TITLE:
Influence of Cell Confluency on the Expression of the α4 Integrin Subunit of Retinal Pigment Epithelial Cells
AUTHORS:
Jean-Michel Bourget, Mohib Morcos, Karine Zaniolo, Sylvain L. Guérin, Stéphanie Proulx
KEYWORDS:
Retinal Pigment Epithelium, Integrin Alpha 4 Subunit, Cell Culture, Confluency, Promoter
JOURNAL NAME:
Advances in Biological Chemistry,
Vol.5 No.2,
March
30,
2015
ABSTRACT: Integrins are a family of transmembrane glycoproteins that mediate cell-cell and cell-extracellular matrix interactions. The integrin α4 subunit is widely expressed by cells from the immune system and its expression by non-hematopoietic cells is scarce. In the present study, gene and protein expression of this integrin subunit was characterized in proliferating and quiescent human RPE cells. Immunofluorescent studies confirm that the α4 subunit is expressed in vitro by RPE cells, a result that has been validated by immunofluorescence and FACS analyses. The accumulation of the α4 integrin at cell-cell junctions in post-confluent RPE cell cultures negatively correlated with the level of expression of the mRNA transcript. Accordingly, transient transfection analyses reveal that the α4 promoter activity is considerably reduced when RPE cells form a confluent monolayer. Moreover, transfection of recombinant constructs bearing 5’-deletions of the α4 promoter segment allows the localization of strong negative regulatory elements on the -76 to -300 region of the α4 gene suggesting that its expression is intimately linked to the proliferative state of primary cultured RPE cells.