Atg18 phosphoregulation controls organellar dynamics by modulating its phosphoinositide-binding activity.
Naoki Tamura1, Masahide Oku, Moemi Ito
1Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
The Journal of Cell Biology
|August 14, 2013
Summary
Phosphorylation of autophagy protein Atg18 controls its binding to membranes, regulating vacuole shape and fusion. This phosphoregulation is key for cellular reorganization during stress responses.
Area of Science:
- Cell Biology
- Molecular Biology
- Autophagy Research
Background:
- Atg18 is a PROPPIN protein crucial for autophagy.
- It binds phosphoinositides via a seven β-propeller motif.
- Its role in vacuolar dynamics requires further elucidation.
Purpose of the Study:
- To investigate the role of Atg18 phosphorylation in regulating its phosphoinositide-binding activity.
- To understand how Atg18 phosphorylation affects vacuolar membrane association and dynamics.
- To explore the link between Atg18 phosphorylation and cellular responses to environmental stress.
Main Methods:
- Site-directed mutagenesis to alter Atg18 phosphorylation sites.
- Analysis of Atg18 binding affinity to phosphatidylinositol 3,5-bisphosphate.
- Microscopy to observe vacuolar morphology and dynamics in Pichia pastoris.
- Correlation of Atg18 phosphorylation status with cellular stress conditions.
Main Results:
- Phosphorylation of Atg18 at specific loops (blade 6 and 7) reduced binding to phosphatidylinositol 3,5-bisphosphate.
- Dephosphorylation was essential for Atg18 vacuolar membrane association and vacuole septation.
- Rephosphorylation upon dissociation led to vacuole fusion and rounding.
- Vacuolar dynamics were modulated by osmotic changes, oxidative stress, and nutrient availability via Atg18 phosphorylation.
Conclusions:
- Atg18 phosphoregulation directly impacts its membrane-binding activity.
- This mechanism is critical for coordinating intracellular reorganization, including vacuolar dynamics.
- Atg18 phosphorylation serves as a regulatory switch for cellular adaptation to various stresses.
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