Modification of Nerve Growth Factor Receptor Properties by Wheat Germ

PC12 is a nerve growth factor (NGF) responsive cell line which exhibits two classes of NGF receptors distinguishable by different kinetic rate constants, sensitivity to trypsin and resistance to Triton detergent solubilization. Whereas incubation of PC12 cells with wheat germ agglutinin (WGA) prior to addition of ‘“1NGF inhibits binding of NGF to both classes of receptors, treatment with WGA subsequent to incubation with NGF does not inhibit NGF binding but causes the class of NGF receptors which exhibit rapid or “Fast” dissociation kinetics prior to lectin treatment to be converted to the form which exhibits “Slow” dissociation kinetics. This WGA-mediated receptor conversion is lectin specific, blocked by N-acetyl-D-glucosamine, occurs at similar rates at 4 and 37 “C, and is not impaired by a metabolic poison. NGF receptors converted by WGA, like pre-existing Slow receptors, are resistant to trypsinization and remain associated to Triton X-100 extracted “cytoskeletons.” Very similar results were obtained for NGF receptors on a human melanoma cell line A875. These results suggest that Fast and Slow receptors are two interconvertible forms of a single protein, rather than distinct proteins. The significance of the generality of these properties for NGF receptors from diverse species and cell types is discussed.