Cell-surface expression of glia maturation factor beta in astrocytes.
Glia maturation factor beta (GMF-beta) is a 17-kDa acidic protein isolated from the brain. When added to cultured cells, GMF-beta promotes the phenotypic expression of glia and neurons and inhibits the proliferation of their respective tumors. Although astrocytes produce GMF-beta and store it inside the cells, they do not secrete the protein into the cultured medium. This poses a question as to how GMF-beta mediates intercellular communication. This paper provides an answer by demonstrating the presence of GMF-beta on the surface of astrocytes, using gold-labeled antibody enhanced with silver. It appears that cell-surface GMF-beta acts on the target cells at close range when cells are in direct contact. In contrast to astrocytes, we failed to detect GMF-beta on the surface of C6 glioma cells, although these cells, like astrocytes, possess endogenous intracellular GMF-beta and are also responsive to GMF-beta added to the medium. The lack of cell-surface expression of GMF-beta in C6 cells may reflect a breakdown in intercellular communication in these malignant cells.
Lim
R
R
Department of Neurology, University of Iowa College of Medicine, Iowa City 52242.
Liu
Y X
YX
Zaheer
A
A
D000818:Animals; D001253:Astrocytes / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry; D003593:Cytoplasm / Q000737:chemistry; D020904:Glia Maturation Factor; D005910:Glioma / Q000737:chemistry; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured
D020904:Glia Maturation Factor; D009419:Nerve Tissue Proteins