Inhibitory myelin components and their putative receptors. Three myelin membrane proteins that inhibit axonal growth are Nogo, OMgp, and MAG. All three may bind to the Nogo receptor (NgR) in the axonal growth cone, although downstream signaling events are less clear. MAG has also been shown to bind both to ganglioside GT1b and to the p75 low-affinity neurotrophin receptor. p75 may regulate the affects of MAG through Rho-GTPase signaling to the actin cytoskeleton. (OMgp, oligodendrocyte-myelin glycoprotein; MAG, myelin associated glycoprotein; see text for details.).