The lysis of human erythrocytes by complement proteins C5b-9 is inhibited by a phosphatidylinositol-linked protein (CD59) present on the surface of these cells. We have recently detected immunologically cross-reactive and functionally-similar proteins in the plasma membranes of human platelets and endothelial cells. Our overall goal is to elucidate the structural and functional properties of these cell-surface C5b-9 inhibitors, and to determine their role in the expression and control of cell-stimulatory and procoagulant responses elicited by the C5b-9 proteins.
Our specific aims i nclude: (i) to isolate and characterize the C5b-9 inhibitor expressing CD59 antigen from human platelets, (ii) to deduce the mechanism by which CD59 (and related proteins) modulate activation of the C5b-9 complex and alter the structural and functional properties of the C5b-9 pore, (iii) to determine whether the topologic distribution of the CD59 proteins in the plasma membrane of platelets and endothelial cells is altered by cell activation, or, through their interaction with components of the C5b-9 complex, (iv) to determine whether interaction with the CD59 proteins affects the cell-stimulatory responses elicited by the bound C5b-9 proteins, and whether these cell surface components participate in vesiculation or endocytic removal of C5b-9 from the plasma membrane, (v) to determine how the cell surface expression of CD59 antigens are regulated, and whether a change in the surface concentration of these membrane proteins alters the response of platelets and endothelial cells exposed to activated complement, (vi) to determine whether exogenously added CD59 (or, functional peptide fragments derived from this protein) can inhibit the procoagulant responses of platelets and endothelial cells exposed to activated complement. It is proposed that the data derived from these studies will provide new and basic insight into the etiology of thrombotic sequelae that can accompany intravascular complement activation. Furthermore it is proposed that this research is likely to yield reagents that will prove useful for protecting platelets exposed to activated complement during storage and transfusion, and of benefit in the treatment of hypercoagulable states associated with immune and inflammatory vascular disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
2R01HL036061-06
Application #
3350627
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1985-09-01
Project End
1995-08-31
Budget Start
1990-09-01
Budget End
1991-08-31
Support Year
6
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Oklahoma Medical Research Foundation
Department
Type
DUNS #
937727907
City
Oklahoma City
State
OK
Country
United States
Zip Code
73104
Giddings, Kara S; Zhao, Ji; Sims, Peter J et al. (2004) Human CD59 is a receptor for the cholesterol-dependent cytolysin intermedilysin. Nat Struct Mol Biol 11:1173-8
Sims, P J; Wiedmer, T (2001) Unraveling the mysteries of phospholipid scrambling. Thromb Haemost 86:266-75
Christiansen, V J; Sims, P J; Hamilton, K K (1997) Complement C5b-9 increases plasminogen binding and activation on human endothelial cells. Arterioscler Thromb Vasc Biol 17:164-71
Husler, T; Lockert, D H; Sims, P J (1996) Role of a disulfide-bonded peptide loop within human complement C9 in the species-selectivity of complement inhibitor CD59. Biochemistry 35:3263-9
Petranka, J; Zhao, J; Norris, J et al. (1996) Structure-function relationships of the complement regulatory protein, CD59. Blood Cells Mol Dis 22:281-96
Lockert, D H; Kaufman, K M; Chang, C P et al. (1995) Identity of the segment of human complement C8 recognized by complement regulatory protein CD59. J Biol Chem 270:19723-8
Husler, T; Lockert, D H; Kaufman, K M et al. (1995) Chimeras of human complement C9 reveal the site recognized by complement regulatory protein CD59. J Biol Chem 270:3483-6
Chang, C P; Husler, T; Zhao, J et al. (1994) Identity of a peptide domain of human C9 that is bound by the cell-surface complement inhibitor, CD59. J Biol Chem 269:26424-30
Kennedy, S P; Rollins, S A; Burton, W V et al. (1994) Protection of porcine aortic endothelial cells from complement-mediated cell lysis and activation by recombinant human CD59. Transplantation 57:1494-501
Hamilton, K K; Zhao, J; Sims, P J (1993) Interaction between apolipoproteins A-I and A-II and the membrane attack complex of complement. Affinity of the apoproteins for polymeric C9. J Biol Chem 268:3632-8

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