Nogo-A at CNS paranodes is a ligand of Caspr: possible regulation of K(+) channel localization.
Nie DY,
Zhou ZH,
Ang BT,
Teng FY,
Xu G,
Xiang T,
Wang CY,
Zeng L,
Takeda Y,
Xu TL,
Ng YK,
Faivre-Sarrailh C,
Popko B,
Ling EA,
Schachner M,
Watanabe K,
Pallen CJ,
Tang BL,
Xiao ZC.
Department of Clinical Research, Singapore General Hospital, Singapore.
We report Nogo-A as an oligodendroglial component congregating and interacting with the Caspr-F3 complex at paranodes. However, its receptor Nogo-66 receptor (NgR) does not segregate to specific axonal domains. CHO cells cotransfected with Caspr and F3, but not with F3 alone, bound specifically to substrates coated with Nogo-66 peptide and GST-Nogo-66. Binding persisted even after phosphatidylinositol- specific phospholipase C (PI-PLC) removal of GPI-linked F3 from the cell surface, suggesting a direct interaction between Nogo-66 and Caspr. Both Nogo-A and Caspr co-immunoprecipitated with Kv1.1 and Kv1.2, and the developmental expression pattern of both paralleled compared with Kv1.1, implicating a transient interaction between Nogo-A-Caspr and K(+) channels at early stages of myelination. In pathological models that display paranodal junctional defects (EAE rats, and Shiverer and CGT(-/-) mice), distances between the paired labeling of K(+) channels were shortened significantly and their localization shifted toward paranodes, while paranodal Nogo-A congregation was markedly reduced. Our results demonstrate that Nogo-A interacts in trans with axonal Caspr at CNS paranodes, an interaction that may have a role in modulating axon-glial junction architecture and possibly K(+)-channel localization during development.
PMID: 14592966 [PubMed - indexed for MEDLINE]
PMCID: PMC275427