Cdc42, dynein, and dynactin regulate MTOC reorientation independent of Rho-regulated microtubule stabilization.
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.
Palazzo
A F
AF
Department of Anatomy and Cell Biology, Columbia University, New York, NY 10032, USA.
Joseph
H L
HL
Chen
Y J
YJ
Dujardin
D L
DL
Alberts
A S
AS
Pfister
K K
KK
Vallee
R B
RB
Gundersen
G G
GG
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D000818:Animals; D000072159:Dynactin Complex; D004398:Dyneins / Q000037:antagonists & inhibitors*; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors*; D022101:Microtubule-Organizing Center / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D000199:Actins; D000072159:Dynactin Complex; D008246:Lysophospholipids; D008869:Microtubule-Associated Proteins; D012710:Serum Albumin, Bovine; D004398:Dyneins; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins