Genetic targeting of a small fluorescent zinc indicator to cell surface for monitoring zinc secretion

ACS Chem Biol. 2015 Apr 17;10(4):1054-63. doi: 10.1021/cb5007536. Epub 2015 Jan 27.

Abstract

Numerous mammalian cells contain Zn2+ in their secretory granules. During secretion, Zn2+ is coreleased with granular cargos into extracellular medium so Zn2+ serves as a convenient surrogate marker for tracking the dynamics of secretion. Fluorescent Zn2+ sensors that can be selectively targeted to cells of interest would be invaluable tools for imaging Zn2+ release in multicellular systems including tissues and live animals. Exploiting the HaloTag labeling technology and using an optimized linker, we have engineered a fluorescent Zn2+ indicator that displayed a 15-fold fluorescence enhancement upon Zn2+ binding while reacting efficiently with a HaloTag enzyme in a cellular environment. Two-color imaging of ZIMIR-HaloTag and a red-emitting calcium indicator in pancreatic islet beta cells demonstrated that photoactivation of a channelrhodopsin was able to induce exocytosis of Zn2+/insulin granules and revealed heterogeneity in secretory activity along the cell membrane that was uncoupled from cellular Ca2+ activity. This integrated photonic approach for imaging and controlling the release of large dense core granules provides exquisite cellular selectivity and should facilitate future studies of stimulus-secretion coupling and paracrine signaling in secretory cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cell Line
  • Cell Membrane / metabolism*
  • Chemistry Techniques, Synthetic
  • Fluorescent Dyes / analysis*
  • Fluorescent Dyes / chemistry
  • Insulin / metabolism
  • Mice
  • Microscopy, Fluorescence / methods
  • Molecular Sequence Data
  • Optogenetics / methods
  • Protein Engineering / methods
  • Recombinant Proteins / analysis
  • Recombinant Proteins / chemistry*
  • Recombinant Proteins / genetics
  • Spectrophotometry, Ultraviolet
  • Zinc / analysis*
  • Zinc / metabolism*

Substances

  • Fluorescent Dyes
  • Insulin
  • Recombinant Proteins
  • Zinc