title: Calcium-calmodulin signaling induced by epithelial cell differentiation upregulates BRAK/CXCL14 expression via the binding of SP1 to the BRAK promoter region.
abstract: The chemokine BRAK/CXCL14 (BRAK) is expressed in normal squamous epithelium, but is not expressed or is expressed at negligible levels in head and neck squamous cell carcinoma. Malignant cells are known to be dedifferentiated compared with normal epithelial cells, suggesting a role for differentiation cues in the expression of BRAK. Thus, we examined the relationship between BRAK expression and stages of differentiation level in epithelial cells. Immunohistochemical analysis showed that BRAK protein was expressed in cells above the spinous cell layer in normal epithelia. In HSC-3 cells in culture, expression of BRAK mRNA was significantly upregulated by cell contact in a cell density-dependent manner, and mRNA expression of cell differentiation markers such as involucrin, cystatin-A, TGM1, TGM3, and TGM5 was concomitantly augmented. Furthermore, the upregulation of BRAK induced by cell contact was suppressed by chlorpromazine, a specific inhibitor of calmodulin. We previously reported that GC boxes and a TATA-like sequence in the BRAK promoter region are associated with the expression of BRAK. Using a promoter assay and ChIP, we demonstrated that binding of the stimulating protein-1 (SP1) transcription factor to a GC box upstream of the BRAK transcription start site was necessary for cell density-dependent upregulation of BRAK. These results indicated that upregulation of BRAK was accompanied by differentiation of epithelial cells induced by calcium/calmodulin signaling, and that SP1 binding to the BRAK promoter region played an important role in this signaling.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kanagawa Dental College, Yokosuka 238-8580, Japan.
authors.forename: Takeharu
authors.initials: T
authors.lastname: Ikoma
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Ozawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Suzuki
authors.forename: Tadanori
authors.initials: T
authors.lastname: Kondo
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Maehata
authors.forename: Masaichi Chang-il
authors.initials: MC
authors.lastname: Lee
authors.forename: Ryu-Ichiro
authors.initials: R
authors.lastname: Hata
authors.forename: Eiro
authors.initials: E
authors.lastname: Kubota
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002450:Cell Communication / Q000235:genetics; D002452:Cell Count; D002454:Cell Differentiation / Q000235:genetics*; D019743:Chemokines, CXC / Q000235:genetics*; D002746:Chlorpromazine / Q000494:pharmacology; D055312:Cystatin A / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: C118056:CXCL14 protein, human; D002147:Calmodulin; D019743:Chemokines, CXC; D055312:Cystatin A; D016329:Sp1 Transcription Factor; C026407:CSTA protein, human; C498712:TGM3 protein, human; D011503:Transglutaminases; C105804:transglutaminase 1; D002118:Calcium; D002746:Chlorpromazine