Glycophorin expression in murine erythroleukaemia cells.
We have identified mature and putative precursor forms of glycophorins expressed in a virus-transformed murine erythroleukaemia (MEL) cell line and compared them with their normal erythroblast counterparts. The following differences were found: (1) the two major MEL cell glycophorins (apparent Mr values 29-30 and 43(x10(3] have greater mobility on polyacrylamide gels than their normal gp-3 and gp-2 counterparts, due at least in part to differences in their oligosaccharide sidechains; (2) MEL cell gp-3 consists of two discrete proteins; and (3) there are more potential glycophorin precursors in MEL cells than in normal mouse erythroblasts. Four proteins, with apparent Mr values of 21, 23, 26 and 27(x10(3], have tentatively been identified as glycophorin precursors, based on the following findings: (1) they are immunologically related to the glycophorins; and (2) their synthesis was induced by dimethyl sulphoxide coincidentally with that of gp-3 and gp-2. They do not appear to be glycoproteins, as evidenced by their lack of incorporation of [3H]galactose, [3H]glucosamine or [3H]mannose. In contrast, gp-3 and gp-2 incorporated [3H]galactose and [3H]glucosamine but not [3H]mannose. Partial characterization of the glycan moieties of MEL cell glycophorins indicates that they consist mostly of tri- and tetrasaccharides, with no indication of any N-linked chains. Hence, the glycans of MEL cell glycophorins are mostly (if not all) O-linked. Furthermore, treatment with N-glycanase did not change their electrophoretic mobility on polyacrylamide gels. MEL cell glycophorins were also shown to be modified by phosphoryl and fatty acyl groups.
Ulmer
J B
JB
Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.
Dolci
E D
ED
Palade
G E
GE
D000818:Animals; D004900:Erythroblasts / Q000378:metabolism; D006021:Glycophorins / Q000378:metabolism*; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D010449:Peptide Mapping; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism*; D012795:Sialoglycoproteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D006021:Glycophorins; D011498:Protein Precursors; D012795:Sialoglycoproteins