title: Manganese transport via the transferrin mechanism.
abstract: Excessive manganese (Mn) uptake by brain cells, particularly in regions like the basal ganglia, can lead to toxicity. Mn(2+) is transported into cells via a number of mechanisms, while Mn(3+) is believed to be transported similarly to iron (Fe) via the transferrin (Tf) mechanism. Cellular Mn uptake is therefore determined by the activity of the mechanisms transporting Mn into each type of cell and by the amounts of Mn(2+), Mn(3+) and their complexes to which these cells are exposed; this complicates understanding the contributions of each transporter to Mn toxicity. While uptake of Fe(3+) via the Tf mechanism is well understood, uptake of Mn(3+) via this mechanism has not been systematically studied. The stability of the Mn(3+)Tf complex allowed us to form and purify this complex and label it with a fluorescent (Alexa green) tag. Using purified and labeled Mn(3+)Tf and biophysical tools, we have developed a novel approach to study Mn(3+)Tf transport independently of other Mn transport mechanisms. This approach was used to compare the uptake of Mn(3+)Tf into neuronal cell lines with published descriptions of Fe(3+) uptake via the Tf mechanism, and to obtain quantitative information on Mn uptake via the Tf mechanism. Results confirm that in these cell lines significant Mn(3+) is transported by the Tf mechanism similarly to Fe(3+)Tf transport; although Mn(3+)Tf transport is markedly slower than other Mn transport mechanisms. This novel approach may prove useful for studying Mn toxicity in other systems and cell types.
authors.affiliation: Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA. thomas_gunter@urmc.rochester.edu
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Gunter
authors.forename: Brent
authors.initials: B
authors.lastname: Gerstner
authors.forename: Karlene K
authors.initials: KK
authors.lastname: Gunter
authors.forename: Jon
authors.initials: J
authors.lastname: Malecki
authors.forename: Robert
authors.initials: R
authors.lastname: Gelein
authors.forename: William M
authors.initials: WM
authors.lastname: Valentine
authors.forename: Michael
authors.initials: M
authors.lastname: Aschner
authors.forename: David I
authors.initials: DI
authors.lastname: Yule
mesh_terms: D000818:Animals; D001479:Basal Ganglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001667:Binding, Competitive; D001692:Biological Transport; D002478:Cells, Cultured; D002746:Chlorpromazine / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D011992:Endosomes / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006835:Hydrazones / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008345:Manganese / Q000378:metabolism* / Q000633:toxicity; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013054:Spectrophotometry, Atomic; D013056:Spectrophotometry, Ultraviolet; D014168:Transferrin / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D006835:Hydrazones; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; D011990:Receptors, Transferrin; D014168:Transferrin; D008345:Manganese; D007501:Iron; D002746:Chlorpromazine