Differential inhibition of Ca2+ channels in mature rat cerebellar Purkinje cells by sFTX-3.3 and FTX-3.3

Dupere, Jonathan R. B.; Moya, E.; Blagbrough, Ian S.; Usowicz, Maria M.

doi:10.1016/0028-3908(95)00156-5

Cited by 17 publications

(18 citation statements)

References 37 publications

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“…Cell-attached recordings of Ca 2ϩ channel currents (Fig. 6A) from the soma or the first dendritic bifurcation with drug-free pipettes or drug-containing pipettes (6,36) demonstrated inhibition of the majority of the somatic Ca 2ϩ channel current (92%, Fig. 6B) and of the dendritic current (91%, Fig.…”

Section: Resultsmentioning

confidence: 99%

Alternative splicing generates a smaller assortment of Ca_V2.1 transcripts in cerebellar Purkinje cells than in the cerebellum

Kanumilli

Tringham

Payne

et al. 2006

Physiological Genomics

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Alternative splicing generates a smaller assortment of CaV2.1 transcripts in cerebellar Purkinje cells than in the cerebellum. Physiol Genomics 24: 86 -96, 2006. First published November 8, 2005 doi:10.1152/physiolgenomics.00149.2005.-P/Qtype calcium channels control many calcium-driven functions in the brain. The CACNA1A gene encoding the pore-forming CaV2.1 (␣1A) subunit of P/Q-type channels undergoes alternative splicing at multiple loci. This results in channel variants with different phenotypes. However, the combinatorial patterns of alternative splice events at two or more loci, and hence the diversity of CaV2.1 transcripts, are incompletely defined for specific brain regions and types of brain neurons. Using RT-PCR and splice variant-specific primers, we have identified multiple CaV2.1 transcript variants defined by different pairs of splice events in the cerebellum of adult rat. We have uncovered new splice variations between exons 28 and 34 (some of which predict a premature stop codon) and a new variation in exon 47 (which predicts a novel extended COOH-terminus). Single cell RT-PCR reveals that each individual cerebellar Purkinje neuron also expresses multiple alternative CaV2.1 transcripts, but the assortment is smaller than in the cerebellum. Two of these variants encode different extended COOH-termini which are not the same as those previously reported in Purkinje cells of the mouse. Our patch-clamp recordings show that calcium channel currents in the soma and dendrites of Purkinje cells are largely inhibited by a concentration of -agatoxin IVA selective for P-type over Q-type channels, suggesting that the different transcripts may form phenotypic variants of P-type calcium channels in Purkinje cells. These results expand the known diversity of Ca V2.1 transcripts in cerebellar Purkinje cells, and propose the selective expression of distinct assortments of Ca V2.1 transcripts in different brain neurons and species. splice variants; P type; calcium channels; Purkinje neurons 0 VOLTAGE-GATED calcium (Ca 2ϩ ) channels regulate numerous cellular functions, from neuronal electrical activity to intracellular signaling pathways. Diversity of Ca 2ϩ channels in the brain is apparent from the many roles that Ca 2ϩ channels play in different cell types and subcellular compartments (3). The diversity reflects, in part, the existence of nine classes of the pore-forming Ca V (␣1) subunit in the brain and alternative pre-mRNA splicing of the gene encoding each class of Ca V subunit (12, 17). P/Q-type Ca 2ϩ channels control many functions throughout the brain and contain a Ca V 2.1 subunit (also known as ␣ 1A ). However, information about splicing of the CACNA1A gene encoding Ca V 2.1 in different brain regions and neurons is incomplete (2,5,16,30,33,35,37). Augmentation of what is currently known about Ca V 2.1 splicing in the cerebellum and cerebellar Purkinje cells is of particular interest, because P-type currents in Purkinje cells are the prototypical P-type currents against which putative P-type and Q-...

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Section: Resultsmentioning

confidence: 99%

Alternative splicing generates a smaller assortment of Ca_V2.1 transcripts in cerebellar Purkinje cells than in the cerebellum

Kanumilli

Tringham

Payne

et al. 2006

Physiological Genomics

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“…Both an extract of funnel‐web spider venom (FTX) and a synthetic toxin sFTX (Dupere et al . 1996) have been shown to block transmission through the rat SCG (Gonzalez Burgos et al 1995).…”

Section: Resultsmentioning

confidence: 99%

Calcium channel subtypes differ at two types of cholinergic synapse in lumbar sympathetic neurones of guinea‐pigs

Ireland

Davies

McLachlan

1999

The Journal of Physiology

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Depolarization of a presynaptic nerve terminal leads to Ca¥ entry through voltage-dependent Ca¥ channels activating the release of transmitter by initiating exocytosis from vesicles. Functionally, low-voltage-activated (LVA) or highvoltage-activated (HVA) channels, with differing kinetics of inactivation, can be distinguished. These channels can be classified into at least five distinct subtypes (Zhang et al. 1993). The only LVA channel, the T-type channel, is blocked by low concentrations of Ni¥ (100 ìÒ;Fox et al. 1987). Four types of HVA channel have been identified: (i) L-type, blocked by dihydropyridines (e.g. nifedipine) (Fox et al. 1987); (ii) N-type, blocked by ù_conotoxin GVIA (ù_CTX GVIA; ECÛÑ = 0•7 nÒ; Boland et al. 1994); (iii) P_type, blocked by ù_agatoxin IVA (ù_Aga IVA ECÛÑ = 2 nÒ; Mintz et al. 1992;Randall & Tsien, 1995) and by ù_conotoxin MVIIC with slow binding kinetics (ù_CTX MVIIC; ECÛÑ = 50 nÒ; McDonough et al. 1996); and (iv) Q_type, blocked by ù_Aga IVA (ECÛÑ = 90 nÒ) and by ù_CTX MVIIC (fully blocked by 500 nÒ; Randall & Tsien, 1995). Other Ca¥ channels resistant to all these antagonists have been referred to as 'R-type' (Zhang et al. 1993;Randall & Tsien, 1995) but here they are called 'resistant' channels. At skeletal neuromuscular junctions, acetylcholine (ACh) release occurs via N-type channels in amphibians (Katz et al. 1995), whereas in mammals most ACh release is mediated via PÏQ-type channels (Katz et al. 1996), with a small contribution from resistant channels (Lin & Lin-Shiau, 1997). At mammalian sympathetic neuroeffector junctions (e.g. vas deferens; Smith & Cunnane, 1996) and neuro-neuronal synapses in the chick ciliary ganglion (Yawo & Chuhma, 1994), transmission predominantly depends on Ca¥ influx through N-type channels. The Ca¥ channels mediating synaptic transmission have also been widely studied in the central nervous system, for example, in the hippocampus and cerebellum (see Wu & Saggau, 1997) and spinal cord (Takahashi & Momiyama, 1993;Wall & Dale, 1994). Multiple types of presynaptic Ca¥ channel usually contribute to transmitter release at these central synapses. Most neuroneuronal synapses have been studied in brain slices using synaptic responses resulting from simultaneous activation of an unknown, but probably large, number of synaptic connections, so that differences between individual synapses cannot be observed. However, in a few cases, the channels involved in transmission have been determined for single synapses (Regehr & Mintz, 1994;Yawo & Chuhma, 1994;Poncer et al. 1997;Wu et al. 1998) where it has been confirmed that multiple types of presynaptic Ca¥ channel are involved. At the synapses in mammalian sympathetic ganglia, there are two distinct functional types of preganglionic cholinergic input. The majority of inputs give rise to subthreshold or 'weak' synaptic potentials, which must summate to initiate

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“…This toxin also was ineffective on the olfactory and rod CNG channels. Only the arginine polyamine, FTX (38), had a significant effect on CNG channels. When applied at a concentration of 10 M, FTX blocked approximately 80% of the cyclic nucleotide-dependent current at Ϫ80 mV, but was relatively ineffective at positive voltages.…”

Section: Resultsmentioning

confidence: 99%

Pseudechetoxin: A peptide blocker of cyclic nucleotide-gated ion channels

Brown

Haley

West

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

124

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Ion channels activated by the binding of cyclic nucleotides first were discovered in retinal rods where they generate the cell's response to light. In other systems, however, it has been difficult to unambiguously determine whether cyclic nucleotide-dependent processes are mediated by protein kinases, their classical effector enzymes, or cyclic nucleotide-gated (CNG) ion channels. Part of this difficulty has been caused by the lack of specific pharmacological tools. Here we report the purification from the venom of the Australian King Brown snake of a peptide toxin that inhibits current through CNG channels. This toxin, which we have named Pseudechetoxin (PsTx), was purified by cation exchange and RP-HPLC and has a molecular mass of about 24 kDa. When applied to the extracellular face of membrane patches containing the ␣-subunit of the rat olfactory CNG channel, PsTx blocked the cGMP-dependent current with a K i of 5 nM. Block was independent of voltage and required only a single molecule of toxin. PsTx also blocked CNG channels containing the bovine rod ␣-subunit with high affinity (100 nM), but it was less effective on the heteromeric version of the rod channel (K i Ϸ 3 M). We have obtained N-terminal and partial internal sequence data and the amino acid composition of PsTx. These data indicate that PsTx is a basic protein that exhibits some homology with helothermine, a toxin isolated from the venom of the Mexican beaded lizard. PsTx promises to be a valuable pharmacological tool for studies on the structure and physiology of CNG channels.

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Differential inhibition of Ca2+ channels in mature rat cerebellar Purkinje cells by sFTX-3.3 and FTX-3.3

Cited by 17 publications

References 37 publications

Alternative splicing generates a smaller assortment of Ca_V2.1 transcripts in cerebellar Purkinje cells than in the cerebellum

Alternative splicing generates a smaller assortment of Ca_V2.1 transcripts in cerebellar Purkinje cells than in the cerebellum

Calcium channel subtypes differ at two types of cholinergic synapse in lumbar sympathetic neurones of guinea‐pigs

Pseudechetoxin: A peptide blocker of cyclic nucleotide-gated ion channels

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