MagA expression attenuates iron export activity in undifferentiated multipotent P19 cells

• Published in: PloS one 2019-06, Vol.14 (6), p.e0217842
• Main Authors: Liu, Linshan, Alizadeh, Kobra, Donnelly, Sarah C, Dassanayake, Praveen, Hou, Tian Tian, McGirr, Rebecca, Thompson, R Terry, Prato, Frank S, Gelman, Neil, Hoffman, Lisa, Goldhawk, Donna E
• Format: Article
• Language: English
• Subjects: Animals; Bacteria; Bacterial genetics; Biology and Life Sciences; Biophysics; Business travel; CAT scans; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Cell Line, Tumor; Cell Tracking - methods; Collaboration; Contrast agents; Contrast media; Contrast Media - metabolism; Diagnostic imaging; EDTA; Embryos; Exports; Gene expression; Gene Expression - genetics; Genes; Genes, Reporter - genetics; Hemagglutinins; Homeostasis; Immunocytochemistry; Inductively coupled plasma mass spectrometry; Iron; Iron - metabolism; Iron content; Iron transport; Lectins; Localization; Magnetic resonance; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Mammalian cells; Mass spectrometry; Mass spectroscopy; Medical imaging; Medical research; Medicine and Health Sciences; Metabolism; Mice; Multipotent Stem Cells - metabolism; Nanoparticles; NMR; Novels; Nuclear magnetic resonance; Physical Sciences; Protein transport; Proteins; Research and Analysis Methods; Resonance; Spectroscopy; Stem cells; Supplements; Teratocarcinoma; Tracking; Transcription factors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0217842

Magnetic resonance imaging (MRI) is a non-invasive imaging modality used in longitudinal cell tracking. Previous studies suggest that MagA, a putative iron transport protein from magnetotactic bacteria, is a useful gene-based magnetic resonance contrast agent. Hemagglutinin-tagged MagA was stably expressed in undifferentiated embryonic mouse teratocarcinoma, multipotent P19 cells to provide a suitable model for tracking these cells during differentiation. Western blot and immunocytochemistry confirmed the expression and membrane localization of MagA in P19 cells. Surprisingly, elemental iron analysis using inductively-coupled plasma mass spectrometry revealed significant iron uptake in both parental and MagA-expressing P19 cells, cultured in the presence of iron-supplemented medium. Withdrawal of this extracellular iron supplement revealed unexpected iron export activity in P19 cells, which MagA expression attenuated. The influence of iron supplementation on parental and MagA-expressing cells was not reflected by longitudinal relaxation rates. Measurement of transverse relaxation rates (R2* and R2) reflected changes in total cellular iron content but did not clearly distinguish MagA-expressing cells from the parental cell type, despite significant differences in the uptake and retention of total cellular iron. Unlike other cell types, the reversible component R2' (R2* ‒ R2) provided only a moderately strong correlation to amount of cellular iron, normalized to amount of protein. This is the first report to characterize MagA expression in a previously unrecognized iron exporting cell type. The interplay between contrast gene expression and systemic iron metabolism substantiates the potential for diverting cellular iron toward the formation of a novel iron compartment, however rudimentary when using a single magnetotactic bacterial gene expression system like magA. Since relatively few mammalian cells export iron, the P19 cell line provides a tractable model of ferroportin activity, suitable for magnetic resonance analysis of key iron-handling activities and their influence on gene-based MRI contrast.