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PAR3-aPKC regulates Tiam1 by modulating suppressive internal interactions
Kenji Matsuzawa1, Hiroki Akita1, Takashi Watanabe1
1Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
Molecular Biology of the Cell
|March 5, 2016
Summary
Tiam1
Area of Science:
- Cellular signaling
- Molecular biology
- Signal transduction
Background:
- Tiam1 (T-cell lymphoma invasion and metastasis 1) is a key activator of the small GTPase Rac.
- Despite its importance, fundamental aspects of Tiam1 regulation remain unclear.
Purpose of the Study:
- To investigate the intramolecular regulation of Tiam1.
- To elucidate the role of the PAR (Partitioning defective) complex in Tiam1 activation.
- To explore the involvement of the PAR complex in PDGF (Platelet-derived growth factor) signaling.
Main Methods:
- Biochemical assays to analyze Tiam1 interactions.
- Phosphorylation studies using atypical protein kinase Cs (aPKCs).
- Analysis of Tiam1 function within PDGF signaling pathways.
Main Results:
- Tiam1 is auto-inhibited by intramolecular interactions between its N-terminal region and its protein-binding/catalytic domains.
- Atypical PKCs phosphorylate Tiam1, relieving this autoinhibition.
- The PAR complex, particularly PAR3, stabilizes Tiam1 activity and localization.
- PAR3 directly interacts with PDGF receptor β, integrating Tiam1 into PDGF signaling.
Conclusions:
- Tiam1 is negatively regulated by intramolecular interactions, which are relieved by aPKC phosphorylation.
- The PAR complex is crucial for the full activation and localized function of Tiam1.
- A novel role for the PAR complex in PDGF receptor signaling is identified.
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