title: Measuring picomolar intracellular exchangeable zinc in PC-12 cells using a ratiometric fluorescence biosensor.
abstract: Zinc plays both physiological and pathological roles in biology, making it of increasing interest. To date, intracellular free zinc has been measured in cell types supplemented with or enriched in zinc, such as hippocampal neurons. Here we quantitatively image intracellular exchangeable zinc in an ordinary resting cell culture line (PC-12), using an excitation ratiometric fluorescent biosensor based on carbonic anhydrase (CA). Human CA II has a K d of 4 pM for zinc and suffers no interference from millimolar calcium or magnesium ions. The CA-based biosensor was readily introduced into the cell by a novel approach: fusing a transactivator of transcription (TAT)-derived cell penetrating peptide to the CA molecule and adding it to the cells. Our results indicate that the resting concentration is approximately 5-10 pM in cytoplasm and nucleus. Interestingly, the tetrakis(2-pyridylmethyl)ethylenediamine (TPEN)-Zn complex and TPEN are both apoptogenic for this cell line.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, Maryland 21201, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Bozym
authors.forename: Richard B
authors.initials: RB
authors.lastname: Thompson
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Stoddard
authors.forename: Carol A
authors.initials: CA
authors.lastname: Fierke
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry*; D008856:Microscopy, Fluorescence / Q000379:methods; D009474:Neurons / Q000737:chemistry* / Q000378:metabolism*; D016716:PC12 Cells; D051381:Rats; D015032:Zinc / Q000032:analysis*
chemical_list: D015032:Zinc