Subcellular propagation of calcium waves in Müller glia does not require autocrine/paracrine purinergic signaling

Abstract

The polarized morphology of radial glia allows them to functionally interconnect different layers of CNS tissues including the retina, cerebellum, and cortex. A likely mechanism involves propagation of transcellular Ca 2C waves which were proposed to involve purinergic signaling. Because it is not known whether ATP release is required for astroglial Ca 2C wave propagation we investigated this in mouse M€ uller cells, radial astroglia-like retinal cells in which in which waves can be induced and supported by Orai/TRPC1 (transient receptor potential isoform 1) channels. We found that depletion of endoplasmic reticulum (ER) stores triggers regenerative propagation of transcellular Ca 2C waves that is independent of ATP release and activation of P 2 X and P 2 Y receptors. Both the amplitude and kinetics of transcellular, depletion-induced waves were resistant to non-selective purinergic P 2 antagonists such as pyridoxalphosphate-6-azophenyl-2 0 ,4 0 -disulfonic acid (PPADS). Thus, storeoperated calcium entry (SOCE) is itself sufficient for the initiation and subcellular propagation of calcium waves in radial glia.

Cholesterol regulates polymodal sensory transduction in Müller glia

“…Müller cells were dissociated as described (Molnár et al, ; Phuong, Yarishkin, & Križaj, ). Following enucleation, retinas were dissected in cold L15 medium containing 20 mM D‐glucose, 10 mM Na‐HEPES, 2 mM Na‐pyruvate, 0.3 mM Na‐ascorbate, and 1 mM glutathione.…”

“…Retinal pieces were incubated in L‐15 medium, and cells dissociated, plated and identified as described (Phuong et al, ). The extracellular recording solution contained (in mM): 98.5 NaCl, 5 KCl, 3 MgCl 2 , 2 CaCl 2 , 10 HEPES, 10 D‐glucose, 93 mannitol (pH 7.4; 300 ± 10 mOsm).…”

TRPV4 Does Not Regulate the Distal Retinal Light Response

“…The strong expression levels of TRPV4 mRNA/protein in the cornea (Mergler et al 2012), ciliary body (Jo et al 2016), trabecular meshwork (Ryskamp et al 2016), lens (Shahidullah et al 2012), and retina (Ryskamp et al 2011) predict that this polymodal nonselective cation channel contributes to the regulation of aqueous fluid transport, accommodation, ocular pressure sensing, endocannabinoid signaling, and/or volume regulation in the eye (Krizaj et al 2014; Krizaj 2016); however whether and what roles TRPV4 plays in visual signaling is unknown. Here, we show that TRPV4 activation in Müller cells, radial glia that play a key role in retinal volume regulation and transretinal propagation of calcium waves (Jo et al 2015; Phuong et al 2016), induces a calcium response in adjacent photoreceptors. Moreover, we tested the hypothesis that TRPV4 activation modulates the light response in the outer retina by recording field potentials in wild-type and TRPV4 −/− mice under scotopic and photopic conditions.…”

Inhibition of altered Orai1 channels in Müller cells protects photoreceptors in retinal degeneration

“…Orai1 expression of MGCs that protect retinal neurons is suspected to buffer Ca 2+ homoeotic (Molnár et al, 2016). SOCE is itself sufficient for the initiation and subcellular propagation of Ca 2+ waves in mouse MGCs that are independent of ATP release and activation of P 2 X and P 2 Y receptors (Phuong et al, 2016). The intraocular pressure‐induced gliotic response is facilitated in the absence of TRPC1 (Molnár et al, 2016).…”