Syntaxin I modulation of presynaptic calcium channel inactivation revealed by botulinum toxin C1

• Published in: The European journal of neuroscience Vol. 17; no. 6; pp. 1303 - 1305
• Main Author: Stanley, Elise F.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01-03-2003
• Subjects: Animals; Antigens, Surface - physiology; Botulinum Toxins - pharmacology; Calcium Channels, N-Type - drug effects; Calcium Channels, N-Type - physiology; CAV2.2; chick ciliary ganglion; Chick Embryo; Ganglia - drug effects; Ganglia - physiology; Membrane Potentials; modulation; N-type calcium channel; Nerve Tissue Proteins - physiology; Neurons - drug effects; Neurons - physiology; Patch-Clamp Techniques; presynaptic terminal; Presynaptic Terminals - drug effects; Presynaptic Terminals - physiology; Syntaxin 1; syntaxin I; transmitter release site
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1046/j.1460-9568.2003.02536.x

The chick ciliary ganglion calyx‐type nerve terminal was used to examine voltage‐sensitive inactivation of presynaptic N‐type Ca2+ channels and to test if this inactivation is modulated by the transmitter release‐associated protein syntaxin I. We tested the role of this protein with botulinum toxin C1 (BtC1) which cleaves syntaxin I close to its membrane anchor. The presynaptic Ca2+ current inactivated as two distinct populations with ∼75% inactivating at a depolarized potential, V1/2∼−15 mV, with the remainder inactivating at ∼−75 mV. BtC1 had no detectable effect on the latter component but resulted in a ∼7 mV positive shift in the V1/2 of the −15 mV inactivating component. These results confirm that the bulk of presynaptic N‐type Ca2+ channels are in general resistant to voltage dependent inactivation and provide the first direct evidence that the physiological properties of presynaptic nerve terminal Ca2+ channels are subject to modulation by release site‐associated proteins.