Ablation of αδ-1 inhibits cell-surface trafficking of endogenous N-type calcium channels in the pain pathway in vivo.

The auxiliary αδ calcium channel subunits play key roles in voltage-gated calcium channel function. Independent of this, αδ-1 has also been suggested to be important for synaptogenesis. Using an epitope-tagged knockin mouse strategy, we examined the effect of αδ-1 on Ca2.2 localization in the pain pathway in vivo, where Ca2.2 is important for nociceptive transmission and αδ-1 plays a critical role in neuropathic pain. We find Ca2.2 is preferentially expressed on the plasma membrane of calcitonin gene-related peptide-positive small nociceptors. This is paralleled by strong presynaptic expression of Ca2.2 in the superficial spinal cord dorsal horn. EM-immunogold localization shows Ca2.2 predominantly in active zones of glomerular primary afferent terminals. Genetic ablation of αδ-1 abolishes Ca2.2 cell-surface expression in dorsal root ganglion neurons and dramatically reduces dorsal horn expression. There was no effect of αδ-1 knockout on other dorsal horn pre- and postsynaptic markers, indicating the primary afferent pathways are not otherwise affected by αδ-1 ablation.