title: Human connexin26 and connexin30 form functional heteromeric and heterotypic channels.
abstract: Mutations in GJB2 and GJB6, the genes that encode the human gap junction proteins connexin26 (Cx26) and connexin30 (Cx30), respectively, cause hearing loss. Cx26 and Cx30 are both expressed in the cochlea, leading to the potential formation of heteromeric hemichannels and heterotypic gap junction channels. To investigate their interactions, we expressed human Cx26 and Cx30 individually or together in HeLa cells. When they were expressed together, Cx26 and Cx30 appeared to interact directly (by their colocalization in gap junction plaques, by coimmunoprecipitation, and by fluorescence resonance energy transfer). Scrape-loading cells that express either Cx26 or Cx30 demonstrated that Cx26 homotypic channels robustly transferred both cationic and anionic tracers, whereas Cx30 homotypic channels transferred cationic but not anionic tracers. Cells expressing both Cx26 and Cx30 also transferred both cationic and anionic tracers by scrape loading, and the rate of calcein (an anionic tracer) transfer was intermediate between their homotypic counterparts by fluorescence recovery after photobleaching. Fluorescence recovery after photobleaching also showed that Cx26 and Cx30 form functional heterotypic channels, allowing the transfer of calcein, which did not pass the homotypic Cx30 channels. Electrophysiological recordings of cell pairs expressing different combinations of Cx26 and/or Cx30 demonstrated unique gating properties of cell pairs expressing both Cx26 and Cx30. These results indicate that Cx26 and Cx30 form functional heteromeric and heterotypic channels, whose biophysical properties and permeabilities are different from their homotypic counterparts.
authors.affiliation: Section of Neurology, St. Christopher's Hospital for Children, Erie Ave. at Front St., Philadelphia, PA 19134, USA. ssy25@drexel.edu
authors.forename: Sabrina W
authors.initials: SW
authors.lastname: Yum
authors.forename: Junxian
authors.initials: J
authors.lastname: Zhang
authors.forename: Virginijus
authors.initials: V
authors.lastname: Valiunas
authors.forename: Giedrius
authors.initials: G
authors.lastname: Kanaporis
authors.forename: Peter R
authors.initials: PR
authors.lastname: Brink
authors.forename: Thomas W
authors.initials: TW
authors.lastname: White
authors.forename: Steven S
authors.initials: SS
authors.lastname: Scherer
mesh_terms: D000838:Anions / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D000072259:Connexin 26; D000075302:Connexin 30; D017630:Connexins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004594:Electrophysiology; D036681:Fluorescence Recovery After Photobleaching; D031541:Fluorescence Resonance Energy Transfer; D017629:Gap Junctions / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008564:Membrane Potentials / Q000502:physiology; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D000838:Anions; D002412:Cations; D000075302:Connexin 30; D017630:Connexins; C000607042:GJB2 protein, human; C491020:GJB6 protein, human; D000072259:Connexin 26