Synergy between L-selectin signaling and chemotactic activation during neutrophil adhesion and transmigration.
L-selectin enables capture and rolling of neutrophils on inflamed endothelium. This may facilitate the binding of agonists such as IL-8 and platelet-activating factor (PAF), which signal CD18-mediated firm adhesion and transmigration. Recent studies demonstrate that L-selectin can mediate transmembrane signaling. However, the functional effects of costimulation through agonist and L-selectin require further study. Here, we quantify cell adhesion, motility, and transmigration in response to co-activation through L-selectin and agonist. The surface expression of CD11b/CD18 increased and L-selectin decreased in proportion to the extent of L-selectin cross-linking. A flow cytometric assay was used to measure CD11b/CD18-dependent adhesion to fluorescent beads adsorbed with albumin. Neutrophil adhesion was detected within seconds of adding PAF (20 pM), IL-8 (50 pM), or cross-linking L-selectin. Costimulation through agonist and L-selectin potentiated by up to threefold the rate and extent of bead capture. Stimulation through L-selectin induced membrane ruffling, whereas PAF or IL-8 induced bipolar shape change. L-selectin cross-linking sustained the transient shape change induced by low concentrations (10-50 pM) of agonist. Chemokinesis stimulated by IL-8 was inhibited in the presence of cross-linking L-selectin. This was attributed to enhanced cell spreading following costimulation. Migration across HUVEC monolayers stimulated with IL-1 was also potentiated in the presence of L-selectin cross-linking. We propose that cross-linking of L-selectin and binding of agonist receptors may act synergistically to amplify neutrophil activation and emigration in the inflamed vasculature.
Tsang
Y T
YT
Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030-2399, USA.
Neelamegham
S
S
Hu
Y
Y
Berg
E L
EL
Burns
A R
AR
Smith
C W
CW
Simon
S I
SI
D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology*; D006801:Humans; D019041:L-Selectin / Q000502:physiology*; D018375:Neutrophil Activation; D009504:Neutrophils / Q000166:cytology / Q000502:physiology*; D015290:Second Messenger Systems; D015398:Signal Transduction
D019041:L-Selectin