Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

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.

92 

Made with FlippingBook - Online magazine maker