Identification and function of transmembrane glycoproteins--the red cell model.
Transmembrane glycoproteins in the red cell membrane traverse the plasma membrane, have their carbohydrate moieties on the extracellular surface, are sialyated (except for band 3) and are tethered to the membrane cytoskeleton proteins on the cytoplasmic surface. This linkage between the transmembrane proteins and the skeletal membrane proteins provides a two-way communication between the extracellular surface and the interior of the red cell; i.e., a transmembrane effect can be initiated from either side. These interactions are discussed in this review, including the example of sickle cell anemia in which the membrane bound hemoglobin may exert a transmembrane effect to change the conformation or distribution of transmembrane glycoproteins and and hence the extracellular surface receptors. This, in turn, may explain why sickle cells adhere to endothelium in vitro. Although the RBC transmembrane sialoglycoproteins may function in communication, regulation of cell shape, and adhesion, uncertainties exist regarding many of their functions. To study these sialoglycoproteins, we have developed a double staining technique (Dzandu et al., 1984) that differentially stains human RBC membrane sialoglycoproteins and asialoproteins in SDS-polyacrylamide gels. This should aid in elucidating the conformational structure and function of transmembrane glycoproteins.
D000755:Anemia, Sickle Cell / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004910:Erythrocyte Membrane / Q000502:physiology* / Q000648:ultrastructure; D004913:Erythrocytes, Abnormal / Q000648:ultrastructure; D005613:Freeze Etching; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D008560:Membrane Fluidity; D012795:Sialoglycoproteins / Q000097:blood*
D006023:Glycoproteins; D012795:Sialoglycoproteins