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Lamellipodin promotes actin assembly by clustering Ena/VASP proteins and tethering them to actin filaments.

Hansen SD, Mullins RD - Elife (2015)

Bottom Line: We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity.We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments.This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco School of Medicine, San Francisco, United States.

ABSTRACT
Enabled/Vasodilator (Ena/VASP) proteins promote actin filament assembly at multiple locations, including: leading edge membranes, focal adhesions, and the surface of intracellular pathogens. One important Ena/VASP regulator is the mig-10/Lamellipodin/RIAM family of adaptors that promote lamellipod formation in fibroblasts and drive neurite outgrowth and axon guidance in neurons. To better understand how MRL proteins promote actin network formation we studied the interactions between Lamellipodin (Lpd), actin, and VASP, both in vivo and in vitro. We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity. We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments. This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly.

No MeSH data available.


Related in: MedlinePlus

Lpd and VASP synergistically bundle actin filaments.(A) Montage of single actin filaments polymerizing in the presence of 2 µM actin (20% Cy5 labeled) and TIRF buffer containing 100 mM KCl. Compared to actin filaments elongating in the presence of 50 nM VASP (tetrameric concentration) or 250 nM GFP-LZ-Lpd850−1250aa (dimer concentration). The combined presence of VASP and GFP-LZ-Lpd850−1250aa produces large actin bundles. Scale bar, 10 µm.DOI:http://dx.doi.org/10.7554/eLife.06585.024
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fig7s1: Lpd and VASP synergistically bundle actin filaments.(A) Montage of single actin filaments polymerizing in the presence of 2 µM actin (20% Cy5 labeled) and TIRF buffer containing 100 mM KCl. Compared to actin filaments elongating in the presence of 50 nM VASP (tetrameric concentration) or 250 nM GFP-LZ-Lpd850−1250aa (dimer concentration). The combined presence of VASP and GFP-LZ-Lpd850−1250aa produces large actin bundles. Scale bar, 10 µm.DOI:http://dx.doi.org/10.7554/eLife.06585.024

Mentions: Supporting the notion that Lpd-VASP complexes can synergistically bind actin filaments, we find that the presence of both VASP and GFP-LZ-Lpd results in a large amount of actin filament bundling in the presence of 100 mM KCl (Figure 7—figure supplement 1). In contrast, individual actin filaments elongating in the presence of 50 nM tetrameric VASP or 250 nM dimeric GFP-LZ-Lpd alone do not bundle actin filaments in high ionic strength buffer. This means that the Lpd-VASP interaction can compensate for the weak actin filament binding observed for the individual proteins in buffer containing 100 mM KCl.


Lamellipodin promotes actin assembly by clustering Ena/VASP proteins and tethering them to actin filaments.

Hansen SD, Mullins RD - Elife (2015)

Lpd and VASP synergistically bundle actin filaments.(A) Montage of single actin filaments polymerizing in the presence of 2 µM actin (20% Cy5 labeled) and TIRF buffer containing 100 mM KCl. Compared to actin filaments elongating in the presence of 50 nM VASP (tetrameric concentration) or 250 nM GFP-LZ-Lpd850−1250aa (dimer concentration). The combined presence of VASP and GFP-LZ-Lpd850−1250aa produces large actin bundles. Scale bar, 10 µm.DOI:http://dx.doi.org/10.7554/eLife.06585.024
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4543927&req=5

fig7s1: Lpd and VASP synergistically bundle actin filaments.(A) Montage of single actin filaments polymerizing in the presence of 2 µM actin (20% Cy5 labeled) and TIRF buffer containing 100 mM KCl. Compared to actin filaments elongating in the presence of 50 nM VASP (tetrameric concentration) or 250 nM GFP-LZ-Lpd850−1250aa (dimer concentration). The combined presence of VASP and GFP-LZ-Lpd850−1250aa produces large actin bundles. Scale bar, 10 µm.DOI:http://dx.doi.org/10.7554/eLife.06585.024
Mentions: Supporting the notion that Lpd-VASP complexes can synergistically bind actin filaments, we find that the presence of both VASP and GFP-LZ-Lpd results in a large amount of actin filament bundling in the presence of 100 mM KCl (Figure 7—figure supplement 1). In contrast, individual actin filaments elongating in the presence of 50 nM tetrameric VASP or 250 nM dimeric GFP-LZ-Lpd alone do not bundle actin filaments in high ionic strength buffer. This means that the Lpd-VASP interaction can compensate for the weak actin filament binding observed for the individual proteins in buffer containing 100 mM KCl.

Bottom Line: We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity.We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments.This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco School of Medicine, San Francisco, United States.

ABSTRACT
Enabled/Vasodilator (Ena/VASP) proteins promote actin filament assembly at multiple locations, including: leading edge membranes, focal adhesions, and the surface of intracellular pathogens. One important Ena/VASP regulator is the mig-10/Lamellipodin/RIAM family of adaptors that promote lamellipod formation in fibroblasts and drive neurite outgrowth and axon guidance in neurons. To better understand how MRL proteins promote actin network formation we studied the interactions between Lamellipodin (Lpd), actin, and VASP, both in vivo and in vitro. We find that Lpd binds directly to actin filaments and that this interaction regulates its subcellular localization and enhances its effect on VASP polymerase activity. We propose that Lpd delivers Ena/VASP proteins to growing barbed ends and increases their polymerase activity by tethering them to filaments. This interaction represents one more pathway by which growing actin filaments produce positive feedback to control localization and activity of proteins that regulate their assembly.

No MeSH data available.


Related in: MedlinePlus