scholarly journals Biochemical properties and subcellular distribution of the BI and rbA isoforms of alpha 1A subunits of brain calcium channels.

1996 ◽  
Vol 134 (2) ◽  
pp. 511-528 ◽  
Author(s):  
T Sakurai ◽  
R E Westenbroek ◽  
J Rettig ◽  
J Hell ◽  
W A Catterall
Keyword(s):  
Calcium Channels ◽  
Subcellular Distribution ◽  
Mossy Fiber ◽  
Biochemical Properties ◽  
Rabbit Brain ◽  
Nerve Terminals ◽  
Brain Membrane ◽  
Receptor Sites ◽  
Molecular Masses ◽  
Affinity Receptor

Biochemical properties and subcellular distribution of the class A calcium channel alpha 1 subunits (alpha 1A) from rat and rabbit brain were examined using site-directed anti-peptide antibodies specific for rat rbA (anti-CNA3) and for rabbit BI (anti-NBI-1 and anti-NBI-2) isoforms of alpha 1A. In immunoblotting experiments, anti-CNA3 specifically identifies multiple alpha 1A polypeptides with apparent molecular masses of 210, 190, and 160 kD, and anti-NBI-1 and anti-NBI-2 specifically recognize 190-kD alpha 1A polypeptides in rat brain membrane. In rabbit brain, anti-NBI-1 or anti-NBI-2 specifically detect alpha 1A polypeptides with apparent molecular masses of 220, 200, and 190 kD, while anti-CNA3 specifically recognizes 190-kD alpha 1A polypeptides. These polypeptides evidently represent multiple isoforms of alpha 1A present in both rat and rabbit brain. Anti-CNA3 specifically immunoprecipitates high affinity receptor sites for omega-conotoxin MVIIC (Kd approximately 100 pM), whereas anti-NBI-2 immunoprecipitates two distinct affinity receptor sites for omega-conotoxin MVIIC (Kd approximately 100 pM and approximately 1 microM). Coimmunoprecipitation experiments indicate that alpha 1A subunits recognized by anti-CNA3 and anti-NBI-2 are associated with syntaxin in a stable, SDS-resistant complex and with synaptotagmin. Immunofluorescence studies reveal that calcium channels recognized by anti-NBI-2 are localized predominantly in dendrites and nerve terminals forming synapses on them, while calcium channels recognized by anti-CNA3 are localized more prominently in cell bodies and in nerve terminals. The mossy fiber terminals in hippocampus and the terminals of climbing and parallel fibers in cerebellum are differentially stained by these isoform-specific antibodies. These results indicate that both rbA and BI isoforms of alpha 1A are expressed in rat and rabbit brain and form calcium channels having alpha 1A subunits with distinct molecular mass, pharmacology, and subcellular localization.

scholarly journals L-Type Calcium Channels Are Required for One Form of Hippocampal Mossy Fiber LTP

1998 ◽  
Vol 79 (4) ◽  
pp. 2181-2190 ◽  
Author(s):  
Ajay Kapur ◽  
Mark F. Yeckel ◽  
Richard Gray ◽  
Daniel Johnston
Keyword(s):  
Calcium Channels ◽  
High Frequency ◽  
Pyramidal Neurons ◽  
Mossy Fiber ◽  
Calcium Influx ◽  
Calcium Transients ◽  
High Frequency Stimulation ◽  
Frequency Stimulation ◽  
Ca3 Pyramidal Neurons ◽  
Postsynaptic Calcium

Kapur, Ajay, Mark F. Yeckel, Richard Gray, and Daniel Johnston. L-type calcium channels are required for one form of hippocampal mossy fiber LTP. J. Neurophysiol. 79: 2181–2190, 1998. The requirement of postsynaptic calcium influx via L-type channels for the induction of long-term potentiation (LTP) of mossy fiber input to CA3 pyramidal neurons was tested for two different patterns of stimulation. Two types of LTP-inducing stimuli were used based on the suggestion that one of them, brief high-frequency stimulation (B-HFS), induces LTP postsynaptically, whereas the other pattern, long high-frequency stimulation (L-HFS), induces mossy fiber LTP presynaptically. To test whether or not calcium influx into CA3 pyramidal neurons is necessary for LTP induced by either pattern of stimulation, nimodipine, a L-type calcium channel antagonist, was added during stimulation. In these experiments nimodipine blocked the induction of mossy fiber LTP when B-HFS was given [34 ± 5% (mean ± SE) increase in control versus 7 ± 4% in nimodipine, P < 0.003]; in contrast, nimodipine did not block the induction of LTP with L-HFS (107 ± 10% in control vs. 80 ± 9% in nimodipine, P > 0.05). Administration of nimodipine after the induction of LTP had no effect on the expression of LTP. In addition, B- and L-HFS delivered directly to commissural/associational fibers in stratum radiatum failed to induce a N-methyl-d-aspartate-independent form of LTP, obviating the possibility that the presumed mossy fiber LTP resulted from potentiation of other synapses. Nimodipine had no effect on calcium transients recorded from mossy fiber presynaptic terminals evoked with the B-HFS paradigm but reduced postsynaptic calcium transients. Our results support the hypothesis that induction of mossy fiber LTP by B-HFS is mediated postsynaptically and requires entry of calcium through L-type channels into CA3 neurons.

scholarly journals Biochemical properties and subcellular distribution of the neuronal class E calcium channel alpha 1 subunit

1995 ◽  
Vol 15 (10) ◽  
pp. 6419-6432 ◽  
Author(s):  
CT Yokoyama ◽  
RE Westenbroek ◽  
JW Hell ◽  
TW Soong ◽  
TP Snutch ◽  
...  
Keyword(s):  
Calcium Channel ◽  
Subcellular Distribution ◽  
Biochemical Properties ◽  
Class E

scholarly journals Characterization of the interleukin 2 receptors (IL-2R) expressed on human natural killer cells activated in vivo by IL-2: association of the p64 IL-2R gamma chain with the IL-2R beta chain in functional intermediate-affinity IL-2R.

1992 ◽  
Vol 176 (2) ◽  
pp. 531-541 ◽  
Author(s):  
S D Voss ◽  
P M Sondel ◽  
R J Robb
Keyword(s):  
Cell Surface ◽  
Nk Cells ◽  
Binding Sites ◽  
Interleukin 2 ◽  
Affinity Binding ◽  
Beta Chain ◽  
Gamma Chain ◽  
Receptor Sites ◽  
Affinity Receptor

Interleukin 2 (IL-2) receptors expressed on the surface of activated T cells and natural killer (NK) cells exhibit a variety of affinity states depending on their subunit composition. Low-affinity binding is associated with a 55-kDa alpha chain, intermediate-affinity binding with a 70-75-kD beta chain, and high-affinity binding with a bimolecular complex of the alpha and beta subunits. In a previous study of the IL-2 receptors expressed on NK cells obtained from cancer patients after in vivo IL-2 therapy, we documented a discrepancy between the level of beta chain and the level of intermediate-affinity IL-2 binding sites expressed on the cell surface. Based on this result, we postulated that formation of intermediate-affinity receptor sites required a component in addition to the beta chain, and that this component was present at limiting levels in the patient NK cells. In the present study we have examined the structure of the intermediate-affinity receptor complex using monoclonal antibodies that recognize the beta chain, but that do not interfere with its ability to bind IL-2. Evidence is presented establishing the physical association of a novel protein of 64 kD with the beta chain in intermediate-affinity IL-2 binding sites. This molecule, termed IL-2R gamma chain, coprecipitated with beta chains prepared from cells that had been incubated with IL-2, but was undetectable in immunoprecipitates prepared in the absence of IL-2. Examination of gamma chain expression in post-IL-2 therapy NK cells, where only low levels of intermediate-affinity IL-2 binding were detectable, revealed that the gamma chain was associated with, on average, only 10-12% of the beta chains expressed on such cells. This contrasted with approximately equal levels of beta and gamma chain expression on YT cells, a cell line that has both high levels of cell surface beta chain expression and high levels of IL-2 binding. Thus, the ratio of gamma chain to beta chain present in the immunoprecipitates roughly correlated with the proportion of beta chain involved in intermediate-affinity receptor sites. This result suggests that the 64-kD gamma chain is the component responsible for regulating the affinity of IL-2 association with the beta subunit. By further defining the structural components necessary for IL-2 receptor formation, these studies provide additional insight into mechanisms whereby lymphocytes might regulate their responsiveness to IL-2.

318 Lambert-eaton syndrome antibodies act on omega-agatoxin ivasensitive calcium channels in cholinergic nerve terminals

1997 ◽  
Vol 28 ◽  
pp. S59 ◽  
Author(s):  
Yutaka Kirino ◽  
Yasushi Satoh ◽  
Naohide Hirashima ◽  
Hiroshi Tokumaru ◽  
Masanori Takahashi ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Nerve Terminals ◽  
Cholinergic Nerve ◽  
Cholinergic Nerve Terminals
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