Leof, Edward B.

The primary mediator of transforming growth factor β (TGFβ) responses are the Smad proteins. Here, we identify sorting nexin 9 (SNX9) as being required for Smad3 (but not Smad2) nuclear translocation and cell stimulation. SNX9 principally interacts with phosphorylated (p) Smad3 and promotes more rapid nuclear delivery from that observed independent of ligand. Although SNX9 does not bind Imp7, Impb, Nup153 or Nup214, it mediates the association of pSmad3 with Imp8 and the nuclear membrane. This facilitates recruitment of pSmad3/SNX9 to the nuclear pore, heterodimerization of Imp8 with Impb, and nuclear translocation of pSmad3, but not SNX9. The demonstration that Smad3 is regulated in a distinct manner from Smad2 provides the opportunity to develop intervention strategies to enhance or dampen specific aspects of the cellular response to TGFβ. Support or Funding Information This work was supported by Public Health Service grants GM‐055816 and GM‐054200 from National Institutes of General Medical Sciences.

Transforming growth factor‐β (TGFβ) is the prototype of a family of secreted polypeptide growth factors with key roles in cellular growth and differentiation. The primary mediators of TGFβ action are the Smad proteins, specifically Smad2 and Smad3. Upon receptor activation these 55–60 kDa proteins are phosphorylated (p) by the type I TGFβ receptor and undergo nuclear translocation to function as co‐modulators of gene expression. While the specific roles of Smad2 and Smad3 are being actively investigated, recent findings have shown that while Smad3 is clearly pro‐fibrotic/pro‐carcinogenic, Smad2 can induce anti‐fibrotic/anti‐carcinogenic responses. Thus, approaches designed to target more downstream TGFβ receptor signaling components may provide equivalent efficacy and greater specificity. To that end, as we previously determined that sorting nexin 9 (SNX9) plays an integral role in the nuclear import of pSmad3 (but not pSmad2), we have extended those findings and identified the functional element in SNX9 critical for pSmad3 binding. Furthermore, we show that a TAT‐fusion encompassing this region can act in a dominant manner to block SNX9/pSmad3 binding, pSmad3 nuclear translocation, and subsequent pro‐fibrotic responses dependent upon pSmad3 both in vitro and in vivo . Support or Funding Information This work was supported by Public Health Service grants GM‐055816 and GM‐054200 from National Institutes of General Medical Sciences.

Alterations in cellular metabolism are known to play critical roles in a variety of normal as well as pathological processes, including (but not limited to) cancer, hepatic steatosis, and cell differentiation. While TGFβ is routinely considered a pleotropic cytokine due to its ability to impact numerous diseases and biological phenotypes, the role of metabolism in profibrotic TGFβ signaling is relatively unexplored/unknown. Fatty Acid Synthase (FASN) is the primary anabolic enzyme responsible for the de novo synthesis of fatty acids. Renewed interest in FASN has been sparked by the recognition of the critical inter‐relation of metabolic dysregulation and tumor progression with the findings that (i) FASN levels are significantly increased in numerous human tumors including breast, prostate, colorectal, and ovarian; and (ii) the efficacy of ErbB receptor inhibitors is enhanced by inhibiting FASN activity. In the current study we show that FASN expression is regulated by TGFβ in multiple murine and human fibroblasts, required for profibrotic TGFβ signaling, and, most importantly, treatment with C75 ((trans‐4‐carboxy‐5‐octyl‐3‐methylenebutyrolactone, a novel cerulenin‐derived semi‐synthetic FASN inhibitor) abrogates pathologic and physiologic changes in a murine model of lung fibrosis. Support or Funding Information This work was supported by Public Health Service grants GM‐055816 and GM‐054200 from National Institutes of General Medical Sciences.

Abstract Immune checkpoint proteins such as programmed death-ligand 1 (PD-L1) retain general immune homeostasis and self-tolerance. PD-L1 binds to programmed cell death protein 1 (PD-1) and inhibits T cell activation or protects tumor cells from T cell-mediated killing. PD-L1 has recently been shown to be up-regulated in invasive lung fibroblasts by p53 and focal adhesion kinase (FAK), any potential role of transforming growth factor-beta (TGFβ) in PD-L1 action is unknown in fibrosis. TGFβ is a mysterious protein with various roles in healthy tissue homeostasis/development as well as the development or progression of cancer, fibrotic disorders, and immune modulation, et al. In the current study, we showed that TGFβ induces the expression of the immunoinhibitory molecule PD-L1 in human and murine fibroblasts in a Smad2/3- and YAP/TAZ-dependent manner. Furthermore, PD-L1 knockdown decreased the TGFβ-dependent induction of extracellular matrix proteins, including collagen Ia1 (colIa1) and alpha-smooth muscle actin (α-SMA), and cell migration/wound healing. In addition to an endogenous role for PD-L1 in profibrotic TGFβ signaling, TGFβ stimulated-human lung fibroblast-derived PD-L1 into extracellular vesicles (EVs) capable of inhibiting T-cell proliferation in response to T cell receptor stimulation and mediating fibroblast cell migration. These findings provide new insights and potential targets for a variety of fibrotic and malignant diseases.

Idiopathic pulmonary fibrosis (IPF) remains an intractably fatal disorder, despite the recent advent of anti-fibrotic medication. Successful treatment of IPF, like many chronic diseases, may benefit from the concurrent use of multiple agents that exhibit synergistic benefit. In this light, phosphodiesterase type 5 inhibitors (PDE5-Is), have been studied in IPF primarily for their established pulmonary vascular effects. However, recent data suggest certain PDE5-Is, particularly vardenafil, may also reduce transforming growth factor beta 1 (TGF-β1) activation and extracellular matrix (ECM) accumulation, making them a potential target for therapy for IPF. We evaluated fibroblast TGF-β1-driven extracellular matrix (ECM) generation and signaling as well as epithelial mesenchymal transformation (EMT) with pretreatment using the PDE5-I vardenafil. In addition, combinations of vardenafil and nintedanib were evaluated for synergistic suppression of EMC using a fibronectin enzyme-linked immunosorbent assay (ELISA). Finally, the effects of vardenafil on fibrosis were investigated in a bleomycin mouse model. Our findings demonstrate that vardenafil suppresses ECM generation alone and also exhibits significant synergistic suppression of ECM in combination with nintedanib in vitro. Interestingly, vardenafil was shown to improve fibrosis markers and increase survival in bleomycin-treated mice. Vardenafil may represent a potential treatment for IPF alone or in combination with nintedanib. However, additional studies will be required.

Transforming growth factor beta (TGF‐β) is an enigmatic protein with various roles in normal tissue homeostasis/development as well as the development and/or progression of cancer, wound healing, fibrotic disorders, and immune modulation, to name a few. As TGF‐β is causal to various fibroproliferative disorders featuring localized or systemic tissue/organ fibrosis as well as the activated stroma observed in numerous malignancies, characterizing the pathways and players mediating its action is fundamental. To that end, in the current study we found that (i) TGF‐β induces the expression of the immunoinhibitory molecule Programmed Death‐Ligand 1 (PD‐L1) in human and murine fibroblasts in a Smad2/3‐dependent manner; (ii) profibrotic TGF‐β signaling is dependent upon PD‐L1 expression; and (iii) following treatment with TGF‐β, human lung fibroblasts secrete PD‐L1 into extracellular vesicles (EVs) capable of inhibiting T‐cell proliferation in response to T cell receptor stimulation. These findings provide new insights and potential targets for a variety of fibrotic and/or malignant diseases. Support or Funding Information This work was supported by Public Health Service grants GM‐55816 and GM‐54200 from the National Institute of General Medical Sciences. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

The mechanisms underlying E‐cadherin clustering and AJ maturation are not fully understood although the E‐cadherin‐mediated formation of adherens junctions (AJs) is essential for the morphogenesis of epithelial cells. Here we report that the association between type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) and Exo70 regulated the transport and clustering of Ecadherin on the plasma membrane and, subsequently, the extension of nascent E‐cadherin adhesions. We also observed that PI4,5P(2) accumulation at E‐cadherin clusters during the assembly of E‐cadherin adhesions. PIPKIγ‐generated PI4,5P(2) is required for recruiting Exo70 to newly formed E‐cadherin junctions and facilitates the assembly and maturation of AJs. Additionally, Rho activity and actin structure were impaired by loss of Exo70 and/or PIPKIγ. These results support a model in which PIPKIγ and PIPKIγ‐generated PI4,5P(2) pools at nascent E‐cadherin contacts cue Exo70 targeting and orients the tethering of exocyst‐associated E‐cadherin. This could be an important mechanism that regulates E‐cadherin clustering and AJ maturation, and actin reorganization, which is essential for the establishment of solid, polarized epithelial structures.

Transforming growth factor beta (TGF‐β) plays a significant role in diverse biologic processes, including the regulation of cell growth, survival, differentiation, development, inflammation, immunity, hematopoiesis, and tissue remodeling. TGF‐β is essential for wound healing, stimulates matrix molecule deposition, and has been implicated in the pathogenesis of a variety of fibrotic disorders, including idiopathic pulmonary fibrosis, scleroderma, radiation‐induced pulmonary fibrosis, and asthma. Furthermore, activation of profibrotic TGF‐β signaling has a central role in glucose‐induced cell hypertrophy, induces glucose transporter 1, and regulates mitochondrial energetics. However, the mechanisms by which TGF‐β induces specific metabolic alterations in the fibrogenic process have not been fully defined. In this study, we demonstrate that TGF‐β stimulates type I TGF β receptor (TβRI) translocation to the mitochondria and induction of hexokinase 2 (HK2) via both Smad‐dependent and –independent pathways. Also, we showed that TbRI association with HK2 and the mitochondrial voltage‐dependent ion channel (VDAC). These findings suggest that TβRI plays a novel role in controlling mitochondrial function and regulation of glucose metabolism. Support or Funding Information This work was supported by Public Health Service grants GM‐055816 and GM‐054200 from the National Institutes of General Medical Sciences. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Abstract In the current work we show that the profibrotic actions of TGF‐β are mediated, at least in part, through a metabolic maladaptation in glutamine metabolism and how the inhibition of glutaminase 1 (GLS1) reverses pulmonary fibrosis. GLS1 was found to be highly expressed in fibrotic vs normal lung fibroblasts and the expression of profibrotic targets, cell migration, and soft agar colony formation stimulated by TGF‐β required GLS1 activity. Moreover, knockdown of SMAD2 or SMAD3 as well as inhibition of PI3K, mTORC2, and PDGFR abrogated the induction of GLS1 by TGF‐β. We further demonstrated that the NAD‐dependent protein deacetylase, SIRT7, and the FOXO4 transcription factor acted as endogenous brakes for GLS1 expression, which are inhibited by TGF‐β. Lastly, administration of the GLS1 inhibitor CB‐839 attenuated bleomycin‐induced pulmonary fibrosis. Our study points to an exciting and unexplored connection between epigenetic and transcriptional processes that regulate glutamine metabolism and fibrotic development in a TGF‐β‐dependent manner.