Endocellular polyamine availability modulates epithelial-to-mesenchymal transition and unfolded protein response in MDCK cells.

Epithelial-to-mesenchymal transition (EMT) is involved in embryonic development as well as in several pathological conditions. Literature indicates that polyamine availability may affect transcription of c-myc, matrix metalloproteinase (MMP)1, MMP2, TGFbeta(1), and collagen type I mRNA. The aim of this study was to elucidate polyamines role in EMT in vitro. Madin-Darby canine kidney (MDCK) cells were subjected to experimental manipulation of intracellular levels of polyamines. Acquisition of mesenchymal phenotype was evaluated by means of immunofluorescence, western blots, and zymograms. MDCK cells were then subjected to 2D gel proteomic study and incorporation of a biotinilated polyamine (BPA). Polyamine endocellular availability modulated EMT process. Polyamine-depleted cells treated with TGFbeta(1) showed enhanced EMT with a marked decrease of E-cadherin expression at plasma membrane level and an increased expression of mesenchymal markers such as fibronectin and alpha-smooth muscle actin. Polyamine-depleted cells showed a twofold increased expression of the rough endoplasmic reticulum (ER)-stress proteins GRP78, GRP94, and HSP90 alpha/beta in 2D gels. The latter data were confirmed by western blot analysis. Administration of BPA showed that polyamines are covalently linked, within the cell, to ER-stress proteins. Intracellular polyamine availability affects EMT in MDCK cells possibly through the modulation of ER-stress protein homeostasis.