Requirement of Smad3 and CREB-1 in Mediating Transforming Growth Factor-β (TGFβ) Induction of TGFβ3 Secretion

Abstract

Because increased transforming growth factor-␤ (TGF␤) production by tumor cells contributes to cancer progression through paracrine mechanisms, identification of critical points that can be targeted to block TGF␤ production is important. Previous studies have identified the precise signaling components and promoter elements required for TGF␤ induction of TGF␤1 expression in epithelial cells (Yue, J., and Mulder, K. M. (2000) J. Biol. Chem. 275, 30765-30773). To determine how regulation of TGF␤3 expression differs from that of TGF␤1, we identified the precise signaling pathways and transcription factor-binding sites that are required for TGF␤3 gene expression. By using mutational analysis in electrophoresis mobility shift assays (EMSAs), we demonstrated that the c-AMP-responsive element (CRE) site in the TGF␤3 promoter was required for TGF␤-inducible TGF␤3 expression. Electrophoresis mobility supershift assays indicated that CRE-binding protein 1 (CREB1) and Smad3 were the major components present in this TGF␤-inducible complex. Furthermore, by using chromatin immunoprecipitation assays, we demonstrated that CREB-1, ATF-2, and c-Jun bound constitutively at the TGF␤3 promoter (؊100 to ؉1), whereas Smad3 bound at this site only after TGF␤ stimulation. In addition, inhibition of JNK and p38 suppressed TGF␤ induction of TGF␤3 transactivation, whereas inhibition of ERK and protein kinase A had no effect. Small interfering RNA-CREB1 and small interfering RNA-Smad3 significantly inhibited TGF␤ stimulation of TGF␤3 promoter reporter activity and TGF␤3 production. Our results indicate that TGF␤ activation of the TGF␤3 promoter CRE site, which leads to TGF␤3 production, is required for TGF␤RII, JNK, p38, and Smad3 but was independent of protein kinase A, ERK, and Smad4.

PTP-Pez: A novel regulator of TGFβ signaling

“…Although MDCK cells stably overexpressing Pez express significantly elevated transcript levels of all three TGFβ isoforms (TGFβ 1 , TGFβ 2 and TGFβ 3 ), 10 it is well documented that TGFβ signaling can autoinduce transcription of its own mRNA, [39][40][41][42] and we have observed this to be the case in the MDCK cell culture model used in our studies (Wyatt L and Khew-Goodall Y, unpublished observations). The increase in TGFβ transcript levels detected following stable overexpression of Pez may therefore be due either to a direct effect of Pez on TGFβ transcription, or the auto-induction of TGFβ transcription down-stream of TGFβ-mediated signal transduction.…”

Active CREB1 Promotes a Malignant TGFβ2 Autocrine Loop in Glioblastoma

“…3A ). CREB1 has been shown to interact and cooperate with SMADs in the transcriptional activation of certain genes ( 30,31 ). This suggested that CREB1 cooperates with SMADs to activate TGFB2 gene transcription.…”

“…CREB factors promote tumorigenesis in many cancers, including non-small cell lung carcinoma, acute myelogenous leukemia, and glioma ( 19 , 23-27 ). Interestingly, the CREB/ATF family of transcription factors has been shown to regulate and cooperate with SMADs in the transcriptional regulation of multiple genes (28)(29)(30)(31).…”

Transmembrane TNF-α Reverse Signaling Inhibits Lipopolysaccharide-Induced Proinflammatory Cytokine Formation in Macrophages by Inducing TGF-β: Therapeutic Implications

“…4A) and activate CREB-dependent gene expression (30,31). Because the promoter of both TGF-b2 (32) and -b3 (33,34) contains cAMP response element, we decided to investigate whether selective inhibition of p38 MAPKs by SB203580 (10 mM) could interfere with the mTNF-a-induced TGF-b production. As seen in Fig.…”