title: The 2,2',4,4',5,5'-hexachlorobiphenyl-enhanced degradation of connexin 43 involves both proteasomal and lysosomal activities.
abstract: One of the toxic effects of non-dioxin-like polychlorinated biphenyls (NDL-PCBs) is the acute inhibition of gap junctional intercellular communication (GJIC), an event possibly associated with tumor promotion. The model NDL-PCB-2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153)-induces a sustained GJIC inhibition in rat liver epithelial WB-F344 cells. As this effect might be related to deregulation of connexin 43 (Cx43) synthesis, trafficking, or degradation, we investigated the impact of PCB 153 on these events. Although PCB 153 had no effect on Cx43 mRNA levels, it induced a gradual loss of Cx43 protein and significantly decreased the amount of gap junction plaques in plasma membrane. PCB 153 contributed to extracellular signal-regulated kinases 1 and 2 (ERK1/2)-dependent accumulation of hyperphosphorylated Cx43-P3 form, thus indicating that ERK1/2 activation by PCB 153 might contribute to its effects on Cx43 internalization or degradation. Inhibition of either proteasomes or lysosomes with their specific inhibitors largely restored total Cx43 protein levels, thus suggesting that both proteasomes and lysosomes may participate in the PCB 153-enhanced Cx43 internalization and degradation. However, neither the proteasomal nor the lysosomal inhibitors restored normal GJIC or number/size of gap junction plaques. Finally, PCB 153 also interfered with restoration of gap junction plaques following the inhibition of Cx43 transport to plasma membrane. Taken together, multiple modes of action seem to contribute to downregulation of Cx43 in PCB 153-treated rat liver epithelial cells. The enhanced degradation of Cx43, together with persistent inhibition of GJIC, might contribute to tumor-promoting effects of NDL-PCBs.
authors.affiliation: Department of Chemistry and Toxicology, Veterinary Research Institute, 62100 Brno, Czech Republic.
authors.forename: Pavlína
authors.initials: P
authors.lastname: Simecková
authors.forename: Jan
authors.initials: J
authors.lastname: Vondrácek
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Andrysík
authors.forename: Jirina
authors.initials: J
authors.lastname: Zatloukalová
authors.forename: Pavel
authors.initials: P
authors.lastname: Krcmár
authors.forename: Alois
authors.initials: A
authors.lastname: Kozubík
authors.forename: Miroslav
authors.initials: M
authors.lastname: Machala
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects* / Q000378:metabolism; D061988:Proteasome Inhibitors; D051381:Rats
chemical_list: D018031:Connexin 43; D007976:Leupeptins; D061988:Proteasome Inhibitors; D011078:Polychlorinated Biphenyls; D048049:Extracellular Signal-Regulated MAP Kinases; D046988:Proteasome Endopeptidase Complex; C032854:leupeptin; C014024:2,4,5,2',4',5'-hexachlorobiphenyl