Trix, a novel Rac guanine-nucleotide exchange factor from Dictyostelium discoideum is an actin-binding protein and accumulates at endosomes

2006 ◽  
Vol 85 (9-10) ◽  
pp. 1035-1045 ◽  
Author(s):  
Axel Strehle ◽  
Michael Schleicher ◽  
Jan Faix
Keyword(s):  
Dictyostelium Discoideum ◽  
Binding Protein ◽  
Guanine Nucleotide Exchange Factor ◽  
Actin Binding ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Actin Binding Protein ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Tara, a novel F-actin binding protein, associates with the Trio guanine nucleotide exchange factor and regulates actin cytoskeletal organization

2001 ◽  
Vol 114 (2) ◽  
pp. 389-399 ◽  
Author(s):  
K. Seipel ◽  
S.P. O'Brien ◽  
E. Iannotti ◽  
Q.G. Medley ◽  
M. Streuli
Keyword(s):  
Actin Cytoskeleton ◽  
Binding Protein ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Actin Remodeling ◽  
Cytoskeletal Organization ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Reorganization of the actin cytoskeleton is essential to numerous cellular processes including cell locomotion and cytokinesis. This actin remodeling is regulated in part by Rho family GTPases. Previous studies implicated Trio, a Dbl-homology guanine nucleotide exchange factor with two exchange factor domains, in regulating actin cytoskeleton reorganization, cell motility and cell growth via activation of Rho GTPases. Trio is essential for mouse embryonic development and Trio-deficiency is associated with abnormal skeletal muscle and neural tissue development. Furthermore, genetic analyses in Caenorhabditis elegans and Drosophila demonstrate a role for trio-like genes in cell migration and axon guidance. Herein we characterize a novel Trio-binding protein, Tara, that is comprised of an N-terminal pleckstrin homology domain and a C-terminal coiled-coil region. Trio and Tara associate as assessed by the yeast interaction-trap assays and mammalian co-immunoprecipitation studies. Ectopically expressed Tara localizes to F-actin in a periodic pattern that is highly similar to the pattern of myosin II. Furthermore, a direct interaction between Tara and F-actin is indicated by in vitro binding studies. Cells that transiently or stably overexpress Tara display an extensively flattened cell morphology with enhanced stress fibers and cortical F-actin. Tara expression does not alter the ability of the cell to attach or to initially spread, but rather increases cell spreading following these initial events. Tara stabilizes F-actin structures as indicated by the relative resistance of Tara-expressing cells to the F-actin destabilizer Latrunculin B. We propose that Tara regulates actin cytoskeletal organization by directly binding and stabilizing F-actin, and that the localized formation of Tara and Trio complexes functions to coordinate actin remodeling.

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