Ultrastructural study of plasma membrane GM1 in neuroectodermal cells using cholera-peroxidase

Abstract

Cholera toxin was coupled to peroxidase to yield a highly specific ultrastructural marker for G _m1 gangliosides. Study of embryonic brain cells in culture revealed intense binding of choleraperoxidase by plasma membranes of both neurons and glial cells. In contrast, long-term monolayer glioblastoma cultures, including one producing C-type virus, revealed virtually no labelling of their plasma membranes. Such cells were shown to be capable of incorporating exogenously applied G_{m 1} into their plasma membranes. Studies with fixed brain and synaptosomal fractions were in accord with results on embryonic brain cells in culture, and autoradiographic findings with¹²⁵I cholera supported observations made utilizing cholera—peroxidase. From our studies there is some indication that long-term propagation in vitro alters the plasma membrane G _m1.