Polysialic acid is associated with sodium channels and the neural cell adhesion molecule N-CAM in adult rat brain.
We have studied alpha 2,8-linked polysialic acid (polySia) and the neural cell adhesion molecule (N-CAM) in the adult rat brain by immunohistochemistry and Western blot analysis. Both molecules were widely distributed but not ubiquitous. Various brain regions showed colocalization of polySia and N-CAM. Strong immunoreactivity for polySia was seen in regions which were negative for N-CAM, such as the main and accessory olfactory bulbs. Immunohistochemical evidence for the heterogeneity of polySia expression in different brain regions was confirmed by immunoblotting. We present evidence that N-CAM is not the only polySia bearing protein in adult rat brain. Specifically, immunoprecipitation using the polySia-specific monoclonal antibody mAb 735 precipitated not only N-CAM isoforms carrying polySia, but also the sodium channel alpha subunit. Immunoblotting using sodium channel alpha subunit antibody (SP20) revealed a smear from 250 kDa upwards. PolySia removal using an endoneuraminidase specific for alpha 2,8-linked polysialic acid of 8 or more residues long, reduced this smear to a single band at 250 kDa. Thus both N-CAM and sodium channels carry homopolymers of alpha 2,8-linked polysialic acid in adult rat brain.
Zuber
C
C
Department of Pathology, University of Zürich, Switzerland.
Lackie
P M
PM
Catterall
W A
WA
Roth
J
J
D000818:Animals; D000911:Antibodies, Monoclonal; D001921:Brain / Q000166:cytology* / Q000648:ultrastructure; D015816:Cell Adhesion Molecules, Neuronal / Q000032:analysis*; D015151:Immunoblotting; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D008970:Molecular Weight; D009830:Olfactory Bulb / Q000166:cytology / Q000648:ultrastructure; D009928:Organ Specificity; D051381:Rats; D012794:Sialic Acids / Q000032:analysis*; D015222:Sodium Channels / Q000378:metabolism*; D013570:Synaptic Membranes / Q000648:ultrastructure
D000911:Antibodies, Monoclonal; D015816:Cell Adhesion Molecules, Neuronal; D012794:Sialic Acids; D015222:Sodium Channels; C021319:polysialic acid