title: Estrogen-dependent expression and subcellular localization of the tight junction protein claudin-4 in HEC-1A endometrial cancer cells.
abstract: Endometrial cancer is the most common female reproductive cancer in the United States and is associated with deregulated tight junction protein expression. Given the highly estrogen-responsive nature of this tissue, we investigated the effects of estrogen and its agonist, 4-OH TAM, on the expression and subcellular localization of the tight junction protein claudin-4 (CLDN-4), in HEC-1A endometrial cancer cells. In untreated HEC-1A cells, we observed dramatic overexpression of claudin-4 protein. In addition, differential detergent extraction analysis indicated that claudin-4 was localized primarily in the membrane but also found in the cytosolic, nuclear and cytoskeletal fractions. Upon exposure of HEC-1A to estradiol (E2), we observed a biphasic effect both on the overall expression of claudin-4 protein and on its cytosolic and cytoskeletal presence as demonstrated by immunoblot analysis. Immunofluorescence analysis also revealed a biphasic effect of E2 on claudin-4 expression. In contrast, we observed no changes in expression levels nor in the subcellular distribution patterns of claudin-4 in HEC-1A cells treated with different concentrations of 4-OH TAM. The intracellular presence of CLDN-4 coupled with the biphasic effects of E2 on CLDN-4 expression in the cytoskeleton suggest that this protein may be involved in cell signaling to and from TJs.
authors.affiliation: Biology Department, Southwestern University, Georgetown, TX 78626, USA.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Cuevas
authors.affiliation: Biology Department, Southwestern University, Georgetown, TX 78626, USA.
authors.forename: Jenna M
authors.initials: JM
authors.lastname: Gaska
authors.affiliation: Biology Department, Southwestern University, Georgetown, TX 78626, USA.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Gist
authors.affiliation: Biology Department, Trinity University, San Antonio, TX 78212, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: King
authors.affiliation: Biology Department, Southwestern University, Georgetown, TX 78626, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Sheller
authors.affiliation: Biology Department, Southwestern University, Georgetown, TX 78626, USA.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Todd
mesh_terms: D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D062506:Claudin-4 / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D016889:Endometrial Neoplasms / Q000378:metabolism*; D004967:Estrogens / Q000819:agonists / Q000494:pharmacology*; D005260:Female; D006367:HeLa Cells; D006801:Humans; D015398:Signal Transduction; D019108:Tight Junctions / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C568157:CLDN4 protein, human; D062506:Claudin-4; D004967:Estrogens