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Rap1 controls activation of the α(M)β(2) integrin in a talin-dependent manner

Jenson Lim1, Aurélien G Dupuy, David R Critchley

  • 1Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London, UK. jensons_blog@yahoo.co.uk

Journal of Cellular Biochemistry
|July 29, 2010
PubMed

Insights

The small GTPase Rap1 and talin regulate red blood cell (RBC) binding to integrin α(M)β(2). Rap1 acts upstream of talin, influencing its localization and suggesting a novel mechanism for phagocytic cell adhesion.

Area of Science:

  • Cellular biology
  • Immunology
  • Molecular mechanisms of cell adhesion

Background:

  • Integrin α(M)β(2) is crucial for phagocytic cell adhesion.
  • The small GTPase Rap1 and cytoskeletal protein talin are known regulators of integrin function.
  • The precise mechanism linking Rap1, talin, and α(M)β(2) in red blood cell binding remains unclear.

Purpose of the Study:

  • To elucidate the mechanism by which Rap1 and talin regulate the binding of C3bi-opsonised red blood cells (RBCs) to integrin α(M)β(2) in phagocytic cells.
  • To investigate the specific roles of Rap1 and talin in integrin activation and cell adhesion.

Main Methods:

  • Utilized COS-7 cells transfected with integrin α(M)β(2) to study Rap1 effects.
  • Employed talin1 knock-out cells and siRNA-mediated talin1 knockdown in THP-1 cells.
  • Performed co-immunoprecipitation experiments to assess protein interactions.

Main Results:

  • Rap1 activation of α(M)β(2) is mediated through the β(2) subunit, specifically requiring residues 732-761.
  • Rap1 acts upstream of talin, influencing talin localization at phagocytic cups.
  • Rap1 and talin appear to interact and co-localize, suggesting a functional relationship.

Conclusions:

  • Rap1 activation of integrin α(M)β(2) involves specific residues in the β(2) tail and acts upstream of talin.
  • Rap1 and talin functionally and physically interact to regulate phagocytic cell adhesion.
  • This mechanism shares similarities and differences with Rap1 regulation of other integrins, like α(IIb)β(3).

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