Pulsed infrared releases ca2+ from the endoplasmic reticulum of cultured spiral ganglion neurons

John Barrett, Samantha Rincon, Jayanti Singh, Cristina Matthewman, Julio Pasos, Ellen Barrett, Suhrud M Rajguru

Research output: Contribution to journalReview article

1 Citation (Scopus)

Abstract

Inner ear spiral ganglion neurons were cultured from day 4 postnatal mice and loaded with a fluorescent Ca2+ indicator (fluo-4,-5F, or-5N). Pulses of infrared radiation (IR; 1,863 nm, 200 µs, 200–250 Hz for 2–5 s, delivered via an optical fiber) produced a rapid, transient temperature increase of 6–12°C (above a baseline of 24–30°C). These IR pulse trains evoked transient increases in both nuclear and cytosolic Ca2+ concentration ([Ca2+]) of 0.20–1.4 µM, with a simultaneous reduction of [Ca2+] in regions containing endoplasmic reticulum (ER). IR-induced increases in cytosolic [Ca2+] continued in medium containing no added Ca2+ (±Ca2+ buffers) and low [Na+], indicating that the [Ca2+] increase was mediated by release from intracellular stores. Consistent with this hypothesis, the IR-induced [Ca2+] response was prolonged and eventually blocked by inhibition of ER Ca2+-ATPase with cyclopiazonic acid, and was also inhibited by a high concentration of ryanodine and by inhibitors of inositol (1,4,5)-trisphosphate (IP3)-mediated Ca2+ release (xesto-spongin C and 2-aminoethoxydiphenyl borate). The thermal sensitivity of the response suggested involvement of warmth-sensitive transient receptor potential (TRP) channels. The IR-induced [Ca2+] increase was inhibited by TRPV4 inhibitors (HC-067047 and GSK-2193874), and immunostaining of spiral ganglion cultures demonstrated the presence of TRPV4 and TRPM2 that colocalized with ER marker GRP78. These results suggest that the temperature sensitivity of IR-induced [Ca2+] elevations is conferred by TRP channels on ER membranes, which facilitate Ca2+ efflux into the cytosol and thereby contribute to Ca2+-induced Ca2+-release via IP3 and ryanodine receptors. NEW & NOTEWORTHY Infrared radiation-induced photothermal effects release Ca2+ from the endoplasmic reticulum of primary spiral ganglion neurons. This Ca2+ release is mediated by activation of transient receptor potential (TRPV4) channels and involves amplification by Ca2+-induced Ca2+-release. The neurons immunostained for warmth-sensitive channels, TRPV4 and TRPM2, which colocalize with endoplasmic reticulum. Pulsed infrared radiation provides a novel experimental tool for releasing intracellular Ca2+, studying Ca2+ regulatory mechanisms, and influencing neuronal excitability.

Original languageEnglish (US)
Pages (from-to)509-524
Number of pages16
JournalJournal of Neurophysiology
Volume120
Issue number2
DOIs
StatePublished - Aug 1 2018

Fingerprint

Spiral Ganglion
Endoplasmic Reticulum
Transient Receptor Potential Channels
Neurons
Radiation
Inositol 1,4,5-Trisphosphate Receptors
Optical Fibers
Ryanodine
Ryanodine Receptor Calcium Release Channel
Temperature
Inositol 1,4,5-Trisphosphate
Calcium-Transporting ATPases
Inner Ear
Cytosol
Buffers
Hot Temperature
Membranes

Keywords

  • Ca photocontrol
  • Endoplasmic reticulum
  • Infrared stimulation
  • Optical stimulation
  • Spiral ganglion neurons
  • TRP channels

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

Pulsed infrared releases ca2+ from the endoplasmic reticulum of cultured spiral ganglion neurons. / Barrett, John; Rincon, Samantha; Singh, Jayanti; Matthewman, Cristina; Pasos, Julio; Barrett, Ellen; Rajguru, Suhrud M.

In: Journal of Neurophysiology, Vol. 120, No. 2, 01.08.2018, p. 509-524.

Research output: Contribution to journalReview article

Barrett, John ; Rincon, Samantha ; Singh, Jayanti ; Matthewman, Cristina ; Pasos, Julio ; Barrett, Ellen ; Rajguru, Suhrud M. / Pulsed infrared releases ca2+ from the endoplasmic reticulum of cultured spiral ganglion neurons. In: Journal of Neurophysiology. 2018 ; Vol. 120, No. 2. pp. 509-524.
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AU - Rincon, Samantha

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AU - Pasos, Julio

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AU - Rajguru, Suhrud M

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