Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635957
Title: The role of tumour necrosis factor α receptor subtypes in mediating cytosolic phospholipase A2 activation
Author: Jupp, Orla J.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
Abstract:
The TF-1 human erythroleukemic cell line exhibits opposing physiological responses towards tumour necrosis factor-alpha (TNF-alpha) treatment, dependent upon the mitotic state of the cells. Mitotically active cells respond to TNF-alpha by rapidly undergoing apoptosis whereas TNF-alpha exposure stimulates cellular proliferation in mitotically quiescent cells. These intracellular functions of TNF-alpha are transmitted by the type I (TNFR l) and type II (TNFR 2) receptors, but the signalling mechanisms elicited by these two receptors are not fully understood. We show that the expression levels of TNFR2 vary during the TF-1 cell cycle. Furthermore, studies utilising TNF-alpha receptor subtype-specific TNF-alpha mutants implicated the TNFR2 in apoptotic signalling. These data show a bifunctional physiological role for TNF-alpha in TF-1 cells that is dependent on mitotic activity and controlled by the TNFR2. To examine the role of endogenous TNFR2 in mediating TNF-induced signalling, we used KYM-1 human rhabdomyosarcoma cells, which express high levels of the TNFR2 and TNFR l. We also used HeLa human cervical epithelial cells (which express mainly TNFR l) that had been transfected with TNFR2 cDNA and thus engineered to express higher numbers of receptors than KYM-1 cells. The role of TNFR2 activation in enhanced apoptotic cell death was confirmed in these cells expressing high levels of TNFR2. It is reported here that subtype-specific differential kinase activation and cPLA 2 activation is seen in these cell models. KYM-1 and HeLa clones displayed c-Jun N-terminal kinase (JNK) activation by wild-type TNF, TNFRl-specific mutant and TNFR2-specific mutant in combination with TNFR2-specific agonistic monoclonal antisera. Moreover, alternative expression of a TNFR2 deletion mutant lacking its cytoplasmic domain rendered the cells unable to activate .INK activity through this receptor isotype. Conversely, only activation of the TNFRl could stimulate mitogen-activated protein kinase (MAPK) or p38 MAPK activities in a time-dependent manner. In addition to kinase activation cPLA2 activity (previously thought to be mediated solely by TNFRl) was also found to increase in a receptor subtype-specific manner. The TNFRl was shown to lead to the phosphorylation and activation of CPLA2, whilst the TNFR2 was implicated in translocation of cPLAi to perinuclear regions. These findings indicate that both receptors differentially modulate extracellular signal-regulated kinases and CPLA2 and that these enzymes contribute to the TNFs cytotoxic response.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.635957  DOI: Not available
Share: