| First Author | Ratelade J | Year | 2011 |
| Journal | J Biol Chem | Volume | 286 |
| Issue | 52 | Pages | 45156-64 |
| PubMed ID | 22069320 | Mgi Jnum | J:315213 |
| Mgi Id | MGI:6829806 | Doi | 10.1074/jbc.M111.297275 |
| Citation | Ratelade J, et al. (2011) Evidence against cellular internalization in vivo of NMO-IgG, aquaporin-4, and excitatory amino acid transporter 2 in neuromyelitis optica. J Biol Chem 286(52):45156-64 |
| abstractText | Autoantibodies against astrocyte water channel aquaporin-4 (AQP4) are thought to be pathogenic in neuromyelitis optica (NMO). Prior work has suggested that a key component of NMO autoantibody (NMO-IgG) pathogenesis is internalization of AQP4 and the associated glutamate transporter EAAT2, leading to glutamate excitotoxicity. Here, we show selective endocytosis of NMO-IgG and AQP4 in transfected cell cultures, but little internalization in brain in vivo. AQP4-dependent endocytosis of NMO-IgG occurred rapidly in various AQP4-transfected cell lines, with efficient transport from early endosomes to lysosomes. Cell surface AQP4 was also reduced following NMO-IgG exposure. However, little or no internalization of NMO-IgG, AQP4, or EAAT2 was found in primary astrocyte cultures, nor was glutamate uptake affected by NMO-IgG exposure. Following injection of NMO-IgG into mouse brain, NMO-IgG binding and AQP4 expression showed a perivascular astrocyte distribution, without detectable cellular internalization over 24 h. We conclude that astrocyte endocytosis of NMO-IgG, AQP4, and EAAT2 is not a significant consequence of AQP4 autoantibody in vivo, challenging generally accepted views about NMO pathogenesis. |
