Scorpion alpha and alpha-like toxins differentially interact with sodium channels in mammalian CNS and periphery.
Scorpion alpha-toxins from Leiurus quinquestriatus hebraeus, LqhII and LqhIII, are similarly toxic to mice when administered by a subcutaneous route, but in mouse brain LqhII is 25-fold more toxic. Examination of the two toxins effects in central nervous system (CNS), peripheral preparations and expressed sodium channels revealed the basis for their differential toxicity. In rat brain synaptosomes, LqhII binds with high affinity, whereas LqhIII competes only at high concentration for LqhII-binding sites in a voltage-dependent manner. LqhII strongly inhibits sodium current inactivation of brain rBII subtype expressed in HEK293 cells, whereas LqhIII is weakly active at 2 microM, suggesting that LqhIII affects sodium channel subtypes other than rBII in the brain. In the periphery, both toxins inhibit tetrodotoxin-sensitive sodium current inactivation in dorsal root ganglion neurons, and are strongly active directly on the muscle and on expressed muI channels. Only LqhII, however, induced repetitive end-plate potentials in mouse phrenic nerve-hemidiaphragm muscle preparation by direct effect on the motor nerve. Thus, rBII and sodium channel subtypes expressed in peripheral nervous system (PNS) serve as the main targets for LqhII but are mostly not sensitive to LqhIII. Toxicity of both toxins in periphery may be attributed to the direct effect on muscle. Our data elucidate, for the first time, how different toxins affect mammalian central and peripheral excitable cells, and reveal unexpected subtype specificity of toxins that interact with receptor site 3.
Gilles
N
N
CEA, Saclay, Département d'Ingénierie et d'Etudes des Protéines, 91191 Gif-sur-Yvette, France.
Chen
H
H
Wilson
H
H
Le Gall
F
F
Montoya
G
G
Molgo
J
J
Schönherr
R
R
Nicholson
G
G
Heinemann
S H
SH
Gordon
D
D
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D001921:Brain / Q000166:cytology; D001923:Brain Chemistry / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D005727:Ganglia, Spinal / Q000737:chemistry / Q000166:cytology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D007668:Kidney / Q000166:cytology; D008322:Mammals; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology; D009469:Neuromuscular Junction / Q000737:chemistry / Q000166:cytology; D009475:Neurons, Afferent / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010791:Phrenic Nerve / Q000737:chemistry* / Q000166:cytology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000378:metabolism / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry / Q000378:metabolism*; D013574:Synaptosomes / Q000737:chemistry / Q000187:drug effects / Q000502:physiology
C114938:Lqh II toxin; C114939:Lqh III toxin; D012604:Scorpion Venoms; D015222:Sodium Channels