Blood Journal
Leading the way in experimental and clinical research in hematology

A talin mutant that impairs talin-integrin binding in platelets decelerates αIIbβ3 activation without pathological bleeding

  1. Lucia Stefanini1,
  2. Feng Ye2,
  3. Adam K. Snider2,
  4. Kasra Sarabakhsh2,
  5. Raymond Piatt3,
  6. David S. Paul3,
  7. Wolfgang Bergmeier1,3, and
  8. Brian G. Petrich2
  1. 1Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC;
  2. 2Department of Medicine, University of California San Diego, La Jolla, CA; and
  3. 3McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC

ORCID Profiles

Key Points

  • Mice expressing a talin(L325R) mutant that binds to, but does not activate integrin αIIbβ3, have impaired hemostasis.

  • Talin(W359A) reduces integrin binding, decelerates integrin activation and protects mice from thrombosis without pathological bleeding.

Abstract

Tight regulation of integrin affinity is critical for hemostasis. A final step of integrin activation is talin binding to 2 sites within the integrin β cytoplasmic domain. Binding of talin to a membrane-distal NPxY sequence facilitates a second, weaker interaction of talin with an integrin membrane-proximal region (MPR) that is critical for integrin activation. To test the functional significance of these distinct interactions on platelet function in vivo, we generated knock-in mice expressing talin1 mutants with impaired capacity to interact with the β3 integrin MPR (L325R) or NPLY sequence (W359A). Both talin1(L325R) and talin1(W359A) mice were protected from experimental thrombosis. Talin1(L325R) mice, but not talin(W359A) mice, exhibited a severe bleeding phenotype. Activation of αIIbβ3 was completely blocked in talin1(L325R) platelets, whereas activation was reduced by approximately 50% in talin1(W359A) platelets. Quantitative biochemical measurements detected talin1(W359A) binding to β3 integrin, albeit with a 2.9-fold lower affinity than wild-type talin1. The rate of αIIbβ3 activation was slower in talin1(W359A) platelets, which consequently delayed aggregation under static conditions and reduced thrombus formation under physiological flow conditions. Together our data indicate that reduction of talin-β3 integrin binding affinity results in decelerated αIIbβ3 integrin activation and protection from arterial thrombosis without pathological bleeding.

  • Submitted December 10, 2013.
  • Accepted February 25, 2014.
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