ATP regulation of a large conductance voltage-gated cation channel in rough endoplasmic reticulum of rat hepatocytes |
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Authors: | Ashrafpour Manoochehr Eliassi Afsaneh Sauve Remy Sepehri Hamid Saghiri Reza |
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Affiliation: | a Department of Physiology and Neuroscience Research Center, Shaheed Beheshti University (Medical Sciences), Evin, Tehran 19834, Iran b Departement de Physiologie, Membrane Protein Study Group, Universite de Montreal, Montreal, Que., Canada H3C 3J7 c Department of Biochemistry, Pasteur Institute, Tehran, Iran |
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Abstract: | ATP-sensitive K+ channels play an important role in regulating membrane potential during metabolic stress. In this work we report the effect of ATP and ADP-Mg on a K+ channel present in the membrane of rough endoplasmic reticulum (RER) from rat hepatocytes incorporated into lipid bilayers. Channel activity was found to decrease in presence of ATP 100 μM on the cytoplasmic side and was totaly inhibited at ATP concentrations greater than 0.25 mM. The effect appeared voltage dependent, suggesting that the ATP binding site was becoming available upon channel opening. Channel activity was suppressed by the nonhydrolyzable ATP analog (ATPγS), ruling out a phosphorylation-based mechanism. Notably addition of 2.5 mM ADP-Mg to the cytosolic side increased the channel open probability at negative potentials. We conclude that the large conductance voltage-gated cation channel in RER of rat hepatocytes is an ATP and ADP sensitive channel likely to be involved in cellular processes such as Ca2+ signaling or control of membrane potential across the endoplasmic reticulum membrane. |
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Keywords: | Bilayer lipid membrane Potassium channel ATP ADP-Mg Endoplasmic reticulum |
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