Transforming growth factor-beta1 induces the non-classical secretion of peroxiredoxin-I in A549 cells

Recent studies found that peroxiredoxin-I (Prx-I) is secreted from A549 cells although it does not contain a signal peptide and is known to be a cytosolic protein. Transforming growth factor-beta1 (TGF-beta1) treatment dramatically enhanced Prx-I secretion from A549 cells, and this effect was not inhibited by brefeldin A. Further investigation revealed that A549 cells constitutively secrete TGF-beta1. Furin, a TGF-beta1-converting enzyme, was also highly activated in A549 cells. Ectopic expression of alpha(1)-antitrypsin Portland (alpha(1)-PDX), a potent furin inhibitor, blocked both TGF-beta1 activation and Prx-I secretion. Our findings collectively suggest that non-classical secretion of Prx-I is induced by TGF-beta1, which is constitutively activated by furin in A549 cells.