Plasmalemmal insertion and modification of sodium channels at the nerve growth cone.
We have characterized voltage-dependent sodium channels in growth cones (GCPs) isolated from fetal rat brain using saxitoxin and TTX binding as well as recordings from channels reconstituted into lipid bilayer membranes. Both high- and low-affinity binding sites are present in GCP membranes. However, the two binding sites are segregated largely or completely, with the high-affinity binding sites in the plasmalemma, and the low-affinity sites in an internal membrane compartment. Plasmalemmal insertion of these internal sites can be triggered by high-potassium depolarization and depends on a metalloendoprotease-requiring mechanism. These observations indicate that a precursor-product relationship exists between the internal and external sodium channels of the growth cone, and therefore suggest that channel externalization causes conversion of low-affinity to high-affinity saxitoxin receptors. This conversion may represent a step of channel capacitation.
Wood
M R
MR
Department of Cellular and Structural Biology, University of Colorado School of Medicine, Denver 80262.
DeBin
J
J
Strichartz
G R
GR
Pfenninger
K H
KH
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism; D008051:Lipid Bilayers; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D012530:Saxitoxin / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D008051:Lipid Bilayers; D011480:Protease Inhibitors; D015222:Sodium Channels; D012530:Saxitoxin; D013779:Tetrodotoxin