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AKRL1 and AKRL2 activate the JNK pathway.
Takeshi Harada1, Osamu Matsuzaki, Hideko Hayashi
1Department of Biophysics, Graduate School of Science, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Genes to Cells : Devoted to Molecular & Cellular Mechanisms
|April 16, 2003
Summary
Novel proteins AKRL1 and AKRL2 activate the c-Jun N-terminal kinase (JNK) pathway. These Golgi-localized proteins, similar to yeast Akr1p, are key components upstream of JNK signaling.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Protein interactions
Background:
- The c-Jun N-terminal kinase (JNK) pathway, part of the mitogen-activated protein kinase (MAPK) family, is activated by cytokines and environmental stresses.
- MKK4 and MKK7 are known direct activators of JNK.
- While upstream components like MAPKKK family members are described, the full JNK pathway signaling cascade remains incompletely characterized.
Purpose of the Study:
- To identify novel activators of the JNK pathway.
- To characterize the function and localization of newly identified JNK pathway components.
Main Methods:
- Protein expression and analysis
- Kinase assays
- Subcellular localization studies
- Mutagenesis to identify functional domains
Main Results:
- AKRL1 and AKRL2, proteins with sequence similarity to yeast Akr1p, were identified as novel JNK pathway activators.
- Expression of AKRL1 or AKRL2 led to the activation of JNK, MKK4, and MKK7.
- JNK activation by AKRL1/2 was suppressed by a kinase-negative TAK1 mutant, indicating TAK1's role in the pathway.
- AKRL1 and AKRL2 were found to localize to the Golgi apparatus.
- Both N-terminal and C-terminal transmembrane domains of AKRL1/2 are crucial for JNK activation, with the C-terminal domain mediating Golgi localization.
Conclusions:
- AKRL1 and AKRL2 are novel activators of the JNK signaling pathway.
- These proteins localize to the Golgi apparatus, suggesting a role in signal transduction at this organelle.