Dual Regulation of T Cell Receptor-mediated Signaling by Oncogenic Cbl Mutant 70Z*
- From the Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
Abstract
We previously showed that an oncogenic Cbl mutant (70Z) is constitutively active in transcriptional activation of nuclear factor at activated T cells (NFAT). However, the mechanism underlying this effect remains unclear. Here we analyzed the effects of 70Z mutations at an amino-terminal loss of function site (Gly-306) and at carboxyl-terminal potential tyrosine or serine phosphorylation sites on association with signaling proteins and on NFAT activation. Mutation at Gly-306 of 70Z disrupted its association with Zap-70 and almost completely abolished its ability to induce NFAT activation under basal and ionomycin-stimulated conditions. However, mutations at potential tyrosine or serine phosphorylation sites had little effect. In fact, expression of 70Z with Tyr-700, Tyr-731, or Tyr-774 mutated to Phe increased NFAT activity in comparison with unmutated 70Z. These findings suggest that an amino terminus-mediated interaction of 70Z with Zap-70 plays a positive role and that a carboxyl terminus-mediated, phosphotyrosine-dependent interaction with their binding proteins plays a negative role in 70Z-mediated NFAT activation. In support of this notion are the observations that 70Z reduced T cell receptor-induced NFAT activation and that wild-type Cbl further inhibited this event, suggesting that both 70Z and wild-type Cbl employ a similar mechanism by which Cbl proteins dually regulate T cell receptor-mediated signaling.
Footnotes
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↵* This work was supported by Grant CA35299 from the United States Department of Health and Human Services (to A. A.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed: Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 10355 Science Center Dr., San Diego, CA 92121. Tel.: 619-678-4604; Fax: 619-558-3500; E-mail: yuncail{at}liai.org.
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↵2 Z. Zhang, C. Elly, A. Altman, and Y.-C. Liu, unpublished data.
- Abbreviations:
- TCR
-
T cell antigen receptor
- PI3-K
-
phosphatidylinositol 3-kinase
- PTK
-
protein tyrosine kinase
- Tyr(P)
-
phosphotyrosine
- PTB
-
phosphotyrosine binding
- NFAT
-
nuclear factor at activated T cells
- EGF
-
epidermal growth factor
- PDGF
-
platelet-derived growth factor
- HA
-
hemagglutinin
-
- Received August 5, 1998.
- Revision received November 12, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
