Cdc42, dynein, and dynactin regulate MTOC reorientation independent of Rho-regulated microtubule stabilization

Curr Biol. 2001 Oct 2;11(19):1536-41. doi: 10.1016/s0960-9822(01)00475-4.


In migrating adherent cells such as fibroblasts and endothelial cells, the microtubule-organizing center (MTOC) reorients toward the leading edge [1-3]. MTOC reorientation repositions the Golgi toward the front of the cell [1] and contributes to directional migration [4]. The mechanism of MTOC reorientation and its relation to the formation of stabilized microtubules (MTs) in the leading edge, which occurs concomitantly with MTOC reorientation [3], is unknown. We show that serum and the serum lipid, lysophosphatidic acid (LPA), increased Cdc42 GTP levels and triggered MTOC reorientation in serum-starved wounded monolayers of 3T3 fibroblasts. Cdc42, but not Rho or Rac, was both sufficient and necessary for LPA-stimulated MTOC reorientation. MTOC reorientation was independent of Cdc42-induced changes in actin and was not blocked by cytochalasin D. Inhibition of dynein or dynactin blocked LPA- and Cdc42-stimulated MTOC reorientation. LPA also stimulates a Rho/mDia pathway that selectively stabilizes MTs in the leading edge [5, 6]; however, activators and inhibitors of MTOC reorientation and MT stabilization showed that each response was regulated independently. These results establish an LPA/Cdc42 signaling pathway that regulates MTOC reorientation in a dynein-dependent manner. MTOC reorientation and MT stabilization both act to polarize the MT array in migrating cells, yet these processes act independently and are regulated by separate Rho family GTPase-signaling pathways.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Actins / metabolism
  • Animals
  • Dynactin Complex
  • Dyneins / antagonists & inhibitors*
  • Lysophospholipids / pharmacology
  • Mice
  • Microtubule-Associated Proteins / antagonists & inhibitors*
  • Microtubule-Organizing Center / physiology*
  • Microtubules / physiology*
  • Serum Albumin, Bovine / pharmacology
  • Signal Transduction* / drug effects
  • cdc42 GTP-Binding Protein / metabolism*
  • rho GTP-Binding Proteins / metabolism*


  • Actins
  • Dynactin Complex
  • Lysophospholipids
  • Microtubule-Associated Proteins
  • Serum Albumin, Bovine
  • Dyneins
  • cdc42 GTP-Binding Protein
  • rho GTP-Binding Proteins