Functional analysis of protein disulfide isomerase P5 in glioblastoma cells by bioluminescence imaging method at single cell level

Horibe T and Kawakami K

Department of Pharmacoepidemiology, Graduate School of Medicine and Public Health, Kyoto University, Japan.

It is known that P5 is a member of protein disulfide isomerase (PDI) family proteins and has isomerase and chaperone activity. However, the detailed physiological roles and relationships of P5 to the other PDI family proteins in the cells still remain obscure. In order to understand the significant roles of P5 in cancer cells, we examined the expression levels of P5 on normal or cancer cell lines by flow cytometry analysis using affinity purified anti-P5 antibody. It was found that the expression levels of P5 was increased on the surface of many types of cancer cells such as glioblastoma, breast, colon, ovary and uterine cervix cancer, and leukemia compared with that of normal cells. When we performed the knock down experiment of P5 by siRNA in glioblastoma cells, it was found that the knock down affected the Bip promoter activation during the cancer cell growing using real-time monitoring method by bioluminescence imaging at single cell level and inhibited significantly the cancer cell growth and migration. We also performed the immunoprecipitation by anti-P5 antibody in cancer and normal cells, and it was found that vimentin was one of the binding proteins to P5 and bound to this enzyme predominantly in glioblastoma cells. The knock down of P5 in glioblastoma cells did not affected the expression level of vimentin protein but affected several epithelial mesenchymal transition (EMT) markers such as snail and slug proteins in the cells. These results suggest that P5 have significant roles for cancer cell growth and might be attractive and potent target for therapy of glioblastoma.