Integrins are transmembrane receptors formed by non-covalently bound alpha and beta subunits. The beta-1 subunit binds 12 alpha subunits, suggesting that specificity of function of alpha-beta-1 integrins are determined by the alpha subunits. This is seen in the two major collagen binding receptors, integrins alpha-1-beta-1 and alpha-2-beta-1, which not only have different affinities for various collagens (determined by their extracellular domains), but also mediate different signals in a manner that is critically dependent on their transmembrane (TM) and cytoplasmic (CT) domains. The molecular mechanisms whereby the TM and CT domains of beta-1 containing integrins transduce signals are poorly understood, as most published work on these domains was performed with the highly modulatable alpha-s-beta-3 integrins and focused primarily on the beta-3 subunit itself. We recently showed that integrin alpha-1 and alpha-2 TM and CT domains contribute to the very different specificities of integrin alpha-1-beta-1 and alpha-2-beta-1 function. Moreover, key amino acids that regulate specific signaling by the integrin alpha-1 and alpha-2 CT tails have been identified. Thus, the overall goal of this project is to identify the mechanisms whereby the TM and CT domains of integrins alpha-1-beta-1 and alpha-2-beta-1 contribute to their functional specificity. In particular, we will test the hypothesis that specific residues within the TM or CT domains of integrins alpha-1-beta-1 and alpha-2-beta-1 are critical for conferring structural and functional specificity. To test this hypothesis we will:
Aim 1) Determine the structures of the individual integral alpha-1, alpha-2, and beta-1 TM/CT domains and of the alpha-1-beta-1 and alpha-2-beta-1 TM/CT heterodimers.
Aim 2) Determine the critical amino acids that govern the specificity and functionality of the alpha-1 and alpha-2 TM domains of integrins alpha-1-beta-1 and alpha-2-beta-1 in cell function.
Aim 3) Develop models for the roles of the TM/CD domains in integrin alpha-1-beta-1 and alpha-2-beta-1 function and specificity.

Public Health Relevance

We anticipate that this study will generate novel insights into the structural basis whereby the TM and CT domains of integrins alpha-1-beta-1 and alpha-2-beta-1 function. This knowledge is fundamental to our understanding of how integrins transduce signals from collagens within the glomerulus in both health and disease.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BCMB-B (02))
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Ketchum, Christian J
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Vanderbilt University Medical Center
Internal Medicine/Medicine
Schools of Medicine
United States
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