K+ channel distribution and clustering in developing and hypomyelinated axons of the optic nerve.
The localization of Shaker-type K(+) channels in specialized domains of myelinated central nervous system axons was studied during development of the optic nerve. In adult rats Kv1.1, Kv1.2, Kv1.6, and the cytoplasmic beta-subunit Kvbeta2 were colocalized in juxtaparanodal zones. During development, clustering of K(+) channels lagged behind that for nodal Na(+) channels by about 5 days. In contrast to the PNS, K(+) channels were initially expressed fully segregated from nodes and paranodes, the latter identified by immunofluorescence of Caspr, a component of axoglial junctions. Clusters of K(+) channels were first detected at postnatal day 14 (P14) at a limited number of sites. Expression increased until all juxtaparanodes had immunoreactivity by P40. Developmental studies in hypomyelinating Shiverer mice revealed dramatically disrupted axoglial junctions, aberrant Na(+) channel clusters, and little or no detectable clustering of K(+) channels at all ages. These results suggest that in the optic nerve, compact myelin and normal axoglial junctions are essential for proper K(+) channel clustering and localization.
Rasband
M N
MN
Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.
Trimmer
J S
JS
Peles
E
E
Levinson
S R
SR
Shrager
P
P
D000200:Action Potentials / Q000502:physiology; D000367:Age Factors; D000818:Animals; D001369:Axons / Q000737:chemistry / Q000378:metabolism*; D051668:Delayed Rectifier Potassium Channels; D004594:Electrophysiology; D005455:Fluorescent Antibody Technique; D051662:Kv1.1 Potassium Channel; D051663:Kv1.2 Potassium Channel; D051379:Mice; D008809:Mice, Inbred C3H; D008818:Mice, Neurologic Mutants; D009154:Mutation; D009186:Myelin Sheath / Q000378:metabolism* / Q000473:pathology; D009457:Neuroglia / Q000166:cytology; D009900:Optic Nerve / Q000166:cytology* / Q000254:growth & development / Q000473:pathology; D015221:Potassium Channels / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011817:Rabbits; D011901:Ranvier's Nodes / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D051637:Shaker Superfamily of Potassium Channels
D051668:Delayed Rectifier Potassium Channels; C496947:Kcna1 protein, mouse; C496970:Kcna2 protein, mouse; C496972:Kcna2 protein, rat; D051663:Kv1.2 Potassium Channel; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051637:Shaker Superfamily of Potassium Channels; D051662:Kv1.1 Potassium Channel