Question:

Two-pore-domain potassium (K_2P) channels mediate background currents that stabilize the resting membrane potential and contribute to repolarization of action potentials in excitable cells. In the heart, genetic inactivation or inhibition of K_2P currents results in action potential prolongation. However, their contribution to arrhythmogenesis still requires further in vivo-validation. Given anatomical and physiological similarities to the human heart, we hypothesized that porcine in vivo models may be utilized to elucidate the role of cardiac K_2P channels under physiological and pathological conditions.

Methods:

Full coding sequences of pK_2P2.1 and pK_2P3.1 were identified by database analysis and amplified from porcine brain and heart cDNA. Two-electrode voltage clamp electrophysiology was used to record K_2P currents from Xenopus oocytes.

Results:

Cloning of porcine K_2P2.1 revealed three splice variants ranging from 1236 bp to 1281 bp (411, 422, and 426 amino acids, respectively). The 1200 bp open reading frame of pK_2P3.1 cDNA encoded a 399 amino acid channel subunit. Human and porcine proteins exhibit 99% (K_2P2.1) and 97% (K_2P3.1) identity. Residues involved in phosphorylation or glycosylation are conserved between humans and pigs. Macroscopic currents recorded from Xenopus oocytes expressing pK_2P2.1 or pK_2P3.1 channels displayed functional properties largely similar to their human counterparts.

Conclusion:

In summary, we demonstrate that porcine K_2P2.1 and K_2P3.1 channels exhibit structural and biophysical properties similar to their human orthologs. We propose that the pig represents a valuable model to study function, regulation, and cardiac significance of K_2P channels.