Hidden Targets in RAF Signalling Pathways to Block Oncogenic RAS Signalling

Nolan, Aoife A.; Aboud, Nourhan K.; Kölch, Walter; Matallanas, David

doi:10.20944/preprints202103.0510.v1

Cited by 5 publications

(1 citation statement)

References 67 publications

(93 reference statements)

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“…While phosphorylation and activation of MEK1/2 is the only widely accepted catalytic function of the RAF kinases, they can regulate other signalling pathways independent of their kinase activity (Rauch et al, 2011, Baccarini, 2005, Nolan et al, 2021. These include the suppression of proapoptotic pathways mediated by ASK1 (Chen et al, 2001) or MST2 (O'Neill et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Proteasomal downregulation of the pro-apoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

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García-Gutiérrez

Duffy

et al. 2022

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The RAS-RAF-MEK-ERK pathway is hyperactivated in most malignant melanomas, and mutations in BRAF or NRAS account for most of these cases. BRAF inhibitors (BRAFi) are highly efficient for treating patients with BRAFV600E mutations, but tumours frequently acquire resistance within a few months. Multiple resistance mechanisms have been identified, due to mutations or network adaptations that revive ERK signalling. We have previously shown that RAF proteins inhibit the MST2 proapoptotic pathway in a kinase independent fashion. Here, we have investigated the role of the MST2 pathway in mediating resistance to BRAFi. We show that the BRAFV600E mutant protein, but not the wildtype BRAF protein, strongly binds to MST2 and inhibits MST2 pro-apoptotic signalling. Downregulation of MST2 reduces BRAFi induced apoptosis. In BRAFi resistant cell lines MST2 pathway proteins are downregulated by ubiquitination and subsequent proteasomal degradation rendering cells refractory to MST2 pathway induced apoptosis. Restoration of apoptosis is achieved by increasing MST2 pathway protein expression using proteasome inhibitors. In summary, we show that the MST2 pathway is involved in the acquisition of BRAFi resistance in melanoma.

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Section: Discussionmentioning

confidence: 99%

Proteasomal downregulation of the pro-apoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

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García-Gutiérrez

Duffy

et al. 2022

Preprint

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Identification of SIRT4 as a novel paralog-specific interactor and candidate suppressor of C-RAF kinase in MAPK signaling

Mehrabipour,

Dvorsky,

Nakhaei-Rad

et al. 2023

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Cellular responses leading to development, proliferation, and differentiation rely on RAF/MEK/ERK signaling that integrates and amplifies signals from various stimuli to cellular downstream responses. The clinical significance of C-RAF activation has been reported in many types of tumor cell proliferation and developmental disorders, which requires the discovery of potential C-RAF protein regulators. Here, we identify a novel and specific protein interaction between C-RAF, among the RAF kinase paralogs, and SIRT4 among the mitochondrial sirtuin family members SIRT3, SIRT4, and SIRT5. Structurally, C-RAF binds to SIRT4 through the N-terminal cysteine-rich domain (CRD; a.a. 136-187), and on the other side, SIRT4 requires predominantly the C-terminus (a.a. 255-314) for full interaction with C-RAF. Interestingly, SIRT4 interacts specifically with C-RAF in a pre-signaling inactive (serine 259 phosphorylated) state. Consistent with this finding, ectopic expression of SIRT4 in HEK293 cells results in upregulation of pS259-C-RAF levels and concomitant reduction of MAPK signaling as evidenced by strongly decreased phospho-ERK signals. Thus, our findings propose another extra-mitochondrial role of SIRT4 and suggest that SIRT4 functions as a cytosolic tumor suppressor of C-RAF-MAPK signaling, besides its known metabolic tumor suppressor role towards glutamate dehydrogenase and glutamine levels in mitochondria.

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Pseurotin D Induces Apoptosis through Targeting Redox Sensitive Pathways in Human Lymphoid Leukemia Cells

et al. 2021

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Chronic lymphocytic leukemia (CLL) is the most prevalent lymphoid malignancy in many geographical regions of the world. Pseurotin D, a secondary metabolite of fungi, represents a group of bioactive natural products with a newly ascribed range of interesting biological activities. The purpose of this study was to bring new insights into the mechanism behind the effects of pseurotin D on MEC-1 cells as a representative CLL cell line, with a particular focus on selected signaling pathways important in the proliferation of cells and targeting mitochondrial metabolism. Our results showed that pseurotin D was able to significantly inhibit the proliferation of MEC-1 cells and arrested them in the G2/M cell cycle phase. In addition, pseurotin D was able to induce apoptosis. We found that all of these effects were associated with a change in mitochondrial membrane potential and the production of mitochondrial reactive oxygen species (ROS). We showed for the first time that pseurotin D suppresses MEC-1 cell proliferation and induces apoptotic cell death via induction of the collapse of the mitochondria respiratory chain and the ROS-related caspase pathway. Our results show the pseurotins family as promising compounds which could serve as a basis for the development of new compounds in the treatment of lymphoma.

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Hidden Targets in RAF Signalling Pathways to Block Oncogenic RAS Signalling

Cited by 5 publications

References 67 publications

Proteasomal downregulation of the pro-apoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

Proteasomal downregulation of the pro-apoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

Identification of SIRT4 as a novel paralog-specific interactor and candidate suppressor of C-RAF kinase in MAPK signaling

Pseurotin D Induces Apoptosis through Targeting Redox Sensitive Pathways in Human Lymphoid Leukemia Cells

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