Key result
Targeted hERG1 mRNA depletion co-depletes related ion channel transcripts, mitigating expected proarrhythmic effects.
Why the study?
Prior work showed association of mRNAs encoding cardiac NaV1.5 and hERG1, but the functional significance of this association was not established.
Coordinated, cotranslational association of functionally related ion channel mRNAs confers electrical stability by co-regulating complementary ion channels, mitigating proarrhythmic behavior.
Answers are grounded in this paper and cite their sources.
May inform safer ion channel-targeted therapies; hypothesis-generating in animal models, requires human validation.
Coordinated expression of ion channels is crucial for cardiac rhythms, neural signaling, and cell cycle progression. Perturbation of this balance results in many disorders including cardiac arrhythmias. Prior work revealed association of mRNAs encoding cardiac Na V 1.5 ( SCN5A ) and hERG1 ( KCNH2 ), but the functional significance of this association was not established. Here, we provide a more comprehensive picture of KCNH2 , SCN5A , CACNA1C , and KCNQ1 transcripts collectively copurifying with nascent hERG1, Na V 1.5, Ca V 1.2, or KCNQ1 channel proteins. Single-molecule fluorescence in situ hybridization (smFISH) combined with immunofluorescence reveals that the channel proteins are synthesized predominantly as heterotypic pairs from discrete molecules of mRNA, not as larger cotranslational complexes. Puromycin disrupted colocalization of mRNA with its encoded protein, as expected, but remarkably also pairwise mRNA association, suggesting that transcript association relies on intact translational machinery or the presence of the nascent protein. Targeted depletion of KCHN2 by specific shRNA resulted in concomitant reduction of all associated mRNAs, with a corresponding reduction in the encoded channel currents. This co-knockdown effect, originally described for KCNH2 and SCN5A , thus appears to be a general phenomenon among transcripts encoding functionally related proteins. In multielectrode array recordings, proarrhythmic behavior arose when I Kr was reduced by the selective blocker dofetilide at IC 50 concentrations, but not when equivalent reductions were mediated by shRNA, suggesting that co-knockdown mitigates proarrhythmic behavior expected from the selective reduction of a single channel species. We propose that coordinated, cotranslational association of functionally related ion channel mRNAs confers electrical stability by co-regulating complementary ion channels in macromolecular complexes.
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Jameson et al. (2023) studied Cardiac arrhythmias. shRNA-mediated depletion of specific ion channel transcripts vs. Scrambled shRNA or selective pharmacological block was evaluated on Cotranslational association and co-depletion of ion channel mRNAs and currents. Targeted depletion of hERG1 mRNA resulted in concomitant reduction of other functionally related ion channel transcripts, mitigating the proarrhythmic effects expected from selective single-channel reduction.
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