The IQGAP1 Protein Is a Calmodulin-regulated Barbed End Capper of Actin Filaments
| Autor: | Andrea Pelikan-Conchaudron, Dominique Didry, Marie-France Carlier, Christophe Le Clainche |
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| Rok vydání: | 2011 |
| Předmět: |
0303 health sciences
Calmodulin macromolecular substances Cell Biology CDC42 Plasma protein binding Biology Biochemistry Cell biology 03 medical and health sciences 0302 clinical medicine IQGAP1 Cdc42 GTP-Binding Protein Microtubule biology.protein Molecular Biology 030217 neurology & neurosurgery Actin Cytokinesis 030304 developmental biology |
| Zdroj: | Journal of Biological Chemistry. 286:35119-35128 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m111.258772 |
| Popis: | IQGAP1 is a large modular protein that displays multiple partnership and is thought to act as a scaffold in coupling cell signaling to the actin and microtubule cytoskeletons in cell migration, adhesion, and cytokinesis. However the molecular mechanisms underlying the activities of IQGAP1 are poorly understood in part because of its large size, poor solubility and lack of functional assays to challenge biochemical properties in various contexts. We have purified bacterially expressed recombinant human IQGAP1. The protein binds Cdc42, Rac1, and the CRIB domain of N-WASP in a calmodulin-sensitive fashion. We further show that in addition to bundling of filaments via a single N-terminal calponin-homology domain, IQGAP1 actually regulates actin assembly. It caps barbed ends, with a higher affinity for ADP-bound terminal subunits (KB = 4 nm). The barbed end capping activity is inhibited by calmodulin, consistent with calmodulin binding to IQGAP1 with a KC of 40 nm, both in the absence and presence of Ca2+ ions. The barbed end capping activity resides in the C-terminal half of IQGAP1. It is possible that the capping activity of IQGAP1 accounts for its stimulation of cell migration. We further find that bacterially expressed recombinant IQGAP1 fragments easily co-purify with nucleic acids that turn out to activate N-WASP protein to branch filaments with Arp2/3 complex. The present results open perspectives for tackling the function of IQGAP1 in more complex reconstituted systems. |
| Databáze: | OpenAIRE |
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