Nerve growth factor receptors: identification of distinct classes in plasma membranes and nuclei of embryonic dorsal root neurons.

Two classes of receptors for 125I-labeled nerve growth factor in chick embryonic dorsal root neurons have been observed. One type is associated with the plasma membrane (or microsomal fraction) and can be completely solubilized by Triton X-100. These receptors display the nonsaturable binding isotherms and curvilinear Scatchard plots previously reported for nerve growth factor receptors in whole cells. The second class of binding sites is located in the nucleus, firmly bound to chromatin. These receptors are not solubilized by detergent, show saturable binding, and yield linear Scatchard plots of the type associated with a single class of binding sites of high affinity. The presence of the two receptor types suggests a bimodal mechanism of action for nerve growth factor.