Structure/function characterization of micro-conotoxin KIIIA, an analgesic, nearly irreversible blocker of mammalian neuronal sodium channels.
نویسندگان
چکیده
Peptide neurotoxins from cone snails continue to supply compounds with therapeutic potential. Although several analgesic conotoxins have already reached human clinical trials, a continuing need exists for the discovery and development of novel non-opioid analgesics, such as subtype-selective sodium channel blockers. Micro-conotoxin KIIIA is representative of micro-conopeptides previously characterized as inhibitors of tetrodotoxin (TTX)-resistant sodium channels in amphibian dorsal root ganglion neurons. Here, we show that KIIIA has potent analgesic activity in the mouse pain model. Surprisingly, KIIIA was found to block most (>80%) of the TTX-sensitive, but only approximately 20% of the TTX-resistant, sodium current in mouse dorsal root ganglion neurons. KIIIA was tested on cloned mammalian channels expressed in Xenopus oocytes. Both Na(V)1.2 and Na(V)1.6 were strongly blocked; within experimental wash times of 40-60 min, block was reversed very little for Na(V)1.2 and only partially for Na(V)1.6. Other isoforms were blocked reversibly: Na(V)1.3 (IC50 8 microM), Na(V)1.5 (IC50 284 microM), and Na(V)1.4 (IC50 80 nM). "Alanine-walk" and related analogs were synthesized and tested against both Na(V)1.2 and Na(V)1.4; replacement of Trp-8 resulted in reversible block of Na(V)1.2, whereas replacement of Lys-7, Trp-8, or Asp-11 yielded a more profound effect on the block of Na(V)1.4 than of Na(V)1.2. Taken together, these data suggest that KIIIA is an effective tool to study structure and function of Na(V)1.2 and that further engineering of micro-conopeptides belonging to the KIIIA group may provide subtype-selective pharmacological compounds for mammalian neuronal sodium channels and potential therapeutics for the treatment of pain.
منابع مشابه
Interactions of key charged residues contributing to selective block of neuronal sodium channels by μ-conotoxin KIIIA.
Voltage-gated sodium channels are important in initiating and propagating nerve impulses in various tissues, including cardiac muscle, skeletal muscle, the brain, and the peripheral nerves. Hyperexcitability of these channels leads to such disorders as cardiac arrhythmias (Na(v)1.5), myotonias (Na(v)1.4), epilepsies (Na(v)1.2), and pain (Na(v)1.7). Thus, there is strong motivation to identify i...
متن کاملCooccupancy of the outer vestibule of voltage-gated sodium channels by micro-conotoxin KIIIA and saxitoxin or tetrodotoxin.
The guanidinium alkaloids tetrodotoxin (TTX) and saxitoxin (STX) are classic ligands of voltage-gated sodium channels (VGSCs). Like TTX and STX, micro-conotoxin peptides are pore blockers but with greater VGSC subtype selectivity. micro-Conotoxin KIIIA blocks the neuronal subtype Na(V)1.2 with nanomolar affinity and we recently discovered that KIIIA and its mutant with one fewer positive charge...
متن کاملInteractions of Key Charged Residues Contributing to Selective Block of Neuronal Sodium Channels by Μ-conotoxin Kiiia
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Cooccupancy of the Outer Vestibule of Voltage-Gated Sodium Channels by -Conotoxin KIIIA and Saxitoxin or Tetrodotoxin
Zhang M-M, Gruszczynski P, Walewska A, Bulaj G, Olivera BM, Yoshikami D. Cooccupancy of the outer vestibule of voltage-gated sodium channels by -conotoxin KIIIA and saxitoxin or tetrodotoxin. J Neurophysiol 104: 88–97, 2010. First published April 2, 2010; doi:10.1152/jn.00145.2010. The guanidinium alkaloids tetrodotoxin (TTX) and saxitoxin (STX) are classic ligands of voltage-gated sodium chann...
متن کاملThe Tetrodotoxin Receptor of Voltage-Gated Sodium Channels—Perspectives from Interactions with μ-Conotoxins
Neurotoxin receptor site 1, in the outer vestibule of the conducting pore of voltage-gated sodium channels (VGSCs), was first functionally defined by its ability to bind the guanidinium-containing agents, tetrodotoxin (TTX) and saxitoxin (STX). Subsequent studies showed that peptide micro-conotoxins competed for binding at site 1. All of these natural inhibitors block single sodium channels in ...
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عنوان ژورنال:
- The Journal of biological chemistry
دوره 282 42 شماره
صفحات -
تاریخ انتشار 2007