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Identification of an IQGAP1/AKAP79 complex in beta-cells
J Brian Nauert1, Johanna D Rigas, Linda B Lester
1Division of Endocrinology, Diabetes and Clinical Nutrition, Oregon Health and Science University, L607 Portland, Oregon, USA.
Journal of Cellular Biochemistry
|August 26, 2003
Summary
This study identifies a new role for IQGAP1 as a scaffold protein. IQGAP1 directly binds to cyclic AMP-dependent kinase (PKA) via AKAP79, linking PKA signaling to other cellular pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- IQGAP1 is a scaffold protein regulating cytoskeleton dynamics via interactions with F-actin, E-cadherin, beta-catenin, and CLIP170.
- IQGAP1's interactions are modulated by calcium/calmodulin (Ca(++)/CaM) and GTPases (Cdc42, Rac1).
Purpose of the Study:
- To investigate novel scaffolding functions of IQGAP1.
- To identify new protein partners of IQGAP1.
Main Methods:
- Co-purification of IQGAP1 with cyclic AMP-dependent kinase (PKA) using 5'-cyclic AMP (cAMP) affinity chromatography.
- Co-immunoprecipitation of PKA activity with IQGAP1 using an anti-IQGAP1 antibody.
- Demonstration of direct interaction between IQGAP1 and A kinase anchoring protein 79 (AKAP79).
Main Results:
- IQGAP1 was successfully co-purified with PKA.
- PKA activity was confirmed to associate with IQGAP1.
- A direct interaction was identified between AKAP79 and the carboxyl-terminal domain of IQGAP1, mediating the IQGAP1-PKA association.
Conclusions:
- IQGAP1 possesses a novel scaffolding function involving cyclic AMP-dependent kinase (PKA).
- The IQGAP1/AKAP79 complex directly links PKA to IQGAP1.
- This complex potentially integrates cAMP/PKA signaling with Ca(++)/CaM and GTPase pathways.