A New Potassium Channel on the Endoplasmic Reticulum Membrane in a Rat Brain: Electropharmacology and Molecular...

Several types of ion channels found in the plasma membrane have also been identified in the membranes of intracellular organelles. These ion channels, including potassium channels, play a crucial role in regulating intracellular ion homeostasis. An ATP-sensitive potassium (KATP) channel with various functional roles has been identified in the endo/sarcoplasmic reticulum membranes of both excitable and non-excitable cells. Our previous studies investigated the electropharmacological and molecular properties of KATP and BKCa⁺² channels in the rough endoplasmic reticulum (RER) of rat hepatocytes.

In this study, for the first time, we described the electropharmacological and molecular properties of the RER KATP channel in rat brain cells using an incorporated single-channel in a planar lipid bilayer and Western blotting.

The results of the study revealed the presence of a KATP channel with a conductance of 306 pS, and the open probability was found to be voltage-independent at holding potentials ranging from +40 to -60 in an asymmetric solution (200/50 mM KCl; cis/trans). Additionally, we observed that adding ATP (2.5 mM) to both positive and negative potentials, and 100 μM glibenclamide to the positive voltages inhibited channel activity. The addition of 100 mM 5-HD and 100 nM charybdotoxin to the cis side did not affect the channel behavior. Furthermore, a Western blot analysis provided evidence of the expression of Kir6.2, Kir6.1, sulfonylurea receptor (SUR)1, and/or SUR2B, but not SUR2A, in the RER of rat brain fractions.

In this study, we provide strong evidence for the existence of a KATP channel on the RER membrane of rat brain cells, displaying pharmacological properties distinct from those classically described for the plasma membrane and other intracellular organelles.