The Research On The Effect Of PIgR In EMT

Polymeric immunoglobulin receptor (pIgR) belongs to type I trans-membrane glycoprotein. It could specifically bind to polymeric IgA or polymeric IgM, and transport them into the secretion via the process of transcytosis. On basal to apical transport across epithelial cells, the pIgR extracellular domain is cleaved, releasing secreotry component (SC) in association with pIgA. MDCK cell, canine renal epithelial cell line, is a wide used model for epithelial biology investigation. In tissue culture, MDCK cells form tight epithelial monolayers with junctional complexes. Our group have constructed human pIgR over-expressing MDCK cells (MDCK-pIgR cells) and negative control (MDCK-mock cells) to investigate the mechanism of pIgR transcytosis. Surprisingly, during the research, we found a strange phenomenon that the morphology of MDCK-pIgR cells had changed from column to myofibroblastlike. Furthermore, these cells became motile compared to MDCK-mock cells.RNA interference was used to investigate the role of pIgR in EMT. There were three parts.Partâ… The construction of pIgR low expressing cell lines.Three RNA interference plasmids were designed and synthesized. The plasmids were stably transferred to MDCK-pIgR cells RT-PCR , western-blotting and immunofluorescence chemistry were used to detect the efficiency of the RNA interference. The results showed that RNA interference was effective, and the cell lines which low expressed pIgR could be used in the later experiments.Partâ…¡The research on EMT mediated by pIgR in MDCK cellsThe morphology, proliferation and the ability of migration, invasion, adhesion were investigated between each cell lines. The results showed that pIgR lead to the morphology change of MDCK cells. And the transfection of pIgR enhanced the ability of migration and invasion of MDCK cells, attenuated the ability of adhesion on the opposite. All these results demonstrated that pIgR mediated EMT in MDCK cells. Partâ…¢The initial investigation on EMT mediated by pIgRpIgR was widely studied in MDCK models about their transcytosis. It was believed that pIgR could phosphorate after ligand binding or dimeric. To find the mechanism of EMT in pIgR-expression MDCK, the technique of RT-PCR, immunofluorescence chemistry and western-blotting were used to investigate the change of ERK,Snail,keratin,E-cadherin, and F-actin. The phosphorylation state of pIgR was detected using IP method. It was that pIgR high expression lead to the increase phosphorylation level of ERK, which followed by the increase of Snail mRNA level. Then the E-cadherins were downregulated and the skeleton of cells changed. The EMT happened in finally. The activation of this signal pathway might be activated by the Tyr phosphorylation of pIgRThe role of pIgR in EMT can expand its'research territory. And the validation of pIgR's essential role in EMT may be useful for clarifying the function of pIgR in tumor genesis and helpful for cancer research.