title: Gap junctions mediate STAT5-independent β-casein expression in CID-9 mammary epithelial cells.
abstract: Crosstalk between gap junction intracellular communication (GJIC), STAT5 and OCT-1 in gap junction (GJ)-dependent β-casein expression was investigated. CID-9 mammary cells plated with prolactin on non-adherent substratum (poly-HEMA) expressed β-casein independent of STAT5 only in the presence of the GJIC inducer, cAMP. Nuclear STAT5 levels were not detectable. By contrast, cells on EHS-drip expressed β-casein in a STAT5-dependent manner and nuclear STAT5 levels were up-regulated. A 75 kDa OCT-1 isoform was detected in conditions that induced β-casein expression regardless of substratum. Interestingly, 40 and 28 kDa OCT-1 isoforms were induced in cells on polyHEMA with cAMP. Electrophoretic mobility shift assays (EMSA) for OCT-1 revealed two band shifts in cells on polyHEMA with cAMP and on EHS-drip, which were repressed by the GJIC inhibitor, 18α-GA. These studies demonstrated that mammary cells on polyHEMA expressed β-casein in response to prolactin in a pathway that involves GJIC and OCT-1 and is independent of STAT5 nuclear translocation.
authors.affiliation: Department of Biology, American University of Beirut, Beirut, Lebanon. rtalhouk@aub.edu.lb
authors.forename: Rabih S
authors.initials: RS
authors.lastname: Talhouk
authors.forename: Antoine A
authors.initials: AA
authors.lastname: Khalil
authors.forename: Rachid
authors.initials: R
authors.lastname: Bajjani
authors.forename: Gilbert J
authors.initials: GJ
authors.lastname: Rahme
authors.forename: Marwan E
authors.initials: ME
authors.lastname: El-Sabban
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D002364:Caseins / Q000235:genetics / Q000378:metabolism*; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002460:Cell Line; D015342:DNA Probes / Q000737:chemistry; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D017629:Gap Junctions / Q000378:metabolism*; D015870:Gene Expression; D005786:Gene Expression Regulation; D053614:Janus Kinase 2 / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology*; D051379:Mice; D050811:Octamer Transcription Factor-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011388:Prolactin / Q000494:pharmacology / Q000502:physiology; D011485:Protein Binding; D020239:Receptor Cross-Talk; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002364:Caseins; D015342:DNA Probes; D050811:Octamer Transcription Factor-1; C494166:Pou2f1 protein, mouse; D050799:STAT5 Transcription Factor; C494093:Stat5a protein, mouse; D011388:Prolactin; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2