The Integrin α2 Dimorphism E534K Modulates Platelet Binding to Decorin but Not Collagen I,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3256-3256
Author(s):  
Thomas J Kunicki ◽  
Daniel Diaz ◽  
Shirley A Williams ◽  
Richard W. Farndale ◽  
Diane J. Nugent
Keyword(s):  
Cell Adhesion ◽  
Amino Acid ◽  
Binding Site ◽  
Cancer Biology ◽  
Conflicts Of Interest ◽  
Normal Subjects ◽  
Minor Allele ◽  
Collagen I ◽  
Functional Difference ◽  
Major Allele

Abstract Abstract 3256 Background. Integrin a2b1-mediated adhesion to collagens supports cellular attachment, while decorin binding by a2b1 often attenuates adhesion. Collagen I binds to the a2 I-domain via the triple-helical sequence GFOGER, but the decorin binding site is not within the a2 I-domain and has not yet been identified. A single nucleotide polymorphism in the a2 gene ITGA2 (rs1801106) (G1600A) resulting in the amino acid substitution glutamate-534 to lysine-534 (E534K) is the basis for one of the most important human platelet alloantigen (HPA) systems, HPA-5, yet HPA-5 alleles do not influence the binding of a2b1 to collagen I, and the effect of HPA-5 on platelet function, if any, has not been determined. We sought to determine whether the minor allele HPA-5b (534K) might influence the a2b1-mediated adhesion of platelets to a physiologically relevant ligand other than collagen I. One such alternative ligand is decorin, an extracellular matrix small leucine (Leu)-rich proteoglycan (SLRP). Methods/Results. Two groups of normal subjects were compared. The first group (GG) consisted of ten donors homozygous for the major allele rs1801106G. The second group (GA+AA) included one donor homozygous for the minor allele rs1801106A and nine donors heterozygous for these alleles. Aside from this, there were no significant differences between the two groups with respect to platelet count, mean platelet volume, surface expression of four selected platelet receptors, GPIba, GPVI, aIIbb3 or a2b1, or the allelic distribution of five receptor genes, ITGA2B rs5911, ITGB3 rs5918, GP1BA rs6065, GP6 rs1613662 and P2RY1 rs1065776. In direct platelet adhesion assays, we determined that platelets from GG donors bound more strongly to decorin than those from GA+AA donors (p < 0.01), while platelets from either group bound equally well to collagen I (p = 0.73). Using platelets from donors homozygous for the major allele rs1801106G, adhesion to decorin was significantly inhibited by human alloantibodies specific for HPA-5a but not by GFOGER or an a2-specific monoclonal antibody 6F1 known to inhibit cell adhesion to collagen I. Conversely, GFOGER and 6F1 inhibited adhesion to collagen I but not decorin. Conclusions. The simplest explanation of our findings is that 534E, located in the a2 b-propeller domain, is necessary for maximal binding of a2b1 to decorin but not collagen I. These results suggest that 534E contributes to the decorin binding site and that this amino acid represents a potential target for interventions that can modify cell adhesion to decorin and perhaps other proteoglycans. This also represents the first instance of a functional difference attributable to the HPA-5 alleles. These results expand our understanding of the decorin and collagen I interactions described in murine and human studies of cell adhesion and cancer biology, where decorin and collagen I often have opposite effects that are both mediated by a2b1. Decorin knockout (Dcn(−/−)) murine embryonic fibroblasts exhibit greater adhesion to collagen and greater migration on collagen substrates, while decorin attenuates the aggressiveness and metastasis of tumor cells with diverse histologic backgrounds. Further studies of the relationship between the collagen I and decorin binding sites on integrin a2 are warranted, particularly regarding its influence on thrombosis and hemostasis. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Ankyrin-binding proteins related to nervous system cell adhesion molecules: candidates to provide transmembrane and intercellular connections in adult brain.

1993 ◽  
Vol 121 (1) ◽  
pp. 121-133 ◽  
Author(s):  
J Q Davis ◽  
T McLaughlin ◽  
V Bennett
Keyword(s):  
Nervous System ◽  
Cell Adhesion ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Binding Site ◽  
Adhesion Molecules ◽  
Cell Adhesion Molecules ◽  
Binding Proteins ◽  
Cytoplasmic Domain ◽  
System Cell

A major class of ankyrin-binding glycoproteins have been identified in adult rat brain of 186, 155, and 140 kD that are alternatively spliced products of the same pre-mRNA. Characterization of cDNAs demonstrated that ankyrin-binding glycoproteins (ABGPs) share 72% amino acid sequence identity with chicken neurofascin, a membrane-spanning neural cell adhesion molecule in the Ig super-family expressed in embryonic brain. ABGP polypeptides have the following features consistent with a role as ankyrin-binding proteins in vitro and in vivo: (a) ABGPs and ankyrin associate as pure proteins in a 1:1 molar stoichiometry; (b) the ankyrin-binding site is located in the COOH-terminal 21 kD of ABGP186 which contains the predicted cytoplasmic domain; (c) ABGP186 is expressed at approximately the same levels as ankyrin (15 pmoles/milligram of membrane protein); and (d) ABGP polypeptides are co-expressed with the adult form of ankyrinB late in postnatal development and are colocalized with ankyrinB by immunofluorescence. Similarity in amino acid sequence and conservation of sites of alternative splicing indicate that genes encoding ABGPs and neurofascin share a common ancestor. However, the major differences in developmental expression reported for neurofascin in embryos versus the late postnatal expression of ABGPs suggest that ABGPs and neurofascin represent products of gene duplication events that have subsequently evolved in parallel with distinct roles. The predicted cytoplasmic domains of rat ABGPs and chicken neurofascin are nearly identical to each other and closely related to a group of nervous system cell adhesion molecules with variable extracellular domains, which includes L1, Nr-CAM, and Ng-CAM of vertebrates, and neuroglian of Drosophila. The ankyrin-binding site of rat ABGPs is localized to the C-terminal 200 residues which encompass the cytoplasmic domain, suggesting the hypothesis that ability to associate with ankyrin may be a shared feature of neurofascin and related nervous system cell adhesion molecules.

European Chromosome 6 Haplotypes Significantly Augment Fetal Hemoglobin Levels in Brazilian Sickle Cell Anemia Patients: Influence of Four HBS1L-MYB Intergenic Region SNPs

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1002-1002
Author(s):  
Flávia Costa Leonardo ◽  
Stephan Menzel ◽  
Ana Flavia Brugnerotto ◽  
Kleber Yotsumoto Fertrin ◽  
Marcos André Cavalcanti Bezerra ◽  
...  
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Intergenic Region ◽  
Conflicts Of Interest ◽  
Strong Association ◽  
Fetal Hemoglobin ◽  
Brazilian Population ◽  
Minor Allele ◽  
Chromosome 6 ◽  
Major Allele

Abstract Abstract 1002 Fetal hemoglobin (HbF) levels significantly modulate the severity of the 2 major β-hemoglobin disorders - sickle cell anemia (SCA) and β-thalassemia. Three major quantitative trait loci (QTLs; Xmn1-HBG2, the HBS1L-MYB [HMIP] intergenic region on chromosome 6q23, and BCL11A on chromosome 2p16) account for 20–50% of the common variation in HbF levels in SCA and β - thalassemia patients, and in healthy adults (Thein et al., Hum Mol Genet (2009) 18:R216). Lettre et al. (PNAS (2008) 105:11869) confirmed the influence of SNPs at the BCL11A and HBB loci in an African American cohort and a Brazilian cohort of SCA patients; as well as a significant influence of the HMIP region SNPs (rs7776054, rs9389268 and rs4895441) on HbF expression in the Brazilian SCA cohort. A strong association between HMIP polymorphisms that have a high frequency in the European population and modulation of F cell numbers has been reported (Creary et al., PLoS One (2009) 4:e4218). Given the unusually high admixture of the Brazilian population, the current study aimed to look at the influence of such HMIP markers on HbF production in SCA patients from this population (two regions, in the Northeast and Southeast of Brazil). We studied the influence and frequencies of the HMIP allele marker rs9376090 (that specifically tracks European chromosomes), as well as the rs9399137 marker (that has a much higher frequency in European descendents than in African descendents), as well as two HMIP markers (rs9389269 and rs9402686) that are also common in African descendents. Patients (220 HbSS, aged 12–68 years) were recruited at the Hematology Center, UNICAMP and at Fundação Hemope. The study was approved by the local Ethics Committees and informed consent was provided by all participants. Patients presenting the XmnI Gγ polymorphism (N = 2) were identified and excluded from further analysis, as this polymorphism has a known influence on HbF. The HMIP markers were genotyped by Taqman assays. Percentage HbF levels were determined by HPLC, using the Variant™ Bio-Rad kit, and were log transformed to normalize distribution for regression analyses. For those patients on hydroxyurea (HU) therapy, pre-HU HbF levels were used for analyses. Tests for associations between SNPs and HbF levels were conducted using linear regression models (SPSS v.15), including age and sex as covariates. High minor allele frequencies (MAF) for all four HMIP markers were observed in the population of patients studied (MAF; 0.09, 0.10, 0.12 and 0.12 for the rs9376090, rs9399137, rs9389269 and rs9402686 markers, respectively). For all four SNPs studied, higher levels of HbF were observed for the SCA individuals that were homozygotes for the minor allele, with strikingly higher levels of HbF presented by those individuals that were homozygotes for the rs9376090 and rs9399137 polymorphisms (see Table). The clinical courses of these patients were consistent with the higher levels of HbF observed (data not shown). Significantly higher HbF was also found in heterozygotes for the HMIP SNPs, compared to the major allele homozygotes. The variance in HbF levels due to rs9376090 was 7.1% (β= 0.270; p = 6.36 10−5), due to rs9399137 was 7.1% (β= 0.270; p = 9.59 10−5), due to rs9389269 was 8.3% (β= 0.287; p = 2.31 x10−5) and to rs9402686 was 8.3% (β=0.291; p = 2.18 x10−5). Our results confirm the HBS1L-MYB intergenic region as a key determinant of HbF levels in Brazilian SCA patients. The admixture of the Brazilian population has apparently led to a much higher incidence of European haplotypes at chromosome 6 in this population studied, when compared to the British and Tanzanian SCA populations. Importantly, the presence of these SNPs at the HMIP appears to have a very significant effect on HbF levels in the Brazilian SCA population, with probable clinical benefits. Table. HbF Levels in SCA Individuals, according to HMIP genotypes SNP (HBS1L-MYB locus) % HbF (Median ± S.D.) TT TC CC rs9376090 6.35 ± 4.24 8.45 ± 3.63 17.25 ± 1.63 N = 182 N = 32 N=2 p<0.01 p<0.05 rs9399137 6.47 ± 4.38 8.68 ± 3.63 17.25 ± 1.63 N = 167 N=37 N = 2 p<0.05 p< 0.05 rs9389269 6.40 ±4.29 8.59 ± 3.70 12.68 ± 2.45 N = 162 N = 42 N = 5 p< 0.01 p< 0.05 rs9402686 GG AG AA 6.26 ± 4.28 8.36 ± 4.67 12.68 ± 2.45 N =166 N = 41 N = 5 p<0.01 p<0.05 Significant differences for heterozygotes and homozygotes for the minor allele, compared to the homozygote major allele group are indicated by P values. Kruskal-Wallis test, Dunn's multiple comparison post test. Disclosures: No relevant conflicts of interest to declare.

scholarly journals A synthetic peptide derived from the carboxy terminus of the laminin A chain represents a binding site for the alpha 3 beta 1 integrin

1992 ◽  
Vol 117 (2) ◽  
pp. 449-459 ◽  
Author(s):  
KR Gehlsen ◽  
P Sriramarao ◽  
LT Furcht ◽  
AP Skubitz
Keyword(s):  
Cell Adhesion ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Binding Site ◽  
Synthetic Peptide ◽  
Beta 1 Integrin ◽  
Carboxy Terminal Region ◽  
A Chain ◽  
Coated Surfaces ◽  
Carboxy Terminal

The purpose of this study was to identify the binding site(s) within laminin for the alpha 3 beta 1 integrin receptor. It has been previously shown, using proteolytic fragments and anti-laminin antibodies, that the region in laminin for alpha 3 beta 1 integrin binding is localized to the carboxy-terminal region at the end of the long arm (Gehlsen, K. R., E. Engvall, K. Dickerson, W. S. Argraves, and E. Ruoslahti. 1989. J. Biol. Chem. 264:19034-19038; Tomaselli, K. J., D. E. Hall, L. T. Reichardt, L. A. Flier, K. R. Gehlsen, D. C. Turner, and S. Carbonetto. 1990. Neuron. 5:651-662). Using synthetic peptides, we have identified an amino acid sequence within the carboxy-terminal region of the laminin A chain that is recognized by the alpha 3 beta 1 integrin. The amino acid sequence represented by the synthetic peptide GD-6 (KQNCLSSRASFRGCVRNLRLSR residues numbered 3011 to 3032) of the globular domain of the murine A chain supports cell attachment and inhibits cell adhesion to laminin-coated surfaces. By affinity chromatography, peptide GD-6-Sepharose specifically bound solubilized alpha 3 beta 1 from extracts of surface-iodinated cells in a cation-dependent manner, while it did not bind other integrins. In addition, exogenous peptide GD-6 specifically eluted bound alpha 3 beta 1 from laminin-Sepharose columns but did not elute the alpha 3 beta 1 integrin from a fibronectin-Sepharose column. Using integrin subunit-specific monoclonal antibodies, only those antibodies against the alpha 3 and beta 1 subunits inhibited cell adhesion to peptide GD-6-coated surfaces. Finally, a polyclonal antibody made against peptide GD-6 reacted specifically with both murine and human laminin and significantly inhibited cell adhesion to laminin-coated surfaces but not those coated with other matrix proteins. These results identify the laminin A chain amino acid sequence of peptide GD-6 as representing a binding site in laminin for the alpha 3 beta 1 integrin.

The Neutrophil Alloantigen HNA-3a (5b) Is Encoded by an Amino Acid Substitution in Choline Transporter-Like Protein 2 (CTL2)

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. LBA-4-LBA-4
Author(s):  
Brian R Curtis ◽  
Cox J Nancy ◽  
Mia J Sullivan ◽  
Anuar Konkashbaev ◽  
Krista Bowens ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Blood Donors ◽  
Conflicts Of Interest ◽  
Normal Subjects ◽  
Acute Injury ◽  
Spectrometric Analysis ◽  
Gene Frequencies ◽  
Choline Transporter ◽  
Specific Antibodies

Abstract Abstract LBA-4 The HNA-3a/b (5b/a) leukocyte alloantigens were identified in 1964 by van Leeuwen et al. as a biallelic system with gene frequencies of 0.82 (HNA-3a) and 0.18 (HNA-3b), respectively. Despite the passage of more than 40 years, the presumptive protein carrier for HNA-3a/b and the molecular composition of the antigens themselves is unknown. The importance of defining the HNA-3a/b antigens more fully has been heightened by the recognition that HNA-3a-specific antibodies are especially prone to cause severe, often fatal, transfusion-related lung acute injury (TRALI), now the single most important cause of transfusion-related mortality. About 4-5% of the general population is HNA-3a-negative and is at risk to produce HNA-3a-specific antibodies. We performed genome-wide single nucleotide polymorphism (SNP) scanning of DNA from 8 HNA-3a-negative (HNA-3b/b) and 107 unrelated normal individuals and found that each of the HNA-3a-negatives, but only 5 of the normal subjects was homozygous (AA) for a SNP (G>A) located at nt542 of the SLC44A2 gene encoding the choline transporter-like protein CTL2 (p<0.000001 corrected for the number of SNPs surveyed) (Table 1).Table 1.Genotypes of unrelated HNA-3a-negative and normal subjects at SNPrs2288904 (G>A542) in the gene SLC44A2 encoding CTL2.HNA-3-a negative subjects (n = 8)Normal subjects (N = 107)GGGAAAGGGAAA008*64385*p = 2.4 × 10−12 This SNP (rs2288904) is the only one known in SLC44A2 that correlates with the HNA-3a-negative phenotype and predicts an extracellular amino acid substitution (R>Q154) in the mature protein. Gene frequencies of the high and low frequency alleles of SNP rs2288904 are 0.82 and 0.18, respectively, identical to the gene frequencies of HNA-3a and HNA-3b determined by serologic typing. Although HNA-3a is widely considered to be a neutrophil antigen, we found that lymphocytes carry slightly more HNA-3a than neutrophils, and that persons heterozygous for HNA-3a have 50% as much antigen as homozygotes, allowing heterozygotes to be identified by flow cytometry. To validate the SNP analyses, we directly sequenced DNA encoding CTL2 from 4 HNA-3a/a, 4 HNA-3a/b and 8 HNA-3b/b subjects and found that, without exception, nt542G and nt542A correlated with the phenotypes HNA-3a and HNA-3b (determined serologically), respectively. To obtain direct evidence that HNA-3a is carried on CTL2, we sensitized leukocytes with anti-HNA-3a, immunoprecipitated antibody-bound proteins, performed SDS electrophoresis and subjected candidate bands to mass spectrometric analysis. In three independent assays, peptides derived from CTL2 spanning the entire length of the protein were identified (p<0.0001). We conclude that the HPA-3a antigen results from substitution of G for A at nt542 of the SLC44A2 gene, leading to insertion of R for Q at position 154 in the first extracellular loop of CTL2. CTL2 is predicted to have ten transmembrane domains, five extracellular loops, several N-linked oligosaccharides and intracytoplasmic tails at both C- and N-terminae; this complexity probably explains the failure of previous attempts to identify it as the carrier for the HNA-3a/b antigens by immunochemical methods. The function of CTL2 is unknown. However, cross-linking of the antigen by anti-HNA-3a in neutrophils triggers an explosive activation of primed cells, indicating that CTL2 is functional in this cell type and providing a possible explanation for severe TRALI reactions seen in patients transfused with CTL2-specific antibody. Recognition of the molecular basis for the HNA-3a/b antigen system will enable large scale, low cost screening of blood donors to identify the HNA-3a-negative subpopulation that may have HNA-3a-specific antibodies capable of causing TRALI and should facilitate the production of target molecules carrying these antigens that can be used to screen for such antibodies in blood donors and patients. Disclosures: No relevant conflicts of interest to declare.

Mean Platelet Volume and Integrin Alleles Strongly Correlate with Increased Levels of Integrins αIIbβ3 and α2β1: Clinical Implications for Platelet Reactivity in Acute Coronary Syndome

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 32-32
Author(s):  
Thomas J Kunicki ◽  
Shirley A Williams ◽  
Diane J. Nugent ◽  
Mark J Yeager
Keyword(s):  
Mean Platelet Volume ◽  
Conflicts Of Interest ◽  
Platelet Reactivity ◽  
Inverse Correlation ◽  
Normal Subjects ◽  
Adverse Outcomes ◽  
Minor Allele ◽  
Inverse Association ◽  
Platelet Volume ◽  
Coronary Syndrome

Abstract Abstract 32 Background - Differences in the level of integrins expressed on the surface membranes of platelets can have a significant effect on platelet reactivity and adverse outcomes in a variety of thrombotic and hematologic dyscrasias. Among normal individuals, the basal level of platelet integrin aIIbb3 varies at least two-fold, while that of the integrin a2b1 exhibits a greater range of variation. The total number of integrin molecules and other receptors on platelets is influenced to a large extent by the total surface area of plasma membrane and consequently the mean platelet volume (MPV), which itself has a very strong genetic component. We sought to determine the relative contribution of mean platelet volume (MPV) and integrin gene alleles to expression levels of these integrins in patients with acute coronary syndrome (ACS) and normal subjects. Methods and Results - Monoclonal antibodies AP2 and 8C12 (or 12F1) were used in flow cytometry to measure platelet aIIbb3 and a2b1, respectively, in whole blood from 341 patients with ACS and 128 normal subjects. Comparisons were made with MPV, platelet count (PC) and in the normal subjects ITGA2 rs1126643 and ITGB3 rs5918 alleles. In both ACS patients and controls, there was a strong direct correlation between MPV and aIIbb3 level (p < 0.001). In control subjects, MPV and aIIbb3 level did not correlate with ITGB3 rs5918 alleles. For a2b1, MPV contributed modestly in either patients or controls, while ITGA2 rs1126643 alleles exerted the greatest effect. Moreover, we observed an inverse correlation between MPV and the rs1126643 minor allele. Conclusions - Our results indicate that MPV is the major effector of platelet membrane levels of aIIbb3, in both ACS patients and normal subjects, while ITGA2 rs1126643 contributes most strongly to a2b1 levels. Hyperactivity of larger platelets results from increased levels of key platelet receptors, notably integrin aIIbb3, in support of the contention that MPV is an accurate marker of risk for adverse outcome in ACS. This is consistent with published findings that MPV, the most common metric of platelet size, correlates very well with platelet reactivity, such that larger platelets have greater prothombotic potential, and elevated MPV is associated with increased platelet aggregation, thromboxane synthesis, b-thromboglobulin release, and expression of adhesion molecules. The most intriguing finding of our study is the inverse association of the ITGA2 rs1126643 minor allele T with MPV. The rs1126643 minor allele likely exerts this effect via the documented influence of a2b1 on megakaryocyte (MK) maturation. Disclosures: No relevant conflicts of interest to declare.

IGSF4: A Novel Candidate Gene for Venous Thrombosis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 405-405
Author(s):  
Edwin Bovill ◽  
Irene D Bezemer ◽  
Sandra J Hasstedt ◽  
Peter W Callas ◽  
Robert P. Hebbel ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Adhesion ◽  
Protein C ◽  
Fiber Formation ◽  
Minor Allele ◽  
Immunoglobulin Superfamily ◽  
Stress Fiber Formation ◽  
Increased Risk ◽  
The Family ◽  
Major Allele

Abstract Through a combination of genotyping and resequencing we have identified 3 SNPs (rs17564430, rs3802858 and rs6589488) in a venous thrombosis (VT) susceptibility gene encoding Immunoglobulin Superfamily 4 (IGSF4), that interacts with protein C (PC) deficiency (3363InsC) in a large thrombophilic kindred (n=516). The IGSF4 gene is located on chromosome 11q23. To verify the association with VT and to estimate the joint effect with PC deficiency, we genotyped the 3 SNPs in the 450 available kindred members, of whom 40 (32 PC deficient) had experienced VT. For each SNP we estimated the odds ratio (OR) and 95% confidence interval (CI95) for VT, adjusting for age and sex. Because earlier linkage analyses and SNP genotyping had suggested a dominant effect of the gene, we calculated the OR for carriers compared to non-carriers. Two of 3 SNPs in IGSF4 remained associated with VT. Carriers of the rs6589488 minor allele had a more than 10-fold increased risk of VT (OR 10.2, CI95 7.8–13.4), compared to those homozygous for the major allele. The effect was more pronounced in PC deficient family members (OR 17.0, CI95 13.5–21.4). PC deficient carriers of the rs3802858 minor allele had about 5-fold increased risk of VT (OR 4.7 CI95 2.2–10.0). We designed a replication study of these findings in the Leiden Thrombophilia Study (LETS) comprised of 471 VT patients and 471 control subjects. The 2 original and 11 additional SNPs were selected based on linkage disequilibrium (LD) in the locus surrounding the 2 SNPs associated with VT in the family. None of the SNPs was associated with VT across the whole LETS population. However, we observed a potential synergistic effect between some of these SNPs and the factor V Leiden (FVL) mutation, suggesting interaction with the PC system. For example, rs658948 major allele homozygotes who carry FVL have an 11–fold increased risk of VT (OR 11.2, CI95 5.1–24.3) compared to minor allele carriers who do not carry FVL. This is a 3-fold increase (CI95 0.9–9.9) over the VT risk associated with FVL alone. In LETS we took rs6589488 minor allele carriers as reference since the major allele was the higher risk allele. This is opposite of what we observed in the family. Apart from refuting associations, reverse associations in different populations might be true but caused by variation in LD patterns between the rs6589488 and other or true causal variants (Lin et al, Am. J. Hum. Genet.80:531–8, 2007). Potential interactions between IGSF4 and the PC system in VT seem likely based on their functions. Activated protein C (APC) has important anticoagulant, anti-inflammatory and cytoprotective effects. The APC cytoprotective effect is characterized by reduction in endothelial permeability through stabilization of the endothelial cytoskeleton. This effect is mediated by protease activated receptor-1 and the sphingosine 1 phosphate receptor, S1P1, activation by APC bound to the endothelial cell PC receptor (APC-EPCR). The endothelial barrier protective effect likely improves endothelial thromboresistance. For example, exposure of endothelial cells to thrombin leads to transcellular actin stress fiber formation and cellular contraction with the formation of paracellular gaps. These gaps potentially expose plasma to subcellular tissue factor. This effect can be reversed by APC-EPCR which attenuates stress fiber formation and augments the cortical actin ring. (Finigan et al. J Biol Chem.280:17286–93, 2005; Bae et al. Thromb Haemost.100:101–9, 2008). IGSF4 is an immunoglobulin superfamily cell adhesion molecule with a well described role in basolateral cell-cell adhesion of pulmonary epithelial cells. We have demonstrated that IGSF4 is expressed in endothelial cells and has somewhat diminished expression in endothelial cells cultured from PC deficient kindred members compared to controls. It is likely that IGSF4 supports basolateral endothelial cell-cell adhesion. We hypothesize that a variant form or decreased expression of IGSF4, interacting with PC deficiency, impairs APC mediated endothelial barrier protection in response to thrombogenic stimuli and thus increases the risk of VT in this thrombophilic kindred.

Schistosomal Sulfotransferase Interaction with Oxamniquine Involves Hybrid Mechanism of Induced-fit and Conformational Selection

2020 ◽  
Vol 16 (4) ◽  
pp. 451-459 ◽  
Author(s):  
Fortunatus C. Ezebuo ◽  
Ikemefuna C. Uzochukwu
Keyword(s):  
Molecular Dynamics ◽  
Amino Acid ◽  
Binding Energy ◽  
Binding Site ◽  
Conformational Dynamics ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Conformational Selection ◽  
Hybrid Mechanism ◽  
Dynamics Simulations

Background: Sulfotransferase family comprises key enzymes involved in drug metabolism. Oxamniquine is a pro-drug converted into its active form by schistosomal sulfotransferase. The conformational dynamics of side-chain amino acid residues at the binding site of schistosomal sulfotransferase towards activation of oxamniquine has not received attention. Objective: The study investigated the conformational dynamics of binding site residues in free and oxamniquine bound schistosomal sulfotransferase systems and their contribution to the mechanism of oxamniquine activation by schistosomal sulfotransferase using molecular dynamics simulations and binding energy calculations. Methods: Schistosomal sulfotransferase was obtained from Protein Data Bank and both the free and oxamniquine bound forms were subjected to molecular dynamics simulations using GROMACS-4.5.5 after modeling it’s missing amino acid residues with SWISS-MODEL. Amino acid residues at its binding site for oxamniquine was determined and used for Principal Component Analysis and calculations of side-chain dihedrals. In addition, binding energy of the oxamniquine bound system was calculated using g_MMPBSA. Results: The results showed that binding site amino acid residues in free and oxamniquine bound sulfotransferase sampled different conformational space involving several rotameric states. Importantly, Phe45, Ile145 and Leu241 generated newly induced conformations, whereas Phe41 exhibited shift in equilibrium of its conformational distribution. In addition, the result showed binding energy of -130.091 ± 8.800 KJ/mol and Phe45 contributed -9.8576 KJ/mol. Conclusion: The results showed that schistosomal sulfotransferase binds oxamniquine by relying on hybrid mechanism of induced fit and conformational selection models. The findings offer new insight into sulfotransferase engineering and design of new drugs that target sulfotransferase.

scholarly journals Binding Interactions of Peptide Aptamers

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 6055
Author(s):  
Roger R. C. New ◽  
Tam T. T. Bui ◽  
Michal Bogus
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Cyclic Peptides ◽  
Binding Interactions ◽  
Peptide Aptamers ◽  
Linear Peptide ◽  
Signalling Molecules ◽  
Antibody Binding Site ◽  
Linear Chains ◽  
Protein Receptors

Peptide aptamers are short amino acid chains that are capable of binding specifically to ligands in the same way as their much larger counterparts, antibodies. Ligands of therapeutic interest that can be targeted are other peptide chains or loops located on the surface of protein receptors (e.g., GCPR), which take part in cell-to-cell communications either directly or via the intermediary of hormones or signalling molecules. To confer on aptamers the same sort of conformational rigidity that characterises an antibody binding site, aptamers are often constructed in the form of cyclic peptides, on the assumption that this will encourage stronger binding interactions than would occur if the aptamers were simply linear chains. However, no formal studies have been conducted to confirm the hypothesis that linear peptides will engage in stronger binding interactions with cyclic peptides than with other linear peptides. In this study, the interaction of a model cyclic decamer with a series of linear peptide constructs was compared with that of a linear peptide with the same sequence, showing that the cyclic configuration does confer benefits by increasing the strength of binding.

scholarly journals Mitigating the Adverse Effects of Polychlorinated Biphenyl Derivatives on Estrogenic Activity via Molecular Modification Techniques

2021 ◽  
Vol 18 (9) ◽  
pp. 4999
Author(s):  
Wei He ◽  
Wenhui Zhang ◽  
Zhenhua Chu ◽  
Yu Li
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Hydrophobic Interaction ◽  
Oestrogen Receptor ◽  
Polychlorinated Biphenyl ◽  
Hydrophobic Interactions ◽  
Estrogenic Activity ◽  
Average Distance ◽  
Amino Acid Residues ◽  
Hydrophobic Amino Acid

The aim of this paper is to explore the mechanism of the change in oestrogenic activity of PCBs molecules before and after modification by designing new PCBs derivatives in combination with molecular docking techniques through the constructed model of oestrogenic activity of PCBs molecules. We found that the weakened hydrophobic interaction between the hydrophobic amino acid residues and hydrophobic substituents at the binding site of PCB derivatives and human oestrogen receptor alpha (hERα) was the main reason for the weakened binding force and reduced anti-oestrogenic activity. It was consistent with the information that the hydrophobic field displayed by the 3D contour maps in the constructed oestrogen activity CoMSIA model was one of the main influencing force fields. The hydrophobic interaction between PCB derivatives and oestrogen-active receptors was negatively correlated with the average distance between hydrophobic substituents and hydrophobic amino acid residues at the hERα-binding site, and positively correlated with the number of hydrophobic amino acid residues. In other words, the smaller the average distance between the hydrophobic amino acid residues at the binding sites between the two and the more the number of them, and the stronger the oestrogen activity expression degree of PCBS derivative molecules. Therefore, hydrophobic interactions between PCB derivatives and the oestrogen receptor can be reduced by altering the microenvironmental conditions in humans. This reduces the ability of PCB derivatives to bind to the oestrogen receptor and can effectively modulate the risk of residual PCB derivatives to produce oestrogenic activity in humans.

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