B7-1 drives TGF-β stimulated pancreatic carcinoma cell migration and expression of EMT target genes.

B7-1 proteins are routinely expressed on the surface of antigen presenting cells (APC) and within the innate immune system. They function to establish a biologically optimal and dynamic balance between immune activation and inhibition or self-tolerance. Interactions between B7-1 and its receptors, which include CD28, CTLA4 and PD-L1, contribute to both stimulatory as well as inhibitory or homeostatic regulation. In the current study, we investigated whether the tumor-promoting actions of transforming growth factor beta (TGF-β) disrupted this equilibrium in pancreatic cancer to promote malignant progression and an enhanced means to evade immune detection. The data show that B7-1 is (i) upregulated following treatment of pancreatic carcinoma cells with TGF-β; (ii) induced by TGF-β via both Smad2/3-dependent and independent pathways; (iii) required for pancreatic tumor cell in vitro migration/invasion; and (iv) necessary for TGF-β regulated epithelial-mesenchymal transition (EMT) through induction of Snail family members. Results from the proposed studies provide valuable insights into mechanisms whereby TGF-β regulates both the innate immune response and intrinsic properties of pancreatic tumor growth

Ligand-dependent and -independent Transforming Growth Factor-β Receptor Recycling Regulated by Clathrin-mediated Endocytosis and Rab11

Proteins in the transforming growth factor-β (TGF-β) family recognize transmembrane serine/threonine kinases known as type I and type II receptors. Binding of TGF-β to receptors results in receptor down-regulation and signaling. Whereas previous work has focused on activities controlling TGF-β signaling, more recent studies have begun to address the trafficking properties of TGF-β receptors. In this report, it is shown that receptors undergo recycling both in the presence and absence of ligand activation, with the rates of internalization and recycling being unaffected by ligand binding. Recycling occurs as receptors are most likely internalized through clathrin-coated pits, and then returned to the plasma membrane via a rab11-dependent, rab4-independent mechanism. Together, the results suggest a mechanism wherein activated TGF-β receptors are directed to a distinct endocytic pathway for down-regulation and clathrin-dependent degradation after one or more rounds of recycling

Cell-Type-Specific Activation of PAK2 by Transforming Growth Factor β Independent of Smad2 and Smad3

Transforming growth factor β (TGF-β) causes growth arrest in epithelial cells and proliferation and morphological transformation in fibroblasts. Despite the ability of TGF-β to induce various cellular phenotypes, few discernible differences in TGF-β signaling between cell types have been reported, with the only well-characterized pathway (the Smad cascade) seemingly under identical control. We determined that TGF-β receptor signaling activates the STE20 homolog PAK2 in mammalian cells. PAK2 activation occurs in fibroblast but not epithelial cell cultures and is independent of Smad2 and/or Smad3. Furthermore, we show that TGF-β-stimulated PAK2 activity is regulated by Rac1 and Cdc42 and dominant negative PAK2 or morpholino antisense oligonucleotides to PAK2 prevent the morphological alteration observed following TGF-β addition. Thus, PAK2 represents a novel Smad-independent pathway that differentiates TGF-β signaling in fibroblast (growth-stimulated) and epithelial cell (growth-inhibited) cultures

Sorting nexin 9 differentiates ligand-activated Smad3 from Smad2 for nuclear import and transforming growth factor ß signaling

Transforming growth factor ß (TGFß) is a pleiotropic protein secreted from essentially all cell types and primary tissues. While TGFß's actions reflect the activity of a number of signaling networks, the primary mediator of TGFß responses are the Smad proteins. Following receptor activation, these cytoplasmic proteins form hetero-oligomeric complexes that translocate to the nucleus and affect gene transcription. Here, through biological, biochemical, and immunofluorescence approaches, sorting nexin 9 (SNX9) is identified as being required for Smad3-dependent responses. SNX9 interacts with phosphorylated (p) Smad3 independent of Smad2 or Smad4 and promotes more rapid nuclear delivery than that observed independent of ligand. Although SNX9 does not bind nucleoporins Nup153 or Nup214 or some ß importins (Imp7 or Impß), it mediates the association of pSmad3 with Imp8 and the nuclear membrane. This facilitates nuclear translocation of pSmad3 but not SNX9

Noncanonical TGF-β pathways, mTORC1 and Abl, in renal interstitial fibrogenesis

Renal interstitial fibrosis is a major determinant of renal failure in the majority of chronic renal diseases. Transforming growth factor-β (TGF-β) is the single most important cytokine promoting renal fibrogenesis. Recent in vitro studies identified novel non-smad TGF-β targets including p21-activated kinase-2 (PAK2), the abelson nonreceptor tyrosine kinase (c-Abl), and the mammalian target of rapamycin (mTOR) that are activated by TGF-β in mesenchymal cells, specifically in fibroblasts but less in epithelial cells. In the present studies, we show that non-smad effectors of TGF-β including PAK2, c-Abl, Akt, tuberin (TSC2), and mTOR are activated in experimental unilateral obstructive nephropathy in rats. Treatment with c-Abl or mTOR inhibitors, imatinib mesylate and rapamycin, respectively, each blocks noncanonical (non-smad) TGF-β pathways in the kidney in vivo and diminishes the number of interstitial fibroblasts and myofibroblasts as well as the interstitial accumulation of extracellular matrix proteins. These findings indicate that noncanonical TGF-β pathways are activated during the early and rapid renal fibrogenesis of obstructive nephropathy. Moreover, the current findings suggest that combined inhibition of key regulators of these non-smad TGF-β pathways even in dose-sparing protocols are effective treatments in renal fibrogenesis