Insights into the mechanism for transporting copper, iron, and zinc across the placenta have tended to lag behind nutritional understandings. Cell cultures are a powerful tool for elucidating the fine details of the transport mechanism. Here, we analyze placental Cu transport and compare the mechanism with Zn transport and the well-characterized receptor- mediated mechanism for Fe transport (as transferrin). We hypothesize that maternal ceruloplasmin (Cp) is a major plasma source of Cu for the developing fetus; that transport occurs through specific receptors for Cp on the placental surface. We further postulate that placental Cu transport is mediated by specific membrane proteins acting as receptors, that these proteins contain specific binding sites for Cu as well as recognition signals that guide translocation to other areas of the cell. An immediate objective will be to identify the internal Cu-binding proteins; to learn if Cp enters or Cu passes the membrane as a Cp-free ion. Subsequent work will attempt to isolate Cu-binding ligands in the membrane. BeWo cells grown on membrane filters to obtain in situ polarized apical and basolateral surfaces will be used to assay intracellular movement. Apical and basolateral surfaces will be analyzed for Cp binding sites; a Scatchard analysis will characterize binding strength and receptor number. Subsequently, we will isolate the membrane proteins that receive Cu from Cp. The proteins will be sequenced to determine whether targeting residues that route the protein through the cell reside in their structure. Another objective is the learn whether BeWo cells release Cu as Cp, i.e., placental Cp translocates Cu between maternal and fetal circulations. Carriers for Zn will also be studied to expand the understanding to this important metal. We will examine Cu, Fe, and Zn as individual ions and as antagonists or facilitators of one another. The latter pertains to potential interactions between metals. Ultimately, we hope to learn the molecular events in the movement of metals through the placental cells by identifying the key components that take part in the transition.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
1R01HD029952-01
Application #
3331428
Study Section
Special Emphasis Panel (SRC (05))
Project Start
1993-01-01
Project End
1995-12-31
Budget Start
1993-01-01
Budget End
1993-12-31
Support Year
1
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Texas Agrilife Research
Department
Type
Schools of Earth Sciences/Natur
DUNS #
110521739
City
College Station
State
TX
Country
United States
Zip Code
77843
Harris, E D (2000) Cellular copper transport and metabolism. Annu Rev Nutr 20:291-310
Qian, Y; Mikeska, G; Harris, E D et al. (1999) Effect of lead exposure and accumulation on copper homeostasis in cultured C6 rat glioma cells. Toxicol Appl Pharmacol 158:41-9
Qian, Y; Tiffany-Castiglioni, E; Harris, E D (1998) Sequence of a Menkes-type Cu-transporting ATPase from rat C6 glioma cells: comparison of the rat protein with other mammalian Cu-transporting ATPases. Mol Cell Biochem 181:49-61
Harris, E D; Qian, Y; Tiffany-Castiglioni, E et al. (1998) Functional analysis of copper homeostasis in cell culture models: a new perspective on internal copper transport. Am J Clin Nutr 67:988S-995S
Harris, E D; Qian, Y; Reddy, M C (1998) Genes regulating copper metabolism. Mol Cell Biochem 188:57-62
Reddy, M C; Harris, E D (1998) Multiple transcripts coding for the menkes gene: evidence for alternative splicing of Menkes mRNA. Biochem J 334 ( Pt 1):71-7
Qian, Y; Tiffany-Castiglioni, E; Harris, E D (1997) A Menkes P-type ATPase involved in copper homeostasis in the central nervous system of the rat. Brain Res Mol Brain Res 48:60-6
Qian, Y; Majumdar, S; Reddy, M C et al. (1996) Coincident expression of Menkes gene with copper efflux in human placental cells. Am J Physiol 270:C1880-4
Qian, Y; Tiffany-Castiglioni, E; Harris, E D (1996) Functional analysis of a genetic defect of copper transport (Menkes disease) in different cell lines. Am J Physiol 271:C378-84
Qian, Y; Tiffany-Castiglioni, E; Harris, E D (1995) Copper transport and kinetics in cultured C6 rat glioma cells. Am J Physiol 269:C892-8

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