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Distinct endocytic pathways regulate TGF-beta receptor signalling and turnover
Gianni M Di Guglielmo1, Christine Le Roy, Anne F Goodfellow
1Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
Nature Cell Biology
|April 30, 2003
Summary
Transforming growth factor beta (TGF-beta) receptors internalize via distinct pathways. Clathrin-dependent endocytosis promotes signaling, while caveolar pathways regulate receptor turnover.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Endocytosis of cell surface receptors is crucial for regulating signal transduction.
- Transforming growth factor beta (TGF-beta) signaling involves Ser-Thr kinase receptors that are internalized and downregulated.
- Receptor internalization and downregulation are ubiquitin-dependent processes.
Purpose of the Study:
- To investigate the distinct endocytic pathways of TGF-beta receptors.
- To determine how these pathways regulate Smad signaling and receptor turnover.
- To elucidate the role of different endocytic compartments in TGF-beta receptor regulation.
Main Methods:
- Confocal microscopy to track receptor internalization.
- Biochemical assays to analyze receptor ubiquitination and turnover.
- Cellular fractionation to separate membrane domains and endocytic vesicles.
Main Results:
- TGF-beta receptors internalize into both caveolin-positive and EEA1-positive vesicles.
- Receptors reside in both lipid raft and non-raft membrane domains.
- Clathrin-dependent internalization into EEA1-positive endosomes promotes Smad2 activation.
- Lipid raft-caveolar internalization pathways are involved in Smad7-Smurf2-mediated receptor turnover.
Conclusions:
- Distinct endocytic pathways segregate TGF-beta receptors.
- This segregation differentially regulates Smad activation and receptor turnover.
- Understanding these pathways is key to controlling TGF-beta signaling.