Coordination of microtubule and microfilament dynamics by Drosophila Rho1, Spire and Cappuccino

Nat Cell Biol. 2006 Apr;8(4):367-76. doi: 10.1038/ncb1385. Epub 2006 Mar 5.


The actin-nucleation factors Spire and Cappuccino (Capu) regulate the onset of ooplasmic streaming in Drosophila melanogaster. Although this streaming event is microtubule-based, actin assembly is required for its timing. It is not understood how the interaction of microtubules and microfilaments is mediated in this context. Here, we demonstrate that Capu and Spire have microtubule and microfilament crosslinking activity. The spire locus encodes several distinct protein isoforms (SpireA, SpireC and SpireD). SpireD was recently shown to nucleate actin, but the activity of the other isoforms has not been addressed. We find that SpireD does not have crosslinking activity, whereas SpireC is a potent crosslinker. We show that SpireD binds to Capu and inhibits F-actin/microtubule crosslinking, and activated Rho1 abolishes this inhibition, establishing a mechanistic basis for the regulation of Capu and Spire activity. We propose that Rho1, cappuccino and spire are elements of a conserved developmental cassette that is capable of directly mediating crosstalk between microtubules and microfilaments.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Actins / metabolism
  • Animals
  • Cross-Linking Reagents
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / metabolism*
  • Female
  • Male
  • Microfilament Proteins / metabolism*
  • Microtubules / metabolism*
  • rho GTP-Binding Proteins / metabolism*


  • Actins
  • Cross-Linking Reagents
  • Drosophila Proteins
  • Microfilament Proteins
  • capu protein, Drosophila
  • spir protein, Drosophila
  • Rho1 protein, Drosophila
  • rho GTP-Binding Proteins