L. Pedraza et al., BIOSYNTHESIS AND REGULATION OF EXPRESSION OF THE HNK-1 EPITOPE ON MYELIN-ASSOCIATED GLYCOPROTEIN IN A TRANSFECTED CELL MODEL SYSTEM, Journal of neuroscience research, 40(6), 1995, pp. 716-727
The HNK-1 antibody recognizes a carbohydrate epitope expressed by many
cell adhesion molecules in the nervous system that has been proposed
to be an important adhesive determinant, This epitope is particularly
prominent on the myelin-associated glycoprotein (MAG) and is related t
o the antigenic target in an autoimmune mediated demyelinating neuropa
thy. Elucidation of the mechanisms underlying the biosynthesis and reg
ulation of expression of the HNK-1 epitope is therefore likely to have
important functional and clinical implications. In order to investiga
te its biosynthesis and the regulation of its expression, we have expr
essed both human and rat MAG in several different cell lines by retrov
iral infection, These studies indicate that the cellular milieu determ
ines whether the HNK-1 epitope is expressed on the MAG polypeptide and
provide an explanation for the significant variation in HNK-1 levels
that has been noted in different species, Using a transfected human ne
uroblastoma line, we have determined that this epitope is present on t
he fourth and/or fifth immunoglobulin-like domain of rat MAG and that
it is added intracellularly, probably in the trans Golgi, Finally we h
ave found that expression of the HNK-1 epitope is increased by activat
ion of different second messenger systems, providing direct evidence t
hat its expression can be regulated independently from that of the MAG
polypeptide, (C) 1995 Wiley-Liss, Inc.