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bioRxiv · 10.1101/2024.02.26.582057

The intracellular Ca2+ sensitivity of transmitter release from neocortical boutons

Bornschein, G.·Brachtendorf, S.·Eshra, A.·Kraft, R.·Eilers, J.·Hallermann, S.·Schmidt, H.
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Abstract

Synaptotagmin 1 (Syt1) and Syt2 are the main Ca2+ sensors triggering synchronous release in the brain. The Ca2+-sensitivity of Syt2-triggered release has been studied in detail. However, for Syt1, the dominating isoform in the neocortex, quantitative detail is lacking. We measured the Ca2+-dependency of Syt1-triggered release at layer 5 pyramidal neuron synapses by laser photolysis of caged Ca2+. Syt1-triggered release had high Ca2+ affinity and positive cooperativity (EC50, 20 M; Hill coefficient, 3.57). It was steep in a dynamic range between [~]10 and [~]30 M that was covered by action potential-evoked release. A kinetic model reveals significant differences to models of Syt2-triggered release. Our results suggest that Syt1 optimizes neocortical synapses for high reliability at moderate local Ca2+ elevations and for high plastic controllability.

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Bornschein, G., Brachtendorf, S., Eshra, A., Kraft, R., Eilers, J., Hallermann, S., Schmidt, H.. 2024-02-28. The intracellular Ca2+ sensitivity of transmitter release from neocortical boutons. https://doi.org/10.1101/2024.02.26.582057

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