Complete downmodulation of P-selectin glycoprotein ligand in monocytes undergoing apoptosis.
OBJECTIVE
Apoptotic monocytes release membrane microparticles which may play a major role in thrombogenicity through a P-selectin glycoprotein ligand (PGSL-1)-mediated mechanism. We have studied systematically the regulation of PSGL-1 expression and function in apoptotic monocytic cells.


RESULTS
PSGL-1 expression (flow cytometry, immunofluorescence microscopy, immunoblot) was virtually abolished in apoptotic monocytes by proteolytic shedding. This was accompanied by a complete loss of PSGL-1-mediated platelet-leukocyte (flow cytometry) and leukocyte-endothelial cell (parallel plate flow chamber) interactions. Systematic screening of protease inhibitors combined with knock-out and siRNA experiments characterized the PSGL-1-cleaving enzyme as an N-ethylmaleimide-inhibitable metalloproteinase of the ADAM family.


CONCLUSIONS
Downmodulation of PGSL-1 in apoptotic monocytes may prevent ectopic cell clearance in the peripheral vasculature to reduce local inflammatory and proliferative responses. Depletion of PSGL-1 expression on apoptotic microparticles may also act as a molecular switch to modulate their thrombogenic activity.
Stampfuss
Jan-Julius
JJ
Institut für Pharmakologie, Universität Duisburg-Essen, Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany.
Censarek
Petra
P
Fischer
Jens W
JW
Kaber
Gernot
G
Rauch
Bernhard H
BH
Freidel
Kerstin
K
Fischer
Ute
U
Schulze-Osthoff
Klaus
K
Grosser
Tilo
T
Grandoch
Maria
M
Schrör
Karsten
K
Weber
Artur-Aron
AA
D051722:ADAM Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002448:Cell Adhesion; D015536:Down-Regulation; D042783:Endothelial Cells / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009000:Monocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D011480:Protease Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism*; D020298:U937 Cells
D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D011480:Protease Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051722:ADAM Proteins