Abstract
Purpose :
Determine precise localization of arrestin-1 in sub-compartments of rod synaptic terminals and its physiological function in rod synapses in vivo.
Methods :
WT C57bl mice and transgenic mouse lines expressing oligomerization-deficient arrestin-1-(F86A+F198A) at near-physiological level (M10 – 116+3% of WT) or expressing low levels of arrestin-1-(1-377) mutant on arestin-1 -/- background (Tr-4-arr1-/-, 4%; Tr-12-arr1-/-, 12%) were used to determine the localization of arrestin-1 in rod synapses by immunohistochemistry of retina sections and electron microscopy and the effect of arrestin-1 level on ERG b-wave.
Results :
The presence of arrestin-1 in rod synaptic terminals even in light-adapted retina was detected by many labs. These data suggest that arrestin-1 has specific functions in this compartment. To elucidate its function, co-localization of arrestin-1 with known synaptic proteins was assessed in mouse retinas. We found that WT and monomeric arrestin-1 co-localizes with glutamate transporter VGLUT1, but not with NSF, ribbon marker ribeye, or SNARE protein SNAP-25. Vesicles attached to the ribbon appeared devoid of associated arrestin-1. Mice with low levels of arrestin-1 demonstrated reduced ERG b-wave, suggesting that the deficit of arrestin-1 reduces light-dark difference in neurotransmitter release.
Conclusions :
WT and monomeric arrestin-1 localizes to synaptic vesicles, co-localizing with glutamate transporter VGLUT1, but is absent in vesicles docked to the ribbon. ERG data suggest that arrestin-1 plays a role in light-induced reduction of neurotransmitter release from rod terminals, which is the signal we perceive as light.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.