Interaction of the scorpion toxin discrepin with Kv4.3 channels and A-type K(+) channels in cerebellum granular cells.
BACKGROUND
The peptide discrepin from the α-KTx15 subfamily of scorpion toxins preferentially affects transient A-type potassium currents, which regulate many aspects of neuronal function in the central nervous system. However, the specific Kv channel targeted by discrepin and the molecular mechanism of interaction are still unknown.


METHODS
Different variant peptides of discrepin were chemically synthesized and their effects were studied using patch clamp technique on rat cerebellum granular cells (CGC) and HEK cells transiently expressing Kv4.3 channels.


RESULTS
Functional analysis indicated that nanomolar concentrations of native discrepin blocked Kv4.3 expressed channels, as previously observed in CGC. Similarly, the apparent affinities of all mutated peptides for Kv4.3 expressed channels were analogous to those found in CGC. In particular, in the double variant [V6K, D20K] the apparent affinity increased about 10-fold, whereas in variants carrying a deletion (ΔK13) or substitution (K13A) at position K13, the blockage was removed and the apparent affinity decreased more than 20-fold.


CONCLUSIONS
These results indicate that Kv4.3 is likely the target of discrepin and highlight the importance of the basic residue K13, located in the α-helix of the toxin, for current blockage.


CONCLUSIONS
We report the first example of a Kv4 subfamily potassium channel blocked by discrepin and identify the amino acid residues responsible for the blockage. The availability of discrepin variant peptides stimulates further research on the functions and pharmacology of neuronal Kv4 channels and on their possible roles in neurodegenerative disorders.
Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genova, Italy. Electronic address: picco@ge.ibf.cnr.it.
Cristiana
C
Picco
Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología/UNAM, Apartado Postal 510-3, Cuernavaca 62210, Mexico. Electronic address: corzo@ibt.unam.mx.
Gerardo
G
Corzo
Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología/UNAM, Apartado Postal 510-3, Cuernavaca 62210, Mexico.
Lourival D
LD
Possani
Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genova, Italy.
Gianfranco
G
Prestipino
D000595:Amino Acid Sequence; D000818:Animals; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D017433:Protein Structure, Secondary; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D012605:Scorpions / Q000737:chemistry; D017384:Sequence Deletion; D051672:Shal Potassium Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
D012604:Scorpion Venoms; D051672:Shal Potassium Channels; C509989:discrepin protein, Tityus discrepans
A-type currents; Discrepin; Heterologous expression; K(+) channel; Scorpion toxin