KCl cotransporter-3 down-regulates E-cadherin/beta-catenin complex to promote epithelial-mesenchymal transition.
The potassium chloride cotransporter (KCC) is a major determinant of osmotic homeostasis and plays an emerging role in tumor biology. Here, we investigate if KCC is involved in the regulation of epithelial-mesenchymal transition (EMT), a critical cellular event of malignancy. E-cadherin and beta-catenin colocalize in the cell-cell junctions, which becomes more obvious in a time-dependent manner by blockade of KCC activity in cervical cancer SiHa and CaSki cells. Real-time reverse transcription-PCR on the samples collected from the laser microdissection indicates that KCC3 is the most abundant KCC isoform in cervical carcinoma. The characteristics of EMT appear in KCC3-overexpressed, but not in KCC1- or KCC4-overexpressed cervical cancer cells, including the elongated cell shape, increased scattering, down-regulated epithelial markers (E-cadherin and beta-catenin), and up-regulated mesenchymal marker (vimentin). Some cellular functions are enhanced by KCC3 overexpression, such as increased invasiveness and proliferation, and weakened cell-cell association. KCC3 overexpression decreases mRNA level of E-cadherin. The promoter activity assays of various regulatory sequences confirm that KCC3 expression is a potent negative regulator for human E-cadherin gene expression. The proteosome inhibitor restores the decreased protein abundance of beta-catenin by KCC3 overexpression. In the surgical specimens of cervical carcinoma, the decreased E-cadherin amount was accompanied by the increased KCC3 abundance. Vimentin begins to appear at the invasive front and becomes significantly expressed in the tumor nest. In conclusion, KCC3 down-regulates E-cadherin/beta-catenin complex formation by inhibiting transcription of E-cadherin gene and accelerating proteosome-dependent degradation of beta-catenin protein. The disruption of E-cadherin/beta-catenin complex formation promotes EMT, thereby stimulating tumor progression.
Hsu
Yueh-Mei
YM
Institute of Basic Medical Sciences, Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Chen
Yih-Fung
YF
Chou
Cheng-Yang
CY
Tang
Ming-Jer
MJ
Chen
Ji Hshiung
JH
Wilkins
Robert J
RJ
Ellory
J Clive
JC
Shen
Meng-Ru
MR
D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D004848:Epithelium / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008648:Mesoderm / Q000378:metabolism*; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism; D000096922:K Cl- Cotransporters
D015820:Cadherins; D046988:Proteasome Endopeptidase Complex; D020033:Protein Isoforms; D027981:Symporters; D051176:beta Catenin; C119650:SLC12A6 protein, human; D000096922:K Cl- Cotransporters