Synthetic spatially graded Rac activation drives cell polarization and movement

Benjamin Lin, William R. Holmes, C. Joanne Wang, Tasuku Ueno, Andrew Harwell, Leah Edelstein-Keshet, Takanari Inoue, Andre Levchenko

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Migrating cells possess intracellular gradients of active Rho GTPases, which serve as central hubs in transducing signals from extracellular receptors to cytoskeletal and adhesive machinery. However, it is unknown whether shallow exogenously induced intracellular gradients of RhoGTPases are sufficient to drive cell polarity andmotility. Here, we use microfluidic control to generate gradients of a small molecule and thereby directly induce linear gradients of active, endogenous Rac without activation of chemotactic receptors. Gradients as lowas 15%were sufficient not only to trigger cell migration up the chemical gradient but to induce both cell polarization and repolarization. Cellular response times were inversely proportional to the steepness of Rac inducer gradient in agreement with a mathematical model, suggesting a function for chemoattractant gradient amplification upstream of Rac. Increases in activated Rac levels beyond a well-defined threshold augmented polarization and decreased sensitivity to the imposed gradient. The threshold was governed by initial cell polarity and PI3K activity, supporting a role for both in defining responsiveness to Rac activation. Our results reveal that Rac can serve as a starting point in defining cell polarity. Furthermore, our methodology may serve as a template to investigate processes regulated by intracellular signaling gradients.

Original languageEnglish (US)
Pages (from-to)E3668-E3677
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number52
StatePublished - Dec 26 2012


  • Cell signaling
  • Chemotaxis
  • Signal transduction
  • Synthetic biology

ASJC Scopus subject areas

  • General


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