Pairwise biosynthesis of ion channels stabilizes excitability and mitigates arrhythmias.
Margaret B JamesonErick B Ríos-PérezFang LiuCatherine A EichelGail A RobertsonPublished in: Proceedings of the National Academy of Sciences of the United States of America (2023)
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.
Keyphrases
- single molecule
- cell cycle
- binding protein
- left ventricular
- cell proliferation
- poor prognosis
- drug delivery
- high resolution
- radiation therapy
- heart failure
- small molecule
- protein protein
- radiation induced
- long non coding rna
- functional connectivity
- angiotensin ii
- working memory
- amino acid
- resting state
- genome wide analysis