Transcriptional networks of knockout cell lines identify functional specificities of H-Ras and N-Ras: significant involvement of N-Ras in biotic and defense responses

Castellano, Esther; Rivas, Javier De Las; Guerrero, Carmen; Santos, Eugenio

doi:10.1038/sj.onc.1209845

Cited by 32 publications

(62 citation statements)

References 58 publications

(69 reference statements)

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“…In conclusion, the identification of specific and overlapping functions of Ras isoforms, 49 as shown here for H-ras and N-ras in T cells, may have important implications not only for understanding the molecular mechanisms that regulate T-cell differentiation BLOOD, 12 MAY 2011 ⅐ VOLUME 117, NUMBER 19 For personal use only. on May 12, 2018.…”

Section: Discussionmentioning

confidence: 74%

H-ras and N-ras are dispensable for T-cell development and activation but critical for protective Th1 immunity

Iborra

Soto

Aroeira

et al. 2011

Blood

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The small guanine nucleotide binding proteins of the Ras family, including in mammals the highly homologous H-ras, N-ras, and K-ras isoforms, are rapidly activated on ligation of the T-cell antigen receptor (TCR), but whether each isoform plays specific roles in T cells is largely unknown. Here, we show, with the use of mice specifically lacking Hras or N-ras, that these isoforms are dispensable for thymocyte development and mature T-cell activation. By contrast, CD4 ؉ T cells from Ras-deficient mice exhibited markedly decreased production of the Th1 signature cytokine IFN-␥ early after TCR stimulation, concomitantly with impaired induction of the Th1-specific transcription factor T-bet. Accordingly, Ras-deficient mice failed to mount a protective Th1 response in vivo against the intracellular parasite Leishmania major, although they could be rendered resistant to infection if a Th1-biased milieu was provided during parasite challenge. Collectively, our data indicate that the TCR recruits distinct Ras isoforms for signal transduction in developing and mature T cells, thus providing a mechanism for differential signaling from the same surface receptor. IntroductionT cells differentiate in the thymus from CD4 ϩ CD8 ϩ precursors. In the peripheral lymphoid organs, mature CD4 ϩ T cells undergo further differentiation and become T helper effectors which mediate, among others, Th1 and Th2 immune responses controlling intracellular and extracellular pathogen infections, respectively, allergy, and autoimmunity. 1,2 Both differentiation processes are initiated by signals emanating from the TCR. However, the signaling pathways differentially triggered by the TCR during thymic and peripheral differentiation of T cells are not fully understood.The small guanine nucleotide binding proteins of the Ras family, 3 encompassing in mammals the highly homologous H-ras, N-ras, and K-ras (4A and 4B splice variants) isoforms, are rapidly activated after TCR engagement. [4][5][6] Each of the 3 mammalian Ras genes encodes a membrane-associated 21-kDa protein that acts as a molecular switch to convey extracellularly derived signals into the cell interior. Ras proteins cycle between an inactive GDP-bound state and an active GTP-bound state, because of the concerted action of guanine nucleotide exchange factors (GEFs) and GTPaseactivating proteins. 7 GEFs catalyze the release of GDP, allowing binding of the more abundant GTP and inducing a conformational change in the proteins that allow them to interact with their downstream effectors. GTPase-activating proteins, however, stimulate the intrinsic GTPase activity of Ras proteins and therefore catalyze their inactivation.The best-characterized Ras effectors are the Raf kinases, through which Ras activates the MAPK cascade, the PI3Ks, and a family of Ral GEFs. 7 Although Ras proteins are ubiquitously expressed, differences in their expression in various tissues and during development, 3 along with a distinct subcellular distribution and recruitment of downstream effectors, 8 suggest that eac...

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Section: Discussionmentioning

confidence: 74%

H-ras and N-ras are dispensable for T-cell development and activation but critical for protective Th1 immunity

Iborra

Soto

Aroeira

et al. 2011

Blood

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“…Our observations also indicate that knockdown of N-Ras during differentiation induces significantly higher levels of apoptosis. Consistently, N-Ras can protect cells against apoptosis by increasing the ratio of anti-apoptotic molecules Bcl-2 or Bcl-xL to pro-apoptotic molecules Bad or Bax via changes to basal Akt activity and pBad levels through PI3K [36,37]. Therefore, we think that N-Ras plays a distinct role in balancing cell survival and death via the N-Ras/PI3K/ Akt pathway throughout muscle differentiation.…”

Section: Discussionmentioning

confidence: 77%

Proto-oncogenic H-Ras, K-Ras, and N-Ras are involved in muscle differentiation via phosphatidylinositol 3-kinase

et al. 2010

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Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras (c-Ras) in muscle differentiation remains unclear. The active GTP-bound form of Ras has been known to associate with diverse effectors including Raf, phosphatidylinositol 3-kinase (PI3K), Ral-GDS, and other molecules to transmit downstream signals. We hypothesize that c-Ras may stimulate muscle differentiation by selectively activating PI3K, an important mediator for muscle differentiation. In our experiments, inhibition of c-Ras by farnesyltransferase inhibitors and a dominant negative form of H-Ras (Ras S17N) suppressed muscle differentiation. Consistently, individual knockdown of H-Ras, K-Ras, and N-Ras by siRNAs all blocked muscle differentiation. Interestingly, we found that c-Ras preferentially interacts with PI3K rather than its major binding partner c-Raf, during myogenic differentiation, with total c-Ras activity remaining unchanged. PI3K and its downstream myogenic pathway, the Nox2/NF-κB/inducible nitric oxide synthase (iNOS) pathway, were found to be suppressed by inhibition of c-Ras activity during differentiation. Furthermore, expression of a constitutively active form of PI3K completely rescued the differentiation block and reactivated the Nox2/NF-κB/iNOS pathway in c-Ras-inhibited cells. On the basis of our results, we conclude that contrary to oncogenic Ras, proto-oncogenic H-Ras, K-Ras, and N-Ras are directly involved in the promotion of muscle differentiation via PI3K and its downstream signaling pathways. In addition, PI3K pathway activation is associated with a concurrent suppression of the otherwise predominantly activated Raf/ Mek/Erk pathway.

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“…Given the lessons that have been learnt from analysis of oncogenic Ras in promoting tumourigenesis, it would seem to be vital that any comparison of differential Ras isoform signalling is conducted in cells expressing endogenous amounts of each isoform. To date, no genome-wide direct comparison of endogenous H-, K-and N-Ras regulation of gene expression has been conducted although a partial screen using MEFs from homozygous H-and N-Ras knockout mice has provided a promising starting point [41]. By comparing transcriptional profiles of the knockout cell lines with a wild type control, Castellano and colleagues identified only 12 genes differentially regulated in H-Ras knockouts.…”

Section: Introductionmentioning

confidence: 99%

Ras proteins: paradigms for compartmentalised and isoform-specific signalling

Omerovic

Laude

Prior

2007

Cell. Mol. Life Sci.

113

122

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Ras GTPases mediate a wide variety of cellular processes by converting a multitude of extracellular stimuli into specific biological responses including proliferation, differentiation and survival. In mammalian cells, three ras genes encode four Ras isoforms (H-Ras, K-Ras4A, KRas4B and N-Ras) that are highly homologous but functionally distinct. Differences between the isoforms, including their post-translational modifications and intracellular sorting, mean that Ras has emerged as an important model system of compartmentalised signalling and membrane biology. Ras isoforms in different subcellular locations are proposed to recruit distinct upstream and downstream accessory proteins and activate multiple signalling pathways. Here, we summarise data relating to isoform specific signalling, its role in disease and the mechanisms promoting compartmentalised signalling. Further understanding of this field will reveal the role of Ras signalling in development, cellular homeostasis and cancers and may suggest new therapeutic approaches.

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Transcriptional networks of knockout cell lines identify functional specificities of H-Ras and N-Ras: significant involvement of N-Ras in biotic and defense responses

Cited by 32 publications

References 58 publications

H-ras and N-ras are dispensable for T-cell development and activation but critical for protective Th1 immunity

H-ras and N-ras are dispensable for T-cell development and activation but critical for protective Th1 immunity

Proto-oncogenic H-Ras, K-Ras, and N-Ras are involved in muscle differentiation via phosphatidylinositol 3-kinase

Ras proteins: paradigms for compartmentalised and isoform-specific signalling

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