The objective of this proposal is to elucidate the mechanical regulation of molecular interactions between selectins and glycoconjugate ligands, which mediate the first step of a multistep adhesion and signaling cascade for circulating leukocytes to attach to and migrate across vascular endothelium at sites of tissue injury or infection. These interactions are crucial, because their malfunction can result in a number of inflammatory and thrombotic disorders. Selectin-ligand interactions are regulated mechanically as they take place in the hydrodynamic environment of the circulation. Our hypothesis is that mechanical regulation of selectin-ligand binding kinetics results from specific atomic-level interactions that are dictated by the structures of these molecules. Force regulates bond dissociation by changing the energy landscape of these interactions and/or forming new interactions during force-induced fit and/or conformational changes, thereby eliciting slip and catch bonds. Transport regulates bond formation by influencing collision frequency and encounter time between interacting molecules, modulating the dependence of association kinetics on intrinsic docking. Since selectin-ligand binding kinetics determines cellular function under flow, including tethering, rolling, and aggregation, relatively minor structural differences that alter atomic-level interactions may have major consequences for physiology and pathology. This broad hypothesis will be tested in three integrated specific aims: 1) Define impact of structural variations in selectins and ligands on their interactions, 2) Define selectin-ligand interactions at the atomic level by molecular dynamics simulations, and 3) Define the consequences of ligand-specific alterations in L-selectin-dependent adhesion in vivo. The three specific aims combine experimental, theoretical and computational approaches, include in silico, in vitro, and in vivo studies, and span multiple scales from atomic-level mechanisms, single-cell and single-molecule kinetic/mechanics experiments, to whole animal physiology. This systematic study will clarify how the mechanical regulation of selectin-ligand binding kinetics enables leukocytes to adhere to blood vessel wall in the hydrodynamic environment of the circulation. Decoding how molecular structure determines this regulation will provide key insights into vascular physiology and pathology. As a result, the data may offer new therapeutic approaches to inhibiting pathological cell adhesion during inflammation and thrombosis.

Public Health Relevance

We propose to elucidate the mechanical regulation of molecular interactions between selectins and glycoconjugate ligands, which mediate circulating white blood cells to adhere to vascular surface at sites of tissue injury or infection. This regulation is crucial because malfunction of selectin-ligand interactions can result in a number of inflammatory and thrombotic disorders. The data may offer new therapeutic approaches to inhibiting pathological cell adhesion during inflammation and thrombosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI077343-03
Application #
8197385
Study Section
Erythrocyte and Leukocyte Biology Study Section (ELB)
Program Officer
Minnicozzi, Michael
Project Start
2009-12-15
Project End
2014-11-30
Budget Start
2011-12-01
Budget End
2012-11-30
Support Year
3
Fiscal Year
2012
Total Cost
$564,467
Indirect Cost
$134,255
Name
Georgia Institute of Technology
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
097394084
City
Atlanta
State
GA
Country
United States
Zip Code
30332
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Zarnitsyna, Veronika I; Zhu, Cheng (2011) Adhesion frequency assay for in situ kinetics analysis of cross-junctional molecular interactions at the cell-cell interface. J Vis Exp :e3519
Sarangapani, Krishna K; Qian, Jin; Chen, Wei et al. (2011) Regulation of catch bonds by rate of force application. J Biol Chem 286:32749-61