Figure 7
Figure 7. Caveolin-1 inhibits TGF-β signaling and stimulates growth of T-cell lines. (A) Caveolin-1 colocalizes with TβRI. HTLV-1–infected T-cell lines were doubly immunostained with antibodies that specifically recognize caveolin-1 and TβRI. The bound primary antibodies were visualized with Alexa Fluor 488–labeled goat anti–rabbit IgG (green) and Alexa Fluor 546–labeled donkey anti–goat IgG (red). Cells were counterstained with Hoechst 33342 (nuclei stained in blue). (B) Caveolin-1 functionally regulates TGF-β signaling at transcriptional level. Jurkat cells were transfected with p3TP-Lux and a combination of TβRI (T204D), caveolin-1, Tax, or empty vector controls. Cells were harvested 24 hours after transfection, and luciferase activity was measured with a luminometer. The results are expressed as fold induction relative to the basal level measured in cells transfected with the reporter plasmid alone. Data are mean ± SD of 3 independent transfection experiments. (C) Down-regulation of caveolin-1 mRNA and protein by siRNA. C5/MJ and SLB-1 cells were transfected with either caveolin-1 or control siRNA and then incubated for 24 hours. Caveolin-1 mRNA and protein levels were determined by RT-PCR and Western blot analysis, respectively (right). After transfection with siRNA, the cells were treated with TGF-β (10 ng/mL) for 72 hours. The degree of cell proliferation was examined by water-soluble tetrazolium salt-8 (WST-8) assay. Results are expressed as percentages of values obtained from the control TGF-β–free culture (left). Data are mean ± SD of triplicate experiments. *P < .05 compared with the control (Student t test). (D) Effect of recombinant caveolin-1 and caveolin-3 proteins on T-cell lines. The indicated cells were incubated with 1% FBS in the presence or absence of recombinant full-length caveolin-1 or partial caveolin-3 protein (1.5 μg/mL). WST-8 assays were performed on triplicate wells at 24-hour intervals for a total of 3 days. A relative cell proliferation of 100% was designated as the average absorbance numbers of cells without treatment at day 0. Data are mean ± SD of triplicate experiments. *P < .05 compared with the control (Student t test).

Caveolin-1 inhibits TGF-β signaling and stimulates growth of T-cell lines. (A) Caveolin-1 colocalizes with TβRI. HTLV-1–infected T-cell lines were doubly immunostained with antibodies that specifically recognize caveolin-1 and TβRI. The bound primary antibodies were visualized with Alexa Fluor 488–labeled goat anti–rabbit IgG (green) and Alexa Fluor 546–labeled donkey anti–goat IgG (red). Cells were counterstained with Hoechst 33342 (nuclei stained in blue). (B) Caveolin-1 functionally regulates TGF-β signaling at transcriptional level. Jurkat cells were transfected with p3TP-Lux and a combination of TβRI (T204D), caveolin-1, Tax, or empty vector controls. Cells were harvested 24 hours after transfection, and luciferase activity was measured with a luminometer. The results are expressed as fold induction relative to the basal level measured in cells transfected with the reporter plasmid alone. Data are mean ± SD of 3 independent transfection experiments. (C) Down-regulation of caveolin-1 mRNA and protein by siRNA. C5/MJ and SLB-1 cells were transfected with either caveolin-1 or control siRNA and then incubated for 24 hours. Caveolin-1 mRNA and protein levels were determined by RT-PCR and Western blot analysis, respectively (right). After transfection with siRNA, the cells were treated with TGF-β (10 ng/mL) for 72 hours. The degree of cell proliferation was examined by water-soluble tetrazolium salt-8 (WST-8) assay. Results are expressed as percentages of values obtained from the control TGF-β–free culture (left). Data are mean ± SD of triplicate experiments. *P < .05 compared with the control (Student t test). (D) Effect of recombinant caveolin-1 and caveolin-3 proteins on T-cell lines. The indicated cells were incubated with 1% FBS in the presence or absence of recombinant full-length caveolin-1 or partial caveolin-3 protein (1.5 μg/mL). WST-8 assays were performed on triplicate wells at 24-hour intervals for a total of 3 days. A relative cell proliferation of 100% was designated as the average absorbance numbers of cells without treatment at day 0. Data are mean ± SD of triplicate experiments. *P < .05 compared with the control (Student t test).

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