Low Spring Constant Regulates P-Selectin-PSGL-1 Bond Rupture

Abstract

Forced dissociation of selectin-ligand bonds is crucial to such biological processes as leukocyte recruitment, thrombosis formation, and tumor metastasis. Although the bond rupture has been well known at high loading rate r f (≥10 2 pN/s), defined as the product of spring constant k and retract velocity v, how the low r f (<10 2 pN/s) or the low k regulates the bond dissociation remains unclear. Here an optical trap assay was used to quantify the bond rupture at r f ≤ 20 pN/s with low k (∼10 −3–10 −2 pN/nm) when P-selectin and P-selectin glycoprotein ligand 1 (PSGL-1) were respectively coupled onto two glass microbeads. Our data indicated that the bond rupture force f retained the similar values when r f increased up to 20 pN/s. It was also found that f varied with different combinations of k and v even at the same r f. The most probable force, f*, was enhanced with the spring constant when k < 47.0 × 10 −3 pN/nm, indicating that the bond dissociation at low r f was spring constant dependent and that bond rupture force depended on both the loading rate and the mechanical compliance of force transducer. These results provide new insights into understanding the P-selectin glycoprotein ligand 1 bond dissociation at low r f or k.