Evidence of LMP1-TRAF3 interactions in glycosphingolipid-rich complexes oflymphoblastoid and nasopharyngeal carcinoma cells

Latent membrane protein I (LMPI) is an Epstein-Barr virus (EBV) protein exp ressed in EBV-transformed B lymphocytes and in approximately 50% of nasopha ryngeal carcinomas (NPCs). LMP I signaling involves several cellular signal ing intermediates, especially TNF receptor-associated factors (TRAFs). We h ave shown previously that LMPI is highly concentrated in a cell fraction ca lled glycosphingolipid-rich membrane complexes (GSL complexes). We report h ere that parallel accumulation of LMPI and TRAF3, but not TRAF1 or TRADD, w as observed in GSL complexes from lymphoblastoid and LMPI-positive NPC cell s. In contrast, TRAF3 was not concentrated in GSL complexes from LMPI-negat ive cells. Binding of LMPI and TRAF3 in GSL complexes was demonstrated in l ymphoblastoid and NPC cells, by co-immunoprecipitation with both anti-LMPI and anti-TRAF3 antibodies. (C) 1999 Wiley-Liss, Inc.