Neogenin-RGMa signaling at the growth cone is bone morphogenetic protein-independent and involves RhoA, ROCK, and PKC.
The repulsive guidance molecule RGMa has been shown to induce outgrowth inhibition of neurites by interacting with the transmembrane receptor neogenin. Here we show that RGMa-induced growth cone collapse is mediated by activation of the small GTPase RhoA, its downstream effector Rho kinase and PKC. In contrast to DRG cultures from neogenin-/- mice, in which no RGMa-mediated growth cone collapse and activation of RhoA occurred, treatment of wild type DRG neurites with soluble RGMa led to a marked activation of RhoA within 3 min followed by collapse, but left Rac1 and Cdc42 unaffected. Furthermore, preincubation of DRG axons with the bone morphogenetic protein (BMP) antagonist noggin had no effect on RGMa-mediated growth cone collapse, implying that the role of RGM in axonal guidance is neogenin- and not BMP receptor-dependent. Pretreatment with 1) C3-transferase, a specific inhibitor of the Rho GTPase; 2) Y-27632, a specific inhibitor of Rho kinase; and 3) Gö6976, the general PKC inhibitor, strongly inhibited the collapse rate of PC12 neurites. Growth cone collapse induced by RGMa was abolished by the expression of dominant negative RhoA, but not by dominant negative Rac1. In contrast to RGMa, netrin-1 induced no growth cone retraction but instead reduced RGMa-mediated growth cone collapse. These results suggest that activation of RhoA, Rho kinase, and PKC are physiologically relevant and important elements of the RGMa-mediated neogenin signal transduction pathway involved in axonal guidance.
Conrad
Sabine
S
Centre for Regenerative Medicine and Biology, 72074 Tübingen, Germany.
Genth
Harald
H
Hofmann
Fred
F
Just
Ingo
I
Skutella
Thomas
T
D000818:Animals; D052004:Bone Morphogenetic Protein Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D058851:GPI-Linked Proteins; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000378:metabolism* / Q000494:pharmacology; D016501:Neurites / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D016716:PC12 Cells; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000494:pharmacology; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000099176:Noggin Protein
D052004:Bone Morphogenetic Protein Receptors; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D058851:GPI-Linked Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D000099176:Noggin Protein; C484602:Rac1 protein, mouse; C483496:Rgma protein, mouse; C091279:neogenin; C499134:Rac1 protein, rat