In situ dimerization of multiple wild type and mutant zinc transporters in live cells using bimolecular fluorescence complementation.
Zinc transporters (ZnTs) facilitate zinc efflux and zinc compartmentalization, thereby playing a key role in multiple physiological processes and pathological disorders, presumed to be modulated by transporter dimerization. We recently proposed that ZnT2 homodimerization is the underlying basis for the dominant negative effect of a novel heterozygous G87R mutation identified in women producing zinc-deficient milk. To provide direct visual evidence for the in situ dimerization and function of multiple normal and mutant ZnTs, we applied here the bimolecular fluorescence complementation (BiFC) technique, which enables direct visualization of specific protein-protein interactions. BiFC is based upon reconstitution of an intact fluorescent protein including YFP when its two complementary, non-fluorescent N- and C-terminal fragments (termed YN and YC) are brought together by a pair of specifically interacting proteins. Homodimerization of ZnT1, -2, -3, -4, and -7 was revealed by high subcellular fluorescence observed upon co-transfection of non-fluorescent ZnT-YC and ZnT-YN; this homodimer fluorescence localized in the characteristic compartments of each ZnT. The validity of the BiFC assay in ZnT dimerization was further corroborated when high fluorescence was obtained upon co-transfection of ZnT5-YC and ZnT6-YN, which are known to form heterodimers. We further show that BiFC recapitulated the pathogenic role that ZnT mutations play in transient neonatal zinc deficiency. Zinquin, a fluorescent zinc probe applied along with BiFC, revealed the in situ functionality of ZnT dimers. Hence, the current BiFC-Zinquin technique provides the first in situ evidence for the dimerization and function of wild type and mutant ZnTs in live cells.
From the Fred Wyszkowski Cancer Research Laboratory, Department of Biology, and.
Inbal
I
Lasry
Yarden
Y
Golan
Bluma
B
Berman
Noy
N
Amram
Fabian
F
Glaser
Yehuda G
YG
Assaraf
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics; D005816:Genetic Complementation Test; D006801:Humans; D008164:Luminescent Proteins / Q000737:chemistry; D061986:MCF-7 Cells; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D011485:Protein Binding; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D015363:Quinolones / Q000737:chemistry; D014105:Tosyl Compounds / Q000737:chemistry; D014162:Transfection; D015032:Zinc / Q000378:metabolism*
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D008164:Luminescent Proteins; D015363:Quinolones; C498299:SLC30A1 protein, human; C472294:SLC30A7 protein, human; D014105:Tosyl Compounds; C054562:yellow fluorescent protein, Bacteria; D015032:Zinc; C084731:zinquin
Metal Homeostasis; Mutant; Protein-Protein Interactions; Transport Metals; Zinc