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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
92
6-POS
Board 6
The Conotoxin Cr1 Potently Inhibits the Oncogenic Potassium Channel Kv10.1
Enoch Luis Baltazar
1
, Arlet Loza
2
, Sergio Róman-González
3
, Roberto Arreguin-Espinosa
3
,
Hernández-Cruz Arturo
2
, Picones Arturo
2
1
CONACyT - Instituto de Fisiología Celular,
2
Laboratorio Nacional de Canalopatías, Instituto
de Fisiología Celular, UNAM;
3
Instituto de Química, UNAM.
In recent years, ion channels have been proposed as potential tumor-promoters as well as
therapeutic targets for different types of malignancies. One of most studied ion channels in cancer
is the voltage-gated potassium channel ether à go-go 1 (Eag1 or Kv10.1). Different studies have
shown that Kv10.1 expression induces proliferation of several cancer cell lines and in vivo tumor
models, while blockage or silencing of the channel inhibits proliferation. Due to these findings,
Kv10.1 has been proposed as an early cancer biomarker. Moreover, its localization as a
transmembrane protein, makes this channel an ideal drug target. The goal of this work is to identify
new and potent Kv10.1 channel modulators. Using HEK293 cells stably expressing the human
Kv10.1 potassium channel (HEK-Kv10.1), we initially screened 40 different new potential
modulators by measuring Tl+ inflow by a fluorescence-based assay (FLIPR® Potassium Assay
Kit). We found that Cr1, a polypeptide toxin isolated from the marine cone snail Conus regularis
(a worm-hunting species collected along the Pacific coast of Mexico), decreased the Tl+ influx
mediated by Kv10.1 channels. In whole-cell patch-clamp recordings from HEK-Kv10.1, outward
K+ currents were activated from a holding voltage of -70 mV by 1-s duration voltage ramps from
-100 to +50 mV applied every 5 seconds. Cr1 (1 nM) inhibits peak current amplitude by 75%
measured at +50 mV. Cr1 inhibition showed no voltage dependency. Conductance-voltage
relationship fitted with a Boltzmann equation gave that Cr1 shifts the half-activation voltage
(V1/2) from 23.2 ± 1.6 mV to 57.9 ± 14.1 mV (control versus 1 nM Cr1, respectively), without
changing the slope factor. Cr1 exerted a concentration-dependent inhibition of Kv10.1 channels
with an IC50 of 4.5 pM. Cr1 inactivation by heating (75 °C for 30 min) and sonication (10 min)
completely abolished its inhibitory effects on Kv10.1 currents, in accordance with its polypeptide
nature. Our results demonstrate for the first time, a polypeptide toxin with a potent inhibitory
effect on Kv10.1 channel activity, then making Cr1 an attractive compound targeting Kv10.1.with
outstanding therapeutic potential. Supported by grants 279820 (Laboratorio Nacional de
Canalopatías), CB 240305 (Consejo Nacional de Ciencia y Tecnología; CONACYT), México and
Dirección General de Asuntos del Personal Académico (DGAPA-UNAM,) PAPIIT IN211616.