TY - JOUR
T1 - Early intraplatelet signaling enhances the release of human platelet PAR-1 and -4 amino-terminal peptides in response to thrombin
AU - Ofosu, Frederick A.
AU - Dewar, Lori
AU - Song, Yingqi
AU - Cedrone, Aisha C.
AU - Hortelano, Gonzalo
AU - Craven, Sharon J.
N1 - Copyright:
Copyright 2009 Elsevier B.V., All rights reserved.
PY - 2009/2/24
Y1 - 2009/2/24
N2 - Activation of washed human platelets initiated with α-thrombin, SFLLRN, or AYPGKF invariably results in the generation of PAR-1-(1-41) and PAR-4-(1-47). PAR-1-(1-41) and PAR-4-(1-47) are amino-terminal peptides generated when PAR-1 and -4 are cleaved in their first extracellular domains after R41 and R47, respectively, to expose the tethered ligand domains of PAR-1 and -4. Since soybean trypsin inhibitor decreases generation of PAR-1-(1-41) and PAR-4-(1-47) and other platelet aggregation-related responses to these three agonists, but does not inactivate α-thrombin, a platelet trypsinlike proteinase apparently activates PAR-1 and -4 to propagate PAR-dependent platelet responses. This study identified the signaling pathways implicated in the generation of the platelet proteinase that in turn produces PAR-1-(1-41) and PAR-4-(1-47), to thereby drive the subsequent PAR-dependent platelet aggregation-related responses to α-thrombin, SFLLRN, or AYPGKF. Only inhibitors of signaling enzymes that prevented ATP release (forskolin, PGE1, or BIMI-1) prevented or delayed the generation of PAR-1-(1-41) and PAR-4-(1-47) in response to all three agonists. SBTI prevented platelet aggregation initiated by α-thrombin, SFLLRN, or AYPGKF but did so less effectively when it was added 10 s after each agonist. Thus, the platelet-derived proteinase acts within 10 s of each agonist addition to generate PAR-1-(1-41) and PAR-4-(1-47). Furthermore, α-thrombin may not effectively catalyze PAR-1-(1-41) and PAR-4-(1-47) generation. We propose that unidentified ATP-dependent phosphorylation reactions catalyzed by PKC help to generate the platelet-derived proteinase that propagates human platelet PAR-1 and -4 activation by the three agonists.
AB - Activation of washed human platelets initiated with α-thrombin, SFLLRN, or AYPGKF invariably results in the generation of PAR-1-(1-41) and PAR-4-(1-47). PAR-1-(1-41) and PAR-4-(1-47) are amino-terminal peptides generated when PAR-1 and -4 are cleaved in their first extracellular domains after R41 and R47, respectively, to expose the tethered ligand domains of PAR-1 and -4. Since soybean trypsin inhibitor decreases generation of PAR-1-(1-41) and PAR-4-(1-47) and other platelet aggregation-related responses to these three agonists, but does not inactivate α-thrombin, a platelet trypsinlike proteinase apparently activates PAR-1 and -4 to propagate PAR-dependent platelet responses. This study identified the signaling pathways implicated in the generation of the platelet proteinase that in turn produces PAR-1-(1-41) and PAR-4-(1-47), to thereby drive the subsequent PAR-dependent platelet aggregation-related responses to α-thrombin, SFLLRN, or AYPGKF. Only inhibitors of signaling enzymes that prevented ATP release (forskolin, PGE1, or BIMI-1) prevented or delayed the generation of PAR-1-(1-41) and PAR-4-(1-47) in response to all three agonists. SBTI prevented platelet aggregation initiated by α-thrombin, SFLLRN, or AYPGKF but did so less effectively when it was added 10 s after each agonist. Thus, the platelet-derived proteinase acts within 10 s of each agonist addition to generate PAR-1-(1-41) and PAR-4-(1-47). Furthermore, α-thrombin may not effectively catalyze PAR-1-(1-41) and PAR-4-(1-47) generation. We propose that unidentified ATP-dependent phosphorylation reactions catalyzed by PKC help to generate the platelet-derived proteinase that propagates human platelet PAR-1 and -4 activation by the three agonists.
UR - http://www.scopus.com/inward/record.url?scp=61749084117&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=61749084117&partnerID=8YFLogxK
U2 - 10.1021/bi801399c
DO - 10.1021/bi801399c
M3 - Article
C2 - 19182900
AN - SCOPUS:61749084117
SN - 0006-2960
VL - 48
SP - 1562
EP - 1572
JO - Biochemistry
JF - Biochemistry
IS - 7
ER -