A cell surface protein of astrocytes, Ran-2, distinguishes non-myelin-forming Schwann cells from myelin-forming Schwann cells.

Abstract

Defining the molecular phenotype of adult glial cells in the peripheral nervous system in situ forms a good basis for subsequent studies on the development of these cells, and for determining the role of neurons in the attainment and maintenance of the mature glial phenotype. We report here the characterization of the glial surface antigen, Ran-2, and describe its distribution in the peripheral and central nervous system of adult rats. Immunoprecipitation of the antigen from cultured astrocytes with monoclonal Ran-2, antibodies, showed that Ran-2 is a protein with an apparent molecular weight of 140,000 daltons. In immunofluorescence studies of teased nerve preparations, Ran-2 was found on the surface of non-myelin-forming Schwann cells in all nerves surveyed, i.e. the sciatic, dorsal and ventral roots, cervical sympathetic trunk and the brachial plexus. In contrast, it was not detected immunohistochemically on myelin-forming Schwann cells. The antigen was also absent, or present at very low levels, on the satellite cells of dorsal root sensory ganglia, although, as we reported previously, it was present on the glial cells of the enteric nervous system. The Ran-2 antigen was also associated with perineurial cells. In short-term cell cultures of the sciatic nerve and cervical sympathetic trunk from 19-day-old rats, Ran-2 could be localized on the surface of individual viable Schwann cells. In the central nervous system, the antigen was present on astrocytes in sections of the optic nerve.