From autoinhibition to inhibition in trans: the Raf-1 regulatory domain inhibits Rok-α kinase activity

Niault, Théodora; Sobczak, Izabela; Meissl, Katrin; Weitsman, Gregory; Piazzolla, Daniela; Maurer, Gabriele D.; Kern, Florian; Ehrenreiter, Karin; Hamerl, Matthias; Moarefi, Ismail; Leung, Thomas; Carugo, Oliviero; Ng, Tony; Baccarini, Manuela

doi:10.1083/jcb.200906178

Cited by 47 publications

(60 citation statements)

References 49 publications

(77 reference statements)

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“…These results show that C-Raf homodimer formation is not required for Roka binding or inhibition. They are in line with our previous data showing that C-Raf/Roka interaction is a nonkinase function of C-Raf mediated by the N-terminal regulatory domain of C-Raf (17,23,24) and further support the hypothesis that Ras þ Raf-inhibitor-induced tumors requires both Rafmediated ERK activation and a kinase-independent Roka inhibition by C-Raf.…”

Section: A B Csupporting

confidence: 81%

“…Inhibition is mediated by the physical interaction of the C-Raf regulatory domain with the Roka kinase domain (23). This interaction is not affected by Raf-inhibitor-induced Raf hetero-or A B C Figure 7.…”

Section: Discussionmentioning

confidence: 99%

“…Roka inhibition is a nonkinase function of C-Raf, which can be carried out both by a kinase-dead mutant (17) and by truncated C-Raf lacking the kinase domain (23,24). Inhibition is mediated by the physical interaction of the C-Raf regulatory domain with the Roka kinase domain (23).…”

Section: Discussionmentioning

confidence: 99%

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Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

et al. 2013

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RAF inhibitors achieve unprecedented but mainly transient clinical responses in patients with melanoma whose tumors harbor an activating BRAF mutation. One notable side-effect of RAF inhibitors is the stimulation of cutaneous skin tumors, arising in about 30% of patients receiving these drugs, which are thought to develop as a result of inhibitor-induced activation of wild-type Raf in occult precursor skin lesions. This effect raises the possibility that less manageable tumors might also arise in other epithelial tissues. Here we provide preclinical evidence supporting this disquieting hypothesis by showing that the RAF inhibitors PLX-4032 (vemurafenib) and GDC-0879 precipitate the development of cell-autonomous, Ras-driven tumors in skin and gastric epithelia. The magnitude of the effects correlated with the inhibitors' relative abilities to induce ERK activation. Epidermisrestricted ablation of either B-Raf or C-Raf prevented PLX-4032-induced ERK activation and tumorigenesis. In contrast, GDC-0879 induced ERK activation and tumorigenesis in B-Raf-deficient epidermis, whereas C-Raf ablation blocked GDC-0879-induced tumorigenesis (despite strong ERK activation) by preventing Rokamediated keratinocyte dedifferentiation. Thus, inhibitor-induced ERK activation did not require a specific Raf kinase. ERK activation was necessary, but not sufficient for Ras þ Raf inhibitor-induced tumorigenesis, whereas C-Raf downregulation of Roka was essential even in the face of sustained ERK signaling to prevent differentiation and promote tumorigenesis. Taken together, our findings suggest that combination therapies targeting ERKdependent and -independent functions of Raf may be more efficient but also safer for cancer treatment. Cancer Res; 73(23); 6926-37. Ó2013 AACR.

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Section: A B Csupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

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Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

et al. 2013

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“…7A,B). Craf is known to operate through a number of Mek/Erk-independent signaling pathways (Niault et al 2009), and conceivably, activation of these pathways may account for the unique sets of genes induced by…”

Section: L597vmentioning

confidence: 99%

The intermediate-activity^L597VBRAF mutant acts as an epistatic modifier of oncogenic RAS by enhancing signaling through the RAF/MEK/ERK pathway

et al. 2012

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L597V BRAF mutations are acquired somatically in human cancer samples and are frequently coincident with RAS mutations. Germline L597V BRAF mutations are also found in several autosomal dominant developmental conditions known as RASopathies, raising the important question of how the same mutation can contribute to both pathologies. Using a conditional knock-in mouse model, we show that endogenous expression of L597V Braf leads to approximately twofold elevated Braf kinase activity and weak activation of the Mek/Erk pathway. This is associated with induction of RASopathy hallmarks including cardiac abnormalities and facial dysmorphia but is not sufficient for tumor formation. We combined L597V Braf with G12D Kras and found that L597V Braf modified G12D Kras oncogenesis such that fibroblast transformation and lung tumor development were more reminiscent of that driven by the high-activity V600E Braf mutant. Mek/Erk activation levels were comparable with those driven by V600E Braf in the double-mutant cells, and the gene expression signature was more similar to that induced by V600E Braf than G12D Kras. However, unlike V600E Braf, Mek/Erk pathway activation was mediated by both Craf and Braf, and ATP-competitive RAF inhibitors induced paradoxical Mek/ Erk pathway activation. Our data show that weak activation of the Mek/Erk pathway underpins RASopathies, but in cancer, L597V Braf epistatically modifies the transforming effects of driver oncogenes.

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“…Ceux-ci présentent une particularité importante, à savoir leur indépendance vis-à-vis de l'activité kinase de C-RAF et, a fortiori, vis-à-vis de la cascade MEK-ERK. Ces effets anti-apoptotiques reposent sur la régulation négative par interaction physique de C-RAF avec plusieurs sérine/thréonine kinases qui exercent plus ou moins directement des effets pro-apoptotiques : les kinases MST2 (voir Glossaire) [21], ASK1 [22], ou ROK [23] (Figure 2). Dans ce dernier cas, l'inhibition en trans de ROK par C-RAF semble capable d'influencer la structure du cytosquelette d'actine et, indirectement, la signalisation par les récepteurs de mort cellulaire comme FAS [24].…”

Section: Effets Anti-apoptotiques Des Kinases Rafunclassified

Régulation de la survie cellulaire par les kinases de la famille RAF

Galmiche

Ezzoukhry

2010

Med Sci (Paris)

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Structure et régulation des kinases RAFL'activation des kinases RAF est un des paramètres biochimiques les plus fréquemment altérés dans les tumeurs humaines [1]. Du fait de leur rôle oncogénique, les kinases de la famille RAF 1 ont d'emblée attiré l'attention des biologistes intéressés par la transduction du signal et la physiologie des cellules cancéreuses. Chez les mammifères, la famille des kinases RAF est constituée de trois membres : A-RAF, B-RAF et C-RAF (anciennement Raf-1) [1]. Ces trois isoformes sont codées par des gènes distincts mais présentent d'importantes homologies de séquence (Figure 1). Elles partagent une organisation commune avec un domaine carboxy-terminal qui porte l'activité sérine/thréo-nine kinase, alors que le domaine amino-terminal est régulateur et possède la particularité essentielle d'interagir avec les protéines RAS activées. Le domaine amino-terminal concentre l'essentiel des différences de séquence entre les kinases RAF. Chez les vertébrés, les kinases RAF sont généralement exprimées dans tous les tissus, mais à des niveaux différents [1]. Les isoformes de RAF diffèrent entre elles en termes d'activité kinase. Toutes trois sont capables d'activer une unique cible, MEK1/2 (voir Glossaire), mais présentent d'importantes différences d'activité vis-à-vis de ce substrat [2][3][4][5][6]. Globalement, B-RAF est 1 Voir le glossaire. la kinase la plus active et constitue probablement le principal activateur physiologique de la cascade MEK-ERK. La distribution subcellulaire des isoformes est également différente, notamment au niveau des membranes cellulaires. Alors que C-RAF interagit avec la mitochondrie, A-RAF est présent au niveau endosomal, et B-RAF est cytosolique [7]. L'ensemble de ces particularités suggère que, au-delà de la capacité partagée à activer MEK, chaque isoforme est impliquée dans des régulations cellulaires spécifiques. L'interaction des GTPases RAS avec les kinases RAF est un événement critique pour leur activation. Suivant un modèle généralement accepté, cette interaction active directement les kinases RAF en prévenant une interaction inhibitrice entre les domaines amino-terminal régulateur et carboxy-terminal kinase [8,9]. En plus de leur effet activateur direct, les petites protéines G de la famille RAS favorisent le recrutement des kinases RAF au niveau de structures membranaires spécialisées consistant en un regroupement local des isoformes de RAS entre elles [10]. À ce niveau, la présence de proté-ines d'échaffaudage comme KSR (kinase suppressor of Ras) et l'activité moindre des phosphatases facilitent la signalisation par les kinases RAF [10,11]. En plus de l'interaction avec RAS, les phosphorylations/ déphosphorylations jouent un rôle régulateur essentiel pour l'activité des RAF. Une région concentre plusieurs sites de phosphorylations stimulant directement l'activité des RAF kinases : il s'agit de la région N (nega-> Les protéines RAF (A-RAF, B-RAF et C-RAF) constituent une famille de kinases jouant un rôle déterminant dans des événements cellulaires aussi im...

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From autoinhibition to inhibition in trans: the Raf-1 regulatory domain inhibits Rok-α kinase activity

Abstract: The mechanism by which Raf-1 antagonizes Rok-α to promote migration and tumorigenesis is revealed.

Cited by 47 publications

References 49 publications

Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

The intermediate-activity^L597VBRAF mutant acts as an epistatic modifier of oncogenic RAS by enhancing signaling through the RAF/MEK/ERK pathway

Régulation de la survie cellulaire par les kinases de la famille RAF

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From autoinhibition to inhibition in trans: the Raf-1 regulatory domain inhibits Rok-α kinase activity

Abstract: The mechanism by which Raf-1 antagonizes Rok-α to promote migration and tumorigenesis is revealed.

Cited by 47 publications

References 49 publications

Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

Skin Tumorigenesis Stimulated by Raf Inhibitors Relies Upon Raf Functions That Are Dependent and Independent of ERK

The intermediate-activityL597VBRAF mutant acts as an epistatic modifier of oncogenic RAS by enhancing signaling through the RAF/MEK/ERK pathway

Régulation de la survie cellulaire par les kinases de la famille RAF

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The intermediate-activity^L597VBRAF mutant acts as an epistatic modifier of oncogenic RAS by enhancing signaling through the RAF/MEK/ERK pathway