Glial fibrillary acidic polypeptides in peripheral glia. Molecular weight, heterogeneity and distribution.

Glial fibrillary acidic (GFA) polypeptides are present in major categories of rat peripheral glia including non-myelin-forming Schwann cells, enteric glia and some satellite cells. They can be detected both immunochemically and immunohistochemically. The immunoreactivity is associated with a polypeptide which has an MW of 49 000, indistinguishable from that of glial fibrillary acidic protein (GFAP) from rat brain. In spite of this, the GFA polypeptides found in the peripheral nervous system and central nervous system are not identical since they can be distinguished both immunohistochemically and immunochemically by a monoclonal GFAP antibody which recognizes GFAP in astrocytes and some enteric glia, but not GFAP in non-myelin-forming Schwann cells, satellite cells and many enteric glia. GFA-related molecules can also be detected in human Schwann cells by immunofluorescence. The results suggest, however, that the glial filament polypeptides of peripheral glia and astrocytes are less closely related in the human than in the rat. The glial distribution of GFAP is closely paralleled by 2 cell surface proteins, Ran-2 and A5E3 antigen. Although GFAP, Ran-2 and A5E3 are individually expressed by diverse cell types, the phenotype GFAP+, Ran-2+, A5E3+ defines a narrow group including only non-myelin-forming Schwann cells, enteric glia and astrocytes. These observations suggest that the non-myelin-forming cells of the central and peripheral nervous system may share some common functions.