Distinct binding kinetics of E‐, P‐ and L‐selectins to CD44

Abstract

Molecular‐level selectin‐cluster of differentiation 44 (CD44) interactions are far from clear because of the complexity and diversity of CD44 glycosylation and isoforms expressed on various types of cells. By combining experimental measurements and simulation predictions, the binding kinetics of three selectin members to the recombinant CD44 were quantified and the corresponding microstructural mechanisms were explored, respectively. Experimental results showed that the E‐selectin–CD44 interactions mainly mediated the firm adhesion of microbeads under shear flow with the strongest rupture force. P‐ and L‐selectins had similar interaction strength but different association and dissociation rates by mediating stable rolling and transient adhesions of microbeads, respectively. Molecular docking and molecular dynamics (MD) simulations predicted that the binding epitopes of CD44 to selectins are all located at the side face of each selectin, although the interfaces denoted as the hinge region are between lectin and epidermal growth factor domains of E‐selectin, Lectin domain side of P‐selectin and epidermal growth factor domain side of L‐selectin, respectively. The lowest binding free energy, the largest rupture force and the longest lifetime for E‐selectin, as well as the comparable values for P‐ and L‐selectins, demonstrated in both equilibration and steered MD simulations, supported the above experimental results. These results offer basic data for understanding the functional differences of selectin–CD44 interactions.

Binding of different hyaluronan to CD44 mediates distinct cell adhesion dynamics under shear flow

“…2). In addition, the effective cell accumulation that only occurred below a shear stress of 1.0 dyne·cm −2 indicated that CD44–HA association was not as fast as that of selectin‐ligand interactions [37,38]. On the other hand, our results revealed that the disruption of CD44 clustering regulated the CD44–HA interaction and corresponding cell adhesion (Fig.…”

“…A Bioscope MultiMode8 AFM (Bruker, Billericia, MA, USA) was used to measure the binding strength of CD44–HHA/LHA interactions [37]. Commercial MLCT cantilevers (Veeco; Bruker) were used with a nominal spring constant k c of 10 pN·nm −1 (cantilever C ).…”

“…Flow cytometry assay was used to quantify the constitutive expression density of CD44 or CD18 on U937 cells [37]. In brief, 5 × 10 4 cells were incubated with anti‐CD44 or CD18 antibody at a concentration of 10 μg·mL −1 for 30 min on ice, then resuspended into 400 μL of DPBS.…”

“…Each flow chamber test included two sequential phases [37]. The first one focused on testing CD44-HHA/LHA binding ability by continuously filling with U937 cells solution under a constant shear stress of 0.1, 0.2, 0.5 or 1.0 dyneÁcm À2 for 300 s. The second one was performed just after the first phase by switching the U937 cells solution to blank Hank's balanced salt solution with stepwise shear stress from 1 to 48 dyneÁcm À2 , with 30 s of each stress, to quantify the shear-resistance of CD44-HHA/ LHA interaction.…”

TRAIL in the Treatment of Cancer: From Soluble Cytokine to Nanosystems

“…Another approach targeting NP delivery to tumor cells used an acrylamide-based doxorubicin nanogel (DOX-NG) fabricated by the single emulsion method [ 217 ]. For targeting, the DOX-NGs were coated with platelet membrane since platelets express p -selectin [ 258 ], a molecule that binds to CD44, a receptor often up-regulated on cancer cells [ 259 ]. Finally, the coated DOX-NPs were functionalized with TRAIL using cysteine thiol-conjugation.…”