A high molecular weight component of the human tumor necrosis factor receptor is associated with cytotoxicity

Abstract

We compared the molecular structure of the receptor to human recombinant tumor necrosis factor (HurTNF) on cells of different tissue origin that differ in their response to one of the known activities of TNF. We studied (i) tumor cell lines that respond to the cytotoxic action of TNF and resistant variants that bind TNF, (ii) normal cell lines that are stimulated to proliferate by TNF and those that are not affected by TNF, and (iii) peripheral blood granulocytes whose activation is also augmented by TNF. Using 125I-labeled HurTNF, we found that it bound mainly to four cellular polypeptides (138, 90, 75, and 54 kDa), three of which were found in every cell type examined and one (138 kDa) that was observed only in a human breast carcinoma cell line (MCF-7) that is highly responsive to the cytotoxic action of TNF. The 138-kDa polypeptide was not found in resistant variants of MCF-7 that bind TNF. In contrast to the other polypeptides, the 138-kDa protein was detected 30 min after incubation at 4°C, as compared to 5 min. Scatchard analysis and cross-linking data suggest a model for the TNF receptor structure whereby the receptor is composed of noncovalently linked membrane-bound polypeptides that bind TNF with high affinity (K(d), 0.05-0.8 x 10-9 M) with the 138-kDa protein being the least abundant and/or even absent in most cells.