Transient expression of full-length and truncated forms of the human nerve growth factor receptor

To facilitate the characterization of nerve growth factor (NGF) receptor and mutated forms of the receptor, we have set up a rapid, efficient transient expression system utilizing COS cells. The human NGF receptor is a 427 amino acid protein with a hydrophobic signal sequence, a 222 amino acid extracellular domain, a single transmembrane domain and a 155 amino acid intracellular domain. The NGF receptor and a truncated form lacking the cytoplasmic domain were expressed in a COS cell expression system. Both recombinant proteins were detected on the cell surface and at a perinuclear site. Specific binding of 125I-NGF to the recombinant proteins was detected by chemical cross-linking. The extracellular domain of the NGF receptor was also expressed in the same system and detected in the COS cell endoplasmic reticulum and in the culture supernatant. This recombinant protein also specifically binds NGF.