A dual role for Ca v 1.4 Ca 2+ channels in the molecular and structural organization of the rod photoreceptor synapse.

Synapses are fundamental information processing units that rely on voltage-gated Ca ²⁺ (Ca _v ) channels to trigger Ca ²⁺ -dependent neurotransmitter release. Ca _v channels also play Ca ²⁺ -independent roles in other biological contexts, but whether they do so in axon terminals is unknown. Here, we addressed this unknown with respect to the requirement for Ca _v 1.4 L-type channels for the formation of rod photoreceptor synapses in the retina. Using a mouse strain expressing a non-conducting mutant form of Ca _v 1.4, we report that the Ca _v 1.4 protein, but not its Ca ²⁺ conductance, is required for the molecular assembly of rod synapses; however, Ca _v 1.4 Ca ²⁺ signals are needed for the appropriate recruitment of postsynaptic partners. Our results support a model in which presynaptic Ca _v channels serve both as organizers of synaptic building blocks and as sources of Ca ²⁺ ions in building the first synapse of the visual pathway and perhaps more broadly in the nervous system.
Competing Interests: JM, KR, RY, BW, JH, PD, VK, LD, SB, NA, MH, AL No competing interests declared
(© 2020, Maddox et al.)