Synaptic ribbons foster active zone stability and illumination-dependent active zone enrichment of RIM2 and Cav1.4 in photoreceptor synapses

Sci Rep. 2020 Apr 6;10(1):5957. doi: 10.1038/s41598-020-62734-0.

Abstract

Rod photoreceptor synapses use large, ribbon-type active zones for continuous synaptic transmission during light and dark. Since ribbons are physically connected to the active zones, we asked whether illumination-dependent changes of ribbons influence Cav1.4/RIM2 protein clusters at the active zone and whether these illumination-dependent effects at the active zone require the presence of the synaptic ribbon. We found that synaptic ribbon length and the length of presynaptic Cav1.4/RIM2 clusters are tightly correlated. Dark-adaptation did not change the number of ribbons and active zone puncta. However, mean ribbon length and length of presynaptic Cav1.4/RIM2 clusters increased significantly during dark-adaptation when tonic exocytosis is highest. In the present study, we identified by the analyses of synaptic ribbon-deficient RIBEYE knockout mice that synaptic ribbons are (1) needed to stabilize Cav1.4/RIM2 at rod photoreceptor active zones and (2) are required for the darkness-induced active zone enrichment of Cav1.4/RIM2. These data propose a role of the ribbon in active zone stabilization and suggest a homeostatic function of the ribbon in illumination-dependent active zone remodeling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels, L-Type / genetics
  • Calcium Channels, L-Type / metabolism*
  • Dark Adaptation / physiology*
  • Female
  • Homeostasis / physiology
  • Male
  • Mice
  • Mice, Knockout
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Synapses / metabolism*
  • Synaptic Transmission / physiology
  • rab3 GTP-Binding Proteins / genetics
  • rab3 GTP-Binding Proteins / metabolism*

Substances

  • Cacna1f protein, mouse
  • Calcium Channels, L-Type
  • Rim2 protein, mouse
  • rab3 GTP-Binding Proteins