The proposed work investigates the distribution of heme within hepatocytes. We are engaged in purifying and characterizing cytosolic proteins of rat liver which bind heme and porphyrins. It is our aim to develop experimental systems in which we can study intracellular protein mediation both of heme transfer from the mitochondria to 1) the cytosol, 2) microsomes and 3) peroxisomes, and of its incorporation into the corresponding heme-containing enzymes (cytosolic) tryptophan pyrrolase, the (microsomal) cytochrome P450 isozymes and (peroxisomal) catalase. Parallel to these studies with subcellular organelles it is planned to continue our investigations using liposomes as model membranes for determinations of heme transfer kinetics in order to postulate likely mechanisms for the efflux of heme to cytosol and into subcellular organelles. In addition we will search for membrane proteins of subcellular organelles possibly facilitating the movement of heme into and from organelles. We will examine the association of heme and heme-binding cytosolic proteins putatively functioning as heme-carriers with these membranes and membrane proteins. Once these aspects of intracellular heme transport under normal conditions are defined, we will examine the same parameters under the influence of altered iron and porphyrin metabolism. Decreased hepatic heme levels will be produced by: 1) inhibiting heme synthesis or limiting iron supply; 2) blocking enzymatic steps of heme synthesis with various compounds; and 3) increasing the cellular demand by inducing cytochrome P450 isozymes. The results of the proposed work should provide much needed information on the physiology of intracellular heme transport and distribution, and should enhance our understanding of how aberrations of iron and porphyrin metabolism affect these processes. In addition, the research should provide information clinically useful in the treatment of porphyrias and also in the development of therapies involving porphyrin localization and photochemical mechanisms.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK030664-08
Application #
3229576
Study Section
General Medicine A Subcommittee 2 (GMA)
Project Start
1981-07-01
Project End
1990-06-30
Budget Start
1988-07-01
Budget End
1989-06-30
Support Year
8
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Type
Schools of Medicine
DUNS #
201373169
City
New York
State
NY
Country
United States
Zip Code
10065
Immenschuh, S; Kietzmann, T; Hinke, V et al. (1998) The rat heme oxygenase-1 gene is transcriptionally induced via the protein kinase A signaling pathway in rat hepatocyte cultures. Mol Pharmacol 53:483-91
Taketani, S; Immenschuh, S; Go, S et al. (1998) Hemopexin from four species inhibits the association of heme with cultured hepatoma cells or primary rat hepatocytes exhibiting a small number of species specific hemopexin receptors. Hepatology 27:808-14
Stewart, J M; Slysz, G W; Pritting, M A et al. (1996) Ferriheme and ferroheme are isosteric inhibitors of fatty acid binding to rat liver fatty acid binding protein. Biochem Cell Biol 74:249-55
Immenschuh, S; Iwahara, S; Satoh, H et al. (1995) Expression of the mRNA of heme-binding protein 23 is coordinated with that of heme oxygenase-1 by heme and heavy metals in primary rat hepatocytes and hepatoma cells. Biochemistry 34:13407-11
Iwahara, S; Satoh, H; Song, D X et al. (1995) Purification, characterization, and cloning of a heme-binding protein (23 kDa) in rat liver cytosol. Biochemistry 34:13398-406
Immenschuh, S; Song, D X; Satoh, H et al. (1995) The type II hemopexin interleukin-6 response element predominates the transcriptional regulation of the hemopexin acute phase responsiveness. Biochem Biophys Res Commun 207:202-8
Timmins, G S; Davies, M J; Song, D X et al. (1995) EPR studies on the effects of complexation of heme by hemopexin upon its reactions with organic peroxides. Free Radic Res 23:559-69
Sinclair, P R; Bement, W J; Healey, J F et al. (1994) Effects of hemopexin on heme-mediated repression of 5-aminolevulinate synthase and induction of heme oxygenase in cultured hepatocytes. Hepatology 20:741-6
Satoh, T; Satoh, H; Iwahara, S et al. (1994) Roles of heme iron-coordinating histidine residues of human hemopexin expressed in baculovirus-infected insect cells. Proc Natl Acad Sci U S A 91:8423-7
Immenschuh, S; Nagae, Y; Satoh, H et al. (1994) The rat and human hemopexin genes contain an identical interleukin-6 response element that is not a target of CAAT enhancer-binding protein isoforms. J Biol Chem 269:12654-61

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