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A RIAM/lamellipodin-talin-integrin complex forms the tip of sticky fingers that guide cell migration.

Lagarrigue F, Vikas Anekal P, Lee HS, Bachir AI, Ablack JN, Horwitz AF, Ginsberg MH - Nat Commun (2015)

Bottom Line: The leading edge of migrating cells contains rapidly translocating activated integrins associated with growing actin filaments that form 'sticky fingers' to sense extracellular matrix and guide cell migration.Here we utilized indirect bimolecular fluorescence complementation to visualize a molecular complex containing a Mig-10/RIAM/lamellipodin (MRL) protein (Rap1-GTP-interacting adaptor molecule (RIAM) or lamellipodin), talin and activated integrins in living cells.These data reveal the molecular basis of the formation of 'sticky fingers' at the leading edge of migrating cells and show that an MIT complex drives these protrusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of California San Diego, La Jolla, California 92093, USA.

ABSTRACT
The leading edge of migrating cells contains rapidly translocating activated integrins associated with growing actin filaments that form 'sticky fingers' to sense extracellular matrix and guide cell migration. Here we utilized indirect bimolecular fluorescence complementation to visualize a molecular complex containing a Mig-10/RIAM/lamellipodin (MRL) protein (Rap1-GTP-interacting adaptor molecule (RIAM) or lamellipodin), talin and activated integrins in living cells. This complex localizes at the tips of growing actin filaments in lamellipodial and filopodial protrusions, thus corresponding to the tips of the 'sticky fingers.' Formation of the complex requires talin to form a bridge between the MRL protein and the integrins. Moreover, disruption of the MRL protein-integrin-talin (MIT) complex markedly impairs cell protrusion. These data reveal the molecular basis of the formation of 'sticky fingers' at the leading edge of migrating cells and show that an MIT complex drives these protrusions.

No MeSH data available.


Related in: MedlinePlus

The MIT complex can form with multiple integrins and Lpd.(a) U2-OS cells expressing VN-RIAM, integrin α5-VCβ1 and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (b) U2-OS cells expressing VN-Lpd, integrin α5-VCβ1, and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (c) U2-OS cells expressing VN-Lpd, integrin αIIb-VCβ3, and mCherry-LifeAct were plated on fibrinogen for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm.
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f5: The MIT complex can form with multiple integrins and Lpd.(a) U2-OS cells expressing VN-RIAM, integrin α5-VCβ1 and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (b) U2-OS cells expressing VN-Lpd, integrin α5-VCβ1, and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (c) U2-OS cells expressing VN-Lpd, integrin αIIb-VCβ3, and mCherry-LifeAct were plated on fibrinogen for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm.

Mentions: Our initial analysis was conducted with the complex formed with RIAM and αIIbβ3. We asked whether this approach could be used to visualize complexes of RIAM with other integrins, such as α5β1. In cells expressing α5-VC and VN-RIAM, we observed a similar localization of BiFC in protrusions (Fig. 5a; Supplementary Movie 8). In addition, we observed the αIIbβ3/talin/RIAM complex in similar locales in a spectrum of cell lines (for example, PtK, HeLa, HT-1080 and NIH-3T3) and primary cells (for example, HuVEC, Mouse Embryonic Fibroblasts) (Supplementary Fig. 6a) and was also true with α5β1-RIAM (Supplementary Fig. 6b). Therefore, MIT complex formation and localization is similar in multiple cell and integrin types. We also found that the talin-binding RIAM paralogue, Lpd192438, formed a complex with α5β1 (Fig. 5b; Supplementary Movie 9) and αIIbβ3 (Fig. 5c; Supplementary Movie 10) at the tips of actin-based protrusions. In summary, either mammalian MRL protein can form a complex with talin and activated integrins localized at the tips of ‘sticky fingers' and they can do so in multiple cell types.


A RIAM/lamellipodin-talin-integrin complex forms the tip of sticky fingers that guide cell migration.

Lagarrigue F, Vikas Anekal P, Lee HS, Bachir AI, Ablack JN, Horwitz AF, Ginsberg MH - Nat Commun (2015)

The MIT complex can form with multiple integrins and Lpd.(a) U2-OS cells expressing VN-RIAM, integrin α5-VCβ1 and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (b) U2-OS cells expressing VN-Lpd, integrin α5-VCβ1, and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (c) U2-OS cells expressing VN-Lpd, integrin αIIb-VCβ3, and mCherry-LifeAct were plated on fibrinogen for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm.
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Related In: Results  -  Collection

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f5: The MIT complex can form with multiple integrins and Lpd.(a) U2-OS cells expressing VN-RIAM, integrin α5-VCβ1 and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (b) U2-OS cells expressing VN-Lpd, integrin α5-VCβ1, and mCherry-LifeAct were plated on fibronectin for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm. (c) U2-OS cells expressing VN-Lpd, integrin αIIb-VCβ3, and mCherry-LifeAct were plated on fibrinogen for 2 h. The cells were imaged with time-lapse TIRFM. A segment of the cell edge is enlarged and displayed as a movie montage at 5 s intervals. The arrows show the growth of an actin protrusion with BiFC enriched at its tip. Scale bar, 5 μm.
Mentions: Our initial analysis was conducted with the complex formed with RIAM and αIIbβ3. We asked whether this approach could be used to visualize complexes of RIAM with other integrins, such as α5β1. In cells expressing α5-VC and VN-RIAM, we observed a similar localization of BiFC in protrusions (Fig. 5a; Supplementary Movie 8). In addition, we observed the αIIbβ3/talin/RIAM complex in similar locales in a spectrum of cell lines (for example, PtK, HeLa, HT-1080 and NIH-3T3) and primary cells (for example, HuVEC, Mouse Embryonic Fibroblasts) (Supplementary Fig. 6a) and was also true with α5β1-RIAM (Supplementary Fig. 6b). Therefore, MIT complex formation and localization is similar in multiple cell and integrin types. We also found that the talin-binding RIAM paralogue, Lpd192438, formed a complex with α5β1 (Fig. 5b; Supplementary Movie 9) and αIIbβ3 (Fig. 5c; Supplementary Movie 10) at the tips of actin-based protrusions. In summary, either mammalian MRL protein can form a complex with talin and activated integrins localized at the tips of ‘sticky fingers' and they can do so in multiple cell types.

Bottom Line: The leading edge of migrating cells contains rapidly translocating activated integrins associated with growing actin filaments that form 'sticky fingers' to sense extracellular matrix and guide cell migration.Here we utilized indirect bimolecular fluorescence complementation to visualize a molecular complex containing a Mig-10/RIAM/lamellipodin (MRL) protein (Rap1-GTP-interacting adaptor molecule (RIAM) or lamellipodin), talin and activated integrins in living cells.These data reveal the molecular basis of the formation of 'sticky fingers' at the leading edge of migrating cells and show that an MIT complex drives these protrusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of California San Diego, La Jolla, California 92093, USA.

ABSTRACT
The leading edge of migrating cells contains rapidly translocating activated integrins associated with growing actin filaments that form 'sticky fingers' to sense extracellular matrix and guide cell migration. Here we utilized indirect bimolecular fluorescence complementation to visualize a molecular complex containing a Mig-10/RIAM/lamellipodin (MRL) protein (Rap1-GTP-interacting adaptor molecule (RIAM) or lamellipodin), talin and activated integrins in living cells. This complex localizes at the tips of growing actin filaments in lamellipodial and filopodial protrusions, thus corresponding to the tips of the 'sticky fingers.' Formation of the complex requires talin to form a bridge between the MRL protein and the integrins. Moreover, disruption of the MRL protein-integrin-talin (MIT) complex markedly impairs cell protrusion. These data reveal the molecular basis of the formation of 'sticky fingers' at the leading edge of migrating cells and show that an MIT complex drives these protrusions.

No MeSH data available.


Related in: MedlinePlus