Amplified expression of dominant-negative transforming growth factor-beta type II receptor inhibits collagen type I production via reduced Smad-3 activity.
OBJECTIVE
As a pleiotropic protein, transforming growth factor (TGF)-beta induces its effects by binding to its Ser/Thr kinase receptor type II and then recruiting and activating receptor type I, which is phosphorylated and activates Smads that transduce the signal to the nucleus.


METHODS
In this work, the authors blocked TGF-beta1 signal transduction pathway via delivery of a dominant-negative receptor-II (DeltaCyTbRII)-cDNA lacking Ser/Thr kinase intracytoplasmic domain activity. Thus, Cos-1 and hepatic stellate cells were cotransfected with pCMV5-DeltaCyTbRII and pAdTrack-green fluorescent protein using lipofectamine.


RESULTS
Fluorescence microscopy demonstrated an average 10% transfection efficiency. Radiolabeled 125I-TGF-beta was bound mostly by cell membrane-expressed truncated receptor-II rather than wild-type receptor type II. Electrophoretic mobility shift assays were performed using consensus Smad-2 and -3 sequences rendering a three-fold decrease in DNA-binding activity, reflecting a down-activation in Smad complexes in pCMV5-DeltaCyTbRII-transfected cells, but not in mock-transfected cells. The identity of these transcriptional factors was confirmed using irrelevant double-stranded oligonucleotides and specific antibodies to compete for DNA binding. Also, collagen I mRNA expression showed a five-fold decrease, which was reflected at the protein level as a diminished collagen type I production in pCMV5-DeltaCyTbRII-transfected Cos-1 cells as measured by [3H]proline incorporation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.


CONCLUSIONS
Thus, this could be a useful strategy to downregulate or prevent exacerbated synthesis and deposition of extracellular matrix in a given fibrotic process.
Hernandez-Cañaveral
Ivan
I
Institute for Molecular Biology in Medicine and Gene Therapy, Centro Universitario de Ciencias de la Salud, University of Guadalajara, Guadalajara, Jal, Mexico.
González
Jaime
J
López-Casillas
Fernando
F
Armendariz-Borunda
Juan
J
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D019556:COS Cells; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D024042:Collagen Type I / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000276:immunology; D015870:Gene Expression; D005799:Genes, Dominant; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism; D051900:Smad3 Protein; D015534:Trans-Activators / Q000037:antagonists & inhibitors* / Q000276:immunology; D014162:Transfection
D000911:Antibodies, Monoclonal; D024042:Collagen Type I; D004268:DNA-Binding Proteins; D018125:Receptors, Transforming Growth Factor beta; D051900:Smad3 Protein; D015534:Trans-Activators; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II