Interaction of nerve growth factor with pheochromocytoma cells. Evidence for tight binding and sequestration

When the rat pheochromocytoma clonal cell line PC 12 is incubated with nerve growth factor a portion of the bound ligand does not dissociate from the cells in a medium free of nerve growth factor. This fraction is defined as tightly bound nerve growth factor and is further separable into trypsin sensitive and trypsin resistant compartments.These findings suggest that a series of events occur in which nerve growth factor is bound, sequestered and then taken into the cell. The tight binding of nerve growth factor is linearly dependent on cell density, raising the possibility of its participation in the increase in cell-to-cell and cell-to-substrate adhesivity that is mediated by nerve growth factor.