Secretion polarity of interferon-β in epithelial cell lines

Epithelial cells are an attractive target for local gene delivery in gene therapy for which cytokine genes such as interferon (IFN) genes are promising. However, how the secretion of the gene products is regulated in epithelial cells has been insufficiently investigated. Here, we have studied the secretion polarity of IFN-β expressed via gene transfection in mouse epithelial Pam-T cells on a bicameral culture system. In transient expression, IFN-β was predominantly secreted from the cell membrane side on which the transfection was carried out. Meanwhile, the secretion of constitutive IFN-β from stable transformants was apparently unpolarized. Interestingly, the transformants displayed a polarized secretion of transiently expressed IFN-β in a transfection-side-dependent manner, their stable IFN-β secretion remaining unpolarized. These results suggest that epithelial cells have at least dual protein sorting–secretion pathways, transient and stable, for the same secretory proteins, such as IFNs.