title: Comparison of PSGL-1 microbead and neutrophil rolling: microvillus elongation stabilizes P-selectin bond clusters.
abstract: A cell-scaled microbead system was used to analyze the force-dependent kinetics of P-selectin adhesive bonds independent of micromechanical properties of the neutrophil's surface microvilli, an elastic structure on which P-selectin ligand glycoprotein-1 (PSGL-1) is localized. Microvillus extension has been hypothesized in contributing to the dynamic range of leukocyte rolling observed in vivo during inflammatory processes. To evaluate PSGL-1/P-selectin bond kinetics of microbeads and neutrophils, rolling and tethering on P-selectin-coated substrates were compared in a parallel-plate flow chamber. The dissociation rates for PSGL-1 microbeads on P-selectin were briefer than those of neutrophils for any wall shear stress, and increased more rapidly with increasing flow. The microvillus length necessary to reconcile dissociation constants of PSGL-1 microbeads and neutrophils on P-selectin was 0.21 microm at 0.4 dyn/cm2, and increased to 1.58 microm at 2 dyn/cm2. The apparent elastic spring constant of the microvillus ranged from 1340 to 152 pN/microm at 0.4 and 2.0 dyn/cm2 wall shear stress. Scanning electron micrographs of neutrophils rolling on P-selectin confirmed the existence of micrometer-scaled tethers. Fixation of neutrophils to abrogate microvillus elasticity resulted in rolling behavior similar to PSGL-1 microbeads. Our results suggest that microvillus extension during transient PSGL-1/P-selectin bonding may enhance the robustness of neutrophil rolling interactions.
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Eric Y H
authors.initials: EY
authors.lastname: Park
authors.forename: McRae J
authors.initials: MJ
authors.lastname: Smith
authors.forename: Emily S
authors.initials: ES
authors.lastname: Stropp
authors.forename: Karen R
authors.initials: KR
authors.lastname: Snapp
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: DiVietro
authors.forename: William F
authors.initials: WF
authors.lastname: Walker
authors.forename: David W
authors.initials: DW
authors.lastname: Schmidtke
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
authors.forename: Michael B
authors.initials: MB
authors.lastname: Lawrence
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D055592:Biophysical Phenomena; D001703:Biophysics; D004548:Elasticity; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D018715:Microscopy, Video; D008863:Microspheres; D008871:Microvilli / Q000378:metabolism; D015233:Models, Statistical; D009504:Neutrophils / Q000378:metabolism*; D019007:P-Selectin / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry; D011485:Protein Binding; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D011137:Polystyrenes