title: Single-molecule binding of CD44 to fibrin versus P-selectin predicts their distinct shear-dependent interactions in cancer.
abstract: P-selectin and fibrin(ogen) have pivotal roles in the hematogenous dissemination of tumor cells. CD44 variant isoforms, CD44v, have been identified as the major functional P-selectin ligands and fibrin receptors on metastatic colon carcinoma cells. The molecular recognition of CD44v by fibrin mediates firm adhesion at low shear, whereas CD44v-P-selectin binding supports transient rolling interactions at elevated shear stresses and low site densities of P-selectin. We used single-molecule force spectroscopy to provide a molecular interpretation for these two distinct adhesion events. The CD44v-P-selectin bond has a longer unstressed equilibrium lifetime, a lower reactive compliance and a higher tensile strength relative to the CD44v-fibrin bond. These intrinsic differences confer the ability to the CD44v-P-selectin pair to mediate binding at higher shear stresses. Increasing the duration of receptor-ligand contact (2-200 milliseconds) did not affect the micromechanical properties of the CD44v-P-selectin bond, but it increased the tensile strength and the depth of the free energy barrier of the CD44v-fibrin bond and decreased its reactive compliance. This bond strengthening at longer interaction times might explain why CD44v binding to immobilized fibrin occurs at low shear. Single-molecule characterization of receptor-ligand binding can predict the shear-dependent adhesive interactions between cells and substrates observed both in vitro and in vivo.
authors.affiliation: Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: Phrabha S
authors.initials: PS
authors.lastname: Raman
authors.forename: Christina S
authors.initials: CS
authors.lastname: Alves
authors.forename: Denis
authors.initials: D
authors.lastname: Wirtz
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Konstantopoulos
mesh_terms: D045744:Cell Line, Tumor; D005337:Fibrin / Q000378:metabolism*; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D019007:P-Selectin / Q000378:metabolism*; D011485:Protein Binding; D033081:Shear Strength; D013057:Spectrum Analysis / Q000295:instrumentation / Q000379:methods
chemical_list: C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D019007:P-Selectin; D005337:Fibrin