The conserved C-terminal I/LWEQ module targets Talin1 to focal adhesions.
The cytoskeletal protein Talin1 is a critical link between integrins and the actin cytoskeleton, where it is required for the structural and signaling functions of integrin-containing adhesion complexes. However, the elements in Talin1 that are responsible for localizing it to adhesion complexes are not known. In this report we have used a series of constructs based on the modular structure of Talin1 to determine the structural elements that specify the subcellular localization of Talin1. We show that the conserved actin-binding I/LWEQ module at the C-terminus of Talin1 is necessary and sufficient for targeting to focal adhesion complexes. We also used truncation and site-directed mutagenesis to demonstrate that this novel targeting function correlates with, but is separable from, the actin-binding properties of the Talin1 I/LWEQ module. In addition, we have shown that focal adhesion targeting, unlike actin binding, is not conserved among I/LWEQ module proteins. Finally, we have demonstrated that the subcellular localization of the Talin1 I/LWEQ module is regulated by an intrasteric interaction with an upstream alpha-helix, suggesting that both the actin binding and adhesion-targeting elements are masked in full-length Talin1. Our results define a novel role for the I/LWEQ module as the primary adhesion-complex targeting determinant of Talin1 and suggest that pathways that can relieve inhibition of I/LWEQ module function will be important for regulating the structural and signaling properties of adhesion complexes.
Franco
Santos J
SJ
Program in Cellular and Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706, USA.
Senetar
Melissa A
MA
Simonson
William T N
WT
Huttenlocher
Anna
A
McCann
Richard O
RO
D000199:Actins / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion; D002478:Cells, Cultured; D017124:Conserved Sequence; D005353:Fibronectins / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011817:Rabbits; D017384:Sequence Deletion / Q000235:genetics; D016608:Talin / Q000737:chemistry* / Q000378:metabolism*
D000199:Actins; D005353:Fibronectins; D016608:Talin; C496077:Tln1 protein, mouse