April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
Store-operated Calcium Entry Regulates Intracellular Calcium Homeostasis In Mouse Rod Photoreceptors
Author Affiliations & Notes
  • Tunde Molnar
    Ophthalmology and Visual Science, Moran Eye Ctr, University of Utah, Salt Lake City, Utah
  • Peter Barabas
    Ophthalmology and Visual Science, Moran Eye Ctr, University of Utah, Salt Lake City, Utah
  • Claudio Punzo
    Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts
  • David Krizaj
    Ophthalmology and Visual Science, Moran Eye Ctr, University of Utah, Salt Lake City, Utah
  • Footnotes
    Commercial Relationships  Tunde Molnar, None; Peter Barabas, None; Claudio Punzo, None; David Krizaj, None
  • Footnotes
    Support  NIH Grant EY13870, P30EY014800; The International Retina Research Foundation, Foundation Fighting Blindness, Moran TIGER award, unrestricted grant from RPB to the Moran Eye Center, University of Utah
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 6581. doi:
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    • Get Citation

      Tunde Molnar, Peter Barabas, Claudio Punzo, David Krizaj; Store-operated Calcium Entry Regulates Intracellular Calcium Homeostasis In Mouse Rod Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6581.

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Abstract

Purpose: : To measure resting [Ca2+]i in mouse rods and to determine the properties of store-operated calcium entry (SOCE) within different rod compartments. We also assessed whether SOCE in mouse photoreceptors is mediated by TRPC1 and/or TRPC3 channels which can function as store-operated channels in non-excitable cells.

Methods: : Optical imaging was performed in dissociated mouse rods prepared from wild type and Trpc1/Trpc3 (TRPC1/3-/-) double knockout mouse retinas. Cells were loaded with fura-2 AM, excited at 340/380 nm and visualized using high-resolution 14 bit cooled CCD cameras. Voltage-operated and store-operated signals were evoked with high KCl and prolonged depletion of intracellular Ca2+ stores within the endoplasmic reticulum (ER). RT-PCR and in situ hybridization were performed using primers for mouse SOC channel candidates.

Results: : Resting [Ca2+]i levels in wild type mouse rod somata were 85 ± 15 nM with a median concentration of 55 nM (N=449). Depolarization elevated perikaryal [Ca2+]i >400 nM, indicating the maintained excitability of dissociated rods. Depletion of ER stores in Ca2+-free saline supplemented with cyclopiazonic acid induced SOCE (371 ± 30 nM) manifested as sustained [Ca2+]i overshoots following the return to control Ca2+ -containing saline. Sustained divalent cation entry was visualized as La3+-, and 1-oleoyl-2-acetyl-glycerol (OAG)-sensitive quenching of Fura-2 by Mn2+. Mouse rods showed prominent Trpc1 and Trpc3 mRNA expression that was reduced in Pde6brd1 retinas. Genetic ablation of TRPC1 and TRPC3 channels had little effect on baseline [Ca2+]i (84 ± 7 nM) or SOCE (452 ± 29 nM) in cells isolated from knockout animals. However, analysis of distribution of [Ca2+]i in the TRPC1/3-/- cohort showed a significant decrease in number of rods with elevated (100-250 nM) [Ca2+]i levels.

Conclusions: : We found that SOCE mediates significant Ca2+ influx in mouse rod photoreceptor cell bodies and synaptic terminals. This pathway was activated by low [Ca2+]i and depletion of ER stores, indicating that it may play a disproportionately prominent role under light-adapted conditions. TRPC1 and TRPC3 channels do not mediate rod SOCE but may contribute to Ca2+ overload in stressed rods.

Keywords: photoreceptors • calcium • ion channels 
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