Expression Levels Of Glycoprotein Research Articles

The Glycoprotein (GP)Ib-IX-V Complex on Platelets: GPIbα Protein Expression Is Reduced in HeartMate 3 Patients with Bleeding Complications within the First 3 Months.

Non-surgical bleeding (NSB) remains the most critical complication in patients under left ventricular assist device (LVAD) support. It is well known that blood exposed to high shear stress results in platelet dysfunction. Compared to patients without NSB, decreased surface expression of platelet receptor GPIbα was observed in LVAD patients with NSB. In this study, we aimed to compare the expression level of glycoprotein (GP)Ib-IX-V platelet receptor complex in HeartMate 3 (HM 3) patients with and without bleeding complications to investigate the alterations of the platelet transcriptomic profile on platelet damage and increased bleeding risk. Blood samples were obtained from HM 3 patients with NSB (bleeder group, n = 27) and without NSB (non-bleeder group, n = 55). The bleeder group was further divided into patients with early NSB (bleeder ≤ 3 mo, n = 19) and patients with late NSB (bleeder > 3 mo, n = 8). The mRNA and protein expression of GPIbα, GPIX and GPV were quantified for each patient. Non-bleeder, bleeder ≤ 3 mo and bleeder > 3 mo were comparable regarding the mRNA expression of GPIbα, GPIX and GPV (p > 0.05). The protein analysis revealed a significantly reduced expression level of the main receptor subunit GPIbα in bleeders ≤ 3 mo (p = 0.04). We suggest that the observed reduction of platelet receptor GPIbα protein expression in patients who experienced their first bleeding event within 3 months after LVAD implantation may influence platelet physiology. The alterations of functional GPIbα potentially reduce the platelet adhesion capacities, which may lead to an impaired hemostatic process and the elevated propensity of bleeding in HM 3 patients.

Humic Acids Inhibit Platelet Activation to Reduce Venous Thromboembolism in Mice.

We aimed to investigate the effects of the natural product humic acids (HA) on platelet activation and development of venous thromboembolism (VTE) in mice and further explore the relevant mechanism. Eight-week C57BL/6 mice were randomly assigned to three groups: sham operation group (n = 7), VTE group (n = 8), and VTE + HA group (n = 10). Thrombi were harvested to hematoxylin-eosin staining to evaluate the thrombolysis and recanalization of the thrombus. In addition, flow cytometry was performed to detect the expression levels of protein disulfide isomerase on endothelial-derived exosomes and glycoprotein IIb/IIIa on the surface of the activated platelets surface in plasma. Furthermore, the protein expression level of glycoprotein IIb/IIIa in thrombus was determined by immunohistochemistry and immunofluorescence. The length of thrombosis in the VTE + HA group was significantly shorter than that in the VTE group (P = 0.040). No significant differences were observed in thrombolysis and recanalization between the VTE + HA group and the VTE group (P > 0.05). The content of protein disulfide isomerase carried by endothelial-derived exosomes was significantly increased in the VTE group (P = 0.008) but significantly reduced by native humic acids (P = 0.012). Compared with the VTE group, the expression of glycoprotein IIb/IIIa on activated platelet surface in the VTE + HA group was significantly decreased (P = 0.002). The concentration of plasmatic P-selectin in the VTE group was significantly higher than that in the VTE + HA group (P < 0.001). We demonstrate that HA possess a pharmacological property that decreases venous thrombus formation in mice. The underlying mechanism is that HA could inhibit the expression of glycoprotein IIb/IIIa on the activated platelets surface by suppressing endothelial-derived exosomes carrying on protein disulfide isomerase, thereby blocking platelet activation.

Stanniocalcin 1 is overexpressed in multipotent mesenchymal stromal cells from acute myeloid leukemia patients

ABSTRACT Objectives: Multipotent mesenchymal stromal cells (MSC) play a pivotal role in the bone marrow (BM) niche. Stanniocalcin 1 (STC1) secreted by MSC has been demonstrated to promote the survival of neoplastic cells and was suggested a marker for minimal residual disease of acute myeloid leukemia (AML). Therefore, we evaluated the expression of STC1 in MSC from AML patients (MSCAML) compared to MSC from healthy donors (MSCHD). Methods: Liquid culture assays of MSCAML and MSCHD were performed to compare expansion capacity. Gene expression profiles of MSCAML vs. MSCHD were established. Secretion of STC1 was tested by ELISA in MSCAML vs. MSCHD and expression of STC1 in AML- vs. HD-BM by immunohistochemistry. In addition, co-cultures of AML cells on MSC were initiated and ultrastructural intercellular communication patterns were investigated. Finally, the effect of blocking STC1 on AML cells was evaluated. Results: MSCAML showed significant decreased expansion capacity compared to MSCHD. Gene analysis revealed marked overexpression of STC1 in MSCAML. ELISA and immunohistochemical findings confirmed this observation. Electron microscopy analysis showed reciprocal stimulation between AML cells and MSC. Blockade of STC1 did not significantly affect AML cell proliferation and apoptosis. Discussion: Characteristics of MSC differ depending on whether they originate from AML patients or from HD. STC1 was mostly overexpressed in MSCAML compared to MSCHD. In vitro blockade of STC1, however, was not associated with AML cell proliferation and apoptosis. Conclusion: Differences in expression levels of glycoproteins from MSCAML compared to MSCHD not necessarily assume that these molecules are niche-relevant in leukemic disease.

High-throughput elucidation of thrombus formation reveals sources of platelet function variability.

In combination with microspotting, whole-blood microfluidics can provide high-throughput information on multiple platelet functions in thrombus formation. Based on assessment of the inter- and intra-subject variability in parameters of microspot-based thrombus formation, we aimed to determine the platelet factors contributing to this variation. Blood samples from 94 genotyped healthy subjects were analyzed for conventional platelet phenotyping: i.e. hematologic parameters, platelet glycoprotein (GP) expression levels and activation markers (24 parameters). Furthermore, platelets were activated by ADP, CRP-XL or TRAP. Parallel samples were investigated for whole-blood thrombus formation (6 microspots, providing 48 parameters of adhesion, aggregation and activation). Microspots triggered platelet activation through GP Ib-V-IX, GPVI, CLEC-2 and integrins. For most thrombus parameters, inter-subject variation was 2-4 times higher than the intra-subject variation. Principal component analyses indicated coherence between the majority of parameters for the GPVI-dependent microspots, partly linked to hematologic parameters, and glycoprotein expression levels. Prediction models identified parameters per microspot that were linked to variation in agonist-induced αIIbβ3 activation and secretion. Common sequence variation of GP6 and FCER1G, associated with GPVI-induced αIIbβ3 activation and secretion, affected parameters of GPVI-and CLEC-2-dependent thrombus formation. Subsequent analysis of blood samples from patients with Glanzmann thrombasthenia or storage pool disease revealed thrombus signatures of aggregation-dependent parameters that were subject-dependent, but not linked to GPVI activity. Taken together, this high-throughput elucidation of thrombus formation revealed patterns of inter-subject differences in platelet function, which were partly related to GPVI-induced activation and common genetic variance linked to GPVI, but also included a distinct platelet aggregation component.

Mesenchymal stem cells-derived IL-6 activates AMPK/mTOR signaling to inhibit the proliferation of reactive astrocytes induced by hypoxic-ischemic brain damage

Mesenchymal stem cells (MSCs) treatment is an effective strategy for the functional repair of central nervous system (CNS) insults through the production of bioactive molecules. We have previously demonstrated that the interleukin-6 (IL-6) secreted by MSCs plays an anti-apoptotic role in injured astrocytes and partly promotes functional recovery in neonatal rats with hypoxic-ischemic brain damage (HIBD). However, the mechanisms of IL-6 underlying the proliferation of injured astrocytes have not been fully elucidated. In this study, we investigated the therapeutic effects of MSCs on astrocyte proliferation in neonatal rats subjected to HIBD. A HIBD model was established in Sprague Dawley (SD) rats, and MSCs were administered by intracerebroventricular injection 5 days after HIBD. Rat primary astrocytes were cultured, subjected to oxygen glucose deprivation (OGD) injury and then immediately co-cultured with MSCs in vitro. Immunofluorescence staining, Cell Counting Kit (CCK)-8, flow cytometry, Ca2+ imaging, enzyme-linked immunosorbent assay (ELISA), western blotting, and co-immunoprecipitation (Co-IP) were performed. We found that MSCs transplantation not only promoted the recovery of learning and memory function in HIBD rats but also significantly reduced the number of Ki67+/glial fibrillary acidic protein (GFAP)+ cells in the hippocampi 7–14 days after HIBD. In addition to increasing IL-6 expression in both the hippocampi of HIBD rats and astrocyte culture medium, MSCs treatment in vitro significantly increased the expression levels of glycoprotein (gp) 130 and phosphorylated AMP-activated protein kinase α (p-AMPKα) and decreased the expression levels of p-mammalian target of rapamycin (mTOR) and its downstream targets. Furthermore, MSCs treatment induced a protein-protein interaction between gp130 and p-AMPKα. Suppression of IL-6 expression in MSCs reversed the above regulatory functions of MSCs in hippocampal astrocytes. The utilization of rapamycin further confirmed that mTOR participated in the proliferation of reactive astrocytes. These findings suggest that endogenous IL-6 produced by MSCs in the HIBD microenvironment provides therapeutic advantages by activating AMPK/mTOR signaling, thus reducing the proliferation of reactive astrocytes.

Expression Levels of Glycoprotein O (gO) Vary between Strains of Human Cytomegalovirus, Influencing the Assembly of gH/gL Complexes and Virion Infectivity.

The tropism of human cytomegalovirus (HCMV) is influenced by the envelope glycoprotein complexes gH/gL/gO and gH/gL/UL128-131. During virion assembly, gO and the UL128-131 proteins compete for binding to gH/gL in the endoplasmic reticulum (ER). This assembly process clearly differs among strains, since Merlin (ME) virions contain abundant gH/gL/UL128-131 and little gH/gL/gO, whereas TR contains much higher levels of total gH/gL, mostly in the form of gH/gL/gO, but much lower levels of gH/gL/UL128-131 than ME. Remaining questions include (i) what are the mechanisms behind these assembly differences, and (ii) do differences reflect in vitro culture adaptations or natural genetic variations? Since the UL74(gO) open reading frame (ORF) differs in 25% of amino acids between TR and ME, we analyzed recombinant viruses in which the UL74(gO) ORF was swapped. TR virions were >40-fold more infectious than ME. Transcriptional repression of UL128-131 enhanced the infectivity of ME to the level of TR, despite still far lower levels of gH/gL/gO. Swapping the UL74(gO) ORF had no effect on either TR or ME. A quantitative immunoprecipitation approach revealed that gH/gL expression levels were within 4-fold between TR and ME, but the gO expression level was 20-fold lower for ME, which suggested differences in mRNA transcription, translation, or rapid ER-associated degradation of gO. trans-Complementation of gO expression during ME replication gave a 6-fold enhancement of infectivity beyond the 40-fold effect of UL128-131 repression alone. Overall, strain variations in the assembly of gH/gL complexes result from differences in the expression of gO and UL128-131, and selective advantages for reduced UL128-131 expression during fibroblast propagation are much stronger than those for higher gO expression.IMPORTANCE Specific genetic differences between independently isolated HCMV strains may result from purifying selection on de novo mutations arising during propagation in culture or random sampling among the diversity of genotypes present in clinical specimens. Results presented indicate that while reduced UL128-131 expression may confer a powerful selective advantage during cell-free propagation of HCMV in fibroblast cultures, selective pressures for increased gO expression are much weaker. Thus, variation in gO expression among independent strains may represent natural genotype variability present in vivo This may have important implications for virus-host interactions, such as immune recognition, and underscores the value of studying molecular mechanisms of replication using multiple HCMV strains.

807C/T polymorphism of platelet glycoprotein Ia gene is associated with cerebral hemorrhage in a Chinese population

Platelet glycoprotein (GP) mediated the role of platelet in coagulation. Platelet GP Ia 807C/T is the only GP polymorphism associated with the expression levels of GP Ia/IIa (the platelet collagen receptor). Recently, the GP Ia 807C/T polymorphism has been reported to have no association with cerebral hemorrhage (CH) in two studies pertained to Caucasian populations. The purpose of this study is to evaluate the association between platelet GP Ia 807C/T polymorphism and CH in a Han Chinese population. We performed genotype analysis for platelet GP Ia 807C/T polymorphism in a case-control study involving 195 patients with CH and 116 age- and sex-matched controls. In contrast to previous reports, we found that the frequencies of GP Ia 807C/T T allele, CT and TT genotype were much higher in CH patients than in controls (33.9% vs. 22.8%, p = 0.004; 45.5% and 11.1% vs. 40.4% and 2.6%, p = 0.022). Logistic regression analysis revealed that the presence of GP Ia 807C/T C allele and CC genotype were both associated with a decreased risk of CH compared with T allele, CT and TT genotypes, respectively (adjusted odds ratio [OR] = 0.565, 95% CI: 0.384–0.887, p = 0.005; adjusted OR = 0.172, 95% CI: 0.043–0.639, p = 0.009; adjusted OR = 0.254, 95% CI: 0.085–0.961, p = 0.041, respectively). These findings indicated that platelet GP Ia 807C/T polymorphism could be a protective factor of CH in the Chinese population.

Investigation of platelet function and platelet disorders using flow cytometry

Patients with thrombocytopenia or platelet disorders are at risk of severe bleeding. We report the development and validation of flow cytometry assays to diagnose platelet disorders and to assess platelet function independently of platelet count. The assays were developed to measure glycoprotein levels (panel 1) and platelet function (panel 2) in sodium citrated blood. Twenty healthy volunteers and five patients diagnosed with different platelet disorders were included. Glycoprotein expression levels of the receptors Ia, Ib, IIb, IIIa and IX were measured and normalised with forward scatter (FS) as a measurement of platelet size. Platelet function was assessed by CD63, P-selectin and bound fibrinogen in response to arachidonic acid, adenosine diphosphate (ADP), collagen-related peptide, ristocetin and thrombin receptor-activation peptide-6. All patients except one with suspected δ-granule defect showed aberrant levels of glycoproteins in panel 1. Glanzmann's thrombasthenia and genetically verified Bernard–Soulier syndrome could be diagnosed using panel 1. All patients showed reduced platelet function according to at least one agonist. Using panel 2 it was possible to diagnose Bernard–Soulier syndrome, δ-granule defect and GPVI disorder. By combining the two assays, we were able to diagnose different platelet disorders and investigate platelet function independent of platelet count.

N-linked Glycosylation Enrichment for In-depth Cell Surface Proteomics of Diffuse Large B-cell Lymphoma Subtypes

Global analysis of lymphoma genome integrity and transcriptomes tremendously advanced our understanding of their biology. Technological advances in mass spectrometry-based proteomics promise to complete the picture by allowing the global quantification of proteins and their post-translational modifications. Here we use N-glyco FASP, a recently developed mass spectrometric approach using lectin-enrichment, in conjunction with a super-SILAC approach to quantify N-linked glycoproteins in lymphoma cells. From patient-derived diffuse large B-cell lymphoma cell lines, we mapped 2383 glycosites on 1321 protein groups, which were highly enriched for cell membrane proteins. This N-glyco subproteome alone allowed the segregation of the ABC from the GCB subtypes of diffuse large B-cell lymphoma, which before gene expression studies had been considered one disease entity. Encouragingly, many of the glycopeptides driving the segregation belong to proteins previously characterized as segregators in a deep proteome study of these subtypes (S. J. Deeb et al. MCP 2012 PMID 22442255). This conforms to the high correlation that we observed between the expression level of the glycosites and their corresponding proteins. Detailed examination of glycosites and glycoprotein expression levels uncovered, among other interesting findings, enrichment of transcription factor binding motifs, including known NF-kappa-B related ones. Thus, enrichment of a class of post-translationally modified peptides can classify cancer types as well as reveal cancer specific mechanistic changes.

Different biochemical expression pattern of platelet surface glycoproteins suggests molecular diversity of Glanzmann's thrombasthenia in Iran

Glanzmann's thrombasthenia is a rare congenital bleeding disorder characterized by lack of platelet aggregation induced by most agonists. The disease is caused by different mutations in either GPIIb or GPIIIa genes that lead to a lack or dysfunction of the αIIbβ3. Western blot analysis was performed on the platelet lysates of 95 patients with Glanzmann's thrombasthenia who were referred to the Iranian Blood Transfusion and Hemophilia Clinic. Glanzmann's thrombasthenia was diagnosed based on clinical findings and were classified according to Glanzmann's Thrombasthenia Italian Team (GLATIT) protocol. The platelet glycoprotein expression pattern in Iranian patients with Glanzmann's thrombasthenia was studied and the relationship between the platelet glycoprotein expression levels and clinical symptoms were investigated. Loss or severe reduction of platelet GpIIb and GpIIIa were observed in majority of patients (78%). The remaining patients (22%) showed a relatively sharp decline to the normal amounts of the glycoproteins. None of the patients showed expression of CD41 without CD61. Statistical analysis showed no significant relationship between clinical symptoms and expression of platelet glycoproteins. Different patterns of platelet glycoproteins expression suggest that there is variety of mutations in the patients. Unlike the universal Glanzmann's thrombasthenia database, the majority of Iranian patients may suffer from a GpIIIa gene mutation. This study also confirmed a lack of correlation between clinical manifestation and GPIIb/IIIa expression in the patients.

The Product of Kaposi's Sarcoma-Associated Herpesvirus Immediate Early Gene K4.2 Regulates Immunoglobulin Secretion and Calcium Homeostasis by Interacting with and Inhibiting pERP1

Chaperones are proteins that assist the noncovalent folding and assembly of macromolecular polypeptide chains, ultimately preventing the formation of nonfunctional or potentially toxic protein aggregates. Plasma cell-induced-endoplasmic reticulum (ER)-resident protein 1 (pERP1) is a cellular chaperone that is preferentially expressed in marginal-zone B cells and is highly upregulated during plasma cell differentiation. While initially identified as a dedicated factor for the assembly of secreted IgM, pERP1 has since been implicated in suppressing calcium mobilization, and its expression is misregulated in multiple tumors. A number of herpesvirus immediate early gene products play important roles in the regulation of viral gene expression and/or evasion of host immune responses. Here, we report that the Kaposi's sarcoma-associated herpesvirus (KSHV) immediate early viral gene K4.2 encodes an endoplasmic reticulum-localized protein that interacts with and inhibits pERP1. Consequently, K4.2 expression interfered with immunoglobulin secretion by delaying the kinetics of immunoglobulin assembly and also led to increased responsiveness of B-cell receptor signal transduction by enhancing phosphotyrosine signals and intracellular calcium fluxes. Furthermore, K4.2 expression also appeared to contribute to maximal lytic replication by enhancing viral glycoprotein expression levels and ultimately promoting infectious-virus production. Finally, immunohistochemistry analysis showed that pERP1 expression was readily detected in KSHV-positive cells from multicentric Castleman's disease (MCD) and Kaposi's sarcoma (KS) lesions, suggesting that pERP1 may have potential roles in the KSHV life cycle and malignancy. In conclusion, our data suggest that K4.2 participates in lytic replication by enhancing calcium flux and viral glycoprotein expression, but also by interfering with immunoglobulin assembly to potentially dampen the adaptive immune response.

Inhibitory role of S-nitrosoglutathione in the aggregation of frozen platelets, and its effect on the expression of membrane glycoproteins

The aim of this study was to explore the effects of S-nitrosoglutathione (GSNO) on the aggregation of frozen platelets, the platelet nitric oxide (NO) content and the expression of membrane glycoproteins. The level of frozen platelet aggregation was measured using a platelet aggregation analyzer, while the content of NO was measured by the nitrate reductase method and the expression of frozen platelet membrane glycoproteins was determined by flow cytometry. The level of frozen platelet aggregation was reduced from 35.47±2.93 to 24.43±3.07% following treatment with GSNO. The mean NO concentration in the 32 samples of frozen platelets treated with GSNO was 45.64±6.31 μmol/l, which was significantly higher compared with the concentration in the fresh liquid platelet group. There were no significant differences in the levels of PAC-1 in the fresh liquid platelet, frozen platelet and GSNO-treated frozen platelet groups; by contrast, significant differences were observed in the CD42b and CD62P levels. The platelet membrane glycoprotein expression levels in the frozen platelet and the GSNO-treated frozen platelet groups were not significantly different. The results of the study indicate that GSNO has potential as a cryoprotectant, due to its ability to increase the NO concentration in frozen platelets, inhibit platelet aggregation and maintain platelet function. It is likely that the molecular arrangement and structure of the frozen platelets were altered following GSNO treatment, or that the frozen platelets were affected by alternative mechanisms.

Altered expression of glycoproteins on the cell surface of Jurkat cells during etoposide-induced apoptosis: Shedding and intracellular translocation of glycoproteins

Background The glycoproteins on the cell surface are altered during apoptosis and play an important role in phagocytic clearance of apoptotic cells. Methods We classified Jurkat cells treated with etoposide as viable and early apoptotic cells, late apoptotic cells or secondary necrotic cells based on propidium iodide staining and scattered grams and estimated the expression levels of glycoproteins on the cell surface. Results The cell surface expression levels of intercellular adhesion molecules (ICAM)-2 and -3 on the apoptotic cells were markedly lower, while those of calnexin, calreticulin, and lysosome-associated membrane proteins (LAMP)-1 and -2 were significantly higher compared to non-apoptotic cells. These decreases in ICAM-2 and -3 on the apoptotic cell surface were reduced in the presence of metalloproteinase inhibitors and caspase inhibitors, respectively. Confocal microscopic analysis revealed that calnexin and calreticulin were assembled around fragmented nuclei of blebbed apoptotic cells. Conclusions These results suggest that alteration of glycoproteins on the cell surface during apoptosis is associated with shedding and intracellular translocation of glycoproteins.

Bisecting GlcNAc Structures Act as Negative Sorting Signals for Cell Surface Glycoproteins in Forskolin-treated Rat Hepatoma Cells

The bisecting N-acetylglucosamine residue is formed by UDP-N-acetylglucosamine:beta-D-mannoside-beta-1, 4-N-acetylglucosaminyltransferase III (GnT-III), a key branching enzyme for N-glycans. We found that forskolin, an adenylyl cyclase activator, markedly enhanced GnT-III at the transcriptional level in various hepatoma cells and hepatocytes, resulting in an increase of bisecting GlcNAc residues in various glycoproteins, as judged from the lectin binding to erythroagglutinating phytohemagglutinin (E-PHA). In whole cell lysates, the E-PHA binding was increased, and leukoagglutinating phytohemagglutinin (L-PHA) binding was decreased at 12 h after forskolin treatment, by time, both GnT-III activity and mRNA had reached the maximum levels. In contrast, the binding capacity as to E-PHA, determined by fluorescence-activated cell sorting on the cell surface, was decreased, suggesting that bisecting GlcNAc structures in certain glycoproteins changed the expression levels of glycoproteins and decreased their sorting on the cell surface. Fractionated organelles of M31 cells showed that the binding capacity as to E-PHA was mainly localized in Golgi membranes and lysosomes. This was also supported by a fluorescence microscopy. In order to determine whether or not the bisecting GlcNAc residue acts as a sorting signal for glycoproteins, N-oligosaccharide structures of lysosomal-associated membrane glycoprotein 1 and beta-glucuronidase, gamma-glutamyltranspeptidase, and secretory glycoproteins such as ceruloplasmin and alpha-fetoprotein were measured by E-PHA and L-PHA blotting after immunoprecipitation. The expression levels of lysosomal membrane glycoprotein 1 and gamma-glutamyltranspeptidase on the cell surface were decreased at 12 h after forskolin treatment, indicating that the bisecting GlcNAc structure may act as a negative sorting signal for the cell surface glycoproteins and may alter the characteristics of hepatoma cells. This is the first report on glycoprotein sorting related to a specific structure of oligosaccharides, bisecting GlcNAc.