title: ATP regulation of a large conductance voltage-gated cation channel in rough endoplasmic reticulum of rat hepatocytes.
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 microM on the cytoplasmic side and was totally inhibited at ATP concentrations greater than 0.25mM. 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 (ATPgammaS), ruling out a phosphorylation-based mechanism. Notably addition of 2.5mM 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 Ca(2+) signaling or control of membrane potential across the endoplasmic reticulum membrane.
authors.affiliation: Department of Physiology and Neuroscience Research Center, Shaheed Beheshti University (Medical Sciences), Evin, Tehran 19834, Iran.
authors.forename: Manoochehr
authors.initials: M
authors.lastname: Ashrafpour
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Eliassi
authors.forename: Remy
authors.initials: R
authors.lastname: Sauve
authors.forename: Hamid
authors.initials: H
authors.lastname: Sepehri
authors.forename: Reza
authors.initials: R
authors.lastname: Saghiri
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000502:physiology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D018870:Endoplasmic Reticulum, Rough / Q000737:chemistry / Q000378:metabolism*; D022781:Hepatocytes / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D015640:Ion Channel Gating / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D008274:Magnesium / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; C022571:adenosine 5'-O-(3-thiotriphosphate); D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium