Functional characteristics of heteromeric Cx40-Cx43 gap junction channel formation.
Cx40:Cx43 expression ratio in A7r5 cells is augmented in growth stimulated vs. growth arrested conditions. To determine the impact of changing Cx40:Cx43 expression ratio on gap junction function, we have developed A7r5 cell lines that display Cx40:Cx43 ratios of 1:1 (66B5n) and 10:1 (A7r540C3). When Rin43 cells were paired with these coexpressing cells, there was an increasing asymmetry of voltage dependent gating as the Cx40:Cx43 ratio increased in the coexpressing cell. This asymmetry was opposite to that which is predicted by Cx40/Cx43 heterotypic channels. In addition, when Rin43 cells were paired with coexpressing cells there was a shift toward smaller single channel event amplitudes with increasing Cx40:Cx43 ratio in the coexpressing cell. Again, this is opposite to that which is predicted by Cx40/Cx43 heterotypic channels. In dye coupling experiments, 6B5N, A7r5, and A7r540C3 cells displayed charge and size selectivity that increased with increasing Cx40:Cx43 expression ratio. These data indicate that although the electrophysiological properties of heteromeric/heterotypic channels are not directly related to the proportions of Cx constituents that comprise the channel, the dye permeability data fit what would be predicted by an increase in Cx40:Cx43 ratio.
Cottrell
G T
GT
Department of Physiology, University of Arizona, Tucson 85724, USA. gtcottre@u.arizona.edu
Wu
Y
Y
Burt
J M
JM
D000818:Animals; D002460:Cell Line; D018031:Connexin 43 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D017629:Gap Junctions / Q000737:chemistry / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology; D008845:Microinjections; D018408:Patch-Clamp Techniques; D020836:Protein Structure, Quaternary; D051381:Rats; D000097003:Gap Junction alpha-5 Protein
D018031:Connexin 43; D017630:Connexins; D005456:Fluorescent Dyes; D000097003:Gap Junction alpha-5 Protein