title: I-domain of lymphocyte function-associated antigen-1 mediates rolling of polystyrene particles on ICAM-1 under flow.
abstract: In their active state, beta(2)-integrins, such as LFA-1, mediate the firm arrest of leukocytes by binding intercellular adhesion molecules (ICAMs) expressed on endothelium. Although the primary function of LFA-1 is assumed to be the ability to mediate firm adhesion, recent work has shown that LFA-1 can contribute to cell tethering and rolling under hydrodynamic flow, a role previously largely attributed to the selectins. The inserted (I) domain of LFA-1 has recently been crystallized in the wild-type (wt) and locked-open conformations and has been shown to, respectively, support rolling and firm adhesion under flow when expressed in alpha(L)beta(2) heterodimers or as isolated domains on cells. Here, we report results from cell-free adhesion assays where wt I-domain-coated polystyrene particles were allowed to interact with ICAM-1-coated surfaces in shear flow. We show that wt I-domain can independently mediate the capture of particles from flow and support their rolling on ICAM-1 surfaces in a manner similar to how carbohydrate-selectin interactions mediate rolling. Adhesion is specific and blocked by appropriate antibodies. We also show that the rolling velocity of I-domain-coated particles depends on the wall shear stress in flow chamber, I-domain site density on microsphere surfaces, and ICAM-1 site density on substrate surfaces. Furthermore, we show that rolling is less sensitive to wall shear stress and ICAM-1 substrate density at high density of I-domain on the microsphere surface. Computer simulations using adhesive dynamics can recreate bead rolling dynamics and show that the mechanochemical properties of ICAM-1-I-domain interactions are similar to those of carbohydrate-selectin interactions. Understanding the biophysics of adhesion mediated by the I-domain of LFA-1 can elucidate the complex roles this integrin plays in leukocyte adhesion in inflammation.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, 3320 Smith Walk, Philadelphia, PA 19104, USA.
authors.forename: A Omolola
authors.initials: AO
authors.lastname: Eniola
authors.forename: Ellen F
authors.initials: EF
authors.lastname: Krasik
authors.forename: Lee A
authors.initials: LA
authors.lastname: Smith
authors.forename: Gang
authors.initials: G
authors.lastname: Song
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hammer
mesh_terms: D001665:Binding Sites; D001703:Biophysics / Q000379:methods*; D019921:Biotinylation; D018821:CD18 Antigens / Q000378:metabolism; D002241:Carbohydrates / Q000737:chemistry; D002448:Cell Adhesion; D002474:Cell-Free System; D003198:Computer Simulation; D018076:DNA, Complementary / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007249:Inflammation; D016023:Integrins / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000737:chemistry*; D007700:Kinetics; D007962:Leukocytes / Q000166:cytology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry*; D008863:Microspheres; D015233:Models, Statistical; D011137:Polystyrenes / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D013314:Stress, Mechanical; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D018821:CD18 Antigens; D002241:Carbohydrates; D018076:DNA, Complementary; D016023:Integrins; D016169:Lymphocyte Function-Associated Antigen-1; D011137:Polystyrenes; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D018799:Intercellular Adhesion Molecule-1