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Membrane-targeting sequences on AKAP79 bind phosphatidylinositol-4, 5-bisphosphate
M L Dell'Acqua1, M C Faux, J Thorburn
1Howard Hughes Medical Institute, Vollum Institute, Oregon Health Sciences University, Portland, OR 97201, USA.
The EMBO Journal
|May 26, 1998
Summary
Anchoring proteins like AKAP79, which bind kinases and phosphatases, use specific domains to target cell membranes. Phosphorylation and calcium-calmodulin regulate AKAP79
Area of Science:
- Cellular biology
- Molecular biology
- Biochemistry
Background:
- Protein kinases and phosphatases regulate cellular functions by interacting with anchoring proteins.
- AKAP79 is a multivalent anchoring protein that binds cAMP-dependent protein kinase (PKA), protein kinase C (PKC), and calcineurin (CaN).
Purpose of the Study:
- To map the membrane-targeting domains of AKAP79.
- To investigate the role of phosphorylation and calcium-calmodulin in AKAP79's membrane association.
Main Methods:
- In situ fluorescent techniques using a Green Fluorescent Protein tag.
- Analysis of AKAP79 sequences for putative phosphorylation sites and amino acid composition.
- Binding assays with membrane vesicles containing acidic phospholipids.
Main Results:
- Three linear sequences (regions A, B, and C) in AKAP79 mediate membrane targeting in HEK-293 cells and cortical neurons.
- AKAP79's membrane-targeting domains are rich in basic and hydrophobic amino acids and contain putative phosphorylation sites.
- AKAP79 binding to acidic phospholipids is regulated by phosphorylation and calcium-calmodulin, with PKC or calmodulin activation releasing AKAP79 from membranes.
Conclusions:
- AKAP79 utilizes specific domains for membrane targeting, influenced by phosphorylation and calcium-calmodulin.
- AKAP79 may function as both an anchoring protein and a substrate/effector for its associated enzymes.
- These findings provide insights into the dynamic regulation of enzyme localization and activity within cells.