Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels

Tamas Szikra, Peter Barabas, Theodore M. Bartoletti, Wei Huang, Abram Akopian, Wallace B Thoreson, David Krizaj

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca2+ entry (SOCE) to Ca2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca2+ channels. Exposure to MRS 1845 resulted in ∼40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse.

Original languageEnglish (US)
Article numbere6723
JournalPloS one
Volume4
Issue number8
DOIs
StatePublished - Aug 21 2009

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cones (retina)
ion channels
Cell membranes
Ion Channels
Cones
homeostasis
Homeostasis
plasma membrane
Cell Membrane
Calcium
calcium
1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
Light
Synapses
Retinal Photoreceptor Cell Inner Segment
Cyclic Nucleotide-Gated Cation Channels
Retinal Cone Photoreceptor Cells
Electric potential
Lanthanoid Series Elements
Synaptic Potentials

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels. / Szikra, Tamas; Barabas, Peter; Bartoletti, Theodore M.; Huang, Wei; Akopian, Abram; Thoreson, Wallace B; Krizaj, David.

In: PloS one, Vol. 4, No. 8, e6723, 21.08.2009.

Research output: Contribution to journalArticle

Szikra, Tamas ; Barabas, Peter ; Bartoletti, Theodore M. ; Huang, Wei ; Akopian, Abram ; Thoreson, Wallace B ; Krizaj, David. / Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels. In: PloS one. 2009 ; Vol. 4, No. 8.
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