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Molecular and Cellular Biology, December 2000, p. 9149-9161, Vol. 20, No. 24
Department of Pharmacology and Cancer
Biology, Duke University Medical Center, Durham, North Carolina
277101; Wellcome/CRC Institute,
University of Cambridge, Cambridge, United
Kingdom2; and Department of Immunology,
Mayo Clinic, Rochester, Minnesota 559053
Received 17 July 2000/Returned for modification 15 August
2000/Accepted 26 September 2000
Phospholipase C-
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Pleiotropic Contributions of Phospholipase C-
1
(PLC-
1) to T-Cell Antigen Receptor-Mediated Signaling:
Reconstitution Studies of a PLC-
1-Deficient Jurkat T-Cell
Line
1 (PLC-
1) plays a crucial role in the
coupling of T-cell antigen receptor (TCR) ligation to interleukin-2 (IL-2) gene expression in activated T lymphocytes. In this study, we
have isolated and characterized two novel, PLC-
1-deficient sublines
derived from the Jurkat T-leukemic cell line. The P98 subline displays
a >90% reduction in PLC-
1 expression, while the J.gamma1 subline
contains no detectable PLC-
1 protein. The lack of PLC-
1
expression in J.gamma1 cells caused profound defects in TCR-dependent
Ca2+ mobilization and NFAT activation. In contrast, both of
these responses occurred at normal levels in PLC-
1-deficient P98
cells. Unexpectedly, the P98 cells displayed significant and selective defects in the activation of both the composite CD28 response element
(RE/AP) and the full-length IL-2 promoter following costimulation with
anti-TCR antibodies and phorbol ester. These transcriptional defects
were reversed by transfection of P98 cells with a wild-type PLC-
1
expression vector but not by expression of mutated PLC-
1 constructs
that lacked a functional, carboxyl-terminal SH2 [SH2(C)] domain or
the major Tyr783 phosphorylation site. On the other hand,
the amino-terminal SH2 [SH2(N)] domain was not essential for
reconstitution of RE/AP- or IL-2 promoter-dependent transcription but
was required for the association of PLC-
1 with LAT, as well as the
tyrosine phosphorylation of PLC-
1 itself, in activated P98 cells.
These studies demonstrate that the PLC-
1 SH2(N) and SH2(C) domains
play functionally distinct roles during TCR-mediated signaling and
identify a non-Ca2+-related signaling function linked to
the SH2(C) domain, which couples TCR plus phorbol ester-CD28
costimulation to the activation of the IL-2 promoter in T lymphocytes.
*
Corresponding author. Mailing address: Department of
Pharmacology and Cancer Biology, Room C333B LSRC, Box 3813, Duke
University Medical Center, Durham, NC 27710. Phone: (919) 613-8650. Fax: (919) 681-8461. E-mail: abrah008{at}mc.duke.edu.
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