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Imperatoxin A (IpTx a ) from Pandinus imperator stimulates [ 3 H]ryanodine binding to RyR3 channels
Author(s) -
Simeoni Ilenia,
Rossi Daniela,
Zhu Xinsheng,
Garcı́a Jesus,
Valdivia Hector H.,
Sorrentino Vincenzo
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)03013-7
Subject(s) - ryanodine receptor , ryr1 , ryanodine receptor 2 , gene isoform , calcium , chemistry , biophysics , voltage dependent calcium channel , biology , biochemistry , receptor , organic chemistry , gene
The effect of imperatoxin A (IpTx a ) on the ryanodine receptor type 3 (RyR3) was studied. IpTx a stimulates [ 3 H]ryanodine binding to RyR3‐containing microsomes, but this effect requires toxin concentrations higher than those required to stimulate RyR1 channels. The effect of IpTx a on RyR3 channels was observed at calcium concentrations in the range 0.1 μM to 10 mM. By contrast, RyR2 channels were not significantly affected by IpTx a in the same calcium ranges. Single channel current measurements indicated that IpTx a induced subconductance state in RyR3 channels that was similar to those observed with RyR1 and RyR2 channels. These results indicate that IpTx a is capable of inducing similar subconductance states in all three RyR isoforms, while stimulation of [ 3 H]ryanodine binding by this toxin results in isoform‐specific responses, with RyR1 being the most sensitive channel, RyR3 displaying an intermediate response and RyR2 the least responsive ones.