We propose to examine, at a molecular level, the abnormal rigidity in sickle cell membranes. The effectiveness of the oxidant-defense system in sickle cell membranes under different conditions will be evaluated by measuring the specific oxidation of spin labeled phospholipids in membrane of intact cells and in resealed vesicles. The local membrane lipid fluidity of individual classes of major phospholipids, namely phosphatidylcholine, sphingomyelin, phosphatidylethanolamine and phosphatidylserine in sickle cells will be investigated. Spin labeled phospholipids are to be intercalated, specifically, into either the outer or the inner leaflet of the lipid bilayer in both normal and sickle erythrocytes and simplified vesicle systems, and used as probes to monitor the local environments and dynamics of each class of phospholipid molecules under conditions relevant to sickling and cellular oxidation. Furthermore, the segmental motions of spectrin from sickle cell membranes and of oxidatively cross-linked spectrin will be determined. The effects of hemoglobin on the segmental motions of spectrin will also be examined. The experiments will be carried out under both static and flow conditions to assess the roles of mechanical shear forces on membrane local fluidity properties, and on spectrin segmental motions. Both conventional electron paramagnetic resonance and saturation transfer electron paramagnetic resonance will be used. It is hoped that information on the dynamic properties such as local membrane fluidity of specific phospholipids and the segmental motions in spectrin, and on the effects of oxidants and hemoglobin on these membrane properties in sickle cells under different conditions, including static and flow conditions, will provide not only insight into the mechanisms on irreversibly sickle cell formation, but also the molecular basis for the development efficient membrane drugs for sickle cell anemia.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL038361-01
Application #
3354567
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1987-04-01
Project End
1992-03-31
Budget Start
1987-04-01
Budget End
1988-03-31
Support Year
1
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Loyola University Chicago
Department
Type
Schools of Arts and Sciences
DUNS #
City
Chicago
State
IL
Country
United States
Zip Code
60660
LaBrake, C C; Fung, L W (1998) Sickle hemoglobin is more fusogenic than normal hemoglobin at physiological pH and ionic strength conditions. Biochim Biophys Acta 1406:152-61
Fung, L W; Kalaw, B O; Hatfield, R M et al. (1996) Erythrocyte spectrin maintains its segmental motions on oxidation: a spin-label EPR study. Biophys J 70:841-51
Lusitani, D M; Qtaishat, N; LaBrake, C C et al. (1994) The first human alpha-spectrin structural domain begins with serine. J Biol Chem 269:25955-8
Zhang, Y; Fung, L W (1994) The roles of ascorbic acid and other antioxidants in the erythrocyte in reducing membrane nitroxide radicals. Free Radic Biol Med 16:215-22
LaBrake, C C; Wang, L; Keiderling, T A et al. (1993) Fourier transform infrared spectroscopic studies of the secondary structure of spectrin under different ionic strengths. Biochemistry 32:10296-302
LaBrake, C C; Fung, L W (1992) Phospholipid vesicles promote human hemoglobin oxidation. J Biol Chem 267:16703-11
Akojie, F O; Fung, L W (1992) Antisickling activity of hydroxybenzoic acids in Cajanus cajan. Planta Med 58:317-20
Narasimhan, C; Fung, L W (1991) Cetiedil-induced increase in water exchange in sickle cell anemia erythrocytes. J Pharm Sci 80:1101-2
Xu, Y; Prabhakaran, M; Johnson, M E et al. (1990) Secondary structure prediction for the spectrin 106-amino acid segment, and a proposed model for tertiary structure. J Biomol Struct Dyn 8:55-62
Fung, L W; Zhang, Y (1990) A method to evaluate the antioxidant system for radicals in erythrocyte membranes. Free Radic Biol Med 9:289-98

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