Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Conditional Knockout of Neurexins Alters the Contribution of Calcium Channel Subtypes to Presynaptic Ca2+-Influx

Version 1 : Received: 7 May 2024 / Approved: 7 May 2024 / Online: 7 May 2024 (23:49:57 CEST)

How to cite: Brockhaus, J.; Kahl, I.; Ahmad, M.; Repetto, D.; Reissner, C.; Missler, M. Conditional Knockout of Neurexins Alters the Contribution of Calcium Channel Subtypes to Presynaptic Ca2+-Influx. Preprints 2024, 2024050405. https://doi.org/10.20944/preprints202405.0405.v1 Brockhaus, J.; Kahl, I.; Ahmad, M.; Repetto, D.; Reissner, C.; Missler, M. Conditional Knockout of Neurexins Alters the Contribution of Calcium Channel Subtypes to Presynaptic Ca2+-Influx. Preprints 2024, 2024050405. https://doi.org/10.20944/preprints202405.0405.v1

Abstract

Presynaptic Ca2+-influx through voltage-gated Ca2+-channels (VGCC) is a key signal for synaptic vesicle release. Synaptic neurexins can partially determine the strength of transmission by regulating VGCCs. However, it is unknown whether neurexins modulate Ca2+-influx via all VGCC subtypes similarly. Here, we performed live cell imaging of synaptic boutons from primary hippocampal neurons with a Ca2+-indicator. We used the expression of inactive and active Cre recombinase to compare control to conditional knockout neurons lacking either all or selected neurexin variants. We found that reduced total presynaptic Ca2+-transients caused by the deletion of all neurexins were primarily due to the reduced contribution of P/Q-type VGCCs. The deletion of neurexin1α alone also reduced the total presynaptic Ca2+-influx but increased Ca2+-influx via N-type VGCCs. Moreover, we tested whether the decrease of Ca2+-influx induced by activation of cannabinoid receptor 1 (CB1-receptor) is modulated by neurexins. Unlike earlier observations emphasizing a role for β-neurexins, we found that the decrease of presynaptic Ca2+-transients induced by CB1-receptor activation depended more strongly on the presence of α-neurexins in hippocampal neurons. Together, our results suggest that neurexins have unique roles in the modulation of presynaptic Ca2+-influx through VGCC subtypes and that different neurexin variants may affect specific VGCCs.

Keywords

Neurexin; Calcium Channel Subtypes; Presynapse; Endocannabinoid System; Genetically Encoded Calcium Indicator

Subject

Biology and Life Sciences, Neuroscience and Neurology

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