G proteins and low-molecular-weight GTP-binding proteins in platelets

1991 ◽  
Vol 1 (2) ◽  
pp. 92-98 ◽  
Author(s):  
Lawrence F. Brass ◽  
David R. Manning
Keyword(s):  
Molecular Weight ◽  
G Proteins ◽  
Binding Proteins ◽  
Low Molecular Weight ◽  
Gtp Binding Proteins ◽  
Gtp Binding

The Role of GTP-Binding Proteins in Platelet Activation

1991 ◽  
Vol 66 (04) ◽  
pp. 393-399 ◽  
Author(s):  
David R Manning ◽  
Lawrence F Brass
Keyword(s):  
Molecular Weight ◽  
G Proteins ◽  
Platelet Activation ◽  
Cell Activation ◽  
Binding Proteins ◽  
Protein Transport ◽  
Low Molecular Weight ◽  
Gtp Binding Proteins ◽  
Gtp Binding

SummaryPlatelet activation begins with the binding of an agonist to the cell surface and culminates in the events of platelet aggregation, secretion and clot formation. Recent studies have identified two large families of GTP-binding proteins in platelets that are thought to participate in the events of platelet activation. The first of these are the G proteins, heterotrimeric proteins which are best known for their ability to mediate the interaction between agonist receptors and intracellular enzymes such as adenylyl cyclase, phospholipase C and phospholipase A2. To date, at least six G proteins have been identified in platelets: Gs, Gz, three variants of Gi and either Gq or G11 (or both). An additional, pertussis toxinresistant G protein, Gq, may also be present. The second group of GTP-binding proteins present in platelets is substantially smaller than the heterotrimeric G proteins, ranging in size from 21 to 28 kDa. At least 15 such low molecular weight GTP-binding proteins have been identified in platelets, many of which are homologous to the products of the ras proto-oncogenes. In cells other than platelets, low molecular weight GTP-binding proteins have been implicated in protein transport, cell activation events and malignant transformation. Their role in platelets is unknown.

Rap1b Association with the Platelet Cytoskeleton Occurs in the Absence of Glycoproteins IIb/IIIa

1998 ◽  
Vol 79 (04) ◽  
pp. 832-836 ◽  
Author(s):  
Thomas Fischer ◽  
Christina Duffy ◽  
Gilbert White
Keyword(s):  
Molecular Weight ◽  
Divalent Cation ◽  
Binding Proteins ◽  
Binding Protein ◽  
Platelet Membrane ◽  
Low Molecular Weight ◽  
Membrane Glycoproteins ◽  
Gtp Binding Protein ◽  
Gtp Binding Proteins ◽  
Gtp Binding

SummaryPlatelet membrane glycoproteins (GP) IIb/IIIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann’s thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and rap1b is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.

scholarly journals Inherited abnormalities in platelet organelles and platelet formation and associated altered expression of low molecular weight guanosine triphosphate-binding proteins in the mouse pigment mutant gunmetal

Blood ◽  
1993 ◽  
Vol 81 (10) ◽  
pp. 2626-2635 ◽  
Author(s):  
RT Swank ◽  
SY Jiang ◽  
M Reddington ◽  
J Conway ◽  
D Stephenson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Low Molecular Weight ◽  
Guanosine Triphosphate ◽  
Platelet Factor ◽  
Altered Expression ◽  
Gtp Binding Proteins ◽  
Dense Granules ◽  
Gtp Binding ◽  
Platelet Formation

Abstract Gunmetal (gm/gm) is a recessively inherited mouse pigment dilution mutant that has high mortality and poor reproductive rates. In these studies, several hematologic defects were found associated with the mutation, including prolonged bleeding times, together with thrombocytopenia and increased platelet size. A unique feature is the presence of simultaneous abnormalities in two platelet organelles, dense granules and alpha-granules. The dense granule component serotonin is present at about half the normal concentration, as are visible dense granules. Three alpha-granule components (fibrinogen, platelet factor 4, and von Willebrand factor) are also significantly reduced. Thus, in several respects the gunmetal mutant resembles the human gray platelet syndrome. A novel abnormality in expression of low molecular weight guanosine triphosphate (GTP)-binding proteins occurs in platelets of gunmetal. In Western blot assays, two additional GTP- binding proteins of 28.5 and 25 Kd were detected. The abnormal expression of GTP-binding proteins is, like the hematologic defects, genetically recessive and is tissue specific. Liver, kidney, brain, spleen, macrophages, and neutrophils have normal GTP-binding protein expression. The additional GTP-binding proteins are soluble. The data indicate that platelet formation and platelet organelle biogenesis are under common genetic control and that abnormal regulation of GTP- binding proteins may affect one or both processes.

Small GTPase-regulated phospholipase D in granulocytes

1996 ◽  
Vol 74 (4) ◽  
pp. 459-467 ◽  
Author(s):  
Martin G. Houle ◽  
Sylvain Bourgoin
Keyword(s):  
Molecular Weight ◽  
Protein Kinase ◽  
Phospholipase D ◽  
Tyrosine Kinases ◽  
Binding Proteins ◽  
Active Role ◽  
Small Gtpase ◽  
Low Molecular Weight ◽  
Gtp Binding Proteins ◽  
Gtp Binding

This review examines the functional role of phospholipase D in the neutrophil. Phospholipase D is emerging as an important component in the signal transduction pathways leading to granulocyte activation. Through the second messenger it produces, phosphatidic acid, phospholipase D plays an active role in the regulation of granulocyte NADPH oxidase activation and granular secretion. Many factors from both the cytosol and the membrane are necessary for maximal phospholipase D activation. This paper will focus on the regulation of phospholipase D by low molecular weight GTP-binding proteins, tyrosine kinases, and protein kinase C.Key words: phospholipase D, low molecular weight GTP-binding proteins, tyrosine kinases, protein kinase C, granulocytes.

scholarly journals Inherited abnormalities in platelet organelles and platelet formation and associated altered expression of low molecular weight guanosine triphosphate-binding proteins in the mouse pigment mutant gunmetal

Blood ◽  
1993 ◽  
Vol 81 (10) ◽  
pp. 2626-2635 ◽  
Author(s):  
RT Swank ◽  
SY Jiang ◽  
M Reddington ◽  
J Conway ◽  
D Stephenson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Low Molecular Weight ◽  
Guanosine Triphosphate ◽  
Platelet Factor ◽  
Altered Expression ◽  
Gtp Binding Proteins ◽  
Dense Granules ◽  
Gtp Binding ◽  
Platelet Formation

Gunmetal (gm/gm) is a recessively inherited mouse pigment dilution mutant that has high mortality and poor reproductive rates. In these studies, several hematologic defects were found associated with the mutation, including prolonged bleeding times, together with thrombocytopenia and increased platelet size. A unique feature is the presence of simultaneous abnormalities in two platelet organelles, dense granules and alpha-granules. The dense granule component serotonin is present at about half the normal concentration, as are visible dense granules. Three alpha-granule components (fibrinogen, platelet factor 4, and von Willebrand factor) are also significantly reduced. Thus, in several respects the gunmetal mutant resembles the human gray platelet syndrome. A novel abnormality in expression of low molecular weight guanosine triphosphate (GTP)-binding proteins occurs in platelets of gunmetal. In Western blot assays, two additional GTP- binding proteins of 28.5 and 25 Kd were detected. The abnormal expression of GTP-binding proteins is, like the hematologic defects, genetically recessive and is tissue specific. Liver, kidney, brain, spleen, macrophages, and neutrophils have normal GTP-binding protein expression. The additional GTP-binding proteins are soluble. The data indicate that platelet formation and platelet organelle biogenesis are under common genetic control and that abnormal regulation of GTP- binding proteins may affect one or both processes.

scholarly journals Low Molecular Weight GTP-binding Proteins in HL-60 Granulocytes

1995 ◽  
Vol 270 (7) ◽  
pp. 3172-3178 ◽  
Author(s):  
Sylvain Bourgoin ◽  
Danielle Harbour ◽  
Yvan Desmarais ◽  
Yoshimi Takai ◽  
André Beaulieu
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Low Molecular Weight ◽  
Gtp Binding Proteins ◽  
Gtp Binding
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