Structural model and functional significance of pH-dependent talin-actin binding for focal adhesion remodeling
Actin filament binding by the focal adhesion (FA)-associated protein talin stabilizes cell-substrate adhesions and is thought to be rate-limiting in cell migration. Although F-actin binding by talin is known to be pH-sensitive in vitro, with lower affinity at higher pH, the functional significance o...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 38; pp. 14436 - 14441 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences
23.09.2008
National Acad Sciences |
Subjects | |
Online Access | Get full text |
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Summary: | Actin filament binding by the focal adhesion (FA)-associated protein talin stabilizes cell-substrate adhesions and is thought to be rate-limiting in cell migration. Although F-actin binding by talin is known to be pH-sensitive in vitro, with lower affinity at higher pH, the functional significance of this pH dependence is unknown. Because increased intracellular pH (pHi) promotes cell migration and is a hallmark of metastatic carcinomas, we asked whether it increases FA remodeling through lower-affinity talin-actin binding. Talin contains several actin binding sites, but we found that only the COOH-terminal USH-I/LWEQ module showed pH-dependent actin binding, with lower affinity and decreased maximal binding at higher pH. Molecular dynamics simulations and NMR of this module revealed a structural mechanism for pH-dependent actin binding. A cluster of titratable amino acids with upshifted pKa values, including His-2418, was identified at one end of the five-helix bundle distal from the actin binding site. Protonation of His-2418 induces changes in the conformation and dynamics of the remote actin binding site. Structural analyses of a mutant talin-H2418F at pH 6.0 and 8.0 suggested changes different from the WT protein, and we confirmed that actin binding by talin-H2418F was relatively pH-insensitive. In motile fibroblasts, increasing pHi decreased FA lifetime and increased the migratory rate. However, expression of talin-H2418F increased lifetime 2-fold and decreased the migratory rate. These data identify a molecular mechanism for pH-sensitive actin binding by talin and suggest that FA turnover is pH-dependent and in part mediated by pH-dependent affinity of talin for binding actin. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Author contributions: J.S., G.B., D.R.C., M.J.S.K., M.P.J., and D.L.B. designed research; J.S., G.B., S.G., A.R.G., B.T.G., and M.J.S.K. performed research; J.S. and M.P.J. contributed new reagents/analytic tools; J.S., G.B., S.G., A.R.G., D.R.C., M.J.S.K., M.P.J., and D.L.B. analyzed data; and J.S., M.J.S.K., M.P.J., and D.L.B. wrote the paper. Edited by Thomas D. Pollard, Yale University, New Haven, CT, and approved July 10, 2008 |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.0805163105 |