Molecular characterization and functional expression of the human cardiac gap junction channel.
Gap junctions permit the passage of ions and chemical mediators from cell to cell. To identify the molecular genetic basis for this coupling in the human heart, we have isolated clones from a human fetal cardiac cDNA library which encode the full-length human cardiac gap junction (HCGJ) mRNA. The predicted amino acid sequence is homologous to the rat cardiac gap junction protein, connexin43 (Beyer, E. D., D. Paul, and D. A. Goodenough. 1987. J. Cell Biol. 105:2621-2629), differing by 9 of 382 amino acids. HCGJ mRNA is detected as early as fetal week 15 and persists in adult human cardiac samples. Genomic DNA analysis suggests the presence of two highly homologous HCGJ loci, only one of which is functional. Stable transfection of the HCGJ cDNA into SKHep1 cells, a human hepatoma line which is communication deficient, leads to the formation of functional channels. Junctional conductance in pairs of transfectants containing 10 copies of the HCGJ sequence is high (approximately 20 nS). Single channel currents are detectable in this expression system and correspond to conductances of approximately 60 pS. These first measurements of the HCGJ channel are similar to the junctional conductance recorded between pairs of rat or guinea pig cardiocytes.
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461.
G I
GI
Fishman
D C
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Spray
L A
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Leinwand
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017630:Connexins; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005333:Fetus; D006321:Heart / Q000502:physiology; D006801:Humans; D007365:Intercellular Junctions / Q000502:physiology* / Q000648:ultrastructure; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009206:Myocardium / Q000648:ultrastructure*; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012689:Sequence Homology, Nucleic Acid
D017630:Connexins; D008565:Membrane Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D012313:RNA; D004247:DNA