Type II tumour necrosis factor-alpha receptor (TNFR2) activates c-Jun N-terminal kinase (JNK) but not mitogen-activated protein kinase (MAPK) or p38 MAR pathways

The pleitropic actions of tumour necrosis factor-a (TNF) are transmitted by the type 1 55 kDa TNF receptor (TNFR1) and type II 75 kDa TNF receptor (TN FR2), but the signalling mechanisms elicited by these two receptors are not fully understood. In the present study, we report for the first time subty pe-specific differential kinase activation in cell models that respond to T NF by undergoing apoptotic cell death. KYM-1 human rhabdomyosarcoma cells a nd HeLa human cervical epithelial cells, engineered to overexpress TNFR2, d isplayed c-Jun N-terminal kinase (JNK) activation by wild-type TNF, a TNFR1 -specific TNF mutant and a TNFR2-specific mutant TNF in combination with an agonistic TNFR2-specific monoclonal antiserum. A combination of the TNFR2- specific mutant and agonistic antiserum elicited maximal endogenous or exog enous TNFR2 responsiveness. Moreover, alternative expression of a TNFR2 del etion mutant lacking its cytoplasmic domain rendered the cells unable to ac tivate JNK activity through this receptor subtype. The profile of JNK activ ation by TNFR1 was more transient than that of TNFR2, with TNFR2-induced JN K activity also being more sensitive to the caspase inhibitor, benzyloxycar bonyl-Val-Ala-DL-Asp-fluoromethylketone. Conversely, only activation of the TNFR1 could stimulate mitogen-activated protein kinase (MA-PK) or p38 MAPK activities in a time-dependent manner. The role of TNFR2 activation in enh anced apoptotic cell death was confirmed with agonistic monoclonal antisera in cells expressing high levels of TNFR2. Activation of TNFR2 alone elicit ed cell death, but full TNF-induced death required stimulation of both rece ptor types. These findings indicate that efficient activation of TNFR2 by s oluble TNFs is achievable with co-stimulation by antisera, and that both re ceptors differentially modulate extracellular signal-regulated kinases cont ributing to the cytokine's cytotoxic response.