title: E-cadherin differentially regulates the assembly of Connexin43 and Connexin32 into gap junctions in human squamous carcinoma cells.
abstract: It is as yet unknown how the assembly of connexins (Cx) into gap junctions (GJ) is initiated upon cell-cell contact. We investigated whether the trafficking and assembly of Cx43 and Cx32 into GJs were contingent upon cell-cell adhesion mediated by E-cadherin. We also examined the role of the carboxyl termini of these Cxs in initiating the formation of GJs. Using cadherin and Cx-null cells, and by introducing Cx43 and Cx32, either alone or in combination with E-cadherin, our studies demonstrated that E-cadherin-mediated cell-cell adhesion was neither essential nor sufficient to initiate GJ assembly de novo in A431D human squamous carcinoma cells. However, E-cadherin facilitated the growth and assembly of preformed GJs composed of Cx43, although the growth of cells on Transwell filters was required to initiate the assembly of Cx32. Our results also documented that the carboxyl termini of both Cxs were required in this cell type to initiate the formation of GJs de novo. Our findings also showed that GJ puncta composed of Cx43 co-localized extensively with ZO-1 and actin fibers at cell peripheries and that ZO-1 knockdown attenuated Cx43 assembly. These findings suggest that the assembly of Cx43 and Cx32 into GJs is differentially modulated by E-cadherin-mediated cell-cell adhesion and that direct or indirect cross-talk between carboxyl tails of Cxs and actin cytoskeleton via ZO-1 may regulate GJ assembly and growth.
authors.affiliation: Department of Biochemistry and Molecular Biology, Eppley Institute for Research in Cancer and Allied Diseases, Eppley Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
authors.forename: Souvik
authors.initials: S
authors.lastname: Chakraborty
authors.forename: Shalini
authors.initials: S
authors.lastname: Mitra
authors.forename: Matthias M
authors.initials: MM
authors.lastname: Falk
authors.forename: Steve H
authors.initials: SH
authors.lastname: Caplan
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Wheelock
authors.forename: Keith R
authors.initials: KR
authors.lastname: Johnson
authors.forename: Parmender P
authors.initials: PP
authors.lastname: Mehta
mesh_terms: D000199:Actins / Q000378:metabolism; D019921:Biotinylation; D015153:Blotting, Western; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion; D002450:Cell Communication; D002463:Cell Membrane Permeability; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000502:physiology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D062826:Zonula Occludens-1 Protein; D000097002:Gap Junction beta-1 Protein
chemical_list: D000199:Actins; D015820:Cadherins; D018031:Connexin 43; D017630:Connexins; D008565:Membrane Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D062826:Zonula Occludens-1 Protein; D000097002:Gap Junction beta-1 Protein; C569042:TJP1 protein, human