Distribution of the presynaptic calcium sensors, synaptotagmin I/II and synaptotagmin III, in the goldfish and rodent retinas

Amy K. Berntson, Catherine W. Morgans

    Research output: Contribution to journalArticlepeer-review

    26 Scopus citations

    Abstract

    Synaptic vesicle exocytosis is triggered by rises in calcium up to 100 μM at the site of vesicle fusion. The synaptic vesicle proteins synaptotagmin 1 and 2 (Syt I and Syt II) bind calcium at similarly high concentrations and have been proposed as the calcium sensors for fast neurotransmitter release. However, 1 μM calcium produces tonic transmitter release at photoreceptor and bipolar cell synapses in the goldfish retina, suggesting that these synapses use a higher affinity calcium sensor. Immunofluorescent staining with a panel of Syt I/II antibodies detected Syt I/II in both photoreceptor and bipolar cell terminals of the rodent retina. By contrast, no staining of either photoreceptor or protein kinase C (PKC)-labeled bipolar cell terminals was detected in the goldfish retina with any of the Syt I/II antibodies. The high affinity calcium sensor synaptotagmin 3 (Syt III) was localized to the synaptic layers of both goldfish and rodent retinas; however, while Syt III was associated with PKC- labeled bipolar cell terminals in the goldfish retina, it did not co-localize with PKC in the mouse retina. These results suggest that, unlike in their mammalian counterparts, synaptic vesicle exocytosis in goldfish photoreceptor and bipolar cell terminals utilizes a calcium sensor other than Syt I/II, possibly Syt III.

    Original languageEnglish (US)
    Pages (from-to)274-280
    Number of pages7
    JournalJournal of Vision
    Volume3
    Issue number4
    DOIs
    StatePublished - May 22 2003

    Keywords

    • Bipolar cells
    • Photoreceptors
    • Retina

    ASJC Scopus subject areas

    • Ophthalmology
    • Sensory Systems

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