Calcium imaging demonstrates colocalization of calcium influx and extrusion in fly photoreceptors

J Oberwinkler*, DG Stavenga

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)
77 Downloads (Pure)

Abstract

During illumination. Ca2+ enters fly photoreceptor cells through light-activated channels that are located in the rhabdomere, the compartment specialized for phototransduction. From the rhabdomere. Ca2+ diffuses into the cell body. We visualize this process by rapidly imaging the fluorescence in a cross section of a photoreceptor cell injected with a fluorescent Ca2+ indicator in vivo. The free Ca2+ concentration in the rhabdomere shows a very fast and large transient shortly after light onset. The free Ca2+ concentration in the cell body rises more slowly and displays a much smaller transient. After approximate to 400 ms of light stimulation, the Ca2+ concentration in both compartments reaches a steady state, indicating that thereafter an amount of Ca2+. equivalent to the amount of Ca2+ flowing into the cell, is extruded. Quantitative analysis demonstrates that during the steady state, the free Ca2+ concentration in the rhabdomere and throughout the cell body is the same. This shows that Ca2+ extrusion takes place very close to the location of Ca2+ influx, the rhabdomere. because otherwise gradients in the steady-state distribution of Ca2+ should be measured. The close colocalization of Ca2+ influx and Ca2+ extrusion ensures that, after turning off the light, Ca2+ removal from the rhabdomere is faster than from the cell body. This is functionally significant because it ensures rapid dark adaptation.

Original languageEnglish
Pages (from-to)8578-8583
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue number15
DOIs
Publication statusPublished - 18-Jul-2000

Keywords

  • LIMULUS VENTRAL PHOTORECEPTORS
  • LIGHT-SENSITIVE CHANNELS
  • HAIR-CELLS
  • DROSOPHILA PHOTORECEPTORS
  • BLOWFLY PHOTORECEPTORS
  • CA2+ CHANNEL
  • IN-VIVO
  • TRP
  • LOCALIZATION
  • EXCHANGE

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