Characteristics of endogenous γ-aminobutyric acid (GABA) in human platelets: Functional studies of a novel collagen glycoprotein VI inhibitor

Kuan Hung Lin, Wan-Jung Lu, Shwu Huey Wang, Tsorng Harn Fong, Duen Suey Chou, Chao Chien Chang, Nen Chung Chang, Yung Chen Chiang, Shih Yi Huang, Joen Rong Sheu

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12 Citations (Scopus)

Abstract

gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system, and it also appears in peripheral tissues. Platelets are anuclear blood cells that play a central role in hemostatic processes. Although platelets possess a GABA uptake system, the functional activity of GABA in platelets has remained unclear. We determined that GABA is abundantly distributed in the platelets at a concentration of approximately 1.03 ng/10 6 cells. GABA (0.5 μM) specifically inhibited collagen-induced platelet activation accompanied by [Ca2+]i mobilization, phospholipase Cγ2, protein kinase C, Akt phosphorylation, and hydroxyl radical formation. In addition, GABA interfered with fluorescein isothiocyanate-collagen binding to platelet membranes and produced a concentration-dependent shift in the collagen concentration-response curve and a Schild plot slope of -0.96±0.11, indicating competitive inhibition. Platelet activation induced by convulxin, a glycoprotein VI agonist, was inhibited by GABA, whereas activation induced by the integrin α2β1 agonist, aggretin, was not. Immunoprecipitation and surface plasmon resonance revealed that GABA binds directly to glycoprotein VI in human platelets with equilibrium dissociation (binding) constant (K D) of 41.4 nM. The closure time of whole blood and the occlusion time of platelet plug formation were significantly prolonged by GABA in vivo. In this study, GABA is a specific inhibitor of collagen glycoprotein VI and may be involved in an endogenous negative feedback mechanism for platelet activation. Thus, GABA may represent a potential target for the development of novel interventions for the treatment of cardiovascular diseases associated with platelet activation, such as stroke and myocardial infarction. Key messages: GABA is abundantly distributed in the platelets. GABA inhibited platelet activation stimulated by convulxin. GABA directly associated with glycoprotein VI in platelet membrane. GABA prolonged the closure time of whole blood and the occlusion time of platelet plug formation in vivo.

Original languageEnglish
Pages (from-to)603-614
Number of pages12
JournalJournal of Molecular Medicine
Volume92
Issue number6
DOIs
Publication statusPublished - 2014

Fingerprint

Aminobutyrates
gamma-Aminobutyric Acid
Glycoproteins
Collagen
Blood Platelets
Platelet Activation
Surface Plasmon Resonance
Phospholipases
Hemostatics

Keywords

  • Collagen
  • Convulxin
  • Glycoprotein VI antagonist
  • Platelet activation
  • γ-Aminobutyric acid

ASJC Scopus subject areas

  • Molecular Medicine
  • Drug Discovery
  • Genetics(clinical)
  • Medicine(all)

Cite this

@article{c5114d39d4a24606889deeb87de0824e,
title = "Characteristics of endogenous γ-aminobutyric acid (GABA) in human platelets: Functional studies of a novel collagen glycoprotein VI inhibitor",
abstract = "gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system, and it also appears in peripheral tissues. Platelets are anuclear blood cells that play a central role in hemostatic processes. Although platelets possess a GABA uptake system, the functional activity of GABA in platelets has remained unclear. We determined that GABA is abundantly distributed in the platelets at a concentration of approximately 1.03 ng/10 6 cells. GABA (0.5 μM) specifically inhibited collagen-induced platelet activation accompanied by [Ca2+]i mobilization, phospholipase Cγ2, protein kinase C, Akt phosphorylation, and hydroxyl radical formation. In addition, GABA interfered with fluorescein isothiocyanate-collagen binding to platelet membranes and produced a concentration-dependent shift in the collagen concentration-response curve and a Schild plot slope of -0.96±0.11, indicating competitive inhibition. Platelet activation induced by convulxin, a glycoprotein VI agonist, was inhibited by GABA, whereas activation induced by the integrin α2β1 agonist, aggretin, was not. Immunoprecipitation and surface plasmon resonance revealed that GABA binds directly to glycoprotein VI in human platelets with equilibrium dissociation (binding) constant (K D) of 41.4 nM. The closure time of whole blood and the occlusion time of platelet plug formation were significantly prolonged by GABA in vivo. In this study, GABA is a specific inhibitor of collagen glycoprotein VI and may be involved in an endogenous negative feedback mechanism for platelet activation. Thus, GABA may represent a potential target for the development of novel interventions for the treatment of cardiovascular diseases associated with platelet activation, such as stroke and myocardial infarction. Key messages: GABA is abundantly distributed in the platelets. GABA inhibited platelet activation stimulated by convulxin. GABA directly associated with glycoprotein VI in platelet membrane. GABA prolonged the closure time of whole blood and the occlusion time of platelet plug formation in vivo.",
keywords = "Collagen, Convulxin, Glycoprotein VI antagonist, Platelet activation, γ-Aminobutyric acid",
author = "Lin, {Kuan Hung} and Wan-Jung Lu and Wang, {Shwu Huey} and Fong, {Tsorng Harn} and Chou, {Duen Suey} and Chang, {Chao Chien} and Chang, {Nen Chung} and Chiang, {Yung Chen} and Huang, {Shih Yi} and Sheu, {Joen Rong}",
year = "2014",
doi = "10.1007/s00109-014-1140-7",
language = "English",
volume = "92",
pages = "603--614",
journal = "Journal of Molecular Medicine",
issn = "0946-2716",
publisher = "Springer Verlag",
number = "6",

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TY - JOUR

T1 - Characteristics of endogenous γ-aminobutyric acid (GABA) in human platelets

T2 - Functional studies of a novel collagen glycoprotein VI inhibitor

AU - Lin, Kuan Hung

AU - Lu, Wan-Jung

AU - Wang, Shwu Huey

AU - Fong, Tsorng Harn

AU - Chou, Duen Suey

AU - Chang, Chao Chien

AU - Chang, Nen Chung

AU - Chiang, Yung Chen

AU - Huang, Shih Yi

AU - Sheu, Joen Rong

PY - 2014

Y1 - 2014

N2 - gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system, and it also appears in peripheral tissues. Platelets are anuclear blood cells that play a central role in hemostatic processes. Although platelets possess a GABA uptake system, the functional activity of GABA in platelets has remained unclear. We determined that GABA is abundantly distributed in the platelets at a concentration of approximately 1.03 ng/10 6 cells. GABA (0.5 μM) specifically inhibited collagen-induced platelet activation accompanied by [Ca2+]i mobilization, phospholipase Cγ2, protein kinase C, Akt phosphorylation, and hydroxyl radical formation. In addition, GABA interfered with fluorescein isothiocyanate-collagen binding to platelet membranes and produced a concentration-dependent shift in the collagen concentration-response curve and a Schild plot slope of -0.96±0.11, indicating competitive inhibition. Platelet activation induced by convulxin, a glycoprotein VI agonist, was inhibited by GABA, whereas activation induced by the integrin α2β1 agonist, aggretin, was not. Immunoprecipitation and surface plasmon resonance revealed that GABA binds directly to glycoprotein VI in human platelets with equilibrium dissociation (binding) constant (K D) of 41.4 nM. The closure time of whole blood and the occlusion time of platelet plug formation were significantly prolonged by GABA in vivo. In this study, GABA is a specific inhibitor of collagen glycoprotein VI and may be involved in an endogenous negative feedback mechanism for platelet activation. Thus, GABA may represent a potential target for the development of novel interventions for the treatment of cardiovascular diseases associated with platelet activation, such as stroke and myocardial infarction. Key messages: GABA is abundantly distributed in the platelets. GABA inhibited platelet activation stimulated by convulxin. GABA directly associated with glycoprotein VI in platelet membrane. GABA prolonged the closure time of whole blood and the occlusion time of platelet plug formation in vivo.

AB - gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system, and it also appears in peripheral tissues. Platelets are anuclear blood cells that play a central role in hemostatic processes. Although platelets possess a GABA uptake system, the functional activity of GABA in platelets has remained unclear. We determined that GABA is abundantly distributed in the platelets at a concentration of approximately 1.03 ng/10 6 cells. GABA (0.5 μM) specifically inhibited collagen-induced platelet activation accompanied by [Ca2+]i mobilization, phospholipase Cγ2, protein kinase C, Akt phosphorylation, and hydroxyl radical formation. In addition, GABA interfered with fluorescein isothiocyanate-collagen binding to platelet membranes and produced a concentration-dependent shift in the collagen concentration-response curve and a Schild plot slope of -0.96±0.11, indicating competitive inhibition. Platelet activation induced by convulxin, a glycoprotein VI agonist, was inhibited by GABA, whereas activation induced by the integrin α2β1 agonist, aggretin, was not. Immunoprecipitation and surface plasmon resonance revealed that GABA binds directly to glycoprotein VI in human platelets with equilibrium dissociation (binding) constant (K D) of 41.4 nM. The closure time of whole blood and the occlusion time of platelet plug formation were significantly prolonged by GABA in vivo. In this study, GABA is a specific inhibitor of collagen glycoprotein VI and may be involved in an endogenous negative feedback mechanism for platelet activation. Thus, GABA may represent a potential target for the development of novel interventions for the treatment of cardiovascular diseases associated with platelet activation, such as stroke and myocardial infarction. Key messages: GABA is abundantly distributed in the platelets. GABA inhibited platelet activation stimulated by convulxin. GABA directly associated with glycoprotein VI in platelet membrane. GABA prolonged the closure time of whole blood and the occlusion time of platelet plug formation in vivo.

KW - Collagen

KW - Convulxin

KW - Glycoprotein VI antagonist

KW - Platelet activation

KW - γ-Aminobutyric acid

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