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Journal of Virology, October 1998, p. 7796-7806, Vol. 72, No. 10
Department of Microbiology-Immunology,
Northwestern University Medical School, Chicago, Illinois
60611,1 and
GSF, Institut für
Immunologie, D-81377 München, Germany2
Received 7 May 1998/Accepted 23 June 1998
Latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) is
expressed on the plasma membrane of B lymphocytes latently infected
with EBV and blocks B-cell receptor (BCR) signal transduction in
EBV-immortalized B cells in vitro. The LMP2A amino-terminal domain that
is essential for the LMP2A-mediated block on BCR signal transduction
contains eight tyrosine residues. Association of Syk protein tyrosine
kinase (PTK) with LMP2A occurs at the two tyrosines of the LMP2A
immunoreceptor tyrosine-based activation motif, and it is hypothesized
that Lyn PTK associates with the YEEA amino acid motif at LMP2A
tyrosine 112 (Y112). To examine the specific association of Lyn PTK to
LMP2A, a panel of LMP2A cDNA expression vectors containing
LMP2A mutations were transfected into an EBV-negative B-cell line and
analyzed for Lyn and LMP2A coimmunoprecipitation. Lyn associates with
wild-type LMP2A and other LMP2A mutant constructs, but Lyn association
is lost in the LMP2A construct containing a tyrosine
(Y)-to-phenylalanine (F) mutation at LMP2A residue Y112 (LMP2AY112F).
Next, the LMP2AY112F mutation was recombined into the EBV genome
to generate stable lymphoblastoid cell lines (LCLs) transformed
with the LMP2AY112F mutant virus. Analysis of BCR-mediated signal
transduction in the LMP2AY112F LCLs revealed loss of the LMP2A-mediated
block in BCR signal transduction. In addition, LMP2A was not tyrosine phosphorylated in LMP2AY112F LCLs. Together these data
indicate the importance of the LMP2A Y112 residue in the ability of
LMP2A to block BCR-mediated signal transduction and place
the role of this residue and its interaction with Lyn PTK as essential
to LMP2A phosphorylation, PTK loading, and down-modulation of PTKs involved in BCR-mediated signal transduction.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Tyrosine 112 of Latent Membrane Protein 2A Is
Essential for Protein Tyrosine Kinase Loading and Regulation of
Epstein-Barr Virus Latency
*
Corresponding author. Mailing address: Department of
Microbiology-Immunology, Northwestern University Medical School, 303 E. Chicago Ave., Chicago, IL 60611. Phone: (312) 503-0467. Fax: (312)
503-1339. E-mail: r-longnecker{at}nwu.edu.
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