LMP1 transmembrane domain 1 and 2 (TM1-2) FWLY mediates intermolecular interactions with TM3-6 to activate NF-κB

The Epstein-Barr virus oncoprotein LMP1 has six transmembrane domains (TMs) that enable intermolecular aggregation and constitutive signaling through two C-terminal cytosolic domains. Expression of both TMs 1 and 2 without the C terminus (TM1-2 Delta C) and TMs 3 to 6 fused to the C terminus (TM3-6) results in partial association, which is substantially decreased by TM1 F38WLY41 mutation to A(38)ALA(41). We now investigate whether TM1-2 Delta C can functionally interact with TM3-6. TMI-2 Delta C induced TM3-6 to mediate NF-kappa B activation at 59% of LMP1 levels, and the effect was dependent on TMI-2 F38WLY41. TMI-2 Delta C even induced TM3-4 C terminus-mediated NF-kappa B activation to 44% of LMP1 levels. Surprisingly, this effect was TM1 F38WLY41 independent, indicative of a role for TMs 5 and 6 in TM1 F38WLY41 effects. TM3 W-98 was also important for TM1-2 Delta C induction of TM3-6-mediated NF-kappa B activation, for association, and for TM1 F38WLY41 dependence on C-terminal NF-kappa B activation. These data support models in which the TM1 F38WLY41 effects are at least partially dependent on TM3 W-98 and a residue(s) in TMs 5 and 6.