Structural Studies of the Inhibitory Role of Tctex-1 for the Microtubule-associated RhoGEF Lfc

• Main Author: Kim, Bong Kyu
• Other Authors: Ikura, Mitsuhiko
• Language: en_ca
• Published: 2011
• Subjects: biochemistry; structural biology; molecular biology; nuclear magnetic resonance; protein-protein interaction; small GTPases; guanine nucleotide exchange factors; dynein motor complex; 0760
• Online Access: http://hdl.handle.net/1807/29572

Lfc is a guanine nucleotide exchange factor (GEF) for RhoA and is negatively regulated by its association with the microtubule array. Tctex-1, a light chain subunit of the dynein motor complex, was identified as an Lfc-interacting protein in a yeast two-hybrid screen. In mouse embryonic fibroblast (MEF) cells, over-expression of Tctex-1 represses Lfc-induced actin stress fiber and focal adhesion complex formation. Here, we present biochemical evidence obtained from a real-time, nuclear magnetic resonance (NMR)-based assay indicating that the microtubule exerts its inhibitory effect on Lfc through a mechanism that is dependent on the presence of Tctex-1. We also present NMR structure data showing that Lfc and the dynein intermediate chain (DIC) bind to different surfaces of Tctex-1. The biochemical and structural data together support a model in which Lfc is recruited to the microtubules through the dynein cargo adaptor function of Tctex-1, resulting in inhibition of Lfc function.