title: Death of Neurons following Injury Requires Conductive Neuronal Gap Junction Channels but Not a Specific Connexin.
abstract: Pharmacological blockade or genetic knockout of neuronal connexin 36 (Cx36)-containing gap junctions reduces neuronal death caused by ischemia, traumatic brain injury and NMDA receptor (NMDAR)-mediated excitotoxicity. However, whether Cx36 gap junctions contribute to neuronal death via channel-dependent or channel-independent mechanism remains an open question. To address this, we manipulated connexin protein expression via lentiviral transduction of mouse neuronal cortical cultures and analyzed neuronal death twenty-four hours following administration of NMDA (a model of NMDAR excitotoxicity) or oxygen-glucose deprivation (a model of ischemic injury). In cultures prepared from wild-type mice, over-expression and knockdown of Cx36-containing gap junctions augmented and prevented, respectively, neuronal death from NMDAR-mediated excitotoxicity and ischemia. In cultures obtained form from Cx36 knockout mice, re-expression of functional gap junction channels, containing either neuronal Cx36 or non-neuronal Cx43 or Cx31, resulted in increased neuronal death following insult. In contrast, the expression of communication-deficient gap junctions (containing mutated connexins) did not have this effect. Finally, the absence of ethidium bromide uptake in non-transduced wild-type neurons two hours following NMDAR excitotoxicity or ischemia suggested the absence of active endogenous hemichannels in those neurons. Taken together, these results suggest a role for neuronal gap junctions in cell death via a connexin type-independent mechanism that likely relies on channel activities of gap junctional complexes among neurons. A possible contribution of gap junction channel-permeable death signals in neuronal death is discussed.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Fontes
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Jon
authors.initials: J
authors.lastname: Ramsey
authors.affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Polk
authors.affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Andre
authors.initials: A
authors.lastname: Koop
authors.affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Janna V
authors.initials: JV
authors.lastname: Denisova
authors.affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Andrei B
authors.initials: AB
authors.lastname: Belousov
mesh_terms: D000818:Animals; D015153:Blotting, Western; D016923:Cell Death / Q000235:genetics / Q000502:physiology; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism*; D005822:Genetic Vectors / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism; D000097004:Gap Junction delta-2 Protein
chemical_list: D017630:Connexins; D016194:Receptors, N-Methyl-D-Aspartate; D000097004:Gap Junction delta-2 Protein