Neonatal NaV1.5 channels: pharmacological distinctive ness of a cancer-related voltage-gated sodium channel splice variant

摘要

Background and Purpose: Voltage-gated sodium (Na_V) channels are expressed de novo in carcinomas where their activity promotes invasiveness. Breast and colon cancer cells express the neonatal splice variant of Na_V1.5 (nNa_V1.5), which has several amino acid substitutions in the domain I voltage-sensor compared with its adult counterpart (aNa_V1.5). This study aimed to determine whether nNa_V1.5 channels could be distinguished pharmacologically from aNaV1.5 channels. Experimental Approach: Cells expressing either nNa_V1.5 or aNa_V1.5 channels were exposed to low MW inhibitors, an antibody or natural toxins, and changes in electro-physiological parameters were measured. Stable expression in EBNA cells and transient expression in Xenopus laevis oocytes were used. Currents were recorded by whole-cell patch clamp and two-electrode voltage-clamp, respectively. Key Results: Several clinically used blockers of Na_V channels (lidocaine, procaine, phenytoin, mexiletine, ranolazine, and riluzole) could not distinguish between nNa_V 1.5 or aNa_V1.5 channels. However, two tarantula toxins (HaTx and ProTx-II) and a polyclonal antibody (NESOpAb) preferentially inhibited currents elicited by either nNaV1.5 or aNa_V1.5 channels by binding to the spliced region of the channel. Furthermore, the amino acid residue at position 211 (aspartate in aNa_V1.5/lysine in nNaV1.5), that is, the charge reversal in the spliced region of the channel, played a key role in the selectivity, especially in antibody binding. Conclusion and Implications: We conclude that the cancer-related nNaV1.5 channel can be distinguished pharmacologically from its nearest neighbour, aNa_V1.5 channels. Thus, it may be possible to design low MW compounds as antimetastatic drugs for non-toxic therapy of nNa_V1.5-expressing carcinomas.