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cGMP-dependent protein kinase phosphorylates and inactivates RhoA.
N Sawada1, H Itoh, J Yamashita
1Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Biochemical and Biophysical Research Communications
|February 13, 2001
Summary
cGMP-dependent protein kinase (cGK) directly inactivates RhoA signaling by phosphorylating RhoA at Ser188. This interaction blocks RhoA-mediated stress fiber formation, revealing a novel cross-talk between these key cellular pathways.
Area of Science:
- Cellular signaling pathways
- Molecular cell biology
- Biochemistry
Background:
- Small GTPase Rho and cGMP-dependent protein kinase (cGK) pathways have opposing roles in cellular processes.
- Direct interaction and cross-talk between RhoA and cGK pathways remain largely uncharacterized.
Purpose of the Study:
- To investigate the direct interaction between RhoA and cGK signaling pathways.
- To elucidate the mechanism by which cGK influences RhoA activity.
Main Methods:
- In vitro kinase assays to determine cGK phosphorylation of RhoA.
- Cell-based assays using HeLa cells expressing constitutively active cGK (C-cGK) and RhoA mutants.
- Analysis of actin stress fiber formation and RhoA membrane translocation.
Main Results:
- cGK was found to phosphorylate RhoA at Ser188 in vitro.
- C-cGK expression inhibited RhoA-induced stress fiber formation, an effect dependent on RhoA Ser188.
- C-cGK expression blocked RhoA membrane translocation but did not affect Rac1 or Rho-kinase signaling.
Conclusions:
- cGMP-dependent protein kinase (cGK) directly phosphorylates and inactivates RhoA signaling by targeting Ser188.
- This phosphorylation event inhibits RhoA-mediated actin reorganization and membrane recruitment.
- The findings reveal a novel inhibitory mechanism of cGK on RhoA signaling, suggesting a direct cross-talk between these pathways.