Abstract
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.