RESUMO
The growth of injured axons in the adult mammalian CNS is limited after injury. Three myelin proteins, Nogo, MAG (myelin-associated glycoprotein), and OMgp (oligodendrocyte myelin glycoprotein), bind to the Nogo-66 receptor (NgR) and inhibit axonal growth in vitro. Transgenic or viral blockade of NgR function allows axonal sprouting in vivo. Here, we administered the soluble function-blocking NgR ectodomain [aa 27-310; NgR(310)ecto] to spinal-injured rats. Purified NgR(310)ecto-Fc protein was delivered intrathecally after midthoracic dorsal over-hemisection. Axonal sprouting of corticospinal and raphespinal fibers in NgR(310)ecto-Fc-treated animals correlates with improved spinal cord electrical conduction and improved locomotion. The ability of soluble NgR(310)ecto to promote axon growth and locomotor recovery demonstrates a therapeutic potential for NgR antagonism in traumatic spinal cord injury.
Assuntos
Axônios/fisiologia , Proteínas da Mielina/antagonistas & inibidores , Glicoproteína Associada a Mielina/antagonistas & inibidores , Glicoproteína Associada a Mielina/metabolismo , Receptores de Peptídeos/fisiologia , Traumatismos da Medula Espinal/patologia , Animais , Axônios/metabolismo , Potencial Evocado Motor , Feminino , Proteínas Ligadas por GPI , Injeções Espinhais , Atividade Motora , Glicoproteína Mielina-Oligodendrócito , Proteínas Nogo , Receptor Nogo 1 , Oligodendroglia/metabolismo , Fragmentos de Peptídeos/administração & dosagem , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Superfície Celular , Proteínas Recombinantes de Fusão/administração & dosagem , Proteínas Recombinantes de Fusão/farmacologia , Serotonina/metabolismo , Solubilidade , Medula Espinal/fisiopatologia , Medula Espinal/ultraestrutura , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/fisiopatologiaRESUMO
The Nogo66 receptor (NgR1) is a neuronal, leucine-rich repeat (LRR) protein that binds three central nervous system (CNS) myelin proteins, Nogo, myelin-associated glycoprotein, and oligodendrocyte myelin glycoprotein, and mediates their inhibitory effects on neurite growth. Although the LRR domains on NgR1 are necessary for binding to the myelin proteins, the exact epitope(s) involved in ligand binding is unclear. Here we report the generation and detailed characterization of an anti-NgR1 monoclonal antibody, 7E11. The 7E11 monoclonal antibody blocks Nogo, myelin-associated glycoprotein, and oligodendrocyte myelin glycoprotein binding to NgR1 with IC50 values of 120, 14, and 4.5 nm, respectively, and effectively promotes neurite outgrowth of P3 rat dorsal root ganglia neurons cultured on a CNS myelin substrate. Further, we have defined the molecular epitope of 7E11 to be DNAQLR located in the third LRR domain of rat NgR1. Our data demonstrate that anti-NgR1 antibodies recognizing this epitope, such as 7E11, can neutralize CNS myelin-dependent inhibition of neurite outgrowth. Thus, specific anti-NgR1 antibodies may represent a useful therapeutic approach for promoting CNS repair after injury.