Tumor necrosis factor (TNF)-induced protein phosphorylation in a human
rhabdomyosarcoma cell line is mediated by 60-kD TNF receptors (TR60)
A Mire-Sluis and A Meager
Division of Immunobiology, National Institute for Biological Standards and
Control, Potters Bar, Herts, UK.
In the present study, we used a cloned derivative, KYM-1D4, of the human
rhabdomyosarcoma cell line, KYM-1, known to express high numbers of the two
tumor necrosis factor (TNF) receptors, TR60 and TR80, and to be highly
sensitive to TNF alpha-mediated cytotoxicity/antiproliferation, to
investigate the role of TR60 and TR80 in protein phosphorylation. Using
permeabilized KYM-1D4 cells, it was found that TNF alpha strongly induced
phosphorylation of proteins of molecular weight 80, 65, 58, 42, and 30 kD.
Addition of a monoclonal antibody (MoAb) against TR60 was shown to induce
cytotoxicity/antiproliferation in KYM-1D4 cells and the same pattern of
protein phosphorylation as TNF alpha, whereas addition of an MoAb against
TR80 was both noncytotoxic and ineffective in inducing protein
phosphorylation. In contrast, in a highly TNF alpha-resistant KYM-1-
derived cell line, 37B8R, no protein phosphorylation was induced with
either TNF alpha or the agonistic anti-TR60 MoAb. However, when 37B8R was
allowed to revert to partial TNF sensitivity by culture in the absence of
TNF alpha, the resultant cell line, 37B8S, was found to regain inducibility
of protein phosphorylation by TNF alpha. These results indicate that
expression of functional TR60 in KYM-1-related cell lines is principally
involved in TNF-mediated cytotoxicity/antiproliferation and is necessary
for the induction of protein phosphorylation. Nevertheless, the latter,
although apparently strongly associated with cytotoxicity, was probably
involved in protective mechanisms because protein kinase C inhibitors that
inhibited TNF alpha and anti-TR60-induced phosphorylation increased the
cytotoxic/antiproliferative response to these mediators.
Volume 83,
Issue 8,
pp. 2211-2220,
04/15/1994
Copyright © 1994 by The American Society of Hematology
