Glycophorin A requirement for expression of O-linked antigens on the erythrocyte membrane

Background : Glycophorin A (GPA) has a large number of sialic acid-containing oligosaccharide chains. GPA is highly conserved among vertebrates, mice with a GPA deletion have not been reported and GPA's physiologic role remains uncertain. Results : GPA(-/-) homozygotes were obtained by intercrossing GPA(+/-) heterozygotes based on Mendelian genetics. The amount of O-linked oligosaccharide chains in the erythrocyte membrane of GPA(-/-) mice decreased to 60% compared to that of the wild-type mice. Flow cytometry and Western blot analysis revealed that the TER antigen that is associated with GPA on the erythrocyte membrane was totally abrogated from the cell surface in GPA(-/-) mice. Several glycoproteins that were detected with peanut agglutinin (PNA), a lectin that recognizes O-linked oligosaccharide chains, were absent from the GPA(-/-) erythrocyte membrane. Erythrocytes lacking GPA were more sensitive to hypo-osmotic stress than wildtype erythrocyte. Conclusions : GPA(-/-) mice show apparently normal phenotypes at least during the early generations. The disappearance of many glycoproteins recognized by PNA lectin on the GPA(-/-) erythrocyte membrane proteins suggests that GPA has an essential role in the expression of O-linked antigens on the erythrocyte membrane protein. These interactions of GPA and other glycoproteins may contribute to maintaining the physical strength of the erythrocyte membrane.