TGFbeta1 regulates gene expression of its own converting enzyme furin.

Abstract

TGF ␤ 1 is known for its potent and diverse biological effects, including immune regulation, and cell growth and differentiation. We have recently shown that TGF ␤ 1 precursor is processed by human furin COOH-terminal to the R-H-R-R 278 cleavage site to generate authentic mature TGF ␤ 1. In the present study, we demonstrate that steady-state furin mRNA levels are increased in rat synovial cells by 2 and 20 ng/ml TGF ␤ 1. Stimulation with TGF ␤ 1 results in a significant increase in furin mRNA levels, starting at 3 h with the peak effect observed at 12 h (2.5-fold increase Ϯ 0.4). TGF ␤ 1 did not increase furin mRNA stability, and treatment of synovial cells with actinomycin D, before TGF ␤ 1 addition prevented the increase in fur gene expression, suggesting that the observed regulation occurs at the level of gene transcription. Treatment of synovial and NRK-49F fibroblastic cells with exogenous TGF ␤ 1 (5 ng/ml) or TGF ␤ 2 (10 ng/ml) translates into an increase in pro-TGF ␤ 1 processing as evidenced by the appearance of a 40-kD immunoreactive band corresponding to the TGF ␤ 1 NH 2 -terminal pro-region. Furin processing activity stimulated by TGF ␤ 2 correlates with significant increase in extracellular mature and heat-activable TGF ␤ 1 as determined by an isoform-specific ELISA assay. Taken together, these results demonstrate for the first time that TGF ␤ 1 upregulates gene expression of its own converting enzyme, and that this expression is translated into augmented processing of the TGF ␤ 1 precursor form. Such adaptive responsiveness of the TGF ␤ 1 convertase may represent an important aspect of TGF ␤ 1 bioavailibility in TGF ␤ 1-related processes and pathological conditions. ( J.

Processing of Immunosuppressive Pro-TGF-β1,2 by Human Glioblastoma Cells Involves Cytoplasmic and Secreted Furin-Like Proteases

“…In contrast to other cell types (10,11), TGF-␤ appears not to promote furin mRNA expression or activity to enhance its own release in a positive autocrine loop in glioma cells (data not shown).…”

“…3 H]thymidine (1 Ci/well) for additional 16 h. Cell culture supernatants were obtained by seeding 10 6 cells in a 25-cm 2 culture flask. After 24 h, the cells were washed with PBS and then incubated with serum-free medium.…”

“…Activation to the mature 12.5-kDa TGF-␤1, which needs to dimerize to exert its biological effects, depends on the action of subtilisin-like proprotein convertases such as furin, as shown for purified proteins obtained from cell culture supernatants in a cellfree system (9). In fact, it has been suggested that TGF-␤ promotes furin gene expression as part of an amplification cascade of its own activation in fibroblasts and rat hepatocytes (10,11). The subtilisin-like proprotein convertases of mammalian cells constitute a family of proprotein convertases related to bacterial subtilisins and yeast Kex2p that process multiple protein precursors, including growth factors, proteases of the coagulation and complement cascades, glycoproteins of viral envelopes and bacterial exotoxins at multibasic recognition sites (12)(13)(14).…”

Platelet-Derived Growth Factor Receptor Activation Promotes the Prodestructive Invadosome-Forming Phenotype of Synoviocytes from Patients with Rheumatoid Arthritis

“…In arthritic synoviocytes, evidence suggests that at least two pathways may be involved in PDGFR phosphorylation and activation. First, RA or growth factor-activated synoviocytes were shown to secrete PDGF ligands and to express the intracellular (e.g., furin) or extracellular (e.g., tPA, uPA) proteases required for their activation (59,60,(64)(65)(66). In this study, the findings that RA FLS overexpressed PDGF-B and that the invadosome-forming phenotype of RA cells was inhibited using PDGF-BB-specific or PAN-PDGF-neutralizing Abs suggest direct phosphorylation of PDGFR as a result of ligation by autocrine PDGF-B.…”

Proprotein Convertase Subtilisin/Kexin Type 7 (PCSK7) Is Essential for the Zebrafish Development and Bioavailability of Transforming Growth Factor β1a (TGFβ1a)

“…From previous experiments, it is also noteworthy that TGF␤1 can directly up-regulate the expression of furin (45). However, PCSK7 can also proteolytically process the TGF␤ superfamily cytokines.…”