Influence of Mediating K2P and NALCN Channel Function on Cardiac Pacing with Alterations in Ionic Concentrations, Temperature and Expression

Alaina Taul, Elizabeth Elliott and Robin Cooper

Background and Objective: The Sodium Leak Channel (NALCN) and the two-pore-domain K⁺ (K2P) channel are known leak channels responsible for maintaining cell resting membrane potential through, respectively, the regulation of sodium and potassium ion flux across the cell membrane. Though some characterization of these channels exists, very little is known about them or the effects of abnormal expression beyond a connection to various human pathologies (e.g., cancer, neurological disorders). This study further examines how cardiac pacing behaviors are affected by altered ion channel expression and environmental conditions within Drosophila melanogaster. Materials and Methods: Several D. melanogaster strains were utilized to observe abnormal channel expression in the larval heart: One line to demonstrate K2P channel overexpression and two RNAi lines to exhibit reduced NALCN expression. Third-instar larvae were dissected to reveal the larval heart tube for observation and cardiac behaviors were observed in response to variations in temperature, ion concentrations in the surrounding saline and exposure to NALCN blocker CP-96345. Results: The use of RNAi techniques to decrease NALCN function resulted in a substantial increase in heart rate with higher external Ca²⁺ and increased temperature, as compared to control strains or increased cardiac K2P expression. The DMSO was used to solubilize CP-96345 and control experiments with the solvent alone yielded decreased heart rate, especially with K2P overexpression or NALCN knockdown. The CP-96345 exposure decreased heart rate in all strains tested. Conclusion: The data reported herein represent a preliminary examination into the effects of altered channel expression and, thus, provide further information into human pathologies and the treatment thereof.

View Fulltext Back