Costars, a Dictyostelium protein similar to the C-terminal domain of STARS, regulates the actin cytoskeleton and motility

J Cell Sci. 2010 Nov 1;123(Pt 21):3745-55. doi: 10.1242/jcs.064709. Epub 2010 Oct 12.


Through analysis of a chemotaxis mutant obtained from a genetic screen in Dictyostelium discoideum, we have identified a new gene involved in regulating cell migration and have named it costars (cosA). The 82 amino acid Costars protein sequence appears highly conserved among diverse species, and significantly resembles the C-terminal region of the striated muscle activator of Rho signaling (STARS), a mammalian protein that regulates the serum response factor transcriptional activity through actin binding and Rho GTPase activation. The cosA-null (cosA(-)) cells formed smooth plaques on bacterial lawns, produced abnormally small fruiting bodies when developed on the non-nutrient agar and displayed reduced migration towards the cAMP source in chemotactic assays. Analysis of cell motion in cAMP gradients revealed decreased speed but wild-type-like directional persistence of cosA(-) cells, suggesting a defect in the cellular machinery for motility rather than for chemotactic orientation. Consistent with this notion, cosA(-) cells exhibited changes in the actin cytoskeleton, showing aberrant distribution of F-actin in fluorescence cell staining and an increased amount of cytoskeleton-associated actin. Excessive pseudopod formation was also noted in cosA(-) cells facing chemoattractant gradients. Expressing cosA or its human counterpart mCostars eliminated abnormalities of cosA(-) cells. Together, our results highlight a role for Costars in modulating actin dynamics and cell motility.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Amino Acid Sequence
  • Cell Movement* / genetics
  • Conserved Sequence / genetics
  • Cytoskeleton / metabolism*
  • Dictyostelium
  • Evolution, Molecular
  • Genetic Testing
  • Humans
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Molecular Sequence Data
  • Mutation / genetics
  • Protein Structure, Tertiary / genetics
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • Sequence Homology, Amino Acid
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • ABRA protein, human
  • Actins
  • Microfilament Proteins
  • Protozoan Proteins
  • Transcription Factors