Depletion of calcium stores regulates calcium influx and signal transmission in rod photoreceptors

Tamas Szikra, Karen Cusato, Wallace B Thoreson, Peter Barabas, Theodore M. Bartoletti, David Krizaj

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Tonic synapses are specialized for sustained calcium entry and transmitter release, allowing them to operate in a graded fashion over a wide dynamic range. We identified a novel plasma membrane calcium entry mechanism that extends the range of rod photoreceptor signalling into light-adapted conditions. The mechanism, which shares molecular and physiological characteristics with store-operated calcium entry (SOCE), is required to maintain baseline [Ca2+]i in rod inner segments and synaptic terminals. Sustained Ca2+ entry into rod cytosol is augmented by store depletion, blocked by La3+ and Gd3+ and suppressed by organic antagonists MRS-1845 and SKF-96365. Store depletion and the subsequent Ca2+ influx directly stimulated exocytosis in terminals of light-adapted rods loaded with the activity-dependent dye FM1-43. Moreover, SOCE blockers suppressed rod-mediated synaptic inputs to horizontal cells without affecting presynaptic voltage-operated Ca2+ entry. Silencing of TRPC1 expression with small interference RNA disrupted SOCE in rods, but had no effect on cone Ca2+ signalling. Rods were immunopositive for TRPC1 whereas cone inner segments immunostained with TRPC6 channel antibodies. Thus, SOCE modulates Ca2+ homeostasis and light-evoked neurotransmission at the rod photoreceptor synapse mediated by TRPC1.

Original languageEnglish (US)
Pages (from-to)4859-4875
Number of pages17
JournalJournal of Physiology
Volume586
Issue number20
DOIs
StatePublished - Oct 23 2008

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Retinal Rod Photoreceptor Cells
Calcium
Retinal Photoreceptor Cell Inner Segment
1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
Light
Synapses
Exocytosis
Presynaptic Terminals
RNA Interference
Synaptic Transmission
Cytosol
Homeostasis
Coloring Agents
Cell Membrane
Antibodies

ASJC Scopus subject areas

  • Physiology

Cite this

Depletion of calcium stores regulates calcium influx and signal transmission in rod photoreceptors. / Szikra, Tamas; Cusato, Karen; Thoreson, Wallace B; Barabas, Peter; Bartoletti, Theodore M.; Krizaj, David.

In: Journal of Physiology, Vol. 586, No. 20, 23.10.2008, p. 4859-4875.

Research output: Contribution to journalArticle

Szikra, Tamas ; Cusato, Karen ; Thoreson, Wallace B ; Barabas, Peter ; Bartoletti, Theodore M. ; Krizaj, David. / Depletion of calcium stores regulates calcium influx and signal transmission in rod photoreceptors. In: Journal of Physiology. 2008 ; Vol. 586, No. 20. pp. 4859-4875.
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