title: Effect of extracellular pH on selectin adhesion: theory and experiment.
abstract: Selectins mediate circulatory leukocyte trafficking to sites of inflammation and trauma, and the extracellular microenvironments at these sites often become acidic. In this study, we investigated the influence of slightly acidic pH on the binding dynamics of selectins (P-, L-, and E-selectin) to P-selectin glycoprotein ligand-1 (PSGL-1) via computational modeling (molecular dynamics) and experimental rolling assays under shear in vitro. The P-selectin/PSGL-1 binding is strengthened at acidic pH, as evidenced by the formation of a new hydrogen bond (seen computationally) and the observed decrease in the rolling velocities of model cells. In the case of L-selectin/PSGL-1 binding dynamics, the binding strength and frequency increase at acidic pH, as indicated by the greater cell-rolling flux of neutrophils and slower rolling velocities of L-selectin-coated microspheres, respectively. The cell flux is most likely due to an increased population of L-selectin in the high-affinity conformation as pH decreases, whereas the velocities are due to increased L-selectin/PSGL-1 contacts. In contrast to P- and L-selectin, the E-selectin/PSGL-1 binding does not exhibit significant changes at acidic pH levels, as shown both experimentally and computationally.
authors: Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.
authors: Thong M
authors: TM
authors: Cao
authors: Tait
authors: T
authors: Takatani
authors: Michael R
authors: MR
authors: King
mesh_terms: D000268:Adhesiveness / Q000187:drug effects; D000328:Adult; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D019040:E-Selectin / Q000737:chemistry / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D019041:L-Selectin / Q000378:metabolism; D036904:Leukocyte Rolling / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000378:metabolism; D008863:Microspheres; D008954:Models, Biological; D056004:Molecular Dynamics Simulation; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019007:P-Selectin / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011994:Recombinant Proteins / Q000494:pharmacology; D019087:Selectins / Q000378:metabolism*
chemical_list: D019040:E-Selectin; D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D011994:Recombinant Proteins; D019087:Selectins; D019041:L-Selectin; D006639:Histidine