title: Selective effect of PDGF on connexin43 versus connexin40 comprised gap junction channels.
abstract: The goals of the current study were to determine whether the conductance of Cx40 and Cx40-Cx43 mixed composition junctions was regulated by platelet-derived growth factor (PDGF)-activated signaling cascades, to ascertain the minimum number of Cx43 subunits/connexon required to confer PDGF sensitivity, and to identify specific residues in Cx43 required for this regulation. Junctional and channel conductances (g(j) and gamma(j), respectively) were determined for Cx40/Cx40, Cx43/Cx43, Cx40/Cx43, and Cx40-Cx43/Cx40-Cx43 mixed composition channels. PDGF had no effect on g(j) in Cx40/Cx40 pairs, but decreased g(j) in the remaining combinations by 53% (Cx43/Cx43), 48% (Cx40/Cx43), 41% (4:1 Cx40:Cx43 expression ratio) and 24% (10:1 Cx40:Cx43 expression ratio). Based on the predicted connexin composition of channels in cells expressing Cx40 and Cx43 at either 4:1 or 10:1 ratios, these decreases in g(j) suggest that a single subunit of Cx43 is sufficient to confer PDGF sensitivity. The effect of PDGF on g(j) involved a decrease in both gamma(j) and Po and required serine 368 in the C-terminus. These data implicate protein kinase C as the mediator of the PDGF effect and strongly suggest that acute regulation of gap junction function by PDGF-activated signaling cascades is conferred by low levels of expression of a sensitive connexin in cells that otherwise express insensitive connexins.
authors.affiliation: Department of Physiology, University of Arizona, Tucson, AZ 85724, USA. jburt@u.arizona.edu
authors.forename: Janis M
authors.initials: JM
authors.lastname: Burt
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Steele
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism*; D017630:Connexins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004553:Electric Conductivity; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D000097003:Gap Junction alpha-5 Protein
chemical_list: D018031:Connexin 43; D017630:Connexins; D017868:Cyclic AMP-Dependent Protein Kinases; D010982:Platelet-Derived Growth Factor; D021122:Protein Subunits; D000097003:Gap Junction alpha-5 Protein