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Immunoglobulin G fractions from patients with Lambert-Eaton myasthenic syndrome (LEMS), an autoimmune disease of neuromuscular transmission, immunoprecipitate 125I-labeled omega-conotoxin GVIA-labeled calcium channels solubilized from rat brain. A 58-kDa antigen was detected by probing Western blots of partially purified calcium channels with LEMS plasma(More)
A toxin was purified to homogeneity from the venom of the South American armed spider Phoneutria nigriventer and found to have a molecular mass of 8600 Da and a C-terminally amidated glycine residue. It appears to be identical to Toxin 1 (Tx1) isolated previously from this venom. Tx1 reversibly inhibited sodium currents in Chinese hamster ovary cells(More)
Neurotransmitter release from synaptic vesicles is triggered by voltage-gated calcium influx through P/Q-type or N-type calcium channels. Purification of N-type channels from rat brain synaptosomes initially suggested molecular interactions between calcium channels and two key proteins implicated in exocytosis: synaptotagmin I and syntaxin 1.(More)
Recent studies suggested that autoantibodies that bind to voltage-dependent calcium channels and activate calcium entry may play a role in the progressive degeneration of motoneurons in sporadic amyotrophic lateral sclerosis. Immunoassays were performed to assess autoantibody titer in patients with amyotrophic lateral sclerosis or Lambert-Eaton myasthenic(More)
P- and Q-type calcium channels, which trigger rapid neurotransmitter release at many mammalian synapses, are blocked by omega-conotoxin MVIIC. 125I-omega-Conotoxin MVIIC binding to rat cerebellar synaptosomes was not displaced by omega-conotoxins GVIA or MVIIA (Ki > 1 microM), which are selective for N-type calcium channels. Solubilized 125I-omega-conotoxin(More)
omega-Conotoxin-sensitive N-type calcium channels control neurotransmitter release at the nerve terminal and interact with proteins implicated in secretion. Solubilized omega-conotoxin receptors from rat brain synaptic membrane were immunoprecipitated by antibodies against calcium channel alpha 1 subunits, syntaxin, and a 105-kDa plasma membrane protein. A(More)
The binding of omega-conotoxin to isolated rat neurohypophysial nerve terminals, its effect on the depolarization-induced increase of cytoplasmic Ca2+ and on the potassium and electrically-induced release of vasopressin (AVP) have been studied. The results show that isolated neurosecretory nerve endings have calcium channels with a high affinity for(More)
Despite their high sequence homology, the peptide neurotoxins omega-conotoxin MVIIA and MVIIC selectively block N- and P/Q-type calcium channels, respectively. To study the recognition mechanism of calcium channel subtypes, two chimeric analogs of omega-conotoxin MVIIA and MVIIC were synthesized by exchanging their N- and C-terminal halves. Binding assay(More)
omega-Phonetoxin IIA (omegaPtxIIA), a peptide from spider venom (Phoneutria nigriventer), inhibits high threshold voltage-dependent calcium currents in neurons. To define its pharmacological specificity, we have used patch-clamp methods in cell lines expressing recombinant Ca(v)2.1, Ca(v)2.2, and Ca(v)2.3 channels (P/Q-, N-, and R-type currents,(More)