All three domains of the Epstein-Barr virus-encoded latent membrane protein LMP-1 are required for transformation of rat-1 fibroblasts

Abstract

LMP-1, the Epstein-Barr virus latent membrane protein 1, is the only protein encoded by the virus that has been shown to have the properties of a transforming oncogene in rodent fibroblasts such as Rat-1 cells. LMP-1 is phosphorylated and proteolytically cleaved in Rat-1 cells in a manner similar to that seen in human lymphocytes. In this study, we demonstrate that all three major domains of LMP-1 (N-terminal, transmembrane, and C-terminal domains) are required for the ability to transform Rat-i cells in culture, as assayed by loss of contact inhibition. This study is the first demonstration of a functional role for the C-terminal domain of LMP-1. Our analysis suggests that there are at least three distinct regions of the C terminus involved in signalling. Amino acids 306 to 334, which generate a toxic signal in the absence of amino acids 334 to 364, and the last 23 amino acids, 364 to 386, are essential for transformation. Biochemical analysis of the LMP-1 mutants with the three domains deleted indicate that the mutant N-terminal with the domain deleted is phosphorylated normally but is inefficiently cleaved compared with the wild-type LMP-1. The mutant with the transmembrane domain deleted is also phosphorylated but is not cleaved, showing that phosphorylation of LMP-1 does not require membrane association. The nontransforming mutant with the C-terminal domain deleted that lacks the last 23 amino acids is phosphorylated and cleaved. Therefore, these processing events alone are insufficient to generate a transforming signal.

Characterization of Epstein–Barr virus (EBV)-infected natural killer (NK) cell proliferation in patients with severe mosquito allergy; establishment of an IL-2-dependent NK-like cell line

“…Expression of LMP1 in B cells provokes many of the phenotypic changes characteristic of B cell immortalization [29]. LMP1 can also induce cellular changes in cell types other than B cells [30,31]. Although most of the changes induced by EBV infection in the NK cell environment remain to be determined, we demonstrated that induction of IL-2Ra expression by IL-2 is augmented in EBV-infected NK cells.…”

Epstein-Barr virus latent membrane protein (LMP1) is not sufficient to maintain proliferation of B cells but both it and activated CD40 can prolong their survival.

“…LMP1 acts as an oncogene in established rodent cells (Wang,D. et al, 1985;Baichwal and Sugden, 1988;Moorthy and Thorley-Lawson, 1993) and blocks differentiation in epithelial cells (Dawson et al, 1990;Fahraeus et al, 1990b;Wilson et al, 1990). In Burkitt's lymphoma cell lines LMP1 induces the expression of B cell activation markers CD23 and CD40 and cell adhesion molecules ICAM1, LFA1 and LFA3 and stimulates NF-iB activity (Wang,F.…”

Latent membrane protein 1of Epstein-Barr virus interacts with JAK3 and activates STAT proteins

“…Nine viral proteins are expressed in established lymphoblastoid cell lines, five of which appear to be absolutely required for B cell immortalization: EBNA1, 2, 3a, 3c and LMP1 (Hammerschmidt and Sugden, 1989;Cohen et al, 1991;Kaye et al, 1993;Tomkinson et al, 1993;Kilger et al, 1998). Latent membrane protein 1 (LMP1) is the only EBV protein which has a transforming potential in established rodent cell lines (Wang et al, 1985;Baichwal and Sugden, 1988;Moorthy and Thorley-Lawson, 1993). Interestingly, LMP1 induces the expression of the B cell activation markers CD23 and CD40, cell adhesion molecules ICAM1, LAF1 and LFA3 (Wang et al, 1990), and the epithelial growth factor receptor (Miller et al, 1997).…”