Altered thymic positive selection and intracellular signals in Cbl-deficient mice

Naramura, Mayumi; Kole, Hemanta K.; Hu, Ren-Ju; Gu, Hua

doi:10.1073/pnas.95.26.15547

Cited by 310 publications

(357 citation statements)

References 57 publications

(65 reference statements)

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“…Consistent with the negative regulation assigned to the Cbl family of proteins, T cells from c-Cbl À/À and Cbl-b À/À mice were hyperactive upon TCR engagement, although some biochemical distinctions between the phenotypes exist [21][22][23][24][25]. T cells from double-knockout mice lacking both c-Cbl and Cbl-b failed to modulate surface TCR after ligand engagement, resulting in sustained TCR signaling and ERK1/2 phosphorylation.…”

Section: Introductionmentioning

confidence: 83%

Reduced Cbl phosphorylation and degradation of the ζ‐chain of the T‐cell receptor/CD3 complex in T cells with low Lck levels

et al. 2008

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T cells with short interfering RNA-mediated Lck-knockdown (kd) display paradoxical hyper-responsiveness upon TCR ligation. We have previously reported a possible mechanism for T-cell activation in cells with low levels of Lck depending on Grb2-SOS1 recruitment to the zeta-chain of TCR/CD3 (Methi et al., Eur. J. Immunol. 2007, 37: 2539-2548. Here, we show that short interfering RNA-mediated targeting of Lck caused a dramatic reduction in c-Cbl phosphorylation and a general reduction in protein ubiquitination after TCR stimulation. Specifically, this resulted in reduced ubiquitination of the zeta-chain, yet internalization of TCR/CD3 appeared to be normal after receptor engagement. However, zeta-chain levels were elevated in Lck-kd cells, and confocal microscopy revealed reduced colocalization of CD3-containing vesicles with endosomal and lysosomal compartments.We hypothesize that prolonged stability of internalized T-cell receptor complex may result in extended signaling in T cells with low Lck levels. Key words: Cbl Á CD3 Á Lck Á T cells Á T-cell receptors IntroductionEngagement of the TCR leads not only to activation of T cells, but also to internalization and lysosomal degradation of the receptor complex [1]. The latter process serves to terminate signaling, and has been shown to be dependent on the tyrosine kinase activity of Lck [2,3] and ubiquitination by c-Cbl [4][5][6]. The E3 ubiquitin ligase c-Cbl functions as a negative regulator of many signaling pathways and ubiquitination marks active enzymes and receptors for degradation [reviewed in 7 and 8]. Notable targets for c-Cbl-mediated ubiquitination are Lck [9], Vav [10], Fyn [11][12][13], , as well as the already mentioned TCR/ CD3-complex. c-Cbl itself is activated by tyrosine phosphorylation on several residues, most importantly Y700, Y731 and Y774 [13,[15][16][17]. These residues are not, however, substrates of Lck or but of Fyn and Syk [13,16,18,19], which are activated directly or indirectly by Lck [20].Cbl exists in two main isoforms, c-Cbl and Cbl-b, with a high level of sequence conservation. Consistent with the negative regulation assigned to the Cbl family of proteins, T cells from c-Cbl À/À and Cbl-b À/À mice were hyperactive upon TCR engagement, although some biochemical distinctions between the phenotypes exist [21][22][23][24][25]. T cells from double-knockout mice lacking both c-Cbl and Cbl-b failed to modulate surface TCR after ligand engagement, resulting in sustained TCR signaling and ERK1/2 phosphorylation. However, signaling through the major TCR pathways were not increased [26]. These observations are comparable to what we found in T cells with low levels of Lck, which also display prolonged ERK1/2 activation while expression levels of other proteins (Fyn, Csk, PKCa, PLCg1, LAT, FAK, and Pyk2) remained unaffected [27,28]. We therefore investigated the impact of short interfering RNA (siRNA)-mediated Lck-knockdown (kd) on c-Cbl activity and TCR/CD3 turnover in T cells. As expected, c-Cbl phosphorylation and ubiquitination of the z-c...

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Section: Introductionmentioning

confidence: 83%

Reduced Cbl phosphorylation and degradation of the ζ‐chain of the T‐cell receptor/CD3 complex in T cells with low Lck levels

et al. 2008

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“…The SLAP-deficient, c-Cbl-deficient, and SLAP c-Cbl doubly deficient mice have been described previously (8,14,16). The mice were backcrossed to C57BL/6 (B6) for at least five generations.…”

Section: Methodsmentioning

confidence: 99%

“…Interestingly, mice deficient in c-Cbl, SLAP, or both have similar thymic phenotypes, suggesting that SLAP and c-Cbl may function in the same biochemical pathway (14)(15)(16). Mice deficient in c-Cbl have alterations in B cell development with increased numbers of B1 B cells in the peritoneal cavity and increased immature B cell numbers in the spleen (17).…”

mentioning

confidence: 99%

Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner

Dragone

Myers

White

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…Though highly related, c-Cbl and Cbl-b appear to have overlapping yet distinct functions in TCR signaling. Although c-Cbl-deficient mice exhibit increased receptor expression and enhanced signaling in thymocytes (27,28), Cbl-b Ϫ/Ϫ results in primarily hyperactive and proliferative T and B cells in the periphery with little effect on thymocyte development (29,30). In more recent studies, Cbl-b is shown to play a critical role in the regulation of peripheral tolerance and anergy in T cells (31).…”

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confidence: 99%

A Novel E3 Ubiquitin Ligase TRAC-1 Positively Regulates T Cell Activation

Zhao

Pardo

et al. 2005

The Journal of Immunology

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TRAC-1 (T cell RING (really interesting new gene) protein identified in activation screen) is a novel E3 ubiquitin ligase identified from a retroviral vector-based T cell surface activation marker screen. The C-terminal truncated TRAC-1 specifically inhibited anti-TCR-mediated CD69 up-regulation in Jurkat cells, a human T leukemic cell line. In this study, we show that TRAC-1 is a RING finger ubiquitin E3 ligase with highest expression in lymphoid tissues. Point mutations that disrupt the Zn2+-chelating ability of its amino-terminal RING finger domain abolished TRAC-1’s ligase activity and the dominant inhibitory effect of C-terminal truncated TRAC-1 on TCR stimulation. The results of in vitro biochemical studies indicate that TRAC-1 can stimulate the formation of both K48- and K63-linked polyubiquitin chains and therefore could potentially activate both degradative and regulatory ubiquitin-dependent pathways. Antisense oligonucleotides to TRAC-1 specifically reduced TRAC-1 mRNA levels in Jurkat and primary T cells and inhibited their activation in response to TCR cross-linking. Collectively, these results indicate that the E3 ubiquitin ligase TRAC-1 functions as a positive regulator of T cell activation.

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Altered thymic positive selection and intracellular signals in Cbl-deficient mice

Cited by 310 publications

References 57 publications

Reduced Cbl phosphorylation and degradation of the ζ‐chain of the T‐cell receptor/CD3 complex in T cells with low Lck levels

Reduced Cbl phosphorylation and degradation of the ζ‐chain of the T‐cell receptor/CD3 complex in T cells with low Lck levels

Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner

A Novel E3 Ubiquitin Ligase TRAC-1 Positively Regulates T Cell Activation

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