Plasma Membrane Glycoproteins Research Articles

Potentials of brentuximab vedotin in the treatment of relapse/refractory cutaneous T-cell lymphomas: literature review and authors’ observation

Primary cutaneous T-cell lymphomas encompass a heterogeneous group of T-cell lymphoproliferative disorders developing primarily in the skin and characterized by a number of specific diagnostic, clinical, and therapeutic features. Mycosis fungoides accounts for more than half of all cutaneous lymphoma cases, while CD30+ lymphoproliferative diseases of the skin (primary cutaneous anaplastic large-cell lymphoma and lymphomatoid papulosis) constitute one-fourth of them and the remaining cases are rare tumour types, including primary cutaneous peripheral T-cell lymphoma, unspecified/not otherwise specified.Activation antigen СD30 is a cell membrane glycoprotein of the tumour necrosis factor family. More than 75 % of primary cutaneous CD30-positive lymphoma cells express CD30; it may be detected in other diseases as well, but to a lesser extent.Most patients with cutaneous CD30+ lymphoproliferative diseases have indolent disease and a favourable prognosis; resistant disease is observed in approximately 30 % of sufferers, and fatal outcomes occur in 8 % of cases [1].Systemic immunomodulatory therapy or chemotherapy is often used in advanced disease. Monoclonal antibodies were recently introduced into clinical practice for the treatment of cutaneous lymphomas. One of these agents is brentuximab vedotin, a CD30-monoclonal antibody conjugated to monomethyl auristatin E.We present two case reports: one of frequently recurring lymphomatoid papulosis and the other of refractory primary cutaneous peripheral T-cell lymphoma, unspecified/not otherwise specified. Targeted therapy with brentuximab vedotin, either alone or in combination with chemotherapy, resulted in a sustained, long-lasting remission in both cases.

Carcinoembryonic Cell Adhesion-Related Molecule 2 Regulates Insulin Secretion and Energy Balance.

The Carcinoembryonic Antigen-Related Cell Adhesion Molecule (CEACAM) family of proteins plays a significant role in regulating peripheral insulin action by participating in the regulation of insulin metabolism and energy balance. In light of their differential expression, CEACAM1 regulates chiefly insulin extraction, whereas CEACAM2 appears to play a more important role in regulating insulin secretion and overall energy balance, including food intake, energy expenditure and spontaneous physical activity. We will focus this review on the role of CEACAM2 in regulating insulin metabolism and energy balance with an overarching goal to emphasize the importance of the coordinated regulatory effect of these related plasma membrane glycoproteins on insulin metabolism and action.

Successful experience of combined immunochemotherapy at refractory course of primary cutaneous peripheral T-cell lymphoma, unspecified

Primary cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of T-cell lymphoproliferative diseases that involve mainly the skin and are characterized by features of their diagnosis, clinical course and therapeutic approach. They include mainly fungal mycosis and CD30 + lymphoproliferative skin diseases (primary cutaneous anaplastic large cell lymphoma and lymphomatoid papulosis) which account for >50% of CTCL and primary cutaneous peripheral T-cell lymphoma, unspecified/ /not otherwise specified (PTL NOS) which occurs extremely rare. Activation antigen CD30 is a cell membrane glycoprotein that belongs to tumor necrosis factor (TNF) superfamily. Tumor cells in primary skin CD30-positive skin lymphomas express CD30 in more than 75%; in other nosological units it also can be detected but to a lesser extent. Most patients with cutaneous CD30 + lymphoproliferative diseases have an indolent the disease course of the disease with a favorable prognosis. Refractory course occurs in approximately 30% patients, and in 8% of cases lymphoma results in deaths. Recently monoclonal antibodies have been included in clinical practice for the treatment of T-cell lymphomas, one of which is brentuximab vedotin, a CD30 monoclonal antibody conjugated to monomethyl auristatin E. This article provides the clinical case of a patient with a refractory form of PTL NOS.

Role of Endoglin Expression in Acute Myeloblastic Leukemia

AbstractBackground: Endoglin (CD105), a cell membrane glyco-protein of approximately 180kDa, has been described as a proliferation-associated antigen of leukemia and endothelial cells, and it represents a powerful marker to quantify tumor angiogenesis. CD105 expression is higher on leukemic cells with immature morphological and phenotypic characteristics compared to normal hematopoietic progenitors. Higher amounts of sCD105 were measured in AML and Chronic Myeloproliferative Disorders (CMD) patients than in healthy subjects. CD105 is involved in the control of vascular en-dothelial cell proliferation, adhesion and migration. CD105 might have a direct involvement in cancer by increase of tumor mass. CD105 levels may be useful as an indicator for disease progression and to identify patients at risk of recurrence and metastasis.Aim of Study: Our aim is to evaluate the role of endoglin (CD 105) expression in patients with AML to clarify its role as a prognostic marker.Material and Methods: This study was carried out on 50 patients with newly diagnosed acute myeloid leukemia who attended the Hematology/Oncology Unit of Tanta University Hospitals. The patients were selected for the study on the basis of standard clinical, hematological and immune pheno-typic criteria for diagnosis of AML. CD105 expression was measured in bone marrow aspirate of AML patients using RD SYSTEMS kits and BD FACS calibur.Subjects included in this study were divided into two groups according to CD 105 exppression; positive and negative groups and classified according to FAB subtypes and immu-nophenotypic features.Results: There was a significant difference in distribution of CD105 expression in different FAB subtypes. There was a significant positive correlation between CD 105 expression and Hb concentration, WBCs count and blast count in periph-eral blood and BM. There was no significant correlation between CD105 expression and platelets count and serum LDH level. Kaplan-Meier survival curve show significant higher overall survival and disease free survival in negative CD105 expression group than in positive CD105 expression group.Conclusions: Positive CD105 expression levels are asso-ciated with a bad outcome in AML patients and its expression can be easy determined in routine flow cytometric analysis. Therefore, it should be regularly investigated as a bad prog-nostic factor for assessment of AML patients.

The CD147-HYALURONAN Axis in Cancer.

CD147 (basigin; EMMPRIN), hyaluronan, and hyaluronan receptors (e.g., CD44) are intimately involved in several phenomena that underlie malignancy. A major avenue whereby they influence tumor progression is most likely their role in the characteristics of cancer stem cells (CSCs), subpopulations of tumor cells that exhibit chemoresistance, invasiveness, and potent tumorigenicity. Both CD147 and hyaluronan have been strongly implicated in chemoresistance and invasiveness, and may be drivers of CSC characteristics, since current evidence indicates that both are involved in epithelial-mesenchymal transition, a crucial process in the acquisition of CSC properties. Hyaluronan is a prominent constituent of the tumor microenvironment whose interactions with cell surface receptors influence several signaling pathways that lead to chemoresistance and invasiveness. CD147 is an integral plasma membrane glycoprotein of the Ig superfamily and cofactor in assembly and activity of monocarboxylate transporters (MCTs). CD147 stimulates hyaluronan synthesis and interaction of hyaluronan with its receptors, in particular CD44 and LYVE-1, which in turn result in activation of multiprotein complexes containing members of the membrane-type matrix metalloproteinase, receptor tyrosine kinase, ABC drug transporter, or MCT families within lipid raft domains. Multivalent hyaluronan-receptor interactions are essential for formation or stabilization of these lipid raft complexes and for downstream signaling pathways or transporter activities. We conclude that stimulation of hyaluronan-receptor interactions by CD147 and the consequent activities of these complexes may be critical to the properties of CSCs and their role in malignancy. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc.

Role and mechanism of the regulation of nuclear factor-κB by heparin binding-epidermal growth factor-like growth factor in the induction of paclitaxel resistance of ovarian cancer

Objective: To investigate the role and mechanism of the regulation of nuclear factor-κB (NF-κB) by heparin binding-epidermal growth factor-like growth factor (HB-EGF) in paclitaxel resistance of ovarian cancer in vitro and in vivo. Methods: (1) The detection of NF-κB expression: parental (A2780) and paclitaxel-resistant (A2780/Taxol) ovarian carcinoma cells were divided into four groups, named A2780 group, A2780+cross-reacting material 197 (CRM197, HB-EGF inhibitor) group, A2780/Taxol group and A2780/Taxol+CRM197 group. Among four groups, the expression level HB-EGF and epidermal growth factor receptor (EGFR) were examined by immunofluorescence double staining on confocal microscopy. Western blot was used to detect the expression level of NF-κB. In vivo, A2780 and A2780/Taxol cells were injected intraperitoneally to nude mouse to determine the expression level of NF-κB of the tumors from these four groups by immunohistochemistry method. (2) The detection on the function of NF-κB: A2780/Taxol cells were divided into four groups, named transfected with empty vector+saline group, NF-κB small interference RNA (siRNA)+saline group, empty vector+CRM197 group and NF-κB siRNA+CRM197 group respectively. Among four groups, the 50% inhibitory concentrations (IC(50)) of A2780/Taxol cells to paclitaxel, the expression level of plasma membrane glycoprotein (P-gp) and the effect of intracellular rhodomine123 (Rh123) accumulation were detected. Results: (1) The detection of NF-κB expression: the expression scores of HB-EGF protein among four groups were 5.6±1.3, 2.1±1.2, 11.7±3.5 and 6.2±1.4; the expression scores of EGFR protein were 5.1±1.6, 2.8±0.6, 10.4±3.1 and 5.6±1.9, respectively. The expression levels of NF-κB protein in the cells of the group named A2780, A2780+CRM197, A2780/Taxol and A2780/Taxol+CRM197 group were 1.89±0.23, 0.74±0.12, 3.45±0.16 and 1.31±0.08, respectively; the expression scores of NF-κB protein in the tissue tumors from four groups were 3.3±1.1, 1.4±0.4, 8.7±2.3 and 3.6±1.2, respectively. The expression level of HB-EGF, EGFR and NF-κB protein between A2780 and A2780/Taxol groups in vivo and in vitro were higher than these in A2780+CRM197 and A2780/Taxol+CRM197 group, while the expression level of HB-EGF, EGFR and NF-κB protein in A2780 group were lower than those in A2780/Taxol groups in vivo and in vitro (P<0.05). (2) The examination of NF-κB function: the IC(50) of A2780/Taxol cells to paclitaxel in groups transfected with empty vector+saline, NF-κB siRNA+saline, empty vector+CRM197 and NF-κB siRNA+CRM197 group were respectively (39.4±0.8), (7.6±0.6), (6.7±0.5) and (4.2±0.4) μmol/L, while the expression levels of P-gp protein among four groups were respectively 3.11±0.23,1.45±0.16, 1.73±0.21 and 0.68±0.14, the cellular Rh123 accumulation among four groups were respectively 110±15, 246±19, 231±22 and 296±24. The expression levels of IC(50) and P-gp protein in groups transfected with NF-κB siRNA+saline, empty vector+CRM197 and NF-κB siRNA+CRM197 group were significantly higher than those in group transfected with empty vector+saline group (P<0.01), while the cellular Rh123 accumulation among three groups were significantly lower than that in group transfected with empty vector+saline (P<0.01). Conclusions: The expression of NF-κB may contributes to the paclitaxel resistance to ovarian cancer. HB-EGF may induce the paclitaxel resistance of ovarian cancer by the regulation of EGFR/NF-κB/P-gp pathway.

Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health.

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5′-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

Boronate affinity-based photoactivatable magnetic nanoparticles for the oriented and irreversible conjugation of Fc-fused lectins and antibodies.

The utilization of immuno-magnetic nanoparticles (MNPs) for the selective capture, enrichment, and separation of specific glycoproteins from complicated biological samples is appealing for the discovery of disease biomarkers. Herein, MNPs were designed and anchored with abundant boronic acid (BA) and photoreactive alkyl diazirine (Diaz) functional groups to obtain permanently tethered Fc-fused Siglec-2 and antiserum amyloid A (SAA) mAb with the assistance of reversible boronate affinity and UV light activation in an orientation-controlled manner. The Siglec-2-Fc-functionalized MNPs showed excellent stability in fetal bovine serum (FBS) and excellent efficiency in the extraction of cell membrane glycoproteins. The anti-SAA mAb-functionalized MNPs maintained active Ab orientation and preserved antigen recognition capability in biological samples. Thus, the BA-Diaz-based strategy holds promise for the immobilization of glycoproteins, such as antibodies, with the original protein binding activity maintained, which can provide better enrichment for the sensitive detection of target proteins.

Clinical associations of mucin 1 in human lung cancer and precancerous lesions.

Mucin 1 (MUC1) is a cell membrane glycoprotein overexpressed in non-small cell lung cancer (NSCLC) and has been implicated in carcinogenesis of premalignant lung lesions. Thus, MUC1 has been a target of interest for vaccine strategies for lung cancer treatment and prevention. Here, we assessed MUC1 expression by immunohistochemistry using tumor samples from patients with biopsy-proven NSCLC. Levels of expression in areas of dysplasia, metaplasia, adenocarcinoma in situ, and carcinoma within the same tissue sample were characterized independently on a scale of 0–3 for paired comparison. We also assessed clinical data for correlations with MUC1 expression. Our analysis included 16 samples from patients with squamous lesions and 19 from patients with adenocarcinoma lesions. Among squamous lesions, MUC1 expression score was significantly increased in dysplastic compared with metaplastic areas (mean difference = 0.83, 95% confidence interval [CI], 0.21-infinity; P = 0.021). MUC1 expression was also increased among areas of squamous cell carcinoma versus dysplastic areas (mean difference = 0.44, 95% CI, −0.006-infinity; P = 0.052). In the adenocarcinoma lesions, MUC1 expression was increased in adenocarcinoma versus adenocarcinoma in situ, although not significantly (mean difference = 0.20, 95% CI, −0.055-infinity; P = 0.094). The increase in MUC1 expression with the progression of premalignant lung lesions to invasive carcinoma in patients with NSCLC supports MUC1 as a possible therapeutic target for the prevention and treatment of lung cancer.

An investigation of NIS expression in gastric tissue of obese individuals

Obesity is seen as one of the top ten (10) illness's listed by World Health Organization (WHO). It is a global problem that can affect people of all ages. Obesity is identified one of the most important factors leading to diabetes, heart disease and hypertension. Individuals with a Body Mass Index (BMI) above 40 kg/m2 are defined with morbid obesity. Sodium Iodide Symporter (NIS) gene is a plasma membrane glycoprotein that mediates iodide uptake in thyroid glands, stomach, salivary glands, lactating mammary glands and intestine. NIS gene transports iodide from the blood to the gastric epithelial cells. NIS gene expression and regulatory role of NIS gene in gastrointestinal tract, hasn't been studied yet in the individuals with obesity (i.e., BMI &gt;40 kg/m2). In this study, gastric tissues were obtained by laparoscopic sleeve gastrectomy from 33 individuals diagnosed with obesity. Control group consisted of gastric tissue of 21 subjects with normal BMI obtained by endoscopy. RNA isolation, cDNA synthesis and qRT-PCR analyses were performed on the samples to determine NIS gene expression. Expression levels of NIS gene were compared between obese and control individuals, although an increase was observed in obese patients this difference was not found to be statistically important (p&gt;0.05).

Real-time quartz crystal microbalance cytosensor based on a signal recovery strategy for in-situ and continuous monitoring of multiple cell membrane glycoproteins

A real-time quartz crystal microbalance (QCM) cytosensor based on a signal recovery strategy was first developed for in-situ and continuous monitoring of multiple cell membrane glycoproteins. In this work, gold nanoparticles (AuNPs) were linked with ligands to fabricate ligand-functionalized mass nanoprobes with signal amplification for increasing monitoring sensitivity. The mass nanoprobes bound to cell surface could be eluted with glycine-hydrochloric acid buffer, which led to a quick recovery of resonance frequency. Using the strategy, folate receptors (FR), CD44 molecule and epidermal growth factor receptor (EGFR) on cell membrane as the models were monitored continuously. The quantification result of MDA-MB-231 cells showed a range of linearity of 3.0 × 104 to 1.0 × 106 cells and a detection limit of 5.0 × 103 cells. Furthermore, the multianalyte cytosensor exhibited three sensitive and recoverable frequency shifts during continuous monitoring for in-situ and continuous evaluation of the expression levels of FR, CD44 and EGFR on cell membrane, which exhibited that the average numbers of molecules of FR, CD44 and EGFR per MDA-MB-231 cell were 0.5 × 106, 0.2 × 106 and 1.4 × 105 with the relative standard deviation of 4.8%, 4.5% and 5.1%, respectively. Compared with monolithic multichannel QCM, the multianalyte cytosensor based on a single microbalance could not only exclude acoustic interference but also reduce instrumental cost. This work provided a simple and efficient QCM cytosensor for in-situ and continuous monitoring of multiple cell membrane glycoproteins that offered a new avenue for early diagnosis of cancer.

Glycosylation as a Main Regulator of Growth and Death Factor Receptors Signaling.

Glycosylation is a very frequent and functionally important post-translational protein modification that undergoes profound changes in cancer. Growth and death factor receptors and plasma membrane glycoproteins, which upon activation by extracellular ligands trigger a signal transduction cascade, are targets of several molecular anti-cancer drugs. In this review, we provide a thorough picture of the mechanisms bywhich glycosylation affects the activity of growth and death factor receptors in normal and pathological conditions. Glycosylation affects receptor activity through three non-mutually exclusive basic mechanisms: (1) by directly regulating intracellular transport, ligand binding, oligomerization and signaling of receptors; (2) through the binding of receptor carbohydrate structures to galectins, forming a lattice thatregulates receptor turnover on the plasma membrane; and (3) by receptor interaction with gangliosides inside membrane microdomains. Some carbohydrate chains, for example core fucose and β1,6-branching, exert a stimulatory effect on all receptors, while other structures exert opposite effects on different receptors or in different cellular contexts. In light of the crucial role played by glycosylation in the regulation of receptor activity, the development of next-generation drugs targeting glyco-epitopes of growth factor receptors should be considered a therapeutically interesting goal.

Isolation and purification of glycosylphosphatidylinositols (GPIs) in the schizont stage of Theileria annulata and determination of antibody response to GPI anchors in vaccinated and infected animals

BackgroundTropical theileriosis is widely distributed from North Africa to East Asia. It is a tick-borne disease caused by Theileria annulata, an obligate two-host intracellular protozoan parasite of cattle. Theileria annulata use leukocytes and red blood cells for completion of the life-cycle in mammalian hosts. The stage of Theileria annulata in monocytes and B lymphocytes of cattle is an important step in pathogenicity and diagnosis of the disease. Glycosylphosphatidylinositols (GPIs) are a distinct class of glycolipid structures found in eukaryotic cells and are implicated in several biological functions. GPIs are particularly abundant in protozoan parasites, where they are found as free glycolipids or attached to proteins in the plasma membrane.ResultsIn this study we first isolated and purified schizonts of Theileria annulata from infected leukocytes in Theileria annulata vaccine cell line (S15) by aerolysin-percoll technique. Then, the free GPIs of schizont stage and isolated GPI from cell membrane glycoproteins were purified by high performance liquid chromatography (HPLC) and confirmed by gas chromatography-mass spectrometry (GC-MS). Furthermore, enzyme linked immunosorbent assay (ELISA) on the serum samples obtained from naturally infected, as well as Theileria annulata-vaccinated animals, confirmed a significant (P < 0.01) high level of anti-GPI antibody in their serum.ConclusionsThe results presented in this study show, to our knowledge for the first time, the isolation of GPI from the schizont stage of Theileria annulata and demonstrate the presence of anti-GPI antibody in the serum of naturally infected as well as vaccinated animals. This finding is likely to be valuable in studies aimed at the evaluation of chemically structures of GPIs in the schizont stage of Theileria annulata and also for pathogenicity and immunogenicity studies with the aim to develop GPI-based therapies or vaccines.

Inside Front Cover: Identification of Plasma Membrane Glycoproteins Specific to Human Glioblastoma Multiforme Cells Using Lectin Arrays and LC‐MS/MS

Inside Front Cover: Identification of Plasma Membrane Glycoproteins Specific to Human Glioblastoma Multiforme Cells Using Lectin Arrays and LC‐MS/MS

Identification of Plasma Membrane Glycoproteins Specific to Human Glioblastoma Multiforme Cells Using Lectin Arrays and LC-MS/MS.

Glioblastoma, also known as glioblastoma multiforme (GBM), is the most malignant type of brain cancer and has poor prognosis with a median survival of less than one year. While the structural changes of tumor cell surface carbohydrates are known to be associated with invasive behavior of tumor cells, the cell surface glycoproteins to differentiate the low- and high-grade glioma cells can be potential diagnostic markers and therapeutic targets for GBMs. In the present study, lectin arrays consisting of eight lectins were employed to explore cell surface carbohydrate expression patterns on low-grade oligodendroglioma cells (Hs683) and GBM cells (T98G). Griffonia simplicifolia I (GS I) was found to selectively bind to T98G cells and not to Hs683 cells. For identification of the glioblastoma-specific cell surface markers, the glycoproteins from each cell type were captured by a GS I lectin column and analyzed by LC-MS/MS. The identified proteins from the two cell types were quantified using label-free quantitative analysis based on spectral counting. Of cell surface glycoproteins showing significant increases in T98G cells, five proteins were selected for verification of both protein and glycosylation level changes using Western blot and GS I lectin-based immunosorbent assay.

Expression of Glut-1 in Malignant Melanoma and Melanocytic Nevi: an Immunohistochemical Study of 400 Cases.

The glucose transporter-1 (Glut-1) is a cell membrane glycoprotein involved in glucose uptake. An increased expression of Glut-1 is an important cell adaptation mechanism against hypoxia. An upregulation of Glut-1 can be found in several types of malignant tumors, which are able to reprogram their metabolism from oxidative phosphorylation to aerobic glycolysis (Warburg effect). However, the data regarding melanocytic lesions is equivocal. We performed comprehensive immunohistochemical analysis of the Glut-1 expression in 225 malignant melanomas (MM) and 175 benign nevi. Only the membranous expression of Glut-1 was regarded as positive. The expression of Glut-1 (the cut-off for positivity was determined as H-score 15) was found in 69/225 malignant melanomas. The number of positive cases and the H-score of Glut-1 increased where there was a higher Breslow thickness (p < 0.00001) when comparing pT1- pT4 MM groups. All benign nevi were classified as negative. In conclusion, the membranous expression of Glut-1 is a common feature of a malignant melanoma but this type of expression is very rare in benign melanocytic nevi. Our results suggest that the membranous expression of Glut-1 can be used as a surrogate marker in the assessing of the biological nature of benign and malignant melanocytic lesions. However, despite its high specificity, the sensitivity of this marker is relatively low. Moreover, due to the fact that the increased expression of Glut-1 correlates with a shorter survival period (10-year disease free survival, recurrence free survival and metastasis free survival and MFS), it can be used as a prognostically adverse factor.

A Comprehensive Review of Our Current Understanding of Red Blood Cell (RBC) Glycoproteins.

Human red blood cells (RBC), which are the cells most commonly used in the study of biological membranes, have some glycoproteins in their cell membrane. These membrane proteins are band 3 and glycophorins A–D, and some substoichiometric glycoproteins (e.g., CD44, CD47, Lu, Kell, Duffy). The oligosaccharide that band 3 contains has one N-linked oligosaccharide, and glycophorins possess mostly O-linked oligosaccharides. The end of the O-linked oligosaccharide is linked to sialic acid. In humans, this sialic acid is N-acetylneuraminic acid (NeuAc). Another sialic acid, N-glycolylneuraminic acid (NeuGc) is present in red blood cells of non-human origin. While the biological function of band 3 is well known as an anion exchanger, it has been suggested that the oligosaccharide of band 3 does not affect the anion transport function. Although band 3 has been studied in detail, the physiological functions of glycophorins remain unclear. This review mainly describes the sialo-oligosaccharide structures of band 3 and glycophorins, followed by a discussion of the physiological functions that have been reported in the literature to date. Moreover, other glycoproteins in red blood cell membranes of non-human origin are described, and the physiological function of glycophorin in carp red blood cell membranes is discussed with respect to its bacteriostatic activity.

Galectin-3 interacts with the cell-surface glycoprotein CD146 (MCAM, MUC18) and induces secretion of metastasis-promoting cytokines from vascular endothelial cells

The galactoside-binding protein galectin-3 is increasingly recognized as an important player in cancer development, progression, and metastasis via its interactions with various galactoside-terminated glycans. We have shown previously that circulating galectin-3, which is increased up to 30-fold in cancer patients, promotes blood-borne metastasis in an animal cancer model. This effect is partly attributable to the interaction of galectin-3 with unknown receptor(s) on vascular endothelial cells and causes endothelial secretion of several metastasis-promoting cytokines. Here we sought to identify the galectin-3-binding molecule(s) on the endothelial cell surface responsible for the galectin-3-mediated cytokine secretion. Using two different galectin-3 affinity purification processes, we extracted four cell membrane glycoproteins, CD146/melanoma cell adhesion molecule (MCAM)/MUC18, CD31/platelet endothelial cell adhesion molecule-1 (PECAM-1), CD144/VE-cadherin, and CD106/Endoglin, from vascular endothelial cells. CD146 was the major galectin-3-binding ligand and strongly co-localized with galectin-3 on endothelial cell surfaces treated with exogenous galectin-3. Moreover, galectin-3 bound to N-linked glycans on CD146 and induced CD146 dimerization and subsequent activation of AKT signaling. siRNA-mediated suppression of CD146 expression completely abolished the galectin-3-induced secretion of IL-6 and G-CSF cytokines from the endothelial cells. Thus, CD146/MCAM is the functional galectin-3-binding ligand on endothelial cell surfaces responsible for galectin-3-induced secretion of metastasis-promoting cytokines. We conclude that CD146/MCAM interactions with circulating galectin-3 may have an important influence on cancer progression and metastasis.

Critical residues and motifs for homodimerization of the first transmembrane domain of the plasma membrane glycoprotein CD36

The plasma transmembrane (TM) glycoprotein CD36 is critically involved in many essential signaling processes, especially the binding/uptake of long-chain fatty acids and oxidized low-density lipoproteins. The association of CD36 potentially activates cytosolic protein tyrosine kinases that are thought to associate with the C-terminal cytoplasmic tail of CD36. To understand the mechanisms by which CD36 mediates ligand binding and signal transduction, we have characterized the homo-oligomeric interaction of CD36 TM domains in membrane environments and with molecular dynamics (MD) simulations. Analysis of pyrene- and coumarin-labeled TM1 peptides in SDS by FRET confirmed the homodimerization of the CD36 TM1 peptide. Homodimerization assays of CD36 TM domains with the TOXCAT technique showed that its first TM (TM1) domain, but not the second TM (TM2) domain, could homodimerize in a cell membrane. Small-residue, site-specific mutation scanning revealed that the CD36 TM1 dimerization is mediated by the conserved small residues Gly12, Gly16, Ala20, and Gly23 Furthermore, molecular dynamics (MD) simulation studies demonstrated that CD36 TM1 exhibited a switching dimerization with two right-handed packing modes driven by the 12GXXXGXXXA20 and 20AXXG23 motifs, and the mutational effect of G16I and G23I revealed these representative conformations of CD36 TM1. This packing switch pattern of CD36 TM1 homodimer was further examined and confirmed by FRET analysis of monobromobimane (mBBr)-labeled CD36 TM1 peptides. Overall, this work provides a structural basis for understanding the role of TM association in regulating signal transduction via CD36.

Reverse of the resistance to paclitaxel of the heparin binding-epidermal growth factor-like growth factor inhibitor in ovarian cancer

Objective: To investigate the effect and mechanism of CRM197, the heparin binding-epidermal growth factor-like growth factor (HB-EGF) inhibitor, on the reverse of the resistance of ovarian cancer to paclitaxel. Methods: (1)The effect of CRM197 on the 50% inhibitory concentrations (IC(50)) of human ovarian carcinoma cell line A2780 and paclitaxel-resistant ovarian carcinoma cell line A2780/Taxol was tested by methyl thiazolyl tetrazolium (MTT) assay. Western blot was used to detect the effect of CRM197 on the expression of HB-EGF, epidermal growth factor receptor (EGFR) and plasma membrane glycoprotein (P-gp) protein in A2780 and A2780/Taxol cells. Real-time PCR was used to examine the MDR1 mRNA expression in these cells. (2) A2780/Taxol cells were divided into 4 groups, including the cells transfected with empty vector and saline treatment (empty vector group), MDR1 small interference RNA (siRNA) vector and saline treatment (MDR1 siRNA group), empty vector and CRM197 treatment (empty vector+CRM197 group) and MDR1 siRNA vector and CRM197 treatment (MDR1 siRNA+CRM197 group), respectively. Flow cytometry was used to detecte the effect of intracellular rhodomine 123 (Rh123) accumulation, and caspase-3 activity assay was used to test the effect of apoptosis in four groups of A2780/Taxol cells. (3) In experiments in vivo, A2780/Taxol cells were inoculated to nude mouse subcutaneously to determine the EGFR and P-gp protein expression following CRM197 treatment by immunohistochemistry. Results: (1) In vitro, MTT examination showed that the IC(50) of A2780/Taxol cells to paclitaxel in A2780/Taxol+CRM197 group [(6.4±0.3) μmol/L] was significantly lower than the IC(50) in A2780/Taxol group [ (34.1±0.5) μmol/L, P<0.01], and the reveral fold of CRM197 was 5.3. The expression level of HB-EGF protein in A2780/Taxol+CRM197 group (1.44±0.29) was significantly lower than HB-EGF protein in A2780/Taxol group (2.72±0.32), respectively (P<0.05). The expression level of EGFR protein (0.71±0.25) and P-gp protein (0.82±0.19) in A2780/Taxol+CRM197 group was significantly lower than EGFR protein (1.87±0.31) and P-gp protein (1.84±0.27) of A2780/Taxol group (P<0.05). Compared with A2780/Taxol group (1.78±0.27) , MDR1 mRNA was significantly down-regulated in A2780/Taxol+CRM197 group (0.79±0.13, P<0.05). (2) The fluorescence intensity of Rh123 of the A2780/Taxol cells in empty vector group, MDR1 siRNA group,empty vector+CRM197 group, MDR1 siRNA+CRM197 group was 33.4±1.6, 56.3±3.3, 43.5±3.1,100.4±7.4, and the pNA of the A2780/Taxol cells was (11.4±1.2) , (52.8±0.9) , (71.2±3.6) , (82.7±3.8) μmol/L. The expression levels in MDR1 siRNA+CRM197 group were both higher than the expression levels in empty vector+CRM197 group, and the expression levels in empty vector+CRM197 group, MDR1 siRNA group were both higher than the expression levels in empty vector group (P<0.05). (3) In vivo, the expression scores of EGFR protein in A2780/Taxol+CRM197 tumors (4.4±1.4) were lower than that in A2780/Taxol tumors (10.2±3.1, P<0.05). The expression scores of P-gp protein in A2780/Taxol+CRM197 tumors (3.8±1.1) were lower than that in A2780/Taxol tumors (8.8±2.7, P<0.05). Conclusion: CRM197 reverses the resistance of ovarian cancer to paclitaxel by increasing caspase-3 activity to advance apoptosis via EGFR/MDR1/P-gp pathway.