Apoptosis-inducing Agents Cause Rapid Shedding of Tumor Necrosis Factor Receptor 1 (TNFR1)

doi:10.1074/jbc.274.19.13643

Apoptosis-inducing Agents Cause Rapid Shedding of Tumor Necrosis Factor Receptor 1 (TNFR1)

A NONPHARMACOLOGICAL EXPLANATION FOR INHIBITION OF TNF-MEDIATED ACTIVATION*

From the Molecular Cardiobiology Program, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536-0812

Abstract

Several chemical compounds not known to interact with tumor necrosis factor (TNF) signal transducing proteins inhibit TNF-mediated activation of vascular endothelial cells (EC). Four structurally diverse agents, arachidonyl trifluoromethylketone, staurosporine, sodium salicylate, and C₆-ceramide, were studied. All four agents caused EC apoptosis at concentrations that inhibited TNF-induced IκBα degradation. However, evidence of apoptosis was not evident until after several (e.g. 3–12) hours of treatment, whereas 2 h of treatment was sufficient to inhibit TNF responses. IL-1-induced IκBα degradation was unaffected by these treatments. Inhibition of TNF signaling could not be prevented with either of the broad spectrum caspase inhibitors zVADfmk or yVADcmk. The inhibition of p38 kinase with SB203580 prevented the inhibition of TNF signaling by all agents except arachidonyl trifluoromethylketone. No changes in the levels or molecular weights of the adaptor proteins TRADD (TNF receptor-associated death domain), RIP (receptor-interacting protein), or TRAF2 (TNF receptor-associated factor-2) were caused by apoptogenic drugs. However, TNF receptor 1 (TNFR1) surface expression was significantly reduced by all four agents. Furthermore, TNF-dependent recruitment of TRADD to surface TNFR1 was also inhibited. These data suggest that several putative inhibitors of TNF signaling work by triggering apoptosis and that an early event coincident with the initiation of apoptosis, preceding evidence of injury, is loss of TNFR1. Consistent with this hypothesis, cotreatment of EC with the metalloproteinase inhibitor Tapi (TNF-α proteinase inhibitor) blocked the reduction in surface TNFR1 by apoptogenic drugs and prevented inhibition of TNF-induced IκBα degradation without blocking apoptosis. TNFR1 loss could be a mechanism to limit inflammation in response to apoptotic cell death.

Footnotes

↵* This work was supported by grants from the National Institutes of Health (HL-36007) and ISIS Pharmaceuticals.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed. Tel.: 203-737-2292; Fax: 203-737-2293; E-mail: Jordan.Pober{at}yale.edu.
Abbreviations:

TNF

tumor necrosis factor

AP-1

activator protein-1

ATK

arachidonyl trifluoromethylketone

EC

endothelial cell(s)

FACS

fluorescence-activated cell sorter

mAb

monoclonal antibody

ICAM-1

intercellular adhesion molecule-1

IL-1

interleukin-1

M199

medium 199

NFκB

nuclear factor κB

IκBα

inhibitor of NFκBα

PARP

poly(ADP-ribose) polymerase

PBS

phosphate-buffered saline

RIP

receptor-interacting protein

stauro

staurosporine

Tapi

TNF-α proteinase inhibitor

TNFR1 and TNFR2

TNF receptor 1 and 2, respectively

TRADD

TNF receptor 1-associated death domain protein

TRAF

TNF receptor-associated factor

VCAM-1

vascular cell adhesion molecule-1
- Received September 28, 1998.
- Revision received February 18, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.