Glycerotoxin stimulates neurotransmitter release from N-type Ca2+ channel expressing neurons.
Glycerotoxin (GLTx) is capable of stimulating neurotransmitter release at the frog neuromuscular junction by directly interacting with N-type Ca2+ (Cav2.2) channels. Here we have utilized GLTx as a tool to investigate the functionality of Cav2.2 channels in various mammalian neuronal preparations. We first adapted a fluorescent-based high-throughput assay to monitor glutamate release from rat cortical synaptosomes. GLTx potently stimulates glutamate secretion and Ca2+ influx in synaptosomes with an EC50 of 50 pm. Both these effects were prevented using selective Cav2.2 channel blockers suggesting the functional involvement of Cav2.2 channels in mediating glutamate release in this system. We further show that both Cav2.1 (P/Q-type) and Cav2.2 channels contribute equally to depolarization-induced glutamate release. We then investigated the functionality of Cav2.2 channels at the neonatal rat neuromuscular junction. GLTx enhances both spontaneous and evoked neurotransmitter release causing a significant increase in the frequency of postsynaptic action potentials. These effects were blocked by specific Cav2.2 channel blockers demonstrating that either GLTx or its derivatives could be used to selectively enhance the neurotransmitter release from Cav2.2-expressing mammalian neurons.
Schenning
Mitja
M
Molecular Dynamics of Synaptic Function Laboratory, The School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Proctor
Dustin T
DT
Ragnarsson
Lotten
L
Barbier
Julien
J
Lavidis
Nickolas A
NA
Molgó
Jordi J
JJ
Zamponi
Gerald W
GW
Schiavo
Giampietro
G
Meunier
Frederic A
FA
D000818:Animals; D020746:Calcium Channels, L-Type / Q000096:biosynthesis* / Q000235:genetics; D020864:Calcium Channels, N-Type; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D015801:Helminth Proteins; D066298:In Vitro Techniques; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism*; D009498:Neurotoxins / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012910:Snake Venoms / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014688:Venoms
C503279:Cacna1b protein, rat; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D015801:Helminth Proteins; D009498:Neurotoxins; D018377:Neurotransmitter Agents; D012910:Snake Venoms; D014688:Venoms; D018698:Glutamic Acid; C042564:glycerotoxin