title: ZnT-1 extrudes zinc from mammalian cells functioning as a Zn(2+)/H(+) exchanger.
abstract: ZnT-1 is a Cation Diffusion Facilitator (CDF) family protein, and is present throughout the phylogenetic tree from bacteria to humans. Since its original cloning in 1995, ZnT-1 has been considered to be the major Zn(2+) extruding transporter, based on its ability to protect cells against zinc toxicity. However, experimental evidence for ZnT-1 induced Zn(2+) extrusion was not convincing. In the present study, based on the 3D crystal structure of the ZnT-1 homologue, YiiP, that predicts a homodimer that utilizes the H(+) electrochemical gradient to facilitate Zn(2+) efflux, we demonstrate ZnT-1 dependent Zn(2+) efflux from HEK 293T cells using FluoZin-3 and Fura 2 by single cell microscope based fluorescent imaging. ZnT-1 facilitates zinc efflux in a sodium-independent, pH-driven and calcium-sensitive manner. Moreover, substitution of two amino acids in the putative zinc binding domain of ZnT-1 led to nullification of Zn(2+) efflux and rendered the mutated protein incapable of protecting cells against Zn(2+) toxicity. Our results demonstrate that ZnT-1 extrudes zinc from mammalian cells by functioning as a Zn(2+)/H(+) exchanger.
authors.affiliation: Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben Gurion University of the Negev, Israel. arie@bgu.ac.il.
authors.forename: Eden
authors.initials: E
authors.lastname: Shusterman
authors.forename: Ofer
authors.initials: O
authors.lastname: Beharier
authors.forename: Levy
authors.initials: L
authors.lastname: Shiri
authors.forename: Raz
authors.initials: R
authors.lastname: Zarivach
authors.forename: Yoram
authors.initials: Y
authors.lastname: Etzion
authors.forename: Craig R
authors.initials: CR
authors.lastname: Campbell
authors.forename: Il-Ha
authors.initials: IH
authors.lastname: Lee
authors.forename: Ken
authors.initials: K
authors.lastname: Okabayashi
authors.forename: Anuwat
authors.initials: A
authors.lastname: Dinudom
authors.forename: David I
authors.initials: DI
authors.lastname: Cook
authors.forename: Amos
authors.initials: A
authors.lastname: Katz
authors.forename: Arie
authors.initials: A
authors.lastname: Moran
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D019610:Cytoprotection / Q000187:drug effects; D004563:Electrochemistry; D057809:HEK293 Cells; D006801:Humans; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008322:Mammals / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015032:Zinc / Q000378:metabolism* / Q000633:toxicity
chemical_list: D027682:Cation Transport Proteins; D050505:Mutant Proteins; C498299:SLC30A1 protein, human; D006859:Hydrogen; D012964:Sodium; D015032:Zinc; D002118:Calcium