In the human erythrocyte, phosphatidylinositol is phosphorylated to phosphatidylinositol phosphate (PI-P) and phosphatidylinositol-4,5-Biphosphate (PI-P2) by two ATP dependent kinase reactions; these phosphorylated derivatives are converted back to phosphatidylinositol by phosphates which are only partially described. This phosphorylation/dephosphorylation cycle has been implicated in the maintenance of red cell shape, membrane protein mobility, and as a significant consumer of red cell ATP. The goals of this proposal involve understanding the enzymology of phosphatidylinositol phosphorylation/dephosphorylation in the red cells of normals and of patients with hemolytic anemia. Specific goals include purification and characterization of phosphatidylinositol kinase; characterization of phosphatidylinositol phosphate kinase; and examination of the phosphatase activities responsible for the degradation of PI-P and PI-P2. The physiological function of these phosphoinositides in the erythrocyte will also be a major focal point of this proposal. Hydrolysis of PI-P and PI-P2 in the erythrocyte results in the formation of echinocytes from these cells rather than the normal biconcave discs. These findings will be extended to determine the importance of phosphoinositides in the maintenance of cellular shape by erythrocytes. This will include the study of effectors which modify the levels of PI-P and PI-P2 as well as examination of the interaction of phosphoinositides with the erythrocyte cytoskeleton. In addition, it has been reported that up to 70% of the net ATP utilized by the erythrocyte may be consumed in the phosphatidylinositol phosphorylation/dephosphorylation cycle; these findings will be examined to determine the implications of such a massive ATP utilization for this cycle. Erythrocytes from patients with hemolytic anemia are being screened for abnormalities involved in the phosphatidylinositol metabolism pathways; these patients will be very useful in delineating the physiological function of phosphoinositides.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK035220-03
Application #
3233502
Study Section
Biochemistry Study Section (BIO)
Project Start
1985-09-23
Project End
1988-08-31
Budget Start
1987-09-01
Budget End
1988-08-31
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Scripps Research Institute
Department
Type
DUNS #
City
San Diego
State
CA
Country
United States
Zip Code
92037
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Peng, J; Friese, P; Heilmann, E et al. (1994) Aged platelets have an impaired response to thrombin as quantitated by P-selectin expression. Blood 83:161-6
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Heilmann, E; Friese, P; Anderson, S et al. (1993) Biotinylated platelets: a new approach to the measurement of platelet life span. Br J Haematol 85:729-35
Dale, G L; Norenberg, S L; Suzuki, T et al. (1989) Altered adenine nucleotide metabolism in senescent erythrocytes from the rabbit. Prog Clin Biol Res 319:259-69;discussion 270-3
Dale, G L (1989) Radioisotopic assay for erythrocyte adenosine 5'-monophosphate deaminase. Clin Chim Acta 182:1-7
Suzuki, T; Dale, G L (1989) Membrane proteins in senescent erythrocytes. Biochem J 257:37-41
Dale, G L; Suzuki, T (1988) Erythrocytes attached to a wheat germ agglutinin coated surface display an altered phospholipid metabolism. J Cell Biochem 38:1-11
Dale, G L (1988) Use of the dye Janus green to facilitate quantitative analysis of phosphoinositides. J Chromatogr 424:445-8

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