Expression and cellular localization of the voltage‐gated calcium channel α 2 δ 3 in the rodent retina

High‐voltage‐activated calcium channels are hetero‐oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca 2+ , neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α 1 pore‐forming subunit, which is associated with an extracellular α 2 δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α 2 δ 3 subunit in the mouse and rat retina is unknown. In this study using RT‐PCR, a single band at ∼305 bp corresponding to the predicted size of the α 2 δ 3 subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123‐kDa band. Immunohistochemistry with an affinity‐purified antibody to the α 2 δ 3 subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α 2 δ 3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α 2 δ 3 calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca‐channel‐mediated signaling in the retina. J. Comp. Neurol. 523:1443–1460, 2015. © 2015 Wiley Periodicals, Inc.