L-type Ca2+ Channels at Low External Calcium Differentially Regulate Neurotransmitter Release in Proximal–Distal Compartments of the Frog Neuromuscular Junction

L-type Ca 2+ channels (LTCCs) are key elements in electromechanical coupling in striated muscles and formation of neuromuscular junctions (NMJs). However, the significance of LTCCs in regulation of neurotransmitter release is still far from understanding. Here, we found that LTCCs can increase evoke...

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Bibliographic Details
Published in:Cellular and molecular neurobiology 2022-11, Vol.42 (8), p.2833-2847
Main Authors: Tsentsevitsky, A. N., Petrov, A. M.
Format: Article
Language:English
Subjects:
Biomedical and Life Sciences
Biomedicine
Calcium channels
Calcium channels (L-type)
Cell Biology
Exocytosis
Kinases
Lipid rafts
Muscles
Neurobiology
Neuromuscular junctions
Neurosciences
Neurotransmitter release
Original Research
Protein kinase C
Synchronization
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Summary:L-type Ca 2+ channels (LTCCs) are key elements in electromechanical coupling in striated muscles and formation of neuromuscular junctions (NMJs). However, the significance of LTCCs in regulation of neurotransmitter release is still far from understanding. Here, we found that LTCCs can increase evoked neurotransmitter release (especially asynchronous component) and spontaneous exocytosis in two functionally different compartment of the frog NMJ, namely distal and proximal parts. The effects of LTCC blockage on evoked and spontaneous release as well as timing of exocytotic events were prevented by inhibition of either protein kinase C (PKC) or P2Y receptors (P2Y-Rs). Hence, endogenous signaling via P2Y-R/PKC axis can sustain LTCC activity. Application of ATP, a co-neurotransmitter able to activate P2Y-Rs, suppressed both evoked and spontaneous exocytosis in distal and proximal parts. Surprisingly, inhibition of LTCCs (but not PKC) decreased the negative action of exogenous ATP on evoked (only in distal part) and spontaneous exocytosis. Lipid raft disruption suppressed (1) action of LTCC antagonist on neurotransmitter release selectively in distal region and (2) contribution of LTCCs in depressant effect of ATP on evoked and spontaneous release. Thus, LTCCs can enhance and desynchronize neurotransmitter release at basal conditions (without ATP addition), but contribute to ATP-mediated decrease in the exocytosis. The former action of LTCCs relies on P2Y-R/PKC axis, whereas the latter is triggered by exogenous ATP and PKC-independent. Furthermore, relevance of lipid rafts for LTCC function as well as LTCCs for ATP effects is different in distal and proximal part of the NMJ. Graphic Abstract
ISSN:0272-4340
1573-6830
DOI:10.1007/s10571-021-01152-w