ARTS-1 promotes TNFR1 shedding from human epithelial and endothelial cells. (a) ARTS-1 protein expression by NCI-H292 cell lines. Immunoblots were performed on membrane fractions from wild-type NCI-H292 cells (WT) or cells stably transfected with either empty pTarget (Mock), or pTarget encoding either sense (ARTS-1) or antisense (AS) ARTS-1 coding sequence. Samples 1 and 2 are from representative clonal lines. (b) ARTS-1 protein expression by transiently transfected HUVECs. Proteins were prepared the same way as for a. Samples 1 and 2 are from two representative transient transfections. (c) Effect of ARTS-1 protein expression on membrane-associated TNFR1 levels in ARTS-1 cell lines. Immunoblots of membrane fractions were performed in duplicate with an anti-TNFR1 antibody. (d) Effect of ARTS-1 protein expression on membrane-associated TNFR1 levels in HUVECs. Immunoblots of membrane fractions of transiently transfected HUVECs were performed with an anti-TNFR1 antibody. Samples 1 and 2 are from two representative transient transfections. (e) Effect of ARTS-1 on TNFR1 shedding from ARTS-1 cell lines. The amounts of sTNFR1 present in cell culture supernatants from two antisense (AS) and two sense ARTS-1 cell lines over a 24-hour period were determined by ELISA (n = 5). *P < 0.05 as compared to mock transfected cells. (f) Effect of ARTS-1 on TNFR1 shedding from HUVECs. The amount of sTNFR1 present in cell culture supernatants from transiently transfected HUVECs over a 24-hour period was determined by ELISA (n = 5). *P < 0.05 as compared with mock-transfected cells.