Intracellular localization of nerve growth factor in PC12 cells. An immuno-gold electron microscopic approach

Nerve growth factor (NGF) localization in the clonal cell line PC12 has been assessed with the immunocytochemical colloidal gold staining (IGS) method. Three distinct fixation and staining procedures have been adopted to avoid possible artifactual localizations and to better assess NGF intracellular targets. Colloidal gold particles are observed in the cytoplasm and also within the nuclear compartment, close to the nuclear envelope. Gold particles are also detectable, in aggregates or patches, in proximity of or in association with, cytoskeletal elements tentatively identified with microfilaments (MF) present in the growth cone and microtubules (MT) running in parallel within the neurites or present in the perikaryon. Neurofilaments (NF), on the contrary, were devoid of any NGF-antibody cross-reacting material detectable with colloidal gold staining. It is postulated that the association of NGF or NGF-receptor complexes with cytoskeletal elements is instrumental for the mechanism of action of NGF.