Purification of Thy-1-related glycoproteins from human brain and fibroblasts: comparisons between these molecules and murine glycoproteins carrying Thy-1.1 and Thy-1.2 antigens.

Abstract

AbstractThe purification and partial characterization of glycoproteins from human brain and fibroblasts which are antigenically and structurally related to the Thy‐1 glycoproteins of rats and mice is described. In addition, Thy‐1 molecules were isolated from the brains of AKR and CBA mice (Thy‐1.1 and Thy‐1.2, respectively). The molecules were purified from sodium deoxycholate extracts of brain tissue by chromatography on lentil lectin‐Sepharose followed by gel filtration, and purification was monitored by radioimmunoassay. Similar molecules were isolated from human brain and fibroblasts using monoclonal antibody columns. Analysis by electrophoresis on 12.5% polyacrylamide gels in sodium dodecyl sulfate (SDS) showed that Thy‐1‐related molecules from human brain migrate as a doublet with apparent molecular weights of 24700 and 26200. Thy‐1 from human foreskin fibroblasts cultured in vitro migrates as a single band of 26500. Thus, human Thy‐1 glycoproteins resemble their rat counterparts in exhibiting tissue‐specific polymorphism. Amino acid analysis of Thy‐1 from human brain and fibroblasts suggests that the polypeptides expressed by different tissues are extremely similar.Thy‐1.1 from AKR mouse brain migrates as a doublet on SDS gel electrophoresis with apparent molecular weights of 23700 and 25100, while Thy‐1.2 molecules isolated from CBA mouse brain run as a single broad symmetrical band with a molecular weight of 25000. Molecules carrying the Thy‐1.1 allotype are readily distinguished from those carrying the Thy‐1.2 allotype by the presence of an additional arginine residue. Amino acid compositions of Thy‐1 from man and the two mouse strains are similar, but each has unique features.Thy‐1 molecules immunoprecipitated from mouse and rat fibroblasts have higher apparent molecular weights than their brain counterparts; the basis of the tissue‐specific polymorphism is discussed.