Neonatal Na
V 1.5: Pharmacological distinctiveness of a cancer-related voltage-gated sodium channel splice variant.
Br J Pharmacol 2021;
179:473-486. [PMID:
34411279 DOI:
10.1111/bph.15668]
[Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 07/26/2021] [Accepted: 07/31/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE
Voltage-gated sodium (NaV ) channels are expressed de novo in carcinomas where their activity promotes invasiveness. Breast and colon cancer cells express the neonatal splice variant of NaV 1.5 (nNaV 1.5) which has several amino acid substitutions in the domain I voltage-sensor compared to its adult counterpart (aNaV 1.5). This study aimed to determine whether nNaV 1.5 could be distinguished pharmacologically from aNaV 1.5.
EXPERIMENTAL APPROACH
Cells expressing either nNaV 1.5 or aNaV 1.5 were exposed to small-molecule inhibitors, an antibody or natural toxins, and changes in electrophysiological 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 Nav channels (lidocaine, procaine, phenytoin, mexiletine, ranolazine and riluzole) could not distinguish between nNaV 1.5 or aNaV 1.5. On the other hand, two tarantula toxins (HaTx and ProTx-II) and a polyclonal antibody (NESOpAb) preferentially inhibited currents elicited by either nNaV 1.5 or aNaV 1.5 by binding to the spliced region of the channel. Furthermore, the amino acid residue at position 211 (aspartate in aNaV 1.5/lysine in nNaV 1.5), i.e. the charge reversal in the spliced region of the channel, played a key role in the selectivity especially in the antibody binding.
CONCLUSION AND IMPLICATIONS
We conclude that the cancer-related nNaV 1.5 channel can be distinguished pharmacologically from its nearest neighbour, aNaV 1.5. Thus, it may be possible to design small molecules as anti-metastatic drugs for non-toxic therapy of nNaV 1.5-expressing carcinomas.
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