The Nerve Growth Factor Receptor on PC 12 Cells: Interconversion Between Two Forms with Different Binding Properties

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Abstract
PC12 cells [rat pheochromocytoma] possess 2 classes of nerve growth factor (NGF) receptors on their surfaces which can be distinguished by kinetic criteria. The majority class binds and releases 125I-NGF at a relatively rapid rate and has been called fast. The 2nd class of receptors has been called slow because of relatively slower rates of binding and release of 125I-NGF and also may be distinguished from fast receptors by their cytoskeletal association and resistance to trypsin. PC12 cell plasma membranes were prepared and shown to have only the fast class of receptors. These membranes were fused to receptorless 3T3 cells with polyethylene glycol. The resultant fused cells were shown to possess NGF receptors, essentially all of which behave like slow receptors. Immunofluorescence microscopy was used to monitor the introduction of PC12 cell membrane and NGF receptors into 3T3 cells. Results obtained with Clo-2, a monoclonal antibody specific for a major PC12 cell-surface antigen, show that up to 90% of 3T3 cells receive PC12 membrane becomes integrally incorporated into the 3T3 cell plasma membrane. Evidently, an association of receptors with cytoskeleton may be involved in the conversion of fast to slow receptor behavior, and the differing proportion of fast and slow receptor behavior, and the differing proportion of fast and slow NGF receptors in PC12 and 3T3 cells reflects the differing cytoskeletal organization of these cells.