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Calcicludine, A Venom Peptide of the Kunitz-Type Protease Inhibitor Family, is a Potent Blocker of High-Threshold Ca2+ Channels with a High Affinity for L-Type Channels in Cerebellar Granule Neurons

Hugues Schweitz, Catherine Heurteaux, Patrick Bois, Danielle Moinier, Georges Romey and Michel Lazdunski
Proceedings of the National Academy of Sciences of the United States of America
Vol. 91, No. 3 (Feb. 1, 1994), pp. 878-882
Stable URL: http://www.jstor.org/stable/2363826
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Calcicludine, A Venom Peptide of the Kunitz-Type Protease Inhibitor Family, is a Potent Blocker of High-Threshold Ca2+ Channels with a High Affinity for L-Type Channels in Cerebellar Granule Neurons
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Abstract

Calcicludine (CaC) is a 60-amino acid polypeptide from the venom of Dendroaspis angusticeps. It is structurally homologous to the Kunitz-type protease inhibitor, to dendrotoxins, which block K+ channels, and to the protease inhibitor domain of the amyloid β protein that accumulates in Alzheimer disease. Voltage-clamp experiments on a variety of excitable cells have shown that CaC specifically blocks most of the high-threshold Ca2+ channels (L-, N-, or P-type) in the 10-100 nM range. Particularly high densities of specific 125I-labeled CaC binding sites were found in the olfactory bulb, in the molecular layer of the dentate gyrus and the stratum oriens of CA3 field in the hippocampal formation, and in the granular layer of the cerebellum. 125I-labeled CaC binds with a high affinity (Kd = 15 pM) to a single class of noninteracting sites in rat olfactory bulb microsomes. The distribution of CaC binding sites in cerebella of three mutant mice (Weaver, Reeler, and Purkinje cell degeneration) clearly shows that the specific high-affinity labeling is associated with granule cells. Electrophysiological experiments on rat cerebellar granule neurons in primary culture have shown that CaC potently blocks the L-type component of the Ca2+ current (K0.5 = 0.2 nM). Then CaC, in the nanomolar range, appears to be a highly potent blocker of an L-subtype of neuronal Ca2+ channels.

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