title: Evidence for a KATP Channel in Rough Endoplasmic Reticulum (rerKATP Channel) of Rat Hepatocytes.
abstract: We report in a previous study the presence of a large conductance K+ channel in the membrane of rough endoplasmic reticulum (RER) from rat hepatocytes incorporated into lipid bilayers. Channel activity in this case was found to decrease in presence of ATP 100 µM on the cytoplasmic side and was totally inhibited at ATP concentrations greater than 0.25 mM. Although such features would be compatible with the presence of a KATP channel in the RER, recent data obtained from a brain mitochondrial inner membrane preparation have provided evidence for a Maxi-K channel which could also be blocked by ATP within the mM concentration range. A series of channel incorporation experiments was thus undertaken to determine if the ATP-sensitive channel originally observed in the RER corresponds to KATP channel. Our results indicate that the gating and permeation properties of this channel are unaffected by the addition of 800 nM charybdotoxin and 1 µM iberiotoxin, but appeared sensitive to 10 mM TEA and 2.5 mM ATP. Furthermore, adding 100 µM glibenclamide at positive potentials and 400 µM tolbutamide at negative or positive voltages caused a strong inhibition of channel activity. Finally Western blot analyses provided evidence for Kir6.2, SUR1 and/or SUR2B, and SUR2A expression in our RER fractions. It was concluded on the basis of these observations that the channel previously characterized in RER membranes corresponds to KATP, suggesting that opening of this channel may enhance Ca2+ releases, alter the dynamics of the Ca2+ transient and prevent accumulation of Ca2+ in the ER during Ca2+ overload.
authors.affiliation: Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sajjad
authors.initials: S
authors.lastname: Salari
authors.affiliation: Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Maedeh
authors.initials: M
authors.lastname: Ghasemi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Javad
authors.initials: J
authors.lastname: Fahanik-Babaei
authors.affiliation: Department of Biochemistry, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Saghiri
authors.affiliation: Department of Molecular and Integrative Physiology and Membrane Protein Research Group, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Remy
authors.initials: R
authors.lastname: Sauve
authors.affiliation: Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Eliassi
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D018870:Endoplasmic Reticulum, Rough / Q000187:drug effects / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D054086:KATP Channels / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D014044:Tolbutamide / Q000494:pharmacology
chemical_list: D054086:KATP Channels; D010455:Peptides; D018999:Charybdotoxin; C064719:iberiotoxin; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D005905:Glyburide; D002118:Calcium