Global Expression Profiling of Fibroblast Responses to Transforming Growth Factor-β1 Reveals the Induction of Inhibitor of Differentiation-1 and Provides Evidence of Smooth Muscle Cell Phenotypic Switching

Abstract

Transforming growth factor-beta1 (TGF-beta1) plays a central role in promoting extracellular matrix protein deposition by promoting the transformation of fibroblasts to myofibroblasts. To gain new insights into the transcriptional programs involved, we profiled human fetal lung fibroblast global gene expression in response to TGF-beta1 up to 24 hours using oligonucleotide microarrays. In this report, we present data for 146 genes that were up-regulated at least twofold at two time points. These genes group into several major functional categories, including genes involved in cytoskeletal reorganization (n = 30), matrix formation (n = 25), metabolism and protein biosynthesis (n = 27), cell signaling (n = 21), proliferation and survival (n = 13), gene transcription (n = 9), and of uncertain function (n = 21). For 80 of these genes, this is the first report that they are TGF-beta1-responsive. The early induction of two members of the inhibitor of differentiation (ID) family of transcriptional regulators, ID1 and ID3, was followed by the up-regulation of a number of genes that are usually expressed by highly differentiated smooth muscle cells, including smooth muscle myosin heavy chain, basic calponin, and smoothelin. These findings were confirmed at the protein level for primary adult lung fibroblasts. ID1 further behaved like a typical immediate-early gene and, unlike ID3, was expressed and induced at the protein level. Immunohistochemical analysis showed that ID1 was highly expressed by (myo)fibroblasts within fibrotic foci in experimentally induced pulmonary fibrosis. ID1 acts as a dominant-negative antagonist of basic helix-loop-helix transcription factors that drive cell lineage commitment and differentiation. These findings have important implications for our understanding of fibroblast transcriptional programming in response to TGF-beta1 during development, oncogenesis, tissue repair, and fibrosis.

Smad3 mediates immediate early induction of Id1 by TGF-β

“…After reaching its peak, Id1 protein level gradually decreased even with the presence of TGF-β1. In accordance with previous reports [5,27], the Id1 protein level at 4 h after TGF-β1 treatment was below the basal level, indicating that the Id1 gene was repressed or Id1 protein was rapidly degraded. Thus, Id1 protein is transiently induced by TGF-β1 in various human cell lines.…”

“…Although previous studies have reported both repression and induction of the Id1 gene by TGF-β [5,27], it is a dominant view that TGF-β primarily represses Id1 transcription [5]. Most of these studies focus on the regulation of the Id1 gene with prolonged TGF-β1 treatment (e.g.…”

“…Although both positive and negative transcriptional regulation of Id1 by TGF-b1 has been reported [5,27], it is generally believed that Id1 gene is repressed for TGF-β to achieve its cytostatic and stress responses in epithelial cells. Furthermore, Id1 induction in certain cell types may be mediated through the ALK1-activated Smad1 pathway, but not through the TbRI-activated Smad2/3 pathway [28].…”

Quantitative Proteomics Analysis of the Effects of Ionizing Radiation in Wild Type and p53K317R Knock-in Mouse Thymocytes

“…Decreased TNF␣ activity in p53 K317R thymocytes is also consistent with the observed lack of change in WARS, TCF7, and ETFDH protein levels after IR; all of these proteins are indirectly regulated by TNF␣ (53)(54)(55)(56)(57)(58). Finally TNF␣ has been shown to induce the expression of TGF␤1 (59), which has been shown to increase the expression of FABP5 and SSRP1 (60,61), two additional proteins that exhibit the same pattern. Thus, the proteins affected differently by IR in wild type compared with mutant thymocytes suggest a change in p53 activity and a decrease in TNF␣ signaling.…”

Id proteins: Novel targets of activin action, which regulate epidermal homeostasis

“…Since the regulation of Id1 expression by TGF-b occurs in a cell-type-specific manner (Chambers et al, 2003;Kurisaki et al, 2003), we tested if this is also the case for activin. Therefore, we treated primary human dermal fibroblasts with either activin A or TGF-b1 for different time periods and subjected the cell lysates to Western blotting.…”