title: Involvement of the helix-loop-helix protein Id-1 in the glucocorticoid regulation of tight junctions in mammary epithelial cells.
abstract: Mammary epithelial cell-cell junctions undergo morphological and structural differentiation during pregnancy and lactation, but little is known about the transcriptional regulators that are involved in this process. In Con8 mammary epithelial tumor cells, we have previously documented that the synthetic glucocorticoid, dexamethasone, induces the reorganization of the tight junction and adherens junction and stimulates the monolayer transepithelial electrical resistance (TER), a reliable in vitro measurement of tight junction sealing. Western blots demonstrated that dexamethasone treatment rapidly and strongly stimulated the level of the Id-1 protein, which is a serum-inducible helix-loop-helix transcriptional repressor. The steroid induction of Id-1 was robust by 4 h of treatment and maintained over a 24-h period. Isopropyl-1-thio-beta-d-galactopyranoside-inducible expression of exogenous Id-1 in Con8 cells was shown to strongly facilitate the dexamethasone induction of TER in the absence of serum without altering the dexamethasone-dependent reorganization of ZO-1, beta-catenin, or F-actin. Ectopic overexpression of Id-1 in the SCp2 nontumorigenic mammary epithelial cells, which does not undergo complete dexamethasone-dependent tight junction reorganization, enhanced the dexamethasone-induced ZO-1 tight junction localization and stimulated the monolayer TER. Moreover, antisense reduction of Id-1 protein in SCp2 cells prevented the apical junction reorganization and dexamethasone-stimulated TER. Our results implicate Id-1 as acting as a critical regulator of mammary epithelial cell-cell interactions at an early step in the glucocorticoid-dependent signaling pathway that controls tight junction integrity.
authors.affiliation: Department of Molecular and Cell Biology and the Cancer Research Laboratory, University of California at Berkeley, Berkeley, California 94720-3200, USA.
authors.forename: P L
authors.initials: PL
authors.lastname: Woo
authors.forename: A
authors.initials: A
authors.lastname: Cercek
authors.forename: P Y
authors.initials: PY
authors.lastname: Desprez
authors.forename: G L
authors.initials: GL
authors.lastname: Firestone
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D003598:Cytoskeletal Proteins / Q000032:analysis; D004268:DNA-Binding Proteins / Q000502:physiology*; D004847:Epithelial Cells / Q000648:ultrastructure; D005938:Glucocorticoids / Q000494:pharmacology*; D018257:Helix-Loop-Helix Motifs; D051798:Inhibitor of Differentiation Protein 1; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology*; D008565:Membrane Proteins / Q000032:analysis; D051379:Mice; D010750:Phosphoproteins / Q000032:analysis; D011817:Rabbits; D012097:Repressor Proteins; D019108:Tight Junctions / Q000187:drug effects* / Q000502:physiology; D015534:Trans-Activators; D014157:Transcription Factors / Q000502:physiology*; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin
chemical_list: D000199:Actins; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; C497455:Idb1 protein, mouse; D051798:Inhibitor of Differentiation Protein 1; D008565:Membrane Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; C569043:Tjp1 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D007544:Isopropyl Thiogalactoside