Unique and Redundant Functions of p70 Ribosomal S6 Kinase Isoforms Regulate Mesenchymal Cell Proliferation and Migration in Pulmonary Fibrosis

Abstract

The p70 ribosomal S6 kinase (p70S6K) is a downstream substrate that is phosphorylated and activated by the mammalian target of rapamycin complex and regulates multiple cellular processes associated with pulmonary fibrogenesis. Two isoforms of the p70S6K have been identified (S6K1 and S6K2), but their relative contributions in mediating pulmonary fibrosis are unknown. To interrogate the roles of the p70S6K isoforms, we overexpressed transforming growth factor (TGF)-a in mice deficient for the S6K1 or S6K2 genes and measured changes in lung histology, morphometry, total lung collagen, lung function, and proliferation between wild-type and isoform-deficient mice. Deficiency of S6K1, but not S6K2, had a significant effect on reducing proliferation in subpleural fibrotic lesions during TGF-a-induced fibrosis. Migration was significantly decreased in mesenchymal cells isolated from the lungs of S6K1 knockout mice compared with wild-type or S6K2 knockout mice. Conversely, increases in subpleural thickening were significantly decreased in S6K2-deficient mice compared with wild type. Deficiency of S6K2 significantly reduced phosphorylation of the downstream S6 ribosomal protein in lung homogenates and isolated mesenchymal cells after TGF-a expression. However, deficiency of neither isoform alone significantly altered TGF-a-induced collagen accumulation or lung function decline in vivo. Furthermore, deficiency in neither isoform prevented changes in collagen accumulation or lung compliance decline after administration of intradermal bleomycin. Together, these findings demonstrate that the p70S6K isoforms have unique and redundant functions in mediating fibrogenic processes, including proliferation, migration, and S6 phosphorylation, signifying that both isoforms must be targeted to modulate p70S6K-mediated pulmonary fibrosis.

Oxyresveratrol Inhibits IL-1β-Induced Inflammation via Suppressing AKT and ERK1/2 Activation in Human Microglia, HMC3

“…Results showed that OXY could significantly inhibit AKT phosphorylation over the course of IL-1β stimulation, whereas ERK1/2 phosphorylation was moderately suppressed. Specifically, we observed a drastic reduction of AKT phosphorylation (Ser473) and p70S6K, which is a target kinase downstream of PI3K/AKT and normally plays a role in regulating multiple cellular processes, including the neuronal system [ 37 , 38 ]. These results suggest that OXY may have more inhibitory preference toward AKT rather than MAPKs in IL-1β-induced HMC3.…”

Dysregulation of Mesenchymal Cell Survival Pathways in Severe Fibrotic Lung Disease: The Effect of Nintedanib Therapy

“…The primary antibodies used were Bak (#12105) and Bax (#2772) from Cell Signaling Technology (Denver, CO, United States), and Collagen1α (Santa Cruz Biotechnology, Dallas, TX, United States) and Gapdh (Bethyl Laboratories). Quantification was performed using the volume integration function of the phosphor imager software, Multigage (Fujifilm, Valhalla, NY, United States) as described (Madala et al, 2016a).…”

Wilms’ tumor 1 drives fibroproliferation and myofibroblast transformation in severe fibrotic lung disease

“…Histology and IHC. Formalin-or OCT-fixed mouse lung tissue sections were prepared and stained with Masson's trichrome or immunostained with antibodies against α-SMA or Ki67 as described previously (65).…”

“…Human and mouse primary lung fibroblast cultures. Human and mouse primary lung fibroblast cell cultures were prepared as previously described (55,65).…”