title: Intracellular magnesium-dependent modulation of gap junction channels formed by neuronal connexin36.
abstract: Gap junction (GJ) channels composed of Connexin36 (Cx36) are widely expressed in the mammalian CNS and form electrical synapses between neurons. Here we describe a novel modulatory mechanism of Cx36 GJ channels dependent on intracellular free magnesium ([Mg(2+)]i). We examined junctional conductance (gj) and its dependence on transjunctional voltage (Vj) at different [Mg(2+)]i in cultures of HeLa or N2A cells expressing Cx36. We found that Cx36 GJs are partially inhibited at resting [Mg(2+)]i. Thus, gj can be augmented or reduced by lowering or increasing [Mg(2+)]i, respectively. Similar changes in gj and Vj-gating were observed using MgATP or K2ATP in pipette solutions, which increases or decreases [Mg(2+)]i, respectively. Changes in phosphorylation of Cx36 or in intracellular free calcium concentration were not involved in the observed Mg(2+)-dependent modulation of gj. Magnesium ions permeate the channel and transjunctional asymmetry in [Mg(2+)]i resulted in asymmetric Vj-gating. The gj of GJs formed of Cx26, Cx32, Cx43, Cx45, and Cx47 was also reduced by increasing [Mg(2+)]i, but was not increased by lowering [Mg(2+)]i; single-channel conductance did not change. We showed that [Mg(2+)]i affects both open probability and the number of functional channels, likely through binding in the channel lumen. Finally, we showed that Cx36-containing electrical synapses between neurons of the trigeminal mesencephalic nucleus in rat brain slices are similarly affected by changes in [Mg(2+)]i. Thus, this novel modulatory mechanism could underlie changes in neuronal synchronization under conditions in which ATP levels, and consequently [Mg(2+)]i, are modified.
authors.affiliation: Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Palacios-Prado
authors.forename: Gregory
authors.initials: G
authors.lastname: Hoge
authors.forename: Alina
authors.initials: A
authors.lastname: Marandykina
authors.forename: Lina
authors.initials: L
authors.lastname: Rimkute
authors.forename: Sandrine
authors.initials: S
authors.lastname: Chapuis
authors.forename: Nerijus
authors.initials: N
authors.lastname: Paulauskas
authors.forename: Vytenis A
authors.initials: VA
authors.lastname: Skeberdis
authors.forename: John
authors.initials: J
authors.lastname: O'Brien
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Pereda
authors.forename: Michael V L
authors.initials: MV
authors.lastname: Bennett
authors.forename: Feliksas F
authors.initials: FF
authors.lastname: Bukauskas
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D055592:Biophysical Phenomena / Q000187:drug effects / Q000502:physiology; D002413:Cations, Divalent / Q000378:metabolism; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013681:Tegmentum Mesencephali / Q000166:cytology; D014162:Transfection; D000097004:Gap Junction delta-2 Protein
chemical_list: D000255:Adenosine Triphosphate; D002413:Cations, Divalent; D002614:Chelating Agents; D000072259:Connexin 26; D017630:Connexins; D004533:Egtazic Acid; D049452:Green Fluorescent Proteins; D008274:Magnesium; D000097004:Gap Junction delta-2 Protein; C000607042:GJB2 protein, human; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid