Single-molecule imaging reveals transforming growth factor-beta-induced type II receptor dimerization
Wei Zhang1, Yaxin Jiang, Qiang Wang
1Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China.
Summary
Transforming growth factor-beta (TGF-beta) signals through receptors that exist as monomers in resting cells. Upon TGF-beta stimulation, these monomers dimerize, activating the signaling pathway.
Area of Science:
- Cellular biology
- Molecular signaling
- Biophysics
Background:
- Transforming growth factor-beta (TGF-beta) signaling is crucial for various cellular processes.
- TGF-beta exerts its effects via transmembrane serine/threonine kinase receptors, specifically type II (TbetaRII) and type I receptors.
- The prevailing hypothesis suggested that receptor activation initiates with pre-formed receptor homodimers.
Purpose of the Study:
- To investigate the initial molecular events of TGF-beta receptor activation.
- To determine if TGF-beta receptors exist as monomers or dimers in resting cells.
- To elucidate the role of receptor dimerization in TGF-beta signal transduction.
Main Methods:
- Utilized single-molecule microscopy to visualize green fluorescent protein (GFP)-labeled TbetaRII.
- Observed receptor dynamics on the surface of living cells.
- Correlated receptor behavior with TGF-beta stimulation.
Main Results:
- Demonstrated that TbetaRII exists as monomers at low expression levels in resting cells.
- Showed that TbetaRII monomers dimerize upon stimulation with TGF-beta.
- Provided evidence against the model of pre-existing homodimers being the initial signaling unit.
Conclusions:
- TGF-beta receptor activation is initiated by the dimerization of receptor monomers upon ligand binding.
- Receptor dimerization is a general mechanism for ligand-induced activation of serine-threonine kinase receptors.
- This finding refines our understanding of TGF-beta signaling pathways and receptor dynamics.
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