Differentiation-dependent sialylation of individual neural cell adhesion molecule polypeptides during postnatal development.
The postnatal sialylation of individual neural cell adhesion molecule (N-CAM) polypeptides by a developmentally regulated sialyltransferase in Golgi-enriched fractions isolated from rat brain is described. The 120-kilodalton polypeptide of N-CAM was found to be sialylated at each developmental age examined. This was in contrast to the 140- and 180-kilodalton N-CAM polypeptides which were only sialylated until postnatal day 10 and from postnatal day 12, respectively. Immunoblotting procedures demonstrated that all N-CAM polypeptides were expressed in the Golgi fractions at each developmental stage examined. The heavily sialylated "embryonic" form of N-CAM was found to be reexpressed at postnatal days 10 and 12, a time coincident with extensive fibre outgrowth. The "embryonic" form of N-CAM incorporated similar amounts of [14C]sialic acid into its constituent polypeptides reflecting the difference in sialic acid to protein ratio, as this form of N-CAM was virtually undetectable in the immunoblots of postnatal material.
Breen
K C
KC
Department of Pharmacology, University College, Belfield, Dublin, Ireland.
Regan
C M
CM
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000378:metabolism; D000954:Antigens, Surface / Q000378:metabolism*; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D015815:Cell Adhesion Molecules; D002454:Cell Differentiation; D006056:Golgi Apparatus / Q000378:metabolism; D019158:N-Acetylneuraminic Acid; D009479:Neuropeptides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012794:Sialic Acids / Q000378:metabolism*
D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D009479:Neuropeptides; D012794:Sialic Acids; D019158:N-Acetylneuraminic Acid