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Apolipoprotein H

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Haider Mehdi – 1st expert on this subject based on the ideXlab platform

  • a functional polymorpHism at tHe transcriptional initiation site in β2 glycoprotein i Apolipoprotein H associated witH reduced gene expression and lower plasma levels of β2 glycoprotein i
    FEBS Journal, 2003
    Co-Authors: Haider Mehdi, Susan Manzi, Qi Chen, Purnima P Desai, Cara Nestlerode, Franklin A Bontempo, Stephen C Strom, Reza Zarnegar, Ilyas M Kamboh

    Abstract:

    Human b2-glycoprotein I (b2GPI), also known as Apolipoprotein H, Has been implicated in Haemostasis and tHe production ofanti-pHospHolipid antibodies. THere is a wide range ofinterindividual variation in b2GPI plasma levels tHat is tHougHt to be under genetic control, but its molecular basis remains unknown. To understand tHe genetic basis of b2GPI variation, we analyzed tHe 5¢ flanking region oftHe b2GPI gene for mutation detection by DHPLC and identified a point mutation at tHe transcriptional initiation site ()1CfiA) witH a carrier frequency of 12.1%. THe mutation was associated witH significantly lower b2GPI plasma levels (P < 0.0001) and low occurrence ofanti-pHospHolipid antibodies in lupus patients (4.8% antibody-positive group vs. 16.6% in tHe antibody-negative group; P ¼ 0.019). NortHern blot analysis confirmed tHat tHe )1Cfi Am utation was associated witH lower mRNA levels and it reduced tHe reporter (luciferase) gene expression by twofold. ElectropHoretic gel mobility sHift assay (EMSA) revealed tHat tHe )1CfiA mutation disrupts tHe binding for crude Hepatic nuclear extracts and purified TFIID. THese results suggest tHat tHe substitution ofC witH A at tHe b2GPI transcriptional initiation site is a causative mutation tHat affects its gene expression at tHe transcriptional level and ultimately b2GPI plasma levels and tHe occurrence ofanti-pHospHolipid anti

  • genetic variation in Apolipoprotein H β2 glycoprotein i affects tHe occurrence of antipHospHolipid antibodies and Apolipoprotein H concentrations in systemic lupus erytHematosus
    Lupus, 1999
    Co-Authors: Ilyas M Kamboh, Susan Manzi, Haider Mehdi, Shirley G Fitzgerald, Dharambir K Sanghera, Lewis H Kuller, Christopher E Atson

    Abstract:

    Apolipoprotein H (apoH, protein; APOH, gene) is a required cofactor for tHe production of antipHospHolipid antibodies (APA). In tHis study we Have examined wHetHer genetic variation in tHe APOH gen…

  • Genetic variation in tHe Apolipoprotein H (β2-glycoprotein I) gene affects plasma Apolipoprotein H concentrations
    Human Genetics, 1999
    Co-Authors: Haider Mehdi, Dharambir K Sanghera, Christopher E. Aston, Richard F. Hamman, Kamboh Mi

    Abstract:

    Apolipoprotein H (apoH, protein; APOH, gene) is a single cHain glycoprotein tHat exists in plasma botH in a free form and in combination witH lipoprotein particles. ApoH Has been implicated in several pHysiologic patHways, including lipid metabolism, coagulation, and tHe production of antipHospHolipid antibodies. THe wide range of interindividual variation in plasma apoH levels is tHougHt to be under genetic control, but its molecular basis is unknown. APOH displays a common structural polymorpHism witH tHe occurrence of tHree common alleles (APOH*1, APOH*2, and APOH*3), tHe APOH*2 allele being tHe most frequent in all populations. THe relationsHip between tHe APOH polymorpHism and plasma apoH levels is unknown. In tHis study, we Have determined tHe impact of tHis APOH polymorpHism on apoH levels in 455 normoglycemic non-Hispanic WHites (220 men and 235 women) from tHe San Luis Valley, Colorado. Mean plasma apoH levels, determined by capture enzyme-linked immunosorbent assay, were 20.0±0.2 mg/dl (range: 3.4–31.2 mg/dl) witH no significant difference between men and women. In women, but not in men, age Had a significant effect on plasma apoH levels explaining 3.4% of its pHenotypic variance. ApoH levels also correlated positively witH cHolesterol (P=0.015), HDL-cHolesterol (P=0.044), and triglyceride (P=0.037) in women, but not in men. An analysis of variance (ANOVA) of adjusted plasma apoH levels sHowed significant association witH tHe APOH polymorpHism in botH men and women (P

Mark E Peeples – 2nd expert on this subject based on the ideXlab platform

  • an altered form of Apolipoprotein H binds Hepatitis b virus surface antigen most efficiently
    Virology, 1996
    Co-Authors: Haider Mehdi, Xu Yang, Mark E Peeples

    Abstract:

    Abstract Using recombinant (r)HBsAg as a ligand, we previously found a 46-kDa Human plasma protein capable of specific binding, and identified tHis protein as Apolipoprotein H (apo H). Apo H is able to bind to rHBsAg containing only tHe small S protein, in botH ligand blot and enzyme immunoassay systems (H. MeHdi, M. J. Kaplan, F. Y. Anlar., X. Yang, R. Bayer, K. SutHerland, and M. E. Peeples, J. Virol. 68, 2415–2424, 1994). Apo H is a plasma glycoprotein, some of wHicH is associated witH lipoproteins, particularly cHylomicrons and HigH-density lipoproteins (HDL). During normal lipid trafficking in tHe bloodstream, cHylomicrons and HDL are targeted to tHe Hepatocyte, tHe primary Host cell for HBV, for degradation. In tHis report tHe metHod of apo H presentation was examined. rHBsAg bound to apo H very poorly if tHe apo H was coated directly on a microtiter well, or if it was presented in a soluble form. Binding was 100-fold more efficient wHen apo H was presented as a complex witH monoclonal antibody (MAb) P2D4. THese results suggest tHat binding to tHis MAb alters apo H, making it HigHly reactive witH rHBsAg. Apo H binding to rHBsAg is not dependent on divalent cations and is optimal at pH 6.5–8.0. Removal of lipids from rHBsAg resulted in denaturation, preventing analysis of binding activity. Removal of sialic acid or complete removal of N-linked carboHydrates from apo H did not cHange its ability to bind rHBsAg, indicating tHat apo H carboHydrates are not involved in rHBsAg binding. Likewise, cHemical modification of tHe arginine residues of apo H Had no effect on binding. However, cHemical modification of as few as tHree of tHe 29 lysine residues of apo H destroyed binding, indicating tHat one or a few lysines in apo H are involved in rHBsAg binding.

  • Hepatitis b virus surface antigen binds to Apolipoprotein H
    Journal of Virology, 1994
    Co-Authors: Haider Mehdi, M J Kaplan, Fehim Yasar Anlar, Xu Yang, R Bayer, K Sutherland, Mark E Peeples

    Abstract:

    We Have previously demonstrated tHat a plasma membrane-enricHed fraction isolated from Human liver is capable of binding recombinant Hepatitis B surface antigen (rHBsAg) (P. Pontisso, M. A. Petit, M. Bankowski, and M. E. Peeples, J. Virol. 63:1981-1988, 1989). In tHis study we Have separated tHe plasma membrane proteins by sodium dodecyl sulfate-polyacrylamide gel electropHoresis and used a ligand-blotting tecHnique to identify a 46-kDa rHBsAg-binding protein. THis protein could be removed from tHe membranes witH a weakly acidic buffer, implying tHat it is peripHerally bound. Examination of Human serum revealed tHat tHe 46-kDa binding protein is a serum protein. Isolation of plasma lipoproteins revealed tHat tHe binding protein is in part associated witH cHylomicrons and HigH-density lipoproteins, botH of wHicH are targeted to tHe Hepatocyte during tHe normal course of lipid metabolism. THe binding protein was identified as Apolipoprotein H (apo H), also known as beta 2-glycoprotein I, on tHe basis of copurification of tHe rHBsAg-binding activity witH tHe apo H protein and tHe ability of cDNA-expressed apo H to bind rHBsAg. Serum-derived HBsAg also binds to apo H, indicating tHat binding is not unique to rHBsAg. Binding is saturable, requires only tHe small S protein of rHBsAg, and is inHibited by excess rHBsAg, antibodies to HBsAg, and antibodies to apo H. THe binding activity of apo H is destroyed upon reduction, indicating tHat 1 or more of its 22 disulfide bonds are required for interaction witH rHBsAg. THe possibility tHat an interaction between Hepatitis B virus particles and lipoprotein particles may facilitate entry of tHe virus into Hepatocytes is discussed.

  • cHaracterization and acute pHase modulation of canine Apolipoprotein H β2 glycoprotein 1
    Biochemical and Biophysical Research Communications, 1993
    Co-Authors: G C Sellar, Haider Mehdi, J Keane, Mark E Peeples, N Browne, Alexander S Whitehead

    Abstract:

    Abstract Apolipoprotein H (ApoH) is a 50 kDa glycoprotein capable of binding to negatively cHarged pHospHolipids and is a probable inHibitor of tHe blood coagulation patHway, platelet aggregation, and platelet protHrombinase activity, as well as being involved in autoimmune disease. We Have cloned and sequenced a full lengtH ApoH cDNA clone from a beagle dog liver library. Its derived amino acid sequence sHows HigH cross-species similarity to ApoH from otHer mammals. Canine ApoH mRNA expression is down regulated during an experimentally induced inflammatory response establisHing tHat it is a negative acute pHase reactant.

Shao Xiong Wang – 3rd expert on this subject based on the ideXlab platform

  • establisHment of an interaction model of Human Apolipoprotein H witH lipid monolayer by capillary sds gel electropHoresis
    Journal of capillary electrophoresis and microchip technology, 2002
    Co-Authors: Qinhua Ru, Yiming Wang, Shao Xiong Wang

    Abstract:

    : Apolipoprotein H (ApoH) is a plasma glycoprotein isolated from Human serum. It plays a key role in tHe interaction witH lipids. For tHe first time, tHe concentration of ApoH adsorbed on tHe lipid monolayer Has been determined, and was done so using capillary electropHoresis. Based on tHis determination, an interaction model of ApoH and lipid monolayer was constructed, and tHis interaction is one of nonspecific adsorption. A neutral coated capillary (50 cm x 100 microm i.d.) and a negative voltage of 15 kV were used to separate ApoH. THe calibration curve of ApoH was built using a detection limit of 50 microg/mL(-1) (near to 1 microM), and tHe RSD of tHe relative migration time of ApoH was 1.4% (n = 7).

  • penetration of Human Apolipoprotein H into air water interface witH and witHout pHospHolipid monolayers
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
    Co-Authors: Shao Xiong Wang

    Abstract:

    Abstract Apolipoprotein H (β 2 -glycoprotein I) is a 54 kDa plasma glycoprotein. THe interaction of ApoH witH pHospHolipids Has been demonstrated to be involved in tHe regulation of tHe function of tHe activated platelets and tHe clearance of pHospHotidylserine (PS)-expressing cells. In tHe present work, tHe monolayer tecHnique is employed to cHaracterize tHe feature of tHe penetration of ApoH into air/water interface witH and witHout pHospHolipid monolayers. THe results indicate tHat ApoH can penetrate into tHe air/water interface and tHere is a protein-concentration dependent lag time in tHe adsorption isotHerm. ApoH can insert into tHe pHospHolipid monolayers spread at tHe air/water interface, but no lag time is observed in tHis case. THe fact tHat ApoH prefers to interact witH anionic pHospHolipid monolayers suggests tHat tHe negative cHarges of tHe pHospHolipid monolayers may play an important role in tHe process of tHe membrane insertion of ApoH.

  • Penetration of Human Apolipoprotein H into air/water interface witH and witHout pHospHolipid monolayers
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
    Co-Authors: Shao Xiong Wang

    Abstract:

    Abstract Apolipoprotein H (β 2 -glycoprotein I) is a 54 kDa plasma glycoprotein. THe interaction of ApoH witH pHospHolipids Has been demonstrated to be involved in tHe regulation of tHe function of tHe activated platelets and tHe clearance of pHospHotidylserine (PS)-expressing cells. In tHe present work, tHe monolayer tecHnique is employed to cHaracterize tHe feature of tHe penetration of ApoH into air/water interface witH and witHout pHospHolipid monolayers. THe results indicate tHat ApoH can penetrate into tHe air/water interface and tHere is a protein-concentration dependent lag time in tHe adsorption isotHerm. ApoH can insert into tHe pHospHolipid monolayers spread at tHe air/water interface, but no lag time is observed in tHis case. THe fact tHat ApoH prefers to interact witH anionic pHospHolipid monolayers suggests tHat tHe negative cHarges of tHe pHospHolipid monolayers may play an important role in tHe process of tHe membrane insertion of ApoH.