Journal
JOURNAL OF VIROLOGY
Volume 77, Issue 6, Pages 3749-3758Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/JVI.77.6.3749-3758.2003
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Funding
- NCI NIH HHS [CA-64610] Funding Source: Medline
- NIAID NIH HHS [AI-01537] Funding Source: Medline
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The latent membrane protein 1 (LMP-1) oncoprotein of Epstein-Barr virus (EBV) is a constitutively active, CD40-like cell surface signaling protein essential for EBV-mediated human B-cell immortalization. Like ligand-activated CD40, LMP-1 activates NF-kappaB and Jun kinase signaling pathways via binding, as a constitutive oligomer, to tumor necrosis factor receptor-associated factors (TRAFs). LMP-1's lipid raft association and oligomerization have been linked to its activation of cell signaling pathways. Both oligomerization and lipid raft association require the function of LMP-1's polytopic multispanning transmembrane domain, a domain that is indispensable for LMP-1's growth-regulatory signaling activities. We have begun to address the sequence requirements of the polytopic hydrophobic transmembrane domain for LMP-1's signaling and biochemical activities. Here we report that transmembrane domains 1 and 2 are sufficient for LMP-1's lipid raft association and cytostatic activity. Transmembrane domains 1 and 2 support NF-kappaB activation, albeit less potently than does the entire polytopic transmembrane domain. Interestingly, LMP-1's first two transmembrane domains are not sufficient for oligomerization or TRAF binding. These results suggest that lipid raft association and oligomerization are mediated by distinct and separable activities of LMP-1's polytopic transmembrane domain. Additionally, lipid raft association, mediated by transmembrane domains 1 and 2, plays a significant role in LMP-1 activation, and LMP-1 can activate NF-kappaB via an oligomerization/TRAF binding-independent mechanism. To our knowledge, this is the first demonstration of an activity's being linked to individual membrane-spanning domains within LMP-1's polytopic transmembrane domain.
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