering are poorly understood. Here we show that, in migrating B16F1 cells, VASP molecules assemble on pre-existing foci of the adaptor protein, lamellipodin, and that dimerization of lamellipodin is essential for cluster formation.VASP/lamellipodin clusters grow by accumulating monomers and by fusing, but their growth is limited by a previously undescribed, size-dependent instability. Our results demonstrate that assembly and disassembly dynamics of filopodia tip complexes are determined, in part, by a network of multivalent interactions between VASP, lamellipodin, and actin.

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“…The PH domain-containing protein lamellipodin (Lpd), also known as Ras association and PH domains 1, is proposed to be a specific PI(3,4)P2-binding protein (29)(30)(31)(32); however, one dissenting study proposed that its PH domain might not be effective in PI binding (33). Lpd was shown to mediate random motility in breast cancer cells (29,34) as well as extension of neuronal processes (35).…”

mentioning

confidence: 99%

Phosphatidylinositol-3,4-Bisphosphate and Its Binding Protein Lamellipodin Regulate Chemotaxis of Malignant B Lymphocytes

Hou

et al. 2016

The Journal of Immunology

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Cell migration is controlled by PI3Ks, which generate lipid messengers phosphatidylinositol-3,4,5-trisphosphate and phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] and consequently recruit pleckstrin homology (PH) domain–containing signaling proteins. PI3K inhibition impairs migration of normal and transformed B cells, an effect thought to partly underlie the therapeutic efficacy of PI3K inhibitors in treatment of B cell malignancies such as chronic lymphocytic leukemia. Although a number of studies have implicated phosphatidylinositol-3,4,5-trisphosphate in cell migration, it remains unknown whether PI(3,4)P2 plays a distinct role. Using the PI(3,4)P2-specific phosphatase inositol polyphosphate 4-phosphatase, we investigate the impact of depleting PI(3,4)P2 on migration behavior of malignant B cells. We find that cells expressing wild-type, but not phosphatase dead, inositol polyphosphate 4-phosphatase show impaired SDF-induced PI(3,4)P2 responses and reduced migration in Transwell chamber assays. Moreover, PI(3,4)P2 depletion in primary chronic lymphocytic leukemia cells significantly impaired their migration capacity. PI(3,4)P2 depletion reduced both overall motility and migration directionality in the presence of a stable chemokine gradient. Within chemotaxing B cells, the PI(3,4)P2-binding cytoskeletal regulator lamellipodin (Lpd) was found to colocalize with PI(3,4)P2 on the plasma membrane via its PH domain. Overexpression and knockdown studies indicated that Lpd levels significantly impact migration capacity. Moreover, the ability of Lpd to promote directional migration of B cells in an SDF-1 gradient was dependent on its PI(3,4)P2-binding PH domain. These results demonstrate that PI(3,4)P2 plays a significant role in cell migration via binding to specific cytoskeletal regulators such as Lpd, and they suggest that impairment of PI(3,4)P2-dependent processes may contribute to the therapeutic efficacy of PI3K inhibitors in B cell malignancies.

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Crystal structure of Lamellipodin implicates diverse functions in actin polymerization and Ras signaling

Cited by 9 publications

References 26 publications

Structural Basis for the Interaction of the Adaptor Protein Grb14 with Activated Ras

Structural Basis for the Interaction of the Adaptor Protein Grb14 with Activated Ras

Leading-edge VASP clusters assemble at sites containing lamellipodin and exhibit size-dependent instability

Phosphatidylinositol-3,4-Bisphosphate and Its Binding Protein Lamellipodin Regulate Chemotaxis of Malignant B Lymphocytes

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