eZinCh-2: A Versatile, Genetically Encoded FRET Sensor for Cytosolic and Intraorganelle Zn(2+) Imaging

ACS Chem Biol. 2015 Sep 18;10(9):2126-34. doi: 10.1021/acschembio.5b00211. Epub 2015 Jul 20.

Abstract

Zn(2+) plays essential and diverse roles in numerous cellular processes. To get a better understanding of intracellular Zn(2+) homeostasis and the putative signaling role of Zn(2+), various fluorescent sensors have been developed that allow monitoring of Zn(2+) concentrations in single living cells in real time. Thus far, two families of genetically encoded FRET-based Zn(2+) sensors have been most widely applied, the eCALWY sensors developed by our group and the ZapCY sensors developed by Palmer and co-workers. Both have been successfully used to measure cytosolic free Zn(2+), but distinctly different concentrations have been reported when using these sensors to measure Zn(2+) concentrations in the ER and mitochondria. Here, we report the development of a versatile alternative FRET sensor containing a de novo Cys2His2 binding pocket that was created on the surface of the donor and acceptor fluorescent domains. This eZinCh-2 sensor binds Zn(2+) with a high affinity that is similar to that of eCALWY-4 (Kd = 1 nM at pH 7.1), while displaying a substantially larger change in emission ratio. eZinCh-2 not only provides an attractive alternative for measuring Zn(2+) in the cytosol but was also successfully used for measuring Zn(2+) in the ER, mitochondria, and secretory vesicles. Moreover, organelle-targeted eZinCh-2 can also be used in combination with the previously reported redCALWY sensors to allow multicolor imaging of intracellular Zn(2+) simultaneously in the cytosol and the ER or mitochondria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Cations, Divalent / analysis
  • Cations, Divalent / metabolism
  • Cytosol / chemistry
  • Cytosol / metabolism*
  • Fluorescence Resonance Energy Transfer / methods*
  • Fluorescent Dyes / chemistry*
  • Fluorescent Dyes / metabolism
  • Green Fluorescent Proteins / chemistry*
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Mitochondria / chemistry
  • Mitochondria / metabolism
  • Models, Molecular
  • Optical Imaging / methods
  • Zinc / analysis*
  • Zinc / metabolism

Substances

  • Cations, Divalent
  • Fluorescent Dyes
  • Green Fluorescent Proteins
  • Zinc