Schwann Cell Surface Proteins and Glycoproteins

Abstract: To identify surface sialoglycoproteins of rat Schwann cells and to compare molecular weights of these sialoglycoproteins with those present in rat peripheral nervous system myelin, we prepared Schwann cells from sciatic nerves of 1–3-day-old rats and cultured them in monolayer. Surface sialoglycoproteins of the cultured cells were tritium-labeled by the periodateborohydride procedure and compared with sialoglycoproteins of adult rat peripheral nervous system myelin by fluorography following polyacrylamide slab gel electrophoresis in sodium dodecyl sulfate. Three radioactive bands with apparent molecular weights of 114,000–132,000, 105,000–115,000, and 44,000–56,000 were observed in both the Schwann cell and myelin preparations. Bands of similar apparent molecular weights were noted in Schwann cells metabolically radiolabeled with d -1,6-³H]glucosamine. A band co-migrating with myelin P₀ glycoprotein was the most intensely radiolabeled of all peptides in periodate-B³H₄^?treated myelin, but was present in only trace amounts in periodate-B³H₄^? or d -1,6-³H]glucosamine radiolabeled Schwann cells. Many presumably non-myelin glycoproteins were identified in the cultured Schwann cells by the periodate-borohydride procedure and by incubation of the cells with d -1,6-³H]glucosamine. An immunoprecipitation technique was used to detect radiolabeled peptides in a nonionic detergent extract of freshly prepared, surface-radioiodinated Schwann cells that were bound by a rabbit anti-Schwann cell serum preabsorbed with rat fibroblasts. Many radioactive peptides were detected in the immunoprecipitate, but the two most intensely radiolabeled had apparent molecular weights of 105,000–115,000 and 95,000–106,000. This study has identified a number of glycoproteins synthesized by cultured rat Schwann cells which resemble in apparent molecular weight the glycoproteins expressed in rat peripheral nervous system myelin and has defined Schwann cell surface proteins recognized by a specific anti-rat Schwann cell antiserum.