|
|
 Previous Article | Table of Contents | Next Article 
The platelet surface expression of glycoprotein V is regulated by two
independent mechanisms: proteolysis and a reversible cytoskeletal- mediated
redistribution to the surface-connected canalicular system
AD Michelson, SE Benoit, MI Furman, MR Barnard, P Nurden and AT Nurden
Department of Pediatrics, University of Massachusetts Medical School,
Worcester 01655, USA.
In this study, we show that the platelet surface expression of glycoprotein
(GP) V is regulated by two independent mechanisms. While confirming that
both thrombin and neutrophil elastase proteolyse GPV, we show that
neutrophil cathepsin G, thrombin receptor activating peptide (TRAP), and a
combination of ADP and epinephrine can each result in a decrease in the
platelet surface expression of GPV by a nonproteolytic mechanism: a
cytoskeletal-mediated redistribution of platelet surface GPV to the
surface-connected canalicular system (SCCS). Four independent lines of
evidence documented the nonproteolytic nature of this decrease in the
platelet surface expression of GPV. First, flow cytometric studies showed
that cathepsin G, TRAP, and ADP/epinephrine decreased the platelet surface
expression of GPV without changing the total platelet content of GPV.
Second, immunoelectron microscopy directly demonstrated translocation of
GPV from the platelet surface to the SCCS. Third, the cathepsin G-, TRAP-,
and ADP/epinephrine-induced decreases in platelet surface GPV were fully
reversible. Fourth, cytochalasin B, an inhibitor of actin polymerization,
completely inhibited the cathepsin G-, TRAP-, and ADP/epinephrine-induced
decreases in platelet surface GPV. The cytoskeletal-mediated redistribution
of GPV occurred in a whole blood milieu and at physiologic temperatures (37
degrees C) and extracellular calcium concentrations (2 mmol/L). This study
also defines the diverse effects on GPV, GPIb, and GPIX of multiple
important platelet agonists. Cathepsin G proteolysed platelet surface GPIb
alpha, but redistributed platelet surface GPIX and GPV to the SCCS.
Thrombin proteolysed platelet surface GPV, but redistributed platelet
surface GPIb and GPIX to the SCCS. Both TRAP and ADP/epinephrine
redistributed platelet surface GPIb, GPIX, and GPV to the SCCS. Elastase
proteolysed platelet surface GPIb alpha and GPV, but, unlike the other
agonists tested, neither proteolysed nor redistributed platelet surface
GPIX. The experiments with TRAP showed that activation of the
seven-transmembrane domain thrombin receptor can result in translocation of
GPIb, GPIX, and GPV to the SCCS independently of the GPIb-mediated pathway
of thrombin- induced platelet activation. This study also provides two
additional lines of support for the recent report that GPV is noncovalently
complexed with GPIb and GPIX in the platelet surface membrane. First,
although only the GPIb alpha subunit of this putative complex is known to
be directly linked to the platelet cytoskeleton via actin-binding protein,
cytochalasin B inhibited the ADP/epinephrine-, cathepsin G-, and
TRAP-induced decrease in platelet surface GPV. Second, triple labeling flow
cytometric experiments showed that, on each individual platelet, the
ADP/epinephrine-induced decrease and subsequent return of the platelet
surface expression of GPV occurred simultaneously with the decrease and
subsequent return of the platelet surface expression of GPIb. In summary,
the platelet surface expression of GPV is regulated by two independent
mechanisms: proteolysis and a reversible, cytoskeletal-mediated
redistribution to the SCCS.
Volume 87,
Issue 4,
pp. 1396-1408,
02/15/1996
Copyright © 1996 by The American Society of Hematology
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
N. Moran, P. A. Morateck, A. Deering, M. Ryan, R. R. Montgomery, D. J. Fitzgerald, and D. Kenny
Surface expression of glycoprotein Ibalpha is dependent on glycoprotein Ibbeta : evidence from a novel mutation causing Bernard-Soulier syndrome
Blood,
July 15, 2000;
96(2):
532 - 539.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. A. Lopez, R. K. Andrews, V. Afshar-Kharghan, and M. C. Berndt
Bernard-Soulier Syndrome
Blood,
June 15, 1998;
91(12):
4397 - 4418.
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. H. van Zanten, H. F.G. Heijnen, Y. Wu, K. M. Schut-Hese, P. J. Slootweg, P. G. de Groot, J. J. Sixma, and R. Nieuwland
A Fifty Percent Reduction of Platelet Surface Glycoprotein Ib Does Not Affect Platelet Adhesion Under Flow Conditions
Blood,
April 1, 1998;
91(7):
2353 - 2359.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
