Continued support is requested for a program to analyze activation of integrin allbB3, a process central to normal hemostasis and to arterial thrombosis. The applicant has developed approaches for analyzing intracellular integrin signaling, identified protein-protein interactions at the integrin cytoplasmic face, and provided structural insight into some of those interactions. His studies proved that talin binding to the integrin B cytoplasmic domain is a final step in activation, provided insights into how talin activates integrins, showed how Rapl cooperates with talin to activate integrins, and validated the anti-thrombotic potential of interfering with the talin-B3 integrin interaction. He will now test the hypothesis that talin and/or kindlin binding to integrin allbB3 is sufficient for activation by reconstituting integrin allbB3 into lipid bilayers and examining the capacity of purified proteins to activate the integrin. He will test the hypothesis that RIAM contains a Rap1-regulated talin binding site and that RIAM uncovers talin's integrin binding by studying fragment of RIAM, and the Rap dependence of their interactions with each other and with talin. In addition he will assess the ability of talin-binding fragments of RIAM to cooperate with talin to induce integrin activation in cells and will use bimolecular fluorescence complementation to assess the capacity of these RIAM fragments to promote the integrin-talin interaction.
A third aim will test the hypothesis that interactions of the a and B transmembrane domains regulate integrin activation by analyzing the interactions of these transmembrane domains in mammalian cell membranes and in lipid bicelles. He will test the hypothesis that talin-induced integrin activation plays a distinct role from talin-mediated linkage of integrins to the cytoskeleton in leukocyte and platelet function in vivo by creating mice that either lack wild type talin in platelets and leukocytes and that express talin mutants that maintain the ability to bind to integrins and cytoplasmic partners such as vinculin, but cannot activate integrins. He will assess platelet and leukocyte function in these animals in collaborations with Drs. Ruggeri, Groisman, and Ley. These fundamental studies will provide novel insight into the regulation of platelet aggregation and will test and advance paradigms that apply to many integrin-dependent biological processes.

Public Health Relevance

Platelet aggregation is required for normal hemostasis and is the proximate cause of arterial thrombosis, the leading cause of heart attack and stroke. Activation of platelet GPIIb-llla (integrin allbB3) is a critical process that controls platelet aggregation. The present studies will continue to elucidate the mechanisms and consequences of activation of GPIIb-llla and may therefore lead to new therapeutic approaches to thrombosis.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Program Projects (P01)
Project #
Application #
Study Section
Heart, Lung, and Blood Initial Review Group (HLBP)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California San Diego
La Jolla
United States
Zip Code
Bajaj, Jeevisha; Konuma, Takaaki; Lytle, Nikki K et al. (2016) CD98-Mediated Adhesive Signaling Enables the Establishment and Propagation of Acute Myelogenous Leukemia. Cancer Cell 30:792-805
Schmidt, Thomas; Ye, Feng; Situ, Alan J et al. (2016) A Conserved Ectodomain-Transmembrane Domain Linker Motif Tunes the Allosteric Regulation of Cell Surface Receptors. J Biol Chem 291:17536-46
Fan, Zhichao; McArdle, Sara; Marki, Alex et al. (2016) Neutrophil recruitment limited by high-affinity bent β2 integrin binding ligand in cis. Nat Commun 7:12658
Fan, Zhichao; Liu, Wei (2016) Keep Eyes on Integrins. J Immunobiol 1:
Block, Helena; Stadtmann, Anika; Riad, Daniel et al. (2016) Gnb isoforms control a signaling pathway comprising Rac1, Plcβ2, and Plcβ3 leading to LFA-1 activation and neutrophil arrest in vivo. Blood 127:314-24
Ley, Klaus; Rivera-Nieves, Jesus; Sandborn, William J et al. (2016) Integrin-based therapeutics: biological basis, clinical use and new drugs. Nat Rev Drug Discov 15:173-83
Marki, Alex; Gutierrez, Edgar; Mikulski, Zbigniew et al. (2016) Microfluidics-based side view flow chamber reveals tether-to-sling transition in rolling neutrophils. Sci Rep 6:28870
Fan, Zhichao; Ley, Klaus (2016) Leukocyte Adhesion Deficiency IV. Monocyte Integrin Activation Deficiency in Cystic Fibrosis. Am J Respir Crit Care Med 193:1075-7
Wurtzel, Jeremy G T; Lee, Seunghyung; Singhal, Sharad S et al. (2015) RLIP76 regulates Arf6-dependent cell spreading and migration by linking ARNO with activated R-Ras at recycling endosomes. Biochem Biophys Res Commun 467:785-91
Lagarrigue, Frederic; Vikas Anekal, Praju; Lee, Ho-Sup et al. (2015) A RIAM/lamellipodin-talin-integrin complex forms the tip of sticky fingers that guide cell migration. Nat Commun 6:8492

Showing the most recent 10 out of 98 publications