Limits...
Demonstration of catch bonds between an integrin and its ligand.

Kong F, García AJ, Mould AP, Humphries MJ, Zhu C - J. Cell Biol. (2009)

Bottom Line: Binding of integrins to ligands provides anchorage and signals for the cell, making them prime candidates for mechanosensing molecules.How force regulates integrin-ligand dissociation is unclear.Binding of monoclonal antibodies that induce the active conformation of the integrin headpiece shifted catch bonds to a lower force range.

View Article: PubMed Central - PubMed

Affiliation: Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.

ABSTRACT
Binding of integrins to ligands provides anchorage and signals for the cell, making them prime candidates for mechanosensing molecules. How force regulates integrin-ligand dissociation is unclear. We used atomic force microscopy to measure the force-dependent lifetimes of single bonds between a fibronectin fragment and an integrin alpha(5)beta(1)-Fc fusion protein or membrane alpha(5)beta(1). Force prolonged bond lifetimes in the 10-30-pN range, a counterintuitive behavior called catch bonds. Changing cations from Ca(2+)/Mg(2+) to Mg(2+)/EGTA and to Mn(2+) caused longer lifetime in the same 10-30-pN catch bond region. A truncated alpha(5)beta(1) construct containing the headpiece but not the legs formed longer-lived catch bonds that were not affected by cation changes at forces <30 pN. Binding of monoclonal antibodies that induce the active conformation of the integrin headpiece shifted catch bonds to a lower force range. Thus, catch bond formation appears to involve force-assisted activation of the headpiece but not integrin extension.

Show MeSH

Related in: MedlinePlus

Lifetimes of antibody–antigen bonds. (A and B) Plots of lifetime (mean ± SEM) versus force of interactions between α5β1-Fc–functionalized Petri dish and P1D6-coated cantilever tips (A) and between HFN7.1 captured by anti–mouse Fc antibody preadsorbed on Petri dish and FNIII7–10-coated cantilever tips (B). Schematics depict the molecular arrangement for the experiments.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2712956&req=5

fig4: Lifetimes of antibody–antigen bonds. (A and B) Plots of lifetime (mean ± SEM) versus force of interactions between α5β1-Fc–functionalized Petri dish and P1D6-coated cantilever tips (A) and between HFN7.1 captured by anti–mouse Fc antibody preadsorbed on Petri dish and FNIII7–10-coated cantilever tips (B). Schematics depict the molecular arrangement for the experiments.

Mentions: For comparison, we also measured force-dependent lifetimes of α5β1 and FNIII7–10 bound to their respective blocking mAbs, P1D6 and HFN7.1 (Fig. 4, schematics), which were also specific to the antigen–antibody interactions (Fig. S2, C and D). Similar to the Fc–GG-7 interaction and consistent with other antibody–antigen interactions characterized previously (Marshall et al., 2003; Sarangapani et al., 2004), slip bonds were observed in both cases (Fig. 4) as the mean lifetimes decreased monotonically with increasing force in the same range where the triphasic transitions between slip and catch bonds were observed for α5β1 interacting with its physiological ligand (Fig. 3, A–C). Despite their similar slip bond behaviors, the P1D6–α5β1-Fc–GG-7 serial bonds were much longer lived than the anti–mouse antibody–HFN7.1–FNIII7–10 serial bonds, especially at low forces (Fig. 4, compare A with B), revealing different interaction characteristics of the different antibody–antigen pairs.


Demonstration of catch bonds between an integrin and its ligand.

Kong F, García AJ, Mould AP, Humphries MJ, Zhu C - J. Cell Biol. (2009)

Lifetimes of antibody–antigen bonds. (A and B) Plots of lifetime (mean ± SEM) versus force of interactions between α5β1-Fc–functionalized Petri dish and P1D6-coated cantilever tips (A) and between HFN7.1 captured by anti–mouse Fc antibody preadsorbed on Petri dish and FNIII7–10-coated cantilever tips (B). Schematics depict the molecular arrangement for the experiments.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2712956&req=5

fig4: Lifetimes of antibody–antigen bonds. (A and B) Plots of lifetime (mean ± SEM) versus force of interactions between α5β1-Fc–functionalized Petri dish and P1D6-coated cantilever tips (A) and between HFN7.1 captured by anti–mouse Fc antibody preadsorbed on Petri dish and FNIII7–10-coated cantilever tips (B). Schematics depict the molecular arrangement for the experiments.
Mentions: For comparison, we also measured force-dependent lifetimes of α5β1 and FNIII7–10 bound to their respective blocking mAbs, P1D6 and HFN7.1 (Fig. 4, schematics), which were also specific to the antigen–antibody interactions (Fig. S2, C and D). Similar to the Fc–GG-7 interaction and consistent with other antibody–antigen interactions characterized previously (Marshall et al., 2003; Sarangapani et al., 2004), slip bonds were observed in both cases (Fig. 4) as the mean lifetimes decreased monotonically with increasing force in the same range where the triphasic transitions between slip and catch bonds were observed for α5β1 interacting with its physiological ligand (Fig. 3, A–C). Despite their similar slip bond behaviors, the P1D6–α5β1-Fc–GG-7 serial bonds were much longer lived than the anti–mouse antibody–HFN7.1–FNIII7–10 serial bonds, especially at low forces (Fig. 4, compare A with B), revealing different interaction characteristics of the different antibody–antigen pairs.

Bottom Line: Binding of integrins to ligands provides anchorage and signals for the cell, making them prime candidates for mechanosensing molecules.How force regulates integrin-ligand dissociation is unclear.Binding of monoclonal antibodies that induce the active conformation of the integrin headpiece shifted catch bonds to a lower force range.

View Article: PubMed Central - PubMed

Affiliation: Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.

ABSTRACT
Binding of integrins to ligands provides anchorage and signals for the cell, making them prime candidates for mechanosensing molecules. How force regulates integrin-ligand dissociation is unclear. We used atomic force microscopy to measure the force-dependent lifetimes of single bonds between a fibronectin fragment and an integrin alpha(5)beta(1)-Fc fusion protein or membrane alpha(5)beta(1). Force prolonged bond lifetimes in the 10-30-pN range, a counterintuitive behavior called catch bonds. Changing cations from Ca(2+)/Mg(2+) to Mg(2+)/EGTA and to Mn(2+) caused longer lifetime in the same 10-30-pN catch bond region. A truncated alpha(5)beta(1) construct containing the headpiece but not the legs formed longer-lived catch bonds that were not affected by cation changes at forces <30 pN. Binding of monoclonal antibodies that induce the active conformation of the integrin headpiece shifted catch bonds to a lower force range. Thus, catch bond formation appears to involve force-assisted activation of the headpiece but not integrin extension.

Show MeSH
Related in: MedlinePlus