Point-mutations related to the loss of batrachotoxin binding abolish the grayanotoxin effect in Na(+) channel isoforms.
The effect of grayanotoxin (GTX) on site-specific mutants of the alpha-subunit of rat skeletal muscle Na(+) channels (micro1) (micro1-I433K, micro1-N434K and micro1-L437K), which are resistant to batrachotoxin (BTX) (Wang and Wang (1998) Proc Natl Acad Sci USA, 95, 2653-2658) was studied using a whole-cell patch-clamp method. The GTX modification of the Na(+) channels was detected as a characteristic-sustained Na(+) current flow with repetitive pulses. We also studied the GTX action on mutants of the alpha-subunit of rat heart Na(+) channels (RH1) (RH1-V406K and RH1-L410K) which match with micro1-I433 and micro1-L437. All the mutants lost their sensitivity to GTX. This finding indicates that GTX may share a binding site with BTX in transmembrane segment I-S6 of two different Na(+) channel isoforms, micro1 and RH1.
Ishii
H
H
Department of Physiology, School of Medicine, Hiroshima University, Hiroshima, 734-8551, Japan.
Kinoshita
E
E
Kimura
T
T
Yakehiro
M
M
Yamaoka
K
K
Imoto
K
K
Mori
Y
Y
Seyama
I
I
D000818:Animals; D001496:Batrachotoxins / Q000378:metabolism / Q000494:pharmacology*; D017931:DNA Primers; D004224:Diterpenes / Q000378:metabolism / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics; D007536:Isomerism; D018482:Muscle, Skeletal / Q000737:chemistry; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D018408:Patch-Clamp Techniques; D017354:Point Mutation; D051381:Rats; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D001496:Batrachotoxins; D017931:DNA Primers; D004224:Diterpenes; D015222:Sodium Channels; C020750:grayanotoxin II