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Immunochemical studies have suggested a tight association of syntaxin with N-type calcium channels. Syntaxin specifically interacts with the fusion proteins containing the cytoplasmic loop (LII-III) between homologous repeats II and III of the alpha 1 subunit of the class B N-type calcium channel (alpha 1B) from rat brain, but not with those of the class A(More)
Presynaptic Ca2+ channels are crucial elements in neuronal excitation-secretion coupling. In addition to mediating Ca2+ entry to initiate transmitter release, they are thought to interact directly with proteins of the synaptic vesicle docking/fusion machinery. Here we report isoform-specific, stoichiometric interaction of the BI and rbA isoforms of the(More)
Neurotransmitter release is initiated by influx of Ca2+ through voltage-gated Ca2+ channels, within 200 microseconds of the action potential arriving at the synaptic terminal, as the Ca2+ concentration increases from 100 nM to > 200 microM. Exocytosis requires high Ca2+ concentration, with a threshold of 20-50 microM and half-maximal activation at 190(More)
In chromaffin cells the number of large dense-core vesicles (LDCVs) which can be released by brief, intense stimuli represents only a small fraction of the 'morphologically docked' vesicles at the plasma membrane. Recently, it was shown that Munc13-1 is essential for a post-docking step of synaptic vesicle fusion. To investigate the role of Munc13-1 in LDCV(More)
Neurotransmitters are released by Ca(2+)-triggered exocytotic fusion of synaptic vesicles. Before fusion, vesicles dock at a specialised presynaptic plasma membrane region, the active zone, where they are primed to a fusion competent state. The nature of this priming reaction has long been enigmatic. Recent evidence demonstrates that priming is an essential(More)
ADP ribosylation factors (ARFs) represent a family of small monomeric G proteins that switch from an inactive, GDP-bound state to an active, GTP-bound state. One member of this family, ARF6, translocates on activation from intracellular compartments to the plasma membrane and has been implicated in regulated exocytosis in neuroendocrine cells. Because GDP(More)
Presynaptic N-type calcium channels interact with syntaxin and synaptosome-associated protein of 25 kDa (SNAP-25) through a binding site in the intracellular loop connecting domains II and III of the alpha1 subunit. This binding region was loaded into embryonic spinal neurons of Xenopus by early blastomere injection. After culturing, synaptic transmission(More)
cAMP-dependent protein kinase A (PKA) can modulate synaptic transmission by acting directly on unknown targets in the neurotransmitter secretory machinery. Here we identify Snapin, a protein of relative molecular mass 15,000 that is implicated in neurotransmission by binding to SNAP-25, as a possible target. Deletion mutation and site-directed mutagenetic(More)
Neurotransmitter release is triggered by the influx of Ca(2+) into the presynaptic terminal through voltage gated Ca(2+)-channels. The shape of the presynaptic Ca(2+) signal largely determines the amount of released quanta and thus the size of the synaptic response. Ca(2+)-channel function is modulated in particular by the auxiliary beta-subunits that(More)
The highly conserved SNARE proteins, SNAP-25, syntaxin and synaptobrevin, form a tight ternary complex, which is essential for exocytosis. Crystallization of this complex revealed a four-helix bundle with an unusual hydrophilic layer (zero layer) in its center. In order to evaluate the role of this layer in different kinetic components of secretion, we used(More)