Engagement of L-selectin impairs the actin polymerizing capacity of beta 2-integrins on neutrophils.
A sequential activation of L-selectin and beta 2-integrins on neutrophils is crucial for the rolling, adherence and subsequent migration of these cells on the endothelium. However, little is known about a possible interplay between these adhesion receptors in the final regulation of cell motility. The results presented here show that sulfatides themselves (here used as tools to activate L-selectins), have no major effect on the cellular content of filamentous actin (F-actin), but cause a time-related decrease in the beta 2-integrin-induced formation of F-actin. This effect of sulfatides was abolished in cells lacking L-selectin as a result of pretreatment with chymotrypsin. A similar sulfatide-induced activation of L-selectin also caused a pronounced and time-related decrease of a subsequent chemotactic peptide-induced F-actin response. The effect of sulfatides on both beta 2-integrin- and chemotactic peptide-induced F-actin were abolished if L-selectin were blocked by preincubating the cells with specific antibodies to L-selectin. These effects of L-selectin engagement on cellular F-actin content were neither abolished by blocking the cytosolic free Ca2+ signal with bis-(2-amino-5-methylphenoxy)ethane-N,N,N',N'-tetraaceticacid tetraacetoxymethyly ester (MAPT/AM) nor by blocking a cAMP-induced activation of protein kinase A by pretreating the cells with adenosine-3',5'-cyclic monophos-phorothioate (Rp-cAMPS). Instead we found that L-selectin engagement impaired an early beta 2-integrin-induced tyrosine kinase activation, an event shown to be necessary for a normal beta 2-integrin-mediated F-actin response. The present demonstration of a negative feed-back function of L-selectin on beta 2-integrin-induced modulations of the actin cytoskeleton, suggests that the relative distribution and/or density of the respective L-selectin and beta 2-integrin ligands on endothelial cells might be important factors in determining the final site of firm adhesion and extravasation of neutrophils.
Ng-Sikorski
J
J
Department of Cell Biology, Linköping University, Sweden.
Lindén
L
L
Eierman
D
D
Franzen
L
L
Molony
L
L
Andersson
T
T
D000199:Actins / Q000378:metabolism*; D001665:Binding Sites; D018821:CD18 Antigens / Q000378:metabolism*; D002448:Cell Adhesion; D002465:Cell Movement; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005246:Feedback; D006801:Humans; D066298:In Vitro Techniques; D019041:L-Selectin / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism; D013433:Sulfoglycosphingolipids / Q000494:pharmacology
D000199:Actins; D018821:CD18 Antigens; D011108:Polymers; D013433:Sulfoglycosphingolipids; D019041:L-Selectin; D009240:N-Formylmethionine Leucyl-Phenylalanine