OBJECTIVE: To explore the effects of Ena/VASP gene family on the expression of glycoprotein (GP) Ib-IX complex in human megakaryoblastic leukemia Dami cells. METHODS: SiRNAs targeting Ena/VASP gene family were designed and synthesized to interfere Enah, EVL and VASP gene expression. When the siRNAs were transfected into Dami cells by using Lipofectamine^TM 2000 for 48 h, the expression of GPIb-IX complex was detected by quantitative real-time PCR, Western blot and flow cytometry. RESULTS: We successfully established siVASP , siEVL and si Enah Dami cell lines. And it was found that the expression of GPIb-IX complex had no evident reduction in siEVL or siVASP Dami cells at both mRNA and protein level, while the total protein and membrane protein of GPIb-IX complex were obviously reduced when Enah was knocked down. CONCLUSION Enah could affect the expression of GPIb-IX complex in human megakaryoblastic leukemia Dami cells, but the underlying mechanism still needs to be further explored.
Humans ; Cell Line ; Platelet Glycoprotein GPIb-IX Complex/metabolism* ; Leukemia/metabolism* ; Blood Platelets/metabolism*

The structure and function of the glycoprotein (GP) Ib-IX-V complex has been extensively investigated over the decades due to its vital role in platelet activation. For the lack of nucleus in platelets, researchers usually need to study the GPIb-IX-V complex by transfecting wild type or mutant GPIb-IX-V plasmids into other mammalian cell lines, such as CHO or HEK 293T. Therefore, whether the characteristics of the GPIb-IX-V complex in these cell lines can truly represent that in platelets is pivotal to determine whether these cell lines are appropriate for GPIb-IX-V complex studies. In order to determine the most appropriate cell line to study the GPIb-IX-V complex, the surface expression level of the complex in different cell lines was detected and whether difference among cell lines will affect expression of the complex was explored in the present study. The different combinations of the GPIb-IX-V subunits were transfected into cell lines from different species or different tissues, such as CHO, HEK293T and HeLa, and the surface expression levels of the complex were detected by flow cytometry. The results indicated that in both transiently and stably transfected CHO cells, surface expression of GPV depended on the presence of the GPIb-IX complex, which is consistent with that in human platelets. In contrast, GPV could be efficiently expressed on surface in HEK 293T cells even in the absence of GPIb-IX, although the inter-subunit dependence within the GPIb-IX complex is still similar to that in CHO cells or human platelets. Further studies in HeLa, MES13 and HUVEC cell lines revealed that GPV could be efficiently expressed on the surface by itself in HeLa and MES13 cells, but not in HUVEC, suggesting different behaviors of the GPIb-IX-V complex in difference cell lines. It is concluded that this study provides some guidance and advice to future GPIb-IX-V complex studies, especially to the choice of suitable cell line. HEK 293T cell line, for example, is likely to provide misleading results since it could not represent the fact in human platelets, thus is not the optimal choice for the GPIb-IX-V complex, particularly the GPV subunit.
Animals ; CHO Cells ; Cricetinae ; Cricetulus ; HEK293 Cells ; metabolism ; Humans ; Platelet Glycoprotein GPIb-IX Complex ; genetics ; metabolism ; Transfection

OBJECTIVETo study the platelet morphology and function of an inherited macrothrombocytopenia disorder with abnormal large granules.

METHODSPlatelet size and structure were investigated by both light microscopy and electron microscopy. The platelet membrane expression of GP I b, GP II b, GPIII a, P-selectin and CD63 were analyzed by using respective monoclonal antibodies. Platelet 5-hydroxy-tryptamine was measured with spectrophotofluorometer.

RESULTSBoth the patient and her father had large granules in their platelets, with exocytosis being easily observed. The expressions of GP I b, GP II b and GP II a on the platelets were in normal range, while P-selectin and CD63 were somewhat increased. The abnormal large granules were not the alpha granules, lysosomes or dense bodies.

CONCLUSIONBoth morphological and functional abnormalities of the platelets from the patient are clearly distinguishable from other hereditary giant platelet disorders. It would probably represent a novel platelet disorder.

Adult ; Blood Platelets ; metabolism ; ultrastructure ; Female ; Humans ; Integrin beta3 ; biosynthesis ; Microscopy, Immunoelectron ; Platelet Glycoprotein GPIb-IX Complex ; biosynthesis ; Platelet Membrane Glycoprotein IIb ; biosynthesis ; Thrombocytopenia ; genetics ; pathology

Platelet glycoprotein VI (GPVI) is a major receptor for collagen on the platelet surface. It mediates the initial platelet contact with collagen, generates intracellular signals, increases the affinity of integrin receptor, and causes platelet aggregation and thrombosis. Suppression of GPVI function can significantly inhibit collagen-induced platelet adhesion, aggregation and thrombosis, so GPVI has become a novel target for antiplatelet therapy. Within the last few years, major advances have been made in understanding platelet-collagen interactions. In this paper, the advances of study on GPVI, including composition of GPVI, functions of GPVI, factors related with functions of GPVI, GPVI and clinic were summarized.
Humans ; Platelet Adhesiveness ; physiology ; Platelet Aggregation ; physiology ; Platelet Glycoprotein GPIIb-IIIa Complex ; metabolism ; physiology ; Platelet Glycoprotein GPIb-IX Complex ; metabolism ; physiology ; Platelet Membrane Glycoproteins ; chemistry ; metabolism ; physiology ; Protein Binding ; physiology

OBJECTIVETo explore the role of the amino acids between 551 and 565 in the cytoplasmic domain of glycoprotein (GP) I b alpha in the VWF binding to GP I b alpha.

METHODSThe VWF binding to GP I b alpha induced by ristocetin was analyzed by flow cytometry, in three GP I b-IX-expressing Chinese hamster ovary (CHO) cell lines 1b9, delta 565 and delta 551, adhesion of above cells on VWF by flow chamber analysis at shear rate of 200 s(-1). The spread of GP I b-IX-expressing cells were stimulated with botrocetin on VWF-coated coverslips by confocal microscope.

RESULTSThe VWF binding to GP I b alpha was higher in delta 565 cells stimulated by ristocetin than in delta 551 or 1b9 cells. The number of delta 565 cells adhered on the VWF-coated-chamber was more than that of controls at shear rate of 200 s(-1). Moreover, the surface spreading areas of delta 565 cells were greater than that of the controls on VWF-coated coverslips.

CONCLUSIONSThe amino acids between 551 and 565 in the cytoplasmic domain of GP I b alpha regulates the VWF binding to GP I b alpha.

Amino Acid Sequence ; Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Female ; Platelet Adhesiveness ; Platelet Glycoprotein GPIb-IX Complex ; genetics ; metabolism ; von Willebrand Factor ; metabolism

In resting platelets, the 17 ^th domain of filamin a (FLNa17) constitutively binds to the platelet membrane glycoprotein Ibα (GPIbα) at its cytoplasmic tail (GPIbα-CT) and inhibits the downstream signal activation, while the binding of ligand and blood shear force can activate platelets. To imitate the pull force transmitted from the extracellular ligand of GPIbα and the lateral tension from platelet cytoskeleton deformation, two pulling modes were applied on the GPIbα-CT/FLNa17 complex, and the molecular dynamics simulation method was used to explore the mechanical regulation on the affinity and mechanical stability of the complex. In this study, at first, nine pairs of key hydrogen bonds on the interface between GPIbα-CT and FLNa17 were identified, which was the basis for maintaining the complex structural stability. Secondly, it was found that these hydrogen bonding networks would be broken down and lead to the dissociation of FLNa17 from GPIbα-CT only under the axial pull force; but, under the lateral tension, the secondary structures at both terminals of FLNa17 would unfold to protect the interface of the GPIbα-CT/FLNa17 complex from mechanical damage. In the range of 0~40 pN, the increase of pull force promoted outward-rotation of the nitrogen atom of the 563 ^rd phenylalanine (PHE ⁵⁶³-N) at GPIbα-CT and the dissociation of the complex. This study for the first time revealed that the extracellular ligand-transmitted axial force could more effectively relieve the inhibition of FLNa17 on the downstream signal of GPIbα than pure mechanical tension at the atomic level, and would be useful for further understanding the platelet intracellular force-regulated signal pathway.
Filamins/metabolism* ; Platelet Glycoprotein GPIb-IX Complex/metabolism* ; Molecular Dynamics Simulation ; Ligands ; Protein Binding ; Blood Platelets/metabolism* ; von Willebrand Factor/metabolism*

OBJECTIVETo study the expression of specific anti- platelet glycoprotein autoantibodies GP II b/III a, GP I b/IX and GP I a/II a in primary immune thrombocytopenia (ITP), and to evaluate the relationship between the therapeutic effect and the expression of specific anti- platelet glycoprotein antibodies GPIIb/IIIa, GPIb/IX and GPIa/IIa.

METHODSAnti-GPIIb/IIIa, GPIb/ IX and GP I a/II a antibodies were assayed by ELISA for patients with ITP. Total 442 patients in our hospital, who were retrospectively investigated from December 2010 to November 2012, were divided into newly diagnosed ITP, persistent and chronic ITP. The expression of specific anti- platelet glycoprotein antibody in each group was measured separately. The newly diagnosed ITP patients were treated with intravenous IgG (IVIG) and corticosteroids. The relationship between the expression of specific anti- platelet glycoprotein antibodies GPIIb/IIIa, GPIb/IX and GPIa/IIa and the complete response (CR) was studied.

RESULTSPositive rates of anti- platelet glycoprotein antibodies were 59.09%, 26.97% and 37.35% respectively in newly diagnosed ITP, persistent and chronic ITP, the difference was statistical significant (P<0.05). In newly diagnosed ITP, positive rate of antibody against GPIIb/IIIa was 38.64%, double positive rate of antibodies against both GP II b/III a and GP I a/II a was 15.91%, there was statistical significance (P<0.05) compared with that of persistent and chronic ITP. The complete response (CR) rate in newly diagnosed ITP patients with positive antibody against GP II b/III a was 80.39% after treatment with IVIG and corticosteroids. There was statistical significance compared with that in patients having no antibodies (P<0.05).

CONCLUSIONThe expression of antibodies against GP II b/III a and double positive for both GP II b/III a and GP I a/II a autoantibodies increased in newly diagnosed ITP patients. Patients with anti-GP II b/III a autoantibody had good response to medication with IVIG and corticosteroids.

Adolescent ; Adult ; Aged ; Autoantibodies ; metabolism ; Child ; Child, Preschool ; Female ; Humans ; Male ; Middle Aged ; Platelet Glycoprotein GPIIb-IIIa Complex ; immunology ; Platelet Glycoprotein GPIb-IX Complex ; immunology ; Platelet Membrane Glycoproteins ; immunology ; Retrospective Studies ; Thrombocytopenia ; drug therapy ; immunology ; metabolism ; Treatment Outcome ; Young Adult

The aim of this study was to explore the potential relationship between the enhancement of instant hemostatic function in vivo of cryopreserved platelets and its procoagulative related molecule activities. The ability of platelet binding factor V density of GPIb-IX-V (CD42a) at platelet member surface were detected by flow cytometry, the clotting time induced by activated platelets were evaluated by coagulometer and platelet count, MPV and PDW were measured by hemocytometer before and after fresh platelets were cryopreserved. The results showed that the clotting time induced by activated cryopreserved platelets decreased by 43.9%, even quicker than that induced by fresh platelets; the fluorescence intensity of cryopreserved platelet binding factor V increased by 117%, more than that of fresh platelets binding factor V; the GPIb-IX-V (CD42a) density at cryopreserved platelet membrane surface increased by 32%, higher than that at fresh platelet surface. It is concluded that the enhancement of instant hemostatic function in vivo of cryopreserved platelet may be related to higher expression of procoagulative molecules or to their enhanced activity and rapid hemostatic effect.
Blood Coagulation ; physiology ; Blood Coagulation Factors ; metabolism ; Blood Platelets ; physiology ; Blood Preservation ; Cryopreservation ; methods ; Humans ; Platelet Glycoprotein GPIb-IX Complex ; analysis

OBJECTIVESTo study the interaction of beta-2-glycoprotein I (beta 2GPI) with the membrane of hepatocytes and determine whether beta 2GPI participates in HBV infection.

METHODSLigand blotting, fluorescence microscopy, and fluorescence activated cell sorter (FACS) analysis were used to detect the specific interaction of beta 2GPI with the hepatoma cell line smmc7721, the gastric carcinoma cell line SGC7901, and the lymphoma cell line HL-60.

RESULTSA specific 40 kDa beta 2GPI band was observed by ligand blotting in the case of smmc7721 cells. No such band was observed in SGC7901 or HL-60 cells. Fluorescence microscopy also revealed specific binding of FITC-beta 2GPI to smmc7721 cells, but neither to SGC7901 nor HL-60 cells. FACS analysis demonstrated that the binding rate of FITC-beta 2GPI to smmc7721 cells was significantly higher than these in SGC7901 and HL-60 cells (P < 0.01). The binding rate to smmc7721 cells did not increase with increasing amounts of FITC-beta 2GPI.

CONCLUSIONSThere is a specific beta 2GPI-binding protein on the membrane of hepatoma cells in cell line smmc7721 which as the beta 2GPI receptor may participate in HBV infection of hepatocytes.

Animals ; Carcinoma, Hepatocellular ; Cell Membrane ; metabolism ; Flow Cytometry ; Glycoproteins ; metabolism ; Hepatocytes ; metabolism ; Liver Neoplasms, Experimental ; metabolism ; Platelet Glycoprotein GPIb-IX Complex ; analysis ; Platelet Membrane Glycoproteins ; Tumor Cells, Cultured ; beta 2-Glycoprotein I

OBJECTIVETo detect the redistribution of platelet surface glycoprotein (GP)Ib alpha and cytoskeleton reorganization in the course of thrombin receptor activation, and investigate the mechanism of GPIb alpha re-translocation and the role of thrombin receptors in platelet signal transduction.

METHODSThe thrombin receptor activating peptide (PAR1-AP, TRAP) was used for stimulating platelet at different time points (0 - 60 min), then the platelet surface GPIb alpha and P-selectin were examined with flow cytometry, and the alterations of GPIb alpha, actin and myosin were analyzed in cytoskeleton by Western blot and GPIb alpha immunoprecipitation. Cytochalasin D and/or Apyrase VII were used for investigating their inhibitory effect on platelet activation.

RESULTSAn increase of P-selectin and reversible internalization of GPIb alpha were observed within platelets upon TRAP activation, and transient changes of actin, myosin and GPIb alpha/myosin, GPIb alpha/actin association were also found in this course. These changes were apparently blocked by cytochalasin D, which inhibited the incorporation of GPIb alpha, actin and myosin into cytoskeleton. Apyrase VII had a weak effect on GPIb alpha internalization, although it accelerated the return of GPIb alpha to platelet surface. In addition, Apyrase VII also quickened the GPIb alpha disappearance in cytoskeleton and the dissociation of GPIb/myosin or GPIb/actin during activation.

CONCLUSIONThrombin receptor activation takes part in platelet signal transduction, inducing a reversible redistribution of GPIb alpha. This process is related to cytoskeleton reorganisation and ADP.

Actins ; metabolism ; Blood Platelets ; cytology ; drug effects ; metabolism ; Blotting, Western ; Cells, Cultured ; Cytoskeleton ; metabolism ; Humans ; Myosins ; metabolism ; P-Selectin ; metabolism ; Peptide Fragments ; pharmacology ; Platelet Activation ; drug effects ; physiology ; Platelet Glycoprotein GPIb-IX Complex ; metabolism ; Receptors, Thrombin ; metabolism ; physiology