Differential regulation of distinct types of gap junction channels by similar phosphorylating conditions.
Studies on physiological modulation of intercellular communication mediated by protein kinases are often complicated by the fact that cells express multiple gap junction proteins (connexins; Cx). Changes in cell coupling can be masked by simultaneous opposite regulation of the gap junction channel types expressed. We have examined the effects of activators and inhibitors of protein kinase A (PKA), PKC, and PKG on permeability and single channel conductance of gap junction channels composed of Cx45, Cx43, or Cx26 subunits. To allow direct comparison between these Cx, SKHep1 cells, which endogenously express Cx45, were stably transfected with cDNAs coding for Cx43 or Cx26. Under control conditions, the distinct types of gap junction channels could be distinguished on the basis of their permeability and single channel properties. Under various phosphorylating conditions, these channels behaved differently. Whereas agonists/antagonist of PKA did not affect permeability and conductance of all gap junction channels, variable changes were observed under PKC stimulation. Cx45 channels exhibited an additional conductance state, the detection of the smaller conductance states of Cx43 channels was favored, and Cx26 channels were less often observed. In contrast to the other kinases, agonists/antagonist of PKG affected permeability and conductance of Cx43 gap junction channels only. Taken together, these results show that distinct types of gap junction channels are differentially regulated by similar phosphorylating conditions. This differential regulation may be of physiological importance during modulation of cell-to-cell communication of more complex cell systems.
Kwak
B R
BR
Department of Medical Physiology and Sports Medicine, Utrecht University, The Netherlands.
Hermans
M M
MM
De Jonge
H R
HR
Lohmann
S M
SM
Jongsma
H J
HJ
Chanson
M
M
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D002450:Cell Communication; D000072259:Connexin 26; D017630:Connexins / Q000096:biosynthesis / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017629:Gap Junctions / Q000502:physiology*; D015870:Gene Expression; D006706:Homeostasis; D006801:Humans; D008113:Liver Neoplasms; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011493:Protein Kinase C / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
D017630:Connexins; D017931:DNA Primers; D004791:Enzyme Inhibitors; C000607042:GJB2 protein, human; D011994:Recombinant Proteins; D000072259:Connexin 26; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D006152:Cyclic GMP; D013755:Tetradecanoylphorbol Acetate