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[Functional analysis of transforming growth factor-beta type II dominant negative receptor]
1Department of Maxillo-Facial Surgery, Graduate School of Dentistry, Tokyo Medical and Dental University.
Abstract:
The transforming growth factor-beta (TGF-beta) is a multifunctional homodimeric protein with an apparent molecular weight of 25 KDa. TGF-beta transduces signals by forming heteromeric complexes of their type-I (T beta R-I) and type-II (T beta R-II) serin/threonine kinase receptors. TGF-beta binds first to T beta R-II receptor, and then the ligand in this complex is recognized by T beta R-I, resulting in formation of a heteromeric receptor complex composed of T beta R-I and T beta R-II. Once received, T beta R-I becomes phosphorylated in the GS domain by the associated constitutively active T beta R-II and transmits the downstream signal. It has been reported that formation of the heteromeric complex is indispensible at least in epithelial cells for growth inhibition and extracellular matrix production induced by TGF-beta. In this study, the functional role of T beta R-II for the TGF-beta-induced signals in osteoblastic cells was investigated by using a dominant negative type of T beta R-II mutant receptors (T beta RIIDNR). ROS 17/2.8 and MG 63 cells were found to express T beta R-I, T beta R-II, and T beta R-III, and their cell growth was inhibited by TGF-beta, whereas alkaline phosphatase activity was stimulated. Cells that were stably transfected with the T beta RIIDNR plasmid showed decreased response to TGF-beta during growth and alkaline phosphatase activity. These results indicate that the intracellular serine/threonine kinase domain of T beta R-II is essential for signal transduction of the TGF-beta-induced alkaline phosphatase activity as well as growth inhibition.
Insights
Transforming growth factor-beta (TGF-beta) signals require functional type-II receptors (T beta R-II) for osteoblastic cell growth inhibition and alkaline phosphatase activity. The intracellular kinase domain of T beta R-II is essential for TGF-beta signal transduction.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Transforming growth factor-beta (TGF-beta) is a key regulator of cellular processes.
- TGF-beta signals through a heteromeric complex of type-I (T beta R-I) and type-II (T beta R-II) serine/threonine kinase receptors.
- The T beta R-II receptor is crucial for initiating TGF-beta signal transduction.
Purpose of the Study:
- To investigate the functional role of T beta R-II in TGF-beta-induced signaling in osteoblastic cells.
- To determine the importance of the intracellular kinase domain of T beta R-II for TGF-beta responses.
Main Methods:
- Utilized a dominant-negative T beta R-II mutant receptor (T beta RIIDNR) in osteoblastic cell lines (ROS 17/2.8 and MG 63).
- Assessed TGF-beta-induced effects on cell growth and alkaline phosphatase activity.
- Generated stably transfected cell lines expressing T beta RIIDNR.
Main Results:
- Osteoblastic cells express T beta R-I, T beta R-II, and T beta R-III and respond to TGF-beta with inhibited growth and stimulated alkaline phosphatase activity.
- Stable transfection with T beta RIIDNR significantly decreased cellular responsiveness to TGF-beta.
- The intracellular serine/threonine kinase domain of T beta R-II was found to be essential for TGF-beta-induced growth inhibition and alkaline phosphatase activity.
Conclusions:
- The intracellular kinase domain of T beta R-II is indispensable for mediating TGF-beta-induced signals in osteoblastic cells.
- T beta R-II plays a critical role in regulating osteoblast function through TGF-beta signaling.