Table 2.

Summary of 81 proteins from the thrombin-activated platelet releasate identified using MudPIT

Name
Accession no.
Known platelet protein
Known to be released/exocytosed
Function
mRNA rank in platelets
PROTEINS IN THE PLATELET RELEASATE KNOWN TO BE RELEASED FROM PLATELETS      
    Thrombospondin 1   TSP1_HUMAN   Yes   From platelet α-granules   On secretion, can bind αIIbβ3, αvβ3, and GPIV. Can potentiate aggregation by complexing with fibrinogen and becoming incorporated into fibrin clots.   213  
    Fibrinogen α chain   FIBA_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   632  
    Fibrinogen γ chain   FIBG_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   —  
    Platelet basic protein   SZ07_HUMAN   Yes   From platelet α-granules   Proteolytic cleavage yields the chemokines β-thromboglobulin and neutophil-activating peptide (NAP) 2.   23  
    PF4   PLF4_HUMAN   Yes   From platelet α-granules   Platelet-specific chemokine with neutrophil-activating properties.   8  
    Serum albumin   ALBU_HUMAN   Yes   From platelet α-granules   Major plasma protein secreted from the liver into the blood. Endocytosed into platelets from plasma.   —  
    Endothelial cell multimerin   ECM_HUMAN   Yes   From platelet α-granules   Carrier protein for platelet factor V/Vα.   —  
    SPARC (osteonectin)   SPRC_MOUSE   Yes   From platelet α-granules   On secretion, forms a specific complex with thrombospondin.   14  
    α-actinin I   AAC1_HUMAN   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   171  
    α1-antitrypsin   A1AT_HUMAN   Yes   From platelet α-granules   Acute phase protein, similar to complement, inhibits proteinases.   —  
    Fibrinogen β chain   FIBB_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   —  
    Factor V   FA5_HUMAN   Yes   From platelet α-granules   Cofactor that participates with factor Xa to activate prothrombin to thrombin.   —  
    Secretory granule proteoglycan core protein   PGSG_HUMAN   Yes   From platelet α-granules   Function unknown. Associates and coreleased with inflammatory mediators such as PF4.   343  
    Thymosin β-4   TYB4_MOUSE   Yes   From platelets α-granules   G actin—binding protein. Functions as an antimicrobial peptide when secreted.   5  
    Fructose biphosphate aldolase   ALFA_MOUSE   Yes   From platelets and exosomes from dendritic cells   Glycolytic enzymes that convert fructose 1,6-bis phosphate to glyceraldehydes-3-phosphate and dihydroxy acetone phosphate.   79  
    Clusterin   CLUS_HUMAN   Yes   From platelet α-granules   Not clear. Possibly platelet-derived apolipoprotein J participates in short-term wound repair and chronic pathogenic processes at vascular interface.   1  
    Coagulation factor XIIIA chain   F13A_HUMAN   Yes   From platelet α-granules   Coagulation protein involved in the formation of the fibrin clots.   19  
    Metalloproteinase inhibitor 1   TIM1_HUMAN   Yes   From platelet α-granules   Interacts with metalloproteinases and inactivates them. Stimulates growth and differentiation of erythroid progenitors, dependent on disulfide bonds.   112  
    Platelet glycoprotein V   GPV_HUMAN   Yes   Cleaved from platelet surface   Part of the GPIb-IX-V complex on the platelet surface. Cleaved by the protease thrombin during thrombin-induced platelet activation.   —  
    von Willebrand factor   VWF_HUMAN   Yes   From platelet α-granules   Binds GPIb-IX-V.   2465  
    Amyloid β-A4 protein (protease nexin II   A4_HUMAN   Yes   From platelet α-granules   Exhibits potent protease inhibitor and growth factor activity. May play a role in coagulation by inhibiting factors XIa and IXa.   379  
    Latent transforming growth factor β (TGF-β)-binding protein isoform 1S   LTBS_HUMAN   Yes   From platelet α-granules   Subunit of the TGF-β1 complex secreted from platelets.   —  
    α-Actinin 2   AAC2_MOUSE   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   —  
    Latent TGF-β—binding protein 1L   O88349   Yes   From platelet α-granules   Subunit of the TGF-β1 complex secreted from platelets.   617  
    Proactivator polypeptide   SAP_HUMAN   Yes   From lysosomes   Activator proteins for sphingolipid hydrolases (saposins) that stimulate the hydrolysis of sphingolipids by lysosomal enzymes.   147  
    Platelet glycoprotein 1b α chain   GPBA_HUMAN   Yes   Cleaved from platelet surface (glycocalicin)   Surface membrane protein of platelets that participates in formation of platelet plug by binding A1 domain of von Willebrand factor.   26  
    Vitamin K—dependent protein S   PRTS_HUMAN   Yes   From platelet α-granules   Cofactor to protein C in the degradation of coagulation factors Va and VIIIA.   1810  
    PF4 variant   PF4V_HUMAN   Yes   From platelet α-granules   Platelet-specific chemokines with neutrophil-activating properties.   346  
    α2-macroglobulin   A2MG_HUMAN   Yes   From platelet α-granules   Acute phase protein, similar to compliment, inhibits proteinases.   *  
    α-actinin 4   AAC4_HUMAN   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   467  
SECRETORY PROTEINS IN THE PLATELET RELEASATE NOT PREVIOUSLY IDENTIFIED IN PLATELETS      
    Vitamin D—binding protein   VTDB-HUMAN   No   From liver to plasma   Carries vitamin D sterols. Prevents actin polymerization. Has Tlymphocyte surface association.   —  
    β2-microglobulin   B2MG_HUMAN   No   Exosomes from dendritic cells, B cells, enterocytes, tumor cells, and T cells   Is the β chain of the major histocompatibility complex (MHC) class I molecule.   3  
    Hemoglobin α chain   HBA_HUMAN   No   Exosomes from dendritic cells and phagosomes in macrophages   Oxygen transport. Potentiates platelet aggregation through thromboxane receptor.   21  
    Plasminogen   PLMN_HUMAN   Yes   From kidney into plasma   Dissolves fibrin in blood clots, proteolytic factor in tissue remodeling, tumor invasion, and inflammation.   —  
    Serotransferrin   TRFE_HUMAN   Yes   From liver into plasma   Precursor to macromolecular activators of phagocytosis (MAPP), which enhance leukocyte phagocytosis via the FcγRII receptor.   —  
    Pyruvate kinase, M2 isozyme   KPY2_MOUSE   Yes   B-cell exosomes   Involved in final stage of glycolysis. Presented as an autoantigen by dendritic cells.   61  
    Actin, aortic smooth muscle   ACTA_HUMAN   Yes   Exosomes from B cells, dendritic cells, enterocytes, and mastocytes   Major cytoskeletal protein.   —  
    Actin   ACTB_HUMAN   Yes   Exosomes from B cells, dendritic cells, enterocytes, and mastocytes   Major cytoskeletal protein. External function unknown.   11  
    14-3-3 protein ζ/δ   143Z_MOUSE   Yes   Exosomes from dendritic cells and phagosomes in macrophages   External function unknown. Involved intracellularly in signal transduction, however, may have a role in regulating exocytosis.   63  
    Hemopexin   HEMO_HUMAN   No   From liver to plasma   Haem-binding protein with metalloproteinase domains.   —  
    Hemoglobin β chain   HBB_HUMAN   No   From liver to plasma and phagosomes from macrophages   Oxygen transport.   9  
    Peptidyl-prolyl-cis isomerase A (cyclophilin A)   CYPH_MOUSE   No   From smooth muscle cells   Cellular protein with isomerase activity. Secreted vascular smooth muscle cell growth factor.   116  
    Calumenin   CALU_MOUSE   No   From many cells, including fibroblast and COS cells   An inhibitor of the vitamin K epoxide reductase-warfarin interaction.   1816  
    Adenylyl cyclase—associated protein 1 (CAP 1)   CAP1_MOUSE   No   Phagosomes from macrophages   Contains a WH2 actin-binding domain (as β-thymosin 4). Known to regulate actin dynamics. May mediate endocytosis.   174  
    Tubulin   TBA1_HUMAN   Yes   Exosomes from dendritic cells and phagosomes from macrophages   Cytoskeletal protein involved in microtubule formation.   33  
    Apolipoprotein A-1   APA1_HUMAN   Yes   From liver to plasma, from monocytes and exosomes of dendritic cells   Role in high-density lipoprotein binding to platelets.   —  
    Compliment C3   CO3_HUMAN   No   From liver cells and monocytes   Activator of the compliment system. Cleaved to α, β, and γ chains normally prior to secretion and is a mediator of the local inflammatory response.   *  
    Transthyretin   TTHY_HUMAN   No   From choroid plexus into cerebrospinal fluid (CSF)   Thyroid hormone—binding protein secreted from the choroid plexus and the liver into CSF and plasma, respectively.   —  
    Cofilin   COF1_MOUSE   Yes   Exosome from dendritic cells   Actin demolymerization/regulation in cytoplasm.   31  
    Profilin   PRO1_MOUSE   Yes   Exosome from dendritic cells   Actin demolymerization/regulation in cytoplasm.   70  
    Secretogranin III   SG3_MOUSE   No   From neuronal cells   Unclear; possibly involved in secretory granule biogenesis. May be cleaved into active inflammatory peptide like secretogranin II.   *  
    Phosphoglycerate kinase   PGK1_MOUSE   Yes   From tumor cells   Glycotic enzyme. Secreted from tumor cells and involved in angiogenesis.   378  
    α-IB glycoprotein   AIBG_HUMAN   No   From many cell including white blood cells   Found in plasma, not clear, possibly involved in cell recognition as a new member of the immunoglobulin family.   *  
    Compliment C4 precursor   CO4_HUMAN   No   From many cells including white blood cells   Activator of the compliment system. Cleaved normally prior to secretion, its products mediate the local inflammatory response.   —  
    Prothrombin   THRB_HUMAN   No   From liver to plasma   Converts fibrinogen to fibrin and activates coagulation factors including factor V.   2143  
    Glyceraldehyde 3-phosphate dehydrogenase   G3P2_HUMAN   Yes   From B-cell exosomes and phagosomes from macrophages   Mitochondrial enzyme involved in glycolysis. May catalyze membrane fusion.   60  
    α1-acid glycoprotein   A1AH_HUMAN   No   From liver to plasma   Modulates activity of the immune system during the acute phase reaction. Binds platelet surface.   —  
    Gelsolin   GELS_HUMAN   Yes   Secreted isoform released from liver and adipocytes   Two isoforms, a cytoplasmic actin modulating protein and a secreted isoform involved in the inflammatory response.   438  
PROTEINS IN THE PLATELET RELEASATE NOT PREVIOUSLY REPORTED TO BE RELEASED FROM ANY CELL      
    Calmodulin   CALM_HUMAN   Yes   No evidence   Known to regulate calcium-dependent acrosomal exocytosis in neuroendocrine cells.   55  
    Pleckstrin   PLEK_HUMAN   Yes   No evidence   A substrate for protein kinase C, its phosphorylation is important for platelet secretion.   532  
    Nidogen   NIDO_HUMAN   Yes   No evidence   Glycoprotein found in basement membranes, interacts with laminin, collagon, and integrin on neutrophils.   —  
    Fibrinogen-type protein   Q8VCM7   No   No evidence   Similar to fibrinogen.   —  
    Rho GDP-dissociation inhibitor 2   GDIS_MOUSE   Yes   No evidence   Regulates the GDP/GTP exchange reaction of Rho proteins. Regulates platelet aggregation. Involved in exocytosis in mast cells.   97  
    Rho GTPase activating protein   Q92512   Yes   No evidence   Promotes the intrinsic GTP hydrolysis activity of Rho family proteins. Involved in regulating myosin phosphorylation in platelets.   *  
    Transgelin   TAG2_HUMAN   No   No evidence   Actin-binding protein. Loss of transgelin expression important in early tumor progression. May serve as a diagnostic marker for breast and colon cancer.   7  
    Vinculin   VINC_HUMAN   Yes   No evidence   Actin-binding protein.   44  
    WD-repeat protein   WDR1_HUMAN   No   No evidence   Actin-binding protein.   127  
    Superoxide dismutase (SOD)   SODC_HUMAN   Yes   No evidence   Important enzyme in cellular oxygen metabolism, role for SOD-1 in inflammation.   1730  
    78-kDa glucose-related protein   GR78_MOUSE   No   No evidence   Chaperone in the endoplasmic reticulum (ER) involved in inhibition of secreted coagulation factors thus reducing prothrombotic potential of cell.   —  
    Bromodomain and PHD finger-containing protein 3 (fragment)   BRF3_HUMAN   No   No evidence   Unknown.   *  
    Titin   Q8WZ42   Yes   No evidence   Anchoring protein of actinomyosin filaments. Role in secretion of myostatin.   —  
    Similar to hepatocellular carcinoma-associated antigen 59   Q99JW3   No   No evidence   Tumor marker.   —  
    FKSG30   Q9BYX7   No   No evidence   Actin-binding protein.   *  
    RNA-binding protein   Q9UQ35   No   No evidence   RNA-binding protein.   —  
    Hypothetical protein   Q9BTV9   No   No evidence   Unknown.   1744  
    Intracellular hyaluronan-binding protein p57   Q9JKS5   No   No evidence   Unknown.   —  
    Hypothetical protein   Y586_HUMAN   No   No evidence   Unknown.   *  
    Filamin fragment (hypothetical 54-kDa protein)   Q99KQ2   Yes   No evidence   Unknown.   —  
    Filamin   FLNA_HUMAN   Yes   No evidence   Actin-binding protein. Essential for GP 1b-α anchorage at high shear. Substrate for caspase-3.   43  
    Talin   TALI_HUMAN   Yes   No evidence   Actin-binding protein that binds to integrin-β3 domain.   17  
    Zyxin
 		 ZYX_HUMAN
 		 Yes
 		 No evidence
 		 Associates with the actin cytoskeleton near adhesion plaques. Binds α actinin and VASP.
 		 145
 
Name
Accession no.
Known platelet protein
Known to be released/exocytosed
Function
mRNA rank in platelets
PROTEINS IN THE PLATELET RELEASATE KNOWN TO BE RELEASED FROM PLATELETS      
    Thrombospondin 1   TSP1_HUMAN   Yes   From platelet α-granules   On secretion, can bind αIIbβ3, αvβ3, and GPIV. Can potentiate aggregation by complexing with fibrinogen and becoming incorporated into fibrin clots.   213  
    Fibrinogen α chain   FIBA_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   632  
    Fibrinogen γ chain   FIBG_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   —  
    Platelet basic protein   SZ07_HUMAN   Yes   From platelet α-granules   Proteolytic cleavage yields the chemokines β-thromboglobulin and neutophil-activating peptide (NAP) 2.   23  
    PF4   PLF4_HUMAN   Yes   From platelet α-granules   Platelet-specific chemokine with neutrophil-activating properties.   8  
    Serum albumin   ALBU_HUMAN   Yes   From platelet α-granules   Major plasma protein secreted from the liver into the blood. Endocytosed into platelets from plasma.   —  
    Endothelial cell multimerin   ECM_HUMAN   Yes   From platelet α-granules   Carrier protein for platelet factor V/Vα.   —  
    SPARC (osteonectin)   SPRC_MOUSE   Yes   From platelet α-granules   On secretion, forms a specific complex with thrombospondin.   14  
    α-actinin I   AAC1_HUMAN   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   171  
    α1-antitrypsin   A1AT_HUMAN   Yes   From platelet α-granules   Acute phase protein, similar to complement, inhibits proteinases.   —  
    Fibrinogen β chain   FIBB_HUMAN   Yes   From platelet α-granules   Cofactor in platelet aggregation. Endocytosed into platelets from plasma.   —  
    Factor V   FA5_HUMAN   Yes   From platelet α-granules   Cofactor that participates with factor Xa to activate prothrombin to thrombin.   —  
    Secretory granule proteoglycan core protein   PGSG_HUMAN   Yes   From platelet α-granules   Function unknown. Associates and coreleased with inflammatory mediators such as PF4.   343  
    Thymosin β-4   TYB4_MOUSE   Yes   From platelets α-granules   G actin—binding protein. Functions as an antimicrobial peptide when secreted.   5  
    Fructose biphosphate aldolase   ALFA_MOUSE   Yes   From platelets and exosomes from dendritic cells   Glycolytic enzymes that convert fructose 1,6-bis phosphate to glyceraldehydes-3-phosphate and dihydroxy acetone phosphate.   79  
    Clusterin   CLUS_HUMAN   Yes   From platelet α-granules   Not clear. Possibly platelet-derived apolipoprotein J participates in short-term wound repair and chronic pathogenic processes at vascular interface.   1  
    Coagulation factor XIIIA chain   F13A_HUMAN   Yes   From platelet α-granules   Coagulation protein involved in the formation of the fibrin clots.   19  
    Metalloproteinase inhibitor 1   TIM1_HUMAN   Yes   From platelet α-granules   Interacts with metalloproteinases and inactivates them. Stimulates growth and differentiation of erythroid progenitors, dependent on disulfide bonds.   112  
    Platelet glycoprotein V   GPV_HUMAN   Yes   Cleaved from platelet surface   Part of the GPIb-IX-V complex on the platelet surface. Cleaved by the protease thrombin during thrombin-induced platelet activation.   —  
    von Willebrand factor   VWF_HUMAN   Yes   From platelet α-granules   Binds GPIb-IX-V.   2465  
    Amyloid β-A4 protein (protease nexin II   A4_HUMAN   Yes   From platelet α-granules   Exhibits potent protease inhibitor and growth factor activity. May play a role in coagulation by inhibiting factors XIa and IXa.   379  
    Latent transforming growth factor β (TGF-β)-binding protein isoform 1S   LTBS_HUMAN   Yes   From platelet α-granules   Subunit of the TGF-β1 complex secreted from platelets.   —  
    α-Actinin 2   AAC2_MOUSE   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   —  
    Latent TGF-β—binding protein 1L   O88349   Yes   From platelet α-granules   Subunit of the TGF-β1 complex secreted from platelets.   617  
    Proactivator polypeptide   SAP_HUMAN   Yes   From lysosomes   Activator proteins for sphingolipid hydrolases (saposins) that stimulate the hydrolysis of sphingolipids by lysosomal enzymes.   147  
    Platelet glycoprotein 1b α chain   GPBA_HUMAN   Yes   Cleaved from platelet surface (glycocalicin)   Surface membrane protein of platelets that participates in formation of platelet plug by binding A1 domain of von Willebrand factor.   26  
    Vitamin K—dependent protein S   PRTS_HUMAN   Yes   From platelet α-granules   Cofactor to protein C in the degradation of coagulation factors Va and VIIIA.   1810  
    PF4 variant   PF4V_HUMAN   Yes   From platelet α-granules   Platelet-specific chemokines with neutrophil-activating properties.   346  
    α2-macroglobulin   A2MG_HUMAN   Yes   From platelet α-granules   Acute phase protein, similar to compliment, inhibits proteinases.   *  
    α-actinin 4   AAC4_HUMAN   Yes   From platelet α-granules   Actin-binding and actinin cross-linking protein found in platelet α-granules. Interacts with thrombospondin on the platelet surface.   467  
SECRETORY PROTEINS IN THE PLATELET RELEASATE NOT PREVIOUSLY IDENTIFIED IN PLATELETS      
    Vitamin D—binding protein   VTDB-HUMAN   No   From liver to plasma   Carries vitamin D sterols. Prevents actin polymerization. Has Tlymphocyte surface association.   —  
    β2-microglobulin   B2MG_HUMAN   No   Exosomes from dendritic cells, B cells, enterocytes, tumor cells, and T cells   Is the β chain of the major histocompatibility complex (MHC) class I molecule.   3  
    Hemoglobin α chain   HBA_HUMAN   No   Exosomes from dendritic cells and phagosomes in macrophages   Oxygen transport. Potentiates platelet aggregation through thromboxane receptor.   21  
    Plasminogen   PLMN_HUMAN   Yes   From kidney into plasma   Dissolves fibrin in blood clots, proteolytic factor in tissue remodeling, tumor invasion, and inflammation.   —  
    Serotransferrin   TRFE_HUMAN   Yes   From liver into plasma   Precursor to macromolecular activators of phagocytosis (MAPP), which enhance leukocyte phagocytosis via the FcγRII receptor.   —  
    Pyruvate kinase, M2 isozyme   KPY2_MOUSE   Yes   B-cell exosomes   Involved in final stage of glycolysis. Presented as an autoantigen by dendritic cells.   61  
    Actin, aortic smooth muscle   ACTA_HUMAN   Yes   Exosomes from B cells, dendritic cells, enterocytes, and mastocytes   Major cytoskeletal protein.   —  
    Actin   ACTB_HUMAN   Yes   Exosomes from B cells, dendritic cells, enterocytes, and mastocytes   Major cytoskeletal protein. External function unknown.   11  
    14-3-3 protein ζ/δ   143Z_MOUSE   Yes   Exosomes from dendritic cells and phagosomes in macrophages   External function unknown. Involved intracellularly in signal transduction, however, may have a role in regulating exocytosis.   63  
    Hemopexin   HEMO_HUMAN   No   From liver to plasma   Haem-binding protein with metalloproteinase domains.   —  
    Hemoglobin β chain   HBB_HUMAN   No   From liver to plasma and phagosomes from macrophages   Oxygen transport.   9  
    Peptidyl-prolyl-cis isomerase A (cyclophilin A)   CYPH_MOUSE   No   From smooth muscle cells   Cellular protein with isomerase activity. Secreted vascular smooth muscle cell growth factor.   116  
    Calumenin   CALU_MOUSE   No   From many cells, including fibroblast and COS cells   An inhibitor of the vitamin K epoxide reductase-warfarin interaction.   1816  
    Adenylyl cyclase—associated protein 1 (CAP 1)   CAP1_MOUSE   No   Phagosomes from macrophages   Contains a WH2 actin-binding domain (as β-thymosin 4). Known to regulate actin dynamics. May mediate endocytosis.   174  
    Tubulin   TBA1_HUMAN   Yes   Exosomes from dendritic cells and phagosomes from macrophages   Cytoskeletal protein involved in microtubule formation.   33  
    Apolipoprotein A-1   APA1_HUMAN   Yes   From liver to plasma, from monocytes and exosomes of dendritic cells   Role in high-density lipoprotein binding to platelets.   —  
    Compliment C3   CO3_HUMAN   No   From liver cells and monocytes   Activator of the compliment system. Cleaved to α, β, and γ chains normally prior to secretion and is a mediator of the local inflammatory response.   *  
    Transthyretin   TTHY_HUMAN   No   From choroid plexus into cerebrospinal fluid (CSF)   Thyroid hormone—binding protein secreted from the choroid plexus and the liver into CSF and plasma, respectively.   —  
    Cofilin   COF1_MOUSE   Yes   Exosome from dendritic cells   Actin demolymerization/regulation in cytoplasm.   31  
    Profilin   PRO1_MOUSE   Yes   Exosome from dendritic cells   Actin demolymerization/regulation in cytoplasm.   70  
    Secretogranin III   SG3_MOUSE   No   From neuronal cells   Unclear; possibly involved in secretory granule biogenesis. May be cleaved into active inflammatory peptide like secretogranin II.   *  
    Phosphoglycerate kinase   PGK1_MOUSE   Yes   From tumor cells   Glycotic enzyme. Secreted from tumor cells and involved in angiogenesis.   378  
    α-IB glycoprotein   AIBG_HUMAN   No   From many cell including white blood cells   Found in plasma, not clear, possibly involved in cell recognition as a new member of the immunoglobulin family.   *  
    Compliment C4 precursor   CO4_HUMAN   No   From many cells including white blood cells   Activator of the compliment system. Cleaved normally prior to secretion, its products mediate the local inflammatory response.   —  
    Prothrombin   THRB_HUMAN   No   From liver to plasma   Converts fibrinogen to fibrin and activates coagulation factors including factor V.   2143  
    Glyceraldehyde 3-phosphate dehydrogenase   G3P2_HUMAN   Yes   From B-cell exosomes and phagosomes from macrophages   Mitochondrial enzyme involved in glycolysis. May catalyze membrane fusion.   60  
    α1-acid glycoprotein   A1AH_HUMAN   No   From liver to plasma   Modulates activity of the immune system during the acute phase reaction. Binds platelet surface.   —  
    Gelsolin   GELS_HUMAN   Yes   Secreted isoform released from liver and adipocytes   Two isoforms, a cytoplasmic actin modulating protein and a secreted isoform involved in the inflammatory response.   438  
PROTEINS IN THE PLATELET RELEASATE NOT PREVIOUSLY REPORTED TO BE RELEASED FROM ANY CELL      
    Calmodulin   CALM_HUMAN   Yes   No evidence   Known to regulate calcium-dependent acrosomal exocytosis in neuroendocrine cells.   55  
    Pleckstrin   PLEK_HUMAN   Yes   No evidence   A substrate for protein kinase C, its phosphorylation is important for platelet secretion.   532  
    Nidogen   NIDO_HUMAN   Yes   No evidence   Glycoprotein found in basement membranes, interacts with laminin, collagon, and integrin on neutrophils.   —  
    Fibrinogen-type protein   Q8VCM7   No   No evidence   Similar to fibrinogen.   —  
    Rho GDP-dissociation inhibitor 2   GDIS_MOUSE   Yes   No evidence   Regulates the GDP/GTP exchange reaction of Rho proteins. Regulates platelet aggregation. Involved in exocytosis in mast cells.   97  
    Rho GTPase activating protein   Q92512   Yes   No evidence   Promotes the intrinsic GTP hydrolysis activity of Rho family proteins. Involved in regulating myosin phosphorylation in platelets.   *  
    Transgelin   TAG2_HUMAN   No   No evidence   Actin-binding protein. Loss of transgelin expression important in early tumor progression. May serve as a diagnostic marker for breast and colon cancer.   7  
    Vinculin   VINC_HUMAN   Yes   No evidence   Actin-binding protein.   44  
    WD-repeat protein   WDR1_HUMAN   No   No evidence   Actin-binding protein.   127  
    Superoxide dismutase (SOD)   SODC_HUMAN   Yes   No evidence   Important enzyme in cellular oxygen metabolism, role for SOD-1 in inflammation.   1730  
    78-kDa glucose-related protein   GR78_MOUSE   No   No evidence   Chaperone in the endoplasmic reticulum (ER) involved in inhibition of secreted coagulation factors thus reducing prothrombotic potential of cell.   —  
    Bromodomain and PHD finger-containing protein 3 (fragment)   BRF3_HUMAN   No   No evidence   Unknown.   *  
    Titin   Q8WZ42   Yes   No evidence   Anchoring protein of actinomyosin filaments. Role in secretion of myostatin.   —  
    Similar to hepatocellular carcinoma-associated antigen 59   Q99JW3   No   No evidence   Tumor marker.   —  
    FKSG30   Q9BYX7   No   No evidence   Actin-binding protein.   *  
    RNA-binding protein   Q9UQ35   No   No evidence   RNA-binding protein.   —  
    Hypothetical protein   Q9BTV9   No   No evidence   Unknown.   1744  
    Intracellular hyaluronan-binding protein p57   Q9JKS5   No   No evidence   Unknown.   —  
    Hypothetical protein   Y586_HUMAN   No   No evidence   Unknown.   *  
    Filamin fragment (hypothetical 54-kDa protein)   Q99KQ2   Yes   No evidence   Unknown.   —  
    Filamin   FLNA_HUMAN   Yes   No evidence   Actin-binding protein. Essential for GP 1b-α anchorage at high shear. Substrate for caspase-3.   43  
    Talin   TALI_HUMAN   Yes   No evidence   Actin-binding protein that binds to integrin-β3 domain.   17  
    Zyxin
 		 ZYX_HUMAN
 		 Yes
 		 No evidence
 		 Associates with the actin cytoskeleton near adhesion plaques. Binds α actinin and VASP.
 		 145
 

Eighty-one proteins were identified using MudPIT from the thrombin-stimulated platelet supernatant fraction. Spectra were identified using the SEQUEST program and a composite mouse and human database (NCBI July 2002 release) in 3 replicate experiments. Information on their functions and whether they are secretory proteins are provided. Also indicated is whether these proteins have a corresponding platelet mRNA. The rank of abundance of the message is denoted numerically in the last column.

— indicates levels below the threshold for detection on the Affymetrix microarray; *, not present on Affymetrix microarray.

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