Bone morphogenetic proteins (BMPs) belong to TGF-β superfamily and are a group of important cytokines involved in cell differentiation, proliferation and embryonic development. Multiple BMPs play important roles in several functions of vertebrates. Signaling pathway of BMPs is known to be mediated by Smad proteins, which include 8 members while Smad1, Smad5 and Smad8 are involved in BMPs signal transduction while Smad2 and Smad3 are mediated TGF-β signal transduction. Although several BMPs such as BMP4 and BMP9 have been documented in the liver, BMP13 has not been examined in the liver. BMP13 also known as growth differentiation factor (GDF)-6 or cartilage-derived morphogenetic protein (CDMP)-2 is one of the BMPs family members. Function of BMP13 has been investigated in bone and tendon repair. It can stimulate tendon-like cell proliferation. However, our recent findings revealed that there was expression of BMP13 in the liver and its expression was modulated during metabolic disorders. The current article is to understand biological function of BMP13 especially in the liver.
Bone Morphogenetic Proteins ; metabolism ; physiology ; Growth Differentiation Factor 6 ; metabolism ; physiology ; Humans ; Liver ; metabolism ; Liver Diseases ; metabolism ; Smad Proteins ; metabolism

Animals ; Humans ; Liver Cirrhosis ; metabolism ; Signal Transduction ; Smad Proteins ; metabolism ; physiology ; Transforming Growth Factor beta ; metabolism ; physiology

PURPOSETo review the recent developments in the structure and function of Smad proteins.

DATA SOURCESBoth Chinese- and English-language literatures were searched using MEDLINE/CD-ROM (1997 - 2000) and the Index of Chinese-Language Literature (1997 - 2000).

STUDY SELECTIONData from published articles about TGF-beta signal transduction in recent domestic and foreign literature were selected.

DATA EXTRACTIONData were mainly extracted from 22 articles which are listed in the reference section of this review.

RESULTSSmad proteins mediate signal transduction induced by the TGF-beta superfamily. Based on their structural and functional properties, Smad proteins are divided into three groups. The first group, receptor-regulated Smads (R-Smads), are phosphorylated by activated type I receptors and form heteromeric complexes with the second group of Smads, common mediator Smads (Co-Smads). These Smad complexes translocate into the nucleus to influence gene transcription. Inhibitory Smads (I-Smads) are the third group and these antagonize the activity of R-Smads. In the nucleus, Smads can directly contact Smad-binding elements (SBE) in target gene promoters. Through interaction with different transcription factors, transcriptional co-activators or co-repressors, Smads elicit different effects in various cell types. The aberrance of Smad proteins has been noted in several human disorders such as fibrosis, hypertrophic scarring and cancer.

CONCLUSIONThe structure of Smads determines their function as transcriptional factors which translocate signals from the cell surface to the nucleus where Smads regulate TGF-beta superfamily-dependent gene expression.

DNA-Binding Proteins ; chemistry ; physiology ; Humans ; Signal Transduction ; Smad Proteins ; Trans-Activators ; chemistry ; physiology ; Transcription Factors ; physiology ; Transforming Growth Factor beta ; physiology

Bone morphogenetic proteins (BMPs) are the largest subfamily of the transforming growth factor-β superfamily, and they play important roles in the development of numerous organs, including the inner ear. The inner ear is a relatively small organ but has a highly complex structure and is involved in both hearing and balance. Here, we discuss BMPs and BMP signaling pathways and then focus on the role of BMP signal pathway regulation in the development of the inner ear and the implications this has for the treatment of human hearing loss and balance dysfunction.
Body Patterning ; Bone Morphogenetic Protein Receptors/physiology* ; Bone Morphogenetic Proteins/physiology* ; Cell Differentiation ; Cochlea/embryology* ; Ear, Inner/embryology* ; Hedgehog Proteins/physiology* ; Humans ; Signal Transduction/physiology* ; Smad Proteins/physiology* ; Vestibule, Labyrinth/embryology* ; Wnt Signaling Pathway

Transforming growth factor-β (TGF-β) members are key cytokines that control embryogenesis and tissue homeostasis via transmembrane TGF-β type II (TβR II) and type I (TβRI) and serine/threonine kinases receptors. Aberrant activation of TGF-β signaling leads to diseases, including cancer. In advanced cancer, the TGF-β/SMAD pathway can act as an oncogenic factor driving tumor cell invasion and metastasis, and thus is considered to be a therapeutic target. The activity of TGF-β/SMAD pathway is known to be regulated by ubiquitination at multiple levels. As ubiquitination is reversible, emerging studies have uncovered key roles for ubiquitin-removals on TGF-β signaling components by deubiquitinating enzymes (DUBs). In this paper, we summarize the latest findings on the DUBs that control the activity of the TGF-β signaling pathway. The regulatory roles of these DUBs as a driving force for cancer progression as well as their underlying working mechanisms are also discussed.
Animals ; Humans ; Molecular Targeted Therapy ; Receptors, Transforming Growth Factor beta ; metabolism ; Signal Transduction ; Smad Proteins ; physiology ; Transforming Growth Factor beta ; physiology ; Ubiquitin Thiolesterase ; metabolism ; Ubiquitin-Specific Proteases ; Ubiquitination

OBJECTIVETo characterize the role of Smads proteins in alpha 2 (I) collagen (COL1A2) gene expression induced by bone morphogenetic protein-2 (BMP-2) in odontoblast cell line MDPC-23.

METHODSEndogenous Smad protein expression was determined by immunocytochemistry. Smads function and their role in COL1A2 gene expression were investigated in cotransfection experiments using promoter-luciferase reporter gene construct.

RESULTSMDPC-23 cells expressed Smad1, Smad5 and Smad6. BMP-2 promoted the activation of COL1A2 promoter reporter construct. Transient overexpression of Smad1 or Smad5 was enhanced, while overexpression of Smad6 inhibited BMP-2-induced COL1A2 promoter activity. BMP-2 inducibility could be blocked by overexpression of Smad1 or Smad5 dominant negative mutant.

CONCLUSIONSSmad signaling is functioning and appears to be involved in BMP-2-induced COL1A2 collagen transcription in MDPC-23. Smad signaling may play an important role in odontoblast differentiation and dentin extracellular matrix formation mediated by BMP-2.

Animals ; Bone Morphogenetic Protein 2 ; Bone Morphogenetic Proteins ; genetics ; Cell Line ; Collagen ; genetics ; Collagen Type I ; Mice ; Odontoblasts ; cytology ; metabolism ; Smad Proteins ; physiology ; Transforming Growth Factor beta ; genetics

AIMTo study the expression and regulation of Smad1, Smad2 and Smad4 proteins (intracellular signaling molecules of transforming growth factor-b family) in rat testis during postnatal development.

METHODSThe whole testes were collected from SD rats aged 3, 7, 14, 28 and 90 (adult) days. The cellular localization and developmental changes were examined by immunohistochemistry ABC method with the glucose oxidase-DAB-nickel enhancement technique. Quantitative analysis of the immunostaining was made by the image analysis system. The Smads proteins coexistence in the adult rat testis was tested by the double immune staining for CD14-Smad4 and Smad2-Smad4. The protein expression of Smad during rat testicular development was examined by means of Western blots.

RESULTSSmad1, Smad2 and Smad4 were present throughout testicular development. The immunostaining of Smad1 and Smad2 were present in spermatogenic cells. A positive immunoreactivity was located at the cytoplasm, but the nucleus was negative. Smad1 was immunolocalized at the d14, d28 and adult testes, while Smad2, at the d7, d14, d28 and adult testis. There was positive immunoreaction in the Sertoli cells and Leydig cells as well. The immunolocalization of Smad4 was exclusively at the cytoplasm of Leydig cells and the nuclei were negative throughout the testicular development. No expression was detected in the germ cells. The results of image and statistical analysis showed that generally the expression of Smad1, Smad2 and Smad4 in the testis tended to increase gradually with the growth of the rat.

CONCLUSIONThe present data provide direct evidences for the molecular mechanism of TGF-bgr action in rat testes during postnatal development and spermatogenesis.

Animals ; Blotting, Western ; DNA-Binding Proteins ; analysis ; biosynthesis ; Immunohistochemistry ; Male ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; physiology ; Smad Proteins ; Smad1 Protein ; Smad2 Protein ; Smad4 Protein ; Testis ; chemistry ; growth & development ; physiology ; Trans-Activators ; analysis ; biosynthesis

OBJECTIVETo study the protective effect of oxymatrine (OMT) on myocardial fibrosis induced by acute myocardial infarction in rats and its effect on TGF-beta-Smads signal pathway.

METHODArteria coronaria ligation-induced acute myocardial infarction model was established in rats. The survived rats were randomly allotted into the model group, 50, 25, 12.5 mg x kg(-1) OMT groups, the 50 mg x kg(-1) captopril group, and the Sham-operated group which was treated as the model group without the arteria coranaria ligation. After 8 weeks of ligation, myocardial fibrosis was detected by HE and Masson staining, and the RT-PCR method were used to detect the expression of mRNA of TGF-beta-Smads signal system.

RESULTThe histopathological examination showed decrease in cardiocytes, deposition of extra-cellular matrix, and increase of collagen contents after 8 weeks of ligation. RT-PCR results showed that mRNA expressions of TGF-beta1, TbetaR1, Smad2, Smad3 and Smad4 significantly increased, but mRNA expression of Smad7 is remarkable lower than the sham-operated group. Treatment with OMT for 8 weeks could remarkably inhibit myocardial fibrosis, decrease mRNA expressions of TGF-beta1, TbetaR1, Smad2, Smad3, and Smad4, and increase mRNA expressions of Smad7.

CONCLUSIONOMT has the inhibitory effect on the experimental myocardial fibrosis induced by AMI in rats. Its mechanism may be closely related to TGF-beta-Smads signal system.

Acute Disease ; Alkaloids ; therapeutic use ; Animals ; Fibrosis ; Male ; Myocardial Infarction ; complications ; Myocardium ; pathology ; Quinolizines ; therapeutic use ; Rats ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; physiology ; Smad Proteins ; genetics ; physiology ; Transforming Growth Factor beta ; genetics ; physiology

OBJECTIVETo investigate the effects and mechanisms of cordycepin,an effective component of cordyceps militaris, on renal interstitial fibrosis (RIF) and its related eIF2α/TGF-β/Smad signaling pathway.

METHODFirstly, 15 C57BL/6 mice were randomly divided into 3 groups,the control group (Group A), the model group (Group B) and the cordycepin-treated group (Group C). After renal interstitial fibrotic model was successfully established by unilateral ureteral obstruction (UUO), the mice in Group C were intraperitoneally administrated with cordycepin(5 mg x kg(-1) d(-1)) and the ones in Group A and B were administrated with physiological saline for 5 days. At the end of the study, the obstructed kidneys were collected and detected for the pathological changes of RIF, and the mRNA expressions of collagen type I (Col I) and α-smooth muscle actin (α-SMA) in the kidney by Northern blot. Secondly, after renal tubular epithelial (NRK-52E) cells cultured in vitro were exposed to transforming growth factor (TGF) -β with or without cordycepin, the mRNA expressions of Col I and collagen type IV( Col IV) by Northern blot, and the protein expressions of eukaryotic initiation factor 2α (eIF2α), phosphorylated eIF2α ( p-eIF2α), Smad2/3 and phosphorylated Smad2/3 (p-Smad2/3) were tested by Western blot.

RESULTIn vivo, cordycepin alleviated RIF in model mice, including improving fibrotic pathological characteristics and mRNA expressions of Col I and α-SMA. In vitro, cordycepin induced the high expression of p-elF2α, and inhibited the expressions of p-Smad2/3, Col I and Col IV induced by TGF-β in NRK-52E cells.

CONCLUSIONCordycepin attenuates RIF in vivo and in vitro, probably by inducing the phosphorylation of eIF2α, suppressing the expression of p-Smad2/3, a key signaling molecule in TGF-β/Smad signaling pathway, and reducing the expressions of collagens and α-SMA in the kidney.

Actins ; analysis ; Animals ; Deoxyadenosines ; pharmacology ; Fibrosis ; Kidney ; drug effects ; pathology ; Male ; Mice ; Mice, Inbred C57BL ; Phosphorylation ; Protein-Serine-Threonine Kinases ; physiology ; Signal Transduction ; drug effects ; Smad Proteins ; physiology ; Transforming Growth Factor beta ; antagonists & inhibitors ; physiology

Liver fibrosis is a common pathological process for chronic liver injury caused by multiple etiological factors and an inevitable phase leading to liver cirrhosis. According to the previous studies, hesperidin (HDN) shows a very good protective effect on CCl4-induced chemical hepatic fibrosis in rats. In this experiment, based on the findings of the previous studies, a platelet-derived growth factor (PDGF)-induced HSC-T6 model was established to observe the inhibitory effect of HDN on HSC-T6 proliferation. The ELISA method was adopted to detect the content of collagen I in HSC-T6 supernatant. Transforming growth factor (TGF)-beta1, Smad2, Smad3, Smad7 and connective tissue growth factor (CTGF) mRNA expressions were measured by RT-PCR; TGF-beta1 and CT-GF protein expressions in HSC-T6 were determined by Western blot, in order to study HDN's effect on TGF-beta1 signaling pathway in HSC and its potential action mechanism. The results demonstrated that HDN could notably improve HSC-T6 proliferation, Collagen I growth and TGF-beta1, Smad2, Smad3 and CTGF mRNA.expressions. After being intervened with HDN, it could notably inhibit HSC-T6 proliferation and Collagen I growth, reduce TGF-beta1, Smad2, Smad3 and CTGF mRNA and TGF-beta1, CTGF protein expressions and increase Smad7 mRNA expression. HDN's antihepatic fibrosis effect may be related to the inhibition of HSC proliferation and activation by modulating TGF-beta/Smad signaling pathway.
Animals ; Cell Proliferation ; drug effects ; Cells, Cultured ; Connective Tissue Growth Factor ; physiology ; Hesperidin ; pharmacology ; Platelet-Derived Growth Factor ; pharmacology ; Rats ; Signal Transduction ; drug effects ; Smad Proteins ; physiology ; Transforming Growth Factor beta1 ; physiology