O. Dwir et al., An activated L-selectin mutant with conserved equilibrium binding properties but enhanced ligand recognition under shear flow, J BIOL CHEM, 275(25), 2000, pp. 18682-18691
Selectins mediate the initial tethering and rolling of leukocytes on vessel
walls. Adhesion by selectins is a function of both ligand recognition at e
quilibrium and mechanical properties of the selectin-ligand bond under appl
ied force. We describe an EGF domain mutant of L-selectin with profoundly a
ugmented adhesiveness over that of native L-selectin but conserved ligand s
pecificity. This mutant, termed LPL, was derived by a substitution of the E
GF-like domain of L selectin with the homologous domain from P-selectin. Th
e mutant bound soluble carbohydrate L-selectin ligand with affinity compara
ble with that of native L-selectin but interacted with all surface-bound li
gands much more readily than native L-selectin, in particular under elevate
d shear flow. Tethers mediated by both native and mutant L-selectin exhibit
ed similar lifetimes under a range of shear stresses, but the rate of bond
formation by the mutant was at least 10-fold higher than that of native L-s
electin toward distinct L-selectin ligands. Enhanced rate of bond formation
by the mutant was associated with profoundly stronger rolling interactions
and reduced dependence of rolling on a threshold of shear stress. This is
the first demonstration that the EGF domain can modulate the binding of the
lectin domain of a selectin to surface-immobilized ligands under shear flo
w without affecting the equilibrium properties of the selectin toward solub
le ligands.