Epstein-Barr virus latent membrane protein-1 (LMP1) C-terminus activation region 2 (CTAR2) maps to the far C-terminus and requires oligomerisation for NF-κB activation

Abstract

The Epstein-Barr virus Latent Membrane Protein-1 (LMP1) has structural features and functions consistent with it being a constitutively active cell surface receptor. The known association of LMP1 with members of the TRAF family of proteins suggests that LMP1 transduces signals similarly to the Tumour Necrosis Factor Receptor (TNFR) family of cell surface receptors that signal by forming dimers or trimers in response to binding of extracellular ligands. However, interactions between LMP1 and the TRAFs have so far only been described for the C-terminal activation region 1 (CTAR1) of LMP1 and no direct interactions of the TRAFs with the second NF-kB activation domain (CTAR2) have been reported. We have now mapped the NF-kB activation domain of CTAR2 to a highly conserved stretch of 6 amino acids at the far C-terminus (codons 379 to 384 in B95.8 LMP1). In addition, we constructed chimeric receptor molecules which contain the ligand-binding extracellular domain and the transmembrane domain of rat CD2 fused to the C-terminus of LMP1 encoding the CTAR1 and/or the CTAR2 domain. Interestingly, the function of a chimera encoding CTAR2 alone, as well as the function of a chimera encoding both CTAR1 and CTAR2 was found to be inducible upon antibody-mediated crosslinking. These inducible chimeric proteins also allowed us to demonstrate that LMP1 mediated NF-kB activation is an immediate event following activation of LMP1.

Epstein–Barr virus encoded LMP1 downregulates TCL1 oncogene through miR-29b

“…The effector domains of LMP1 are located in the C-terminus activation region 1 (CTAR1) and CTAR2 of the protein (Floettmann and Rowe, 1997). To define the regions of LMP1 responsible for the negative regulation of TCL1 and positive regulation of miR29b, we used LMP1 mutants where point mutations have been introduced into the CTAR1 and CTAR2.…”

IRF7 activation by Epstein–Barr virus latent membrane protein 1 requires localization at activation sites and TRAF6, but not TRAF2 or TRAF3

“…Because LMP1 amino acids 379-381 are critical for IRF7 binding and activation, but are also essential for NF-B and JNK activations (10,12,31,32), assessment of the specific role of IRF7 binding in IRF7 activation required another approach. IRF7 amino acids 194-411 associated with LMP1 CTAR2 at least as strongly as IRF7, but lacks domains that are critical for transactivation, dimerization, and nuclear translocation (Fig.…”

The Viral Etiology of AIDS‐Associated Malignancies

“…LMP-1 acts as a constitutively active, receptor-like molecule that does not need the binding of a ligand (Gires et al, 1997). The six transmembrane domains mediate oligomerization of LMP-1 molecules in the plasma membrane, a prerequisite for LMP-1 function (Floettmann and Rowe, 1997;Gires et al, 1997). Two regions in the C-terminus of LMP-1 have been shown to initiate signaling processes, the C-terminal activator regions 1 (CTAR-1, amino acids 194-231) and 2 (CTAR-2, amino acids 332-386) (Huen et al, 1995;Mitchell and Sugden, 1995).…”

“…Moreover, LMP-1 can partially restore the wildtype phenotype of mice deficient in CD40 (Devergne et al, , 1998Miller et al, 1997Miller et al, , 1998Sandberg et al, 1997). LMP-1 also interacts with TNFR-associated death domain protein (TRADD) and receptor-interacting protein (RIP) at the C terminal (Devergne et al, 1998;Floettmann and Rowe, 1997;Izumi et al, , 1999Kaye et al, 1996). Interaction with these two molecules contributes the majority of the NF-κB activity induced by LMP-1.…”