title: The proteasome regulates the interaction between Cx43 and ZO-1.
abstract: Gap junction (GJ) intercellular communication (GJIC) is vital to ensure proper cell and tissue function. GJ are multimeric structures composed of proteins called connexins. Modifications on stability or subcellular distribution of connexins have a direct impact on the extent of GJIC. In this study we have investigated the role of the proteasome in regulation of connexin 43 (Cx43) internalization. Although the participation of both the proteasome and lysosome has long been suggested in Cx43 degradation, the molecular mechanisms whereby proteasome contributes to regulate Cx43 internalization and intercellular communication are still unclear. The results presented in this study envision a new mechanism whereby proteasome regulates GJIC by modulating interaction between Cx43 and ZO-1. Immunoprecipitation experiments, in the presence of proteasome inhibitors, together with immunofluorescence data indicate that the proteasome regulates interaction between Cx43 and ZO-1. Overexpression of the PDZ2 domain of ZO-1 and the expression of Cx-43 fused in frame with a V5/HIS tag, suggest that interaction between the two proteins occurs through the PDZ2 domain of ZO-1 and the C-terminus of Cx43. When interaction between Cx43 and ZO-1 is reduced, as in the presence of proteasome inhibitors, Cx43 accumulates, forming large GJ plaques at plasma membrane. Data presented in this article suggest a new pathway whereby alterations in proteasome activity may impact on GJIC as well as on non-junctional communication with extracellular environment, contributing to cell and tissue dysfunction.
authors.affiliation: Centre of Ophthalmology, Biomedical Institute for Research in Light and Image (IBILI), Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal.
authors.forename: Henrique
authors.initials: H
authors.lastname: Girao
authors.forename: Paulo
authors.initials: P
authors.lastname: Pereira
mesh_terms: D000818:Animals; D002450:Cell Communication; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D018031:Connexin 43 / Q000378:metabolism*; D017629:Gap Junctions; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010750:Phosphoproteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D025801:Ubiquitin / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: D018031:Connexin 43; D008565:Membrane Proteins; D010750:Phosphoproteins; D061988:Proteasome Inhibitors; C569042:TJP1 protein, human; C569044:Tjp1 protein, rat; D025801:Ubiquitin; D062826:Zonula Occludens-1 Protein; D046988:Proteasome Endopeptidase Complex