scholarly journals The Effects of Platelet-Derived Growth Factor Antagonism in Experimental Glomerulonephritis Are Independent of the Transforming Growth Factor–β System

2002 ◽  
Vol 13 (3) ◽  
pp. 658-667 ◽  
Author(s):  
Tammo Ostendorf ◽  
Uta Kunter ◽  
Claudia van Roeyen ◽  
Steven Dooley ◽  
Nebojsa Janjic ◽  
...  
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Matrix Protein ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Platelet Derived Growth Factor ◽  
Renal Diseases ◽  
Protein Accumulation ◽  
Type I

ABSTRACT. Platelet-derived growth factor B-chain (PDGF-B)– and transforming growth factor beta (TGF-β)–mediated accumulation of extracellular matrix proteins contributes to many progressive renal diseases. In vivo, specific antagonism of either PDGF-B or TGF-β in experimental mesangioproliferative glomerulonephritis resulted in an almost complete inhibition of matrix protein accumulation, which suggests an interaction between signaling pathways of these two growth factors. Because nothing is known on the nature of this possible interaction, PDGF-B was antagonized in the rat anti–Thy 1.1 model of glomerulonephritis by use of specific aptamers and its effects on the TGF-β system were investigated. Antagonism of PDGF-B led to a significant reduction of glomerular matrix accumulation compared with scrambled aptamer-treated nephritic controls. PDGF-B antagonism had no effect on the overexpression of glomerular TGF-β mRNA, TGF-β protein, or the expression of TGF-β receptor type I and II mRNA. By immunohistology, it was possible to detect overexpression of the cytoplasmic TGF-β signaling molecules Smad2 (agonistic) and Smad7 (antagonistic) in glomeruli of nephritic control rats which peaked on day 7 after disease induction, i.e., the peak of mesangial cell proliferation in this model. However, immunohistology and Western blot analysis again revealed no difference in the glomerular expression of both Smad proteins between PDGF-B antagonized and nonantagonized nephritic animals. In addition, no difference in the glomerular expression of phosphorylated Smad2 (P-Smad2) was detected between the differently treated nephritic groups. These observations suggest that the effects of PDGF-B antagonism are independent of TGF-β in mesangioproliferative glomerulonephritides.

Platelet-derived growth factor BB modulates PCNA protein synthesis partially through the transforming growth factor beta signalling pathway in vascular smooth muscle cells

2007 ◽  
Vol 85 (5) ◽  
pp. 606-615 ◽  
Author(s):  
Dabin Pan ◽  
Junwei Yang ◽  
Fengxiang Lu ◽  
Di Xu ◽  
Lei Zhou ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Vascular Smooth Muscle ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Platelet Derived Growth Factor ◽  
Nuclear Antigen ◽  
Type I ◽  
Signalling System ◽  
Alk 5

PDGF-BB (Platelet-derived growth factor BB) and TGF-β1(transforming growth factor β1) are important growth factors in the modulation of vascular smooth muscle cell (VSMC) proliferation and PCNA (proliferating cell nuclear antigen) expression in VSMCs. PCNA expresses at a high level in proliferating cells. The present study aims to assess the effects of PDGF-BB-induced overexpression of TGF-β1 on PCNA in VSMCs. The downstream proteins of the TGF-β signalling system in VSMCs, including TGF-β type I receptor (ALK-5 in VSMCs), Smurf2, Smad2, pSmad2/3, Smad4, and Smad7, were also investigated. Our results revealed that PDGF-BB significantly increased the expressions of TGF-β1 and PCNA, and the increase in PCNA can be partially inhibited by neutralizing anti-TGF-β1 antibody. Furthermore, PDGF-BB increased the expression of ALK-5, Smurf2, pSmad2/3, and Smad4, but lowered the levels of Smad2 and Smad7; these alterations were partially restored by neutralizing anti-TGF-β1 antibody. These findings suggest that PDGF-BB promotes PCNA expression in VSMCs partially through TGF-β1 overexpression, and that the TGF-β signalling system involves the molecular mechanism of PDGF-BB in VSMCs.

scholarly journals Transforming Growth Factor-β Receptors Interact with AP2 by Direct Binding to β2 Subunit

2002 ◽  
Vol 13 (11) ◽  
pp. 4001-4012 ◽  
Author(s):  
Diying Yao ◽  
Marcelo Ehrlich ◽  
Yoav I. Henis ◽  
Edward B. Leof
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Type I ◽  
Coated Pits ◽  
Wide Range ◽  
Cytoplasmic Tails ◽  
Direct Binding

Transforming growth factor-β (TGF-β) superfamily members regulate a wide range of biological processes by binding to two transmembrane serine/threonine kinase receptors, type I and type II. We have previously shown that the internalization of these receptors is inhibited by K+ depletion, cytosol acidification, or hypertonic medium, suggesting the involvement of clathrin-coated pits. However, the involvement of the clathrin-associated adaptor complex AP2 and the identity of the AP2 subunit that binds the receptors were not known. Herein, we have studied these issues by combining studies on intact cells with in vitro assays. Using fluorescence photobleaching recovery to measure the lateral mobility of the receptors on live cells (untreated or treated to alter their coated pit structure), we demonstrated that their mobility is restricted by interactions with coated pits. These interactions were transient and mediated through the receptors' cytoplasmic tails. To measure direct binding of the receptors to specific AP2 subunits, we used yeast two-hybrid screens and in vitro biochemical assays. In contrast to most other plasma membrane receptors that bind to AP2 via the μ2 subunit, AP2/TGF-β receptor binding was mediated by a direct interaction between the β2-adaptin N-terminal trunk domain and the cytoplasmic tails of the receptors; no binding was observed to the μ2, α, or ς2 subunits of AP2 or to μ1 of AP1. The data uniquely demonstrate both in vivo and in vitro the ability of β2-adaptin to directly couple TGF-β receptors to AP2 and to clathrin-coated pits, providing the first in vivo evidence for interactions of a transmembrane receptor with β2-adaptin.

Transforming growth factor-β–induced protein (TGFBIp/β ig-h3) activates platelets and promotes thrombogenesis

Blood ◽  
2009 ◽  
Vol 114 (25) ◽  
pp. 5206-5215 ◽  
Author(s):  
Ha-Jeong Kim ◽  
Pan-Kyung Kim ◽  
Sang Mun Bae ◽  
Hye-Nam Son ◽  
Debraj Singh Thoudam ◽  
...  
Keyword(s):  
Pulmonary Embolism ◽  
Growth Factor ◽  
Platelet Activation ◽  
Matrix Protein ◽  
Transforming Growth Factor ◽  
Thrombus Formation ◽  
Transforming Growth Factor Β ◽  
Extracellular Matrix Protein ◽  
Type I

Abstract Transforming growth factor-β–induced protein (TGFBIp)/βig-h3 is a 68-kDa extracellular matrix protein that is functionally associated with the adhesion, migration, proliferation, and differentiation of various cells. The presence of TGFBIp in platelets led us to study the role of this protein in the regulation of platelet functions. Upon activation, platelet TGFBIp was released and associated with the platelets. TGFBIp mediates not only the adhesion and spread of platelets but also activates them, resulting in phosphatidylserine exposure, α-granule secretion, and increased integrin affinity. The fasciclin 1 domains of TGFBIp are mainly responsible for the activation of platelets. TGFBIp promotes thrombus formation on type I fibrillar collagen under flow conditions in vitro and induces pulmonary embolism in mice. Moreover, transgenic mice, which have approximately a 1.7-fold greater blood TGFBIp concentration, are significantly more susceptible to collagen- and epinephrine-induced pulmonary embolism than wild-type mice. These results suggest that TGFBIp, a human platelet protein, plays important roles in platelet activation and thrombus formation. Our findings will increase our understanding of the novel mechanism of platelet activation, contributing to a better understanding of thrombotic pathways and the development of new antithrombotic therapies.

scholarly journals Functionally diverse heteromeric traps for ligands of the transforming growth factor-β superfamily

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ravindra Kumar ◽  
Asya V. Grinberg ◽  
Huiming Li ◽  
Tzu-Hsing Kuo ◽  
Dianne Sako ◽  
...  
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Type I ◽  
Systematic Analysis ◽  
Activin Receptor ◽  
Naturally Occurring ◽  
Functionally Diverse

AbstractLigands of the transforming growth factor-β (TGF-β) superfamily are important targets for therapeutic intervention but present challenges because they signal combinatorially and exhibit overlapping activities in vivo. To obtain agents capable of sequestering multiple TGF-β superfamily ligands with novel selectivity, we generated soluble, heterodimeric ligand traps by pairing the extracellular domain (ECD) of the native activin receptor type IIB (ActRIIB) alternately with the ECDs of native type I receptors activin receptor-like kinase 4 (ALK4), ALK7, or ALK3. Systematic analysis of these heterodimeric constructs by surface plasmon resonance, and comparison with their homodimeric counterparts, revealed that each type I receptor partner confers a distinct ligand-binding profile to the heterodimeric construct. Additional characterization in cell-based reporter gene assays confirmed that the heterodimeric constructs possessed different profiles of signaling inhibition in vitro, which translated into altered patterns of pharmacological activity when constructs were administered systemically to wild-type mice. Our results detail a versatile platform for the modular recombination of naturally occurring receptor domains, giving rise to inhibitory ligand traps that could aid in defining the physiological roles of TGF-β ligand sets or be directed therapeutically to human diseases arising from dysregulated TGF-β superfamily signaling.

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