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Townley RA, Stacy KS, Cheraghi F, de la Cova CC. The Raf/LIN-45 C-terminal distal tail segment negatively regulates signaling in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.16.603803. [PMID: 39071268 PMCID: PMC11275798 DOI: 10.1101/2024.07.16.603803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Raf protein kinases act as Ras-GTP sensing components of the ERK signal transduction pathway in animal cells, influencing cell proliferation, differentiation, and survival. In humans, somatic and germline mutations in the genes BRAF and RAF1 are associated with malignancies and developmental disorders. Recent studies shed light on the structure of activated Raf, a heterotetramer consisting of Raf and 14-3-3 dimers, and raised the possibility that a Raf C-terminal distal tail segment (DTS) regulates activation. We investigated the role of the DTS using the Caenorhabditis elegans, which has a single Raf ortholog termed lin-45 . We discovered that truncations removing the DTS strongly enhanced lin-45(S312A) , a weak gain-of-function allele equivalent to RAF1 mutations found in patients with Noonan Syndrome. We generated mutations to test three elements of the LIN-45 DTS, which we termed the active site binding sequence (ASBS), the KTP motif, and the aromatic cluster. In the context of lin-45(S312A), mutation of either the ASBS, KTP motif, or aromatic cluster enhanced activity. We used AlphaFold to predict DTS protein interactions for LIN-45, fly Raf, and human BRAF, within the activated heterotetramer complex. We propose distinct functions for the LIN-45 DTS elements: i) the ASBS binds the kinase active site as an inhibitor, ii) phosphorylation of the KTP motif modulates DTS-kinase domain interaction, and iii) the aromatic cluster anchors the DTS in an inhibitory conformation. This work establishes that the Raf/LIN-45 DTS negatively regulates signaling in C. elegans and provides a model for its function in other Raf proteins.
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2
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Spencer-Smith R, Morrison DK. Regulation of RAF family kinases: new insights from recent structural and biochemical studies. Biochem Soc Trans 2024; 52:1061-1069. [PMID: 38695730 PMCID: PMC11346419 DOI: 10.1042/bst20230552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/18/2024] [Accepted: 04/22/2024] [Indexed: 06/27/2024]
Abstract
The RAF kinases are required for signal transduction through the RAS-RAF-MEK-ERK pathway, and their activity is frequently up-regulated in human cancer and the RASopathy developmental syndromes. Due to their complex activation process, developing drugs that effectively target RAF function has been a challenging endeavor, highlighting the need for a more detailed understanding of RAF regulation. This review will focus on recent structural and biochemical studies that have provided 'snapshots' into the RAF regulatory cycle, revealing structures of the autoinhibited BRAF monomer, active BRAF and CRAF homodimers, as well as HSP90/CDC37 chaperone complexes containing CRAF or BRAFV600E. In addition, we will describe the insights obtained regarding how BRAF transitions between its regulatory states and examine the roles that various BRAF domains and 14-3-3 dimers play in both maintaining BRAF as an autoinhibited monomer and in facilitating its transition to an active dimer. We will also address the function of the HSP90/CDC37 chaperone complex in stabilizing the protein levels of CRAF and certain oncogenic BRAF mutants, and in serving as a platform for RAF dephosphorylation mediated by the PP5 protein phosphatase. Finally, we will discuss the regulatory differences observed between BRAF and CRAF and how these differences impact the function of BRAF and CRAF as drivers of human disease.
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Affiliation(s)
- Russell Spencer-Smith
- Laboratory of Cell and Developmental Signaling, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, U.S.A
| | - Deborah K. Morrison
- Laboratory of Cell and Developmental Signaling, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, U.S.A
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3
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Bonsor DA, Simanshu DK. RAS and SHOC2 Roles in RAF Activation and Therapeutic Considerations. ANNUAL REVIEW OF CANCER BIOLOGY 2024; 8:97-113. [PMID: 38882927 PMCID: PMC11178279 DOI: 10.1146/annurev-cancerbio-062822-030450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Mutations in RAS proteins play a pivotal role in the development of human cancers, driving persistent RAF activation and deregulating the Mitogen-Activated Protein Kinase (MAPK) signaling pathway. While progress has been made in targeting specific oncogenic RAS proteins, effective drug-based therapies for the majority of RAS mutations remain limited. Recent investigations on RAS-RAF complexes and the SHOC2-MRAS-PP1C holoenzyme complex have provided crucial insights into the structural and functional aspects of RAF activation within the MAPK signaling pathway. Moreover, these studies have also unveiled new blueprints for developing inhibitors allowing us to think beyond the current RAS and MEK inhibitors. In this review, we explore the roles of RAS and SHOC2 in activating RAF and discuss potential therapeutic strategies to target these proteins. A comprehensive understanding of the molecular interactions involved in RAF activation and their therapeutic implications holds the potential to drive innovative approaches in combating RAS/RAF-driven cancers.
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Affiliation(s)
- Daniel A. Bonsor
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Dhirendra K. Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
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4
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Rasmussen DM, Semonis MM, Greene JT, Muretta JM, Thompson AR, Toledo Ramos S, Thomas DD, Pomerantz WCK, Freedman TS, Levinson NM. Allosteric coupling asymmetry mediates paradoxical activation of BRAF by type II inhibitors. eLife 2024; 13:RP95481. [PMID: 38742856 PMCID: PMC11093583 DOI: 10.7554/elife.95481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024] Open
Abstract
The type II class of RAF inhibitors currently in clinical trials paradoxically activate BRAF at subsaturating concentrations. Activation is mediated by induction of BRAF dimers, but why activation rather than inhibition occurs remains unclear. Using biophysical methods tracking BRAF dimerization and conformation, we built an allosteric model of inhibitor-induced dimerization that resolves the allosteric contributions of inhibitor binding to the two active sites of the dimer, revealing key differences between type I and type II RAF inhibitors. For type II inhibitors the allosteric coupling between inhibitor binding and BRAF dimerization is distributed asymmetrically across the two dimer binding sites, with binding to the first site dominating the allostery. This asymmetry results in efficient and selective induction of dimers with one inhibited and one catalytically active subunit. Our allosteric models quantitatively account for paradoxical activation data measured for 11 RAF inhibitors. Unlike type II inhibitors, type I inhibitors lack allosteric asymmetry and do not activate BRAF homodimers. Finally, NMR data reveal that BRAF homodimers are dynamically asymmetric with only one of the subunits locked in the active αC-in state. This provides a structural mechanism for how binding of only a single αC-in inhibitor molecule can induce potent BRAF dimerization and activation.
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Affiliation(s)
- Damien M Rasmussen
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
- Department of Biochemistry, Molecular Biology, and Biophysics, University of MinnesotaMinneapolisUnited States
| | - Manny M Semonis
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
| | - Joseph T Greene
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
| | - Joseph M Muretta
- Department of Biochemistry, Molecular Biology, and Biophysics, University of MinnesotaMinneapolisUnited States
| | - Andrew R Thompson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of MinnesotaMinneapolisUnited States
| | | | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of MinnesotaMinneapolisUnited States
| | | | - Tanya S Freedman
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
- Center for Immunology, University of MinnesotaMinneapolisUnited States
- Masonic Cancer Center, University of MinnesotaMinneapolisUnited States
| | - Nicholas M Levinson
- Department of Pharmacology, University of MinnesotaMinneapolisUnited States
- Masonic Cancer Center, University of MinnesotaMinneapolisUnited States
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5
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Marsiglia WM, Chow A, Khan ZM, He L, Dar AC. Live-cell target engagement of allosteric MEKi on MEK-RAF/KSR-14-3-3 complexes. Nat Chem Biol 2024; 20:373-381. [PMID: 37919548 PMCID: PMC10948974 DOI: 10.1038/s41589-023-01454-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 09/19/2023] [Indexed: 11/04/2023]
Abstract
The RAS-mitogen-activated protein kinase (MAPK) pathway includes KSR, RAF, MEK and the phospho-regulatory sensor 14-3-3. Specific assemblies among these components drive various diseases and likely dictate efficacy for numerous targeted therapies, including allosteric MEK inhibitors (MEKi). However, directly measuring drug interactions on physiological RAS-MAPK complexes in live cells has been inherently challenging to query and therefore remains poorly understood. Here we present a series of NanoBRET-based assays to quantify direct target engagement of MEKi on MEK1 and higher-order MEK1-bound complexes with ARAF, BRAF, CRAF, KSR1 and KSR2 in the presence and absence of 14-3-3 in living cells. We find distinct MEKi preferences among these complexes that can be compiled to generate inhibitor binding profiles. Further, these assays can report on the influence of the pathogenic BRAF-V600E mutant on MEKi binding. Taken together, these approaches can be used as a platform to screen for compounds intended to target specific complexes in the RAS-MAPK cascade.
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Affiliation(s)
- William M Marsiglia
- Department of Oncological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Pharmacology and Toxicology, The University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Arthur Chow
- Department of Oncological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Program in Chemical Biology, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Zaigham M Khan
- Department of Oncological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Liu He
- Department of Oncological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Program in Chemical Biology, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Arvin C Dar
- Department of Oncological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Center for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Program in Chemical Biology, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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6
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Rasmussen DM, Semonis MM, Greene JT, Muretta JM, Thompson AR, Ramos ST, Thomas DD, Pomerantz WC, Freedman TS, Levinson NM. Allosteric coupling asymmetry mediates paradoxical activation of BRAF by type II inhibitors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.18.536450. [PMID: 37131649 PMCID: PMC10153139 DOI: 10.1101/2023.04.18.536450] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The type II class of RAF inhibitors currently in clinical trials paradoxically activate BRAF at subsaturating concentrations. Activation is mediated by induction of BRAF dimers, but why activation rather than inhibition occurs remains unclear. Using biophysical methods tracking BRAF dimerization and conformation we built an allosteric model of inhibitor-induced dimerization that resolves the allosteric contributions of inhibitor binding to the two active sites of the dimer, revealing key differences between type I and type II RAF inhibitors. For type II inhibitors the allosteric coupling between inhibitor binding and BRAF dimerization is distributed asymmetrically across the two dimer binding sites, with binding to the first site dominating the allostery. This asymmetry results in efficient and selective induction of dimers with one inhibited and one catalytically active subunit. Our allosteric models quantitatively account for paradoxical activation data measured for 11 RAF inhibitors. Unlike type II inhibitors, type I inhibitors lack allosteric asymmetry and do not activate BRAF homodimers. Finally, NMR data reveal that BRAF homodimers are dynamically asymmetric with only one of the subunits locked in the active αC-in state. This provides a structural mechanism for how binding of only a single αC-in inhibitor molecule can induce potent BRAF dimerization and activation.
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Affiliation(s)
- Damien M. Rasmussen
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, 55455
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455
| | - Manny M. Semonis
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, 55455
| | - Joseph T. Greene
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, 55455
| | - Joseph M. Muretta
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455
| | - Andrew R. Thompson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455
| | | | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455
| | | | - Tanya S. Freedman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, 55455
- Center for Immunology, University of Minnesota, Minneapolis, MN, 55455
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, 55455
| | - Nicholas M. Levinson
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, 55455
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, 55455
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7
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Yu A, Nguyen DH, Nguyen TJ, Wang Z. A novel phosphorylation site involved in dissociating RAF kinase from the scaffolding protein 14-3-3 and disrupting RAF dimerization. J Biol Chem 2023; 299:105188. [PMID: 37625591 PMCID: PMC10520314 DOI: 10.1016/j.jbc.2023.105188] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 08/01/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
Rapidly accelerated fibrosarcoma (ARAF, BRAF, CRAF) kinase is central to the MAPK pathway (RAS-RAF-MEK-ERK). Inactive RAF kinase is believed to be monomeric, autoinhibited, and cytosolic, while activated RAF is recruited to the membrane via RAS-GTP, leading to the relief of autoinhibition, phosphorylation of key regulatory sites, and dimerization of RAF protomers. Although it is well known that active and inactive BRAF have differential phosphorylation sites that play a crucial role in regulating BRAF, key details are still missing. In this study, we report the characterization of a novel phosphorylation site, BRAFS732 (equivalent in CRAFS624), located in proximity to the C-terminus binding motif for the 14-3-3 scaffolding protein. At the C terminus, 14-3-3 binds to BRAFpS729 (CRAFpS621) and enhances RAF dimerization. We conducted mutational analysis of BRAFS732A/E and CRAFS624A/E and revealed that the phosphomimetic S→E mutant decreases 14-3-3 association and RAF dimerization. In normal cell signaling, dimerized RAF phosphorylates MEK1/2, which is observed in the phospho-deficient S→A mutant. Our results suggest that phosphorylation and dephosphorylation of this site fine-tune the association of 14-3-3 and RAF dimerization, ultimately impacting MEK phosphorylation. We further characterized the BRAF homodimer and BRAF:CRAF heterodimer and identified a correlation between phosphorylation of this site with drug sensitivity. Our work reveals a novel negative regulatory role for phosphorylation of BRAFS732 and CRAFS624 in decreasing 14-3-3 association, dimerization, and MEK phosphorylation. These findings provide insight into the regulation of the MAPK pathway and may have implications for cancers driven by mutations in the pathway.
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Affiliation(s)
- Alison Yu
- Department of Chemistry & Biochemistry, Rowan University, Glassboro, New Jersey, USA
| | - Duc Huy Nguyen
- Department of Chemistry & Biochemistry, Rowan University, Glassboro, New Jersey, USA
| | - Thomas Joseph Nguyen
- Department of Chemistry & Biochemistry, Rowan University, Glassboro, New Jersey, USA
| | - Zhihong Wang
- Department of Chemistry & Biochemistry, Rowan University, Glassboro, New Jersey, USA.
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8
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Konstantinidou M, Visser EJ, Vandenboorn E, Chen S, Jaishankar P, Overmans M, Dutta S, Neitz RJ, Renslo AR, Ottmann C, Brunsveld L, Arkin MR. Structure-Based Optimization of Covalent, Small-Molecule Stabilizers of the 14-3-3σ/ERα Protein-Protein Interaction from Nonselective Fragments. J Am Chem Soc 2023; 145:20328-20343. [PMID: 37676236 PMCID: PMC10515640 DOI: 10.1021/jacs.3c05161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Indexed: 09/08/2023]
Abstract
The stabilization of protein-protein interactions (PPIs) has emerged as a promising strategy in chemical biology and drug discovery. The identification of suitable starting points for stabilizing native PPIs and their subsequent elaboration into selective and potent molecular glues lacks structure-guided optimization strategies. We have previously identified a disulfide fragment that stabilized the hub protein 14-3-3σ bound to several of its clients, including ERα and C-RAF. Here, we show the structure-based optimization of the nonselective fragment toward selective and highly potent small-molecule stabilizers of the 14-3-3σ/ERα complex. The more elaborated molecular glues, for example, show no stabilization of 14-3-3σ/C-RAF up to 150 μM compound. Orthogonal biophysical assays, including mass spectrometry and fluorescence anisotropy, were used to establish structure-activity relationships. The binding modes of 37 compounds were elucidated with X-ray crystallography, which further assisted the concomitant structure-guided optimization. By targeting specific amino acids in the 14-3-3σ/ERα interface and locking the conformation with a spirocycle, the optimized covalent stabilizer 181 achieved potency, cooperativity, and selectivity similar to the natural product Fusicoccin-A. This case study showcases the value of addressing the structure, kinetics, and cooperativity for molecular glue development.
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Affiliation(s)
- Markella Konstantinidou
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - Emira J. Visser
- Laboratory
of Chemical Biology, Department of Biomedical Engineering and Institute
for Complex Molecular Systems (ICMS), Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Edmee Vandenboorn
- Laboratory
of Chemical Biology, Department of Biomedical Engineering and Institute
for Complex Molecular Systems (ICMS), Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Sheng Chen
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - Priyadarshini Jaishankar
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - Maurits Overmans
- Laboratory
of Chemical Biology, Department of Biomedical Engineering and Institute
for Complex Molecular Systems (ICMS), Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Shubhankar Dutta
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - R. Jeffrey Neitz
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - Adam R. Renslo
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
| | - Christian Ottmann
- Laboratory
of Chemical Biology, Department of Biomedical Engineering and Institute
for Complex Molecular Systems (ICMS), Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Luc Brunsveld
- Laboratory
of Chemical Biology, Department of Biomedical Engineering and Institute
for Complex Molecular Systems (ICMS), Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Michelle R. Arkin
- Department
of Pharmaceutical Chemistry and Small Molecule Discovery Center (SMDC), University of California, San Francisco, California 94143, United States
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9
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Lauinger M, Christen D, Klar RFU, Roubaty C, Heilig CE, Stumpe M, Knox JJ, Radulovich N, Tamblyn L, Xie IY, Horak P, Forschner A, Bitzer M, Wittel UA, Boerries M, Ball CR, Heining C, Glimm H, Fröhlich M, Hübschmann D, Gallinger S, Fritsch R, Fröhling S, O'Kane GM, Dengjel J, Brummer T. BRAF Δβ3-αC in-frame deletion mutants differ in their dimerization propensity, HSP90 dependence, and druggability. SCIENCE ADVANCES 2023; 9:eade7486. [PMID: 37656784 DOI: 10.1126/sciadv.ade7486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 08/02/2023] [Indexed: 09/03/2023]
Abstract
In-frame BRAF exon 12 deletions are increasingly identified in various tumor types. The resultant BRAFΔβ3-αC oncoproteins usually lack five amino acids in the β3-αC helix linker and sometimes contain de novo insertions. The dimerization status of BRAFΔβ3-αC oncoproteins, their precise pathomechanism, and their direct druggability by RAF inhibitors (RAFi) has been under debate. Here, we functionally characterize BRAFΔLNVTAP>F and two novel mutants, BRAFdelinsFS and BRAFΔLNVT>F, and compare them with other BRAFΔβ3-αC oncoproteins. We show that BRAFΔβ3-αC oncoproteins not only form stable homodimers and large multiprotein complexes but also require dimerization. Nevertheless, details matter as aromatic amino acids at the deletion junction of some BRAFΔβ3-αC oncoproteins, e.g., BRAFΔLNVTAP>F, increase their stability and dimerization propensity while conferring resistance to monomer-favoring RAFi such as dabrafenib or HSP 90/CDC37 inhibition. In contrast, dimer-favoring inhibitors such as naporafenib inhibit all BRAFΔβ3-αC mutants in cell lines and patient-derived organoids, suggesting that tumors driven by such oncoproteins are vulnerable to these compounds.
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Affiliation(s)
- Manuel Lauinger
- Institute of Molecular Medicine, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Daniel Christen
- Institute of Molecular Medicine, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
- German Cancer Consortium (DKTK), partner site Freiburg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Rhena F U Klar
- Institute of Molecular Medicine, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
- German Cancer Consortium (DKTK), partner site Freiburg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- Freeze-O Organoid Bank, University Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Internal Medicine I (Hematology, Oncology, and Stem Cell Transplantation), University Hospital of Freiburg, Freiburg, Germany
- Institute of Medical Bioinformatics and Systems Medicine (IBSM), Freiburg University Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Carole Roubaty
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Christoph E Heilig
- Division of Translational Medical Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- German Cancer Consortium (DKTK), Heidelberg, Germany
| | - Michael Stumpe
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Jennifer J Knox
- PanCuRx Translational Research Initiative, Ontario Institute for Cancer Research, Toronto, Ontario, Canada
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Nikolina Radulovich
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Laura Tamblyn
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Irene Y Xie
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Peter Horak
- Division of Translational Medical Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- German Cancer Consortium (DKTK), Heidelberg, Germany
| | - Andrea Forschner
- Department of Dermatology, University Hospital of Tübingen, Tübingen, Germany
- German Cancer Consortium (DKTK), DKFZ partner site Tübingen, Eberhard Karls University, Tübingen, Germany
| | - Michael Bitzer
- German Cancer Consortium (DKTK), DKFZ partner site Tübingen, Eberhard Karls University, Tübingen, Germany
- Center for Personalized Medicine Tübingen, Eberhard Karls University, Tübingen, Germany
- Department of Internal Medicine I, Eberhard-Karls University, Tübingen, Germany
| | - Uwe A Wittel
- Department of General and Visceral Surgery, University of Freiburg Medical Center, Faculty of Medicine, 79106 Freiburg, Germany
| | - Melanie Boerries
- German Cancer Consortium (DKTK), partner site Freiburg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- Institute of Medical Bioinformatics and Systems Medicine (IBSM), Freiburg University Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Comprehensive Cancer Center Freiburg (CCCF), Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Claudia R Ball
- Department for Translational Medical Oncology, National Center for Tumor Diseases (NCT/UCC), Dresden, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
- Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
- Translational Medical Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Cancer Consortium (DKTK), Dresden, Germany
- Technische Universität Dresden, Faculty of Biology, Technische Universität Dresden, Dresden, Germany
| | - Christoph Heining
- Department for Translational Medical Oncology, National Center for Tumor Diseases (NCT/UCC), Dresden, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
- Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
- Translational Medical Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Cancer Consortium (DKTK), Dresden, Germany
| | - Hanno Glimm
- Department for Translational Medical Oncology, National Center for Tumor Diseases (NCT/UCC), Dresden, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
- Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
- Translational Medical Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Cancer Consortium (DKTK), Dresden, Germany
- Translational Functional Cancer Genomics, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Martina Fröhlich
- Computational Oncology Group, Molecular Precision Oncology Program, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Daniel Hübschmann
- German Cancer Consortium (DKTK), Heidelberg, Germany
- Computational Oncology Group, Molecular Precision Oncology Program, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany
- Pattern Recognition and Digital Medicine Group, Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM), Heidelberg, Germany
| | - Steven Gallinger
- PanCuRx Translational Research Initiative, Ontario Institute for Cancer Research, Toronto, Ontario, Canada
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Ralph Fritsch
- Department of Internal Medicine I (Hematology, Oncology, and Stem Cell Transplantation), University Hospital of Freiburg, Freiburg, Germany
- Department of Medical Oncology and Haematology, University Hospital of Zurich, Zurich, Switzerland
| | - Stefan Fröhling
- Division of Translational Medical Oncology, National Center for Tumor Diseases (NCT) Heidelberg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- German Cancer Consortium (DKTK), Heidelberg, Germany
| | - Grainne M O'Kane
- PanCuRx Translational Research Initiative, Ontario Institute for Cancer Research, Toronto, Ontario, Canada
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Tilman Brummer
- Institute of Molecular Medicine, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
- German Cancer Consortium (DKTK), partner site Freiburg and German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
- Freeze-O Organoid Bank, University Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Comprehensive Cancer Center Freiburg (CCCF), Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
- Center for Biological Signalling Studies BIOSS, University of Freiburg, 79104 Freiburg, Germany
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10
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Singh A, Sonawane P, Kumar A, Singh H, Naumovich V, Pathak P, Grishina M, Khalilullah H, Jaremko M, Emwas AH, Verma A, Kumar P. Challenges and Opportunities in the Crusade of BRAF Inhibitors: From 2002 to 2022. ACS OMEGA 2023; 8:27819-27844. [PMID: 37576670 PMCID: PMC10413849 DOI: 10.1021/acsomega.3c00332] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 02/27/2023] [Indexed: 08/15/2023]
Abstract
Serine/threonine-protein kinase B-Raf (BRAF; RAF = rapidly accelerated fibrosarcoma) plays an important role in the mitogen-activated protein kinase (MAPK) signaling cascade. Somatic mutations in the BRAF gene were first discovered in 2002 by Davies et al., which was a major breakthrough in cancer research. Subsequently, three different classes of BRAF mutants have been discovered. This class includes class I monomeric mutants (BRAFV600), class II BRAF homodimer mutants (non-V600), and class III BRAF heterodimers (non-V600). Cancers caused by these include melanoma, thyroid cancer, ovarian cancer, colorectal cancer, nonsmall cell lung cancer, and others. In this study, we have highlighted the major binding pockets in BRAF protein, their active and inactive conformations with inhibitors, and BRAF dimerization and its importance in paradoxical activation and BRAF mutation. We have discussed the first-, second-, and third-generation drugs approved by the Food and Drug Administration and drugs under clinical trials with all four different binding approaches with DFG-IN/OUT and αC-IN/OUT for BRAF protein. We have investigated particular aspects and difficulties with all three generations of inhibitors. Finally, this study has also covered recent developments in synthetic BRAF inhibitors (from their discovery in 2002 to 2022), their unique properties, and importance in inhibiting BRAF mutants.
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Affiliation(s)
- Ankit
Kumar Singh
- Department
of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Pankaj Sonawane
- Department
of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Adarsh Kumar
- Department
of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Harshwardhan Singh
- Department
of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Vladislav Naumovich
- Laboratory
of Computational Modeling of Drugs, Higher Medical and Biological
School, South Ural State University, Chelyabinsk 454008, Russia
| | - Prateek Pathak
- Laboratory
of Computational Modeling of Drugs, Higher Medical and Biological
School, South Ural State University, Chelyabinsk 454008, Russia
| | - Maria Grishina
- Laboratory
of Computational Modeling of Drugs, Higher Medical and Biological
School, South Ural State University, Chelyabinsk 454008, Russia
| | - Habibullah Khalilullah
- Department
of Pharmaceutical Chemistry and Pharmacognosy, Unaizah College of
Pharmacy, Qassim University, Unayzah 51911, Saudi Arabia
| | - Mariusz Jaremko
- Smart-Health
Initiative and Red Sea Research Center, Division of Biological and
Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Abdul-Hamid Emwas
- Core
Laboratories, King Abdullah University of
Science and Technology, Thuwal 23955-6900, Saudi
Arabia
| | - Amita Verma
- Bioorganic
and Medicinal Chemistry Research Laboratory, Department of Pharmaceutical
Sciences, Sam Higginbottom University of
Agriculture, Technology and Sciences, Prayagraj 211007, India
| | - Pradeep Kumar
- Department
of Pharmaceutical Sciences and Natural Products, Central University of Punjab, Ghudda, Bathinda 151401, India
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11
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Park E, Rawson S, Schmoker A, Kim BW, Oh S, Song K, Jeon H, Eck MJ. Cryo-EM structure of a RAS/RAF recruitment complex. Nat Commun 2023; 14:4580. [PMID: 37516774 PMCID: PMC10387098 DOI: 10.1038/s41467-023-40299-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 07/19/2023] [Indexed: 07/31/2023] Open
Abstract
RAF-family kinases are activated by recruitment to the plasma membrane by GTP-bound RAS, whereupon they initiate signaling through the MAP kinase cascade. Prior structural studies of KRAS with RAF have focused on the isolated RAS-binding and cysteine-rich domains of RAF (RBD and CRD, respectively), which interact directly with RAS. Here we describe cryo-EM structures of a KRAS bound to intact BRAF in an autoinhibited state with MEK1 and a 14-3-3 dimer. Analysis of this KRAS/BRAF/MEK1/14-3-3 complex reveals KRAS bound to the RAS-binding domain of BRAF, captured in two orientations. Core autoinhibitory interactions in the complex are unperturbed by binding of KRAS and in vitro activation studies confirm that KRAS binding is insufficient to activate BRAF, absent membrane recruitment. These structures illustrate the separability of binding and activation of BRAF by RAS and suggest stabilization of this pre-activation intermediate as an alternative therapeutic strategy to blocking binding of KRAS.
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Affiliation(s)
- Eunyoung Park
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
- Pfizer R&D Center, 3200 Walnut St, Boulder, CO, 80301, USA
| | - Shaun Rawson
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Anna Schmoker
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Byeong-Won Kim
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
- New Drug Development Center, Osong Medical Innovation Foundation, Cheongju, Chungbuk, 28160, Republic of Korea
| | - Sehee Oh
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Kangkang Song
- Department of Biochemistry & Molecular Biotechnology, University of Massachusetts Chan Medical School, 364 Plantation St, Worcester, MA, 01605, USA
| | - Hyesung Jeon
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Michael J Eck
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA.
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12
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Roy MJ, Surudoi MG, Kropp A, Hou J, Dai W, Hardy JM, Liang LY, Cotton TR, Lechtenberg BC, Dite TA, Ma X, Daly RJ, Patel O, Lucet IS. Structural mapping of PEAK pseudokinase interactions identifies 14-3-3 as a molecular switch for PEAK3 signaling. Nat Commun 2023; 14:3542. [PMID: 37336884 DOI: 10.1038/s41467-023-38869-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 05/16/2023] [Indexed: 06/21/2023] Open
Abstract
PEAK pseudokinases regulate cell migration, invasion and proliferation by recruiting key signaling proteins to the cytoskeleton. Despite lacking catalytic activity, alteration in their expression level is associated with several aggressive cancers. Here, we elucidate the molecular details of key PEAK signaling interactions with the adapter proteins CrkII and Grb2 and the scaffold protein 14-3-3. Our findings rationalize why the dimerization of PEAK proteins has a crucial function in signal transduction and provide biophysical and structural data to unravel binding specificity within the PEAK interactome. We identify a conserved high affinity 14-3-3 motif on PEAK3 and demonstrate its role as a molecular switch to regulate CrkII binding and signaling via Grb2. Together, our studies provide a detailed structural snapshot of PEAK interaction networks and further elucidate how PEAK proteins, especially PEAK3, act as dynamic scaffolds that exploit adapter proteins to control signal transduction in cell growth/motility and cancer.
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Affiliation(s)
- Michael J Roy
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia.
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia.
| | - Minglyanna G Surudoi
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Ashleigh Kropp
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Jianmei Hou
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Weiwen Dai
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Joshua M Hardy
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Lung-Yu Liang
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Thomas R Cotton
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Bernhard C Lechtenberg
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Toby A Dite
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Xiuquan Ma
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Roger J Daly
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Onisha Patel
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Isabelle S Lucet
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia.
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia.
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13
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Tkacik E, Li K, Gonzalez-Del Pino G, Ha BH, Vinals J, Park E, Beyett TS, Eck MJ. Structure and RAF family kinase isoform selectivity of type II RAF inhibitors tovorafenib and naporafenib. J Biol Chem 2023; 299:104634. [PMID: 36963492 PMCID: PMC10149214 DOI: 10.1016/j.jbc.2023.104634] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/17/2023] [Accepted: 03/18/2023] [Indexed: 03/26/2023] Open
Abstract
Upon activation by RAS, RAF family kinases initiate signaling through the MAP kinase cascade to control cell growth, proliferation, and differentiation. Among RAF isoforms (ARAF, BRAF, and CRAF), oncogenic mutations are by far most frequent in BRAF. The BRAFV600E mutation drives more than half of all malignant melanoma and is also found in many other cancers. Selective inhibitors of BRAFV600E (vemurafenib, dabrafenib, encorafenib) are used clinically for these indications, but they are not effective inhibitors in the context of oncogenic RAS, which drives dimerization and activation of RAF, nor for malignancies driven by aberrantly dimerized truncation/fusion variants of BRAF. By contrast, a number of "type II" RAF inhibitors have been developed as potent inhibitors of RAF dimers. Here, we compare potency of type II inhibitors tovorafenib (TAK-580) and naporafenib (LHX254) in biochemical assays against the three RAF isoforms and describe crystal structures of both compounds in complex with BRAF. We find that tovorafenib and naporafenib are most potent against CRAF but markedly less potent against ARAF. Crystal structures of both compounds with BRAFV600E or WT BRAF reveal the details of their molecular interactions, including the expected type II-binding mode, with full occupancy of both subunits of the BRAF dimer. Our findings have important clinical ramifications. Type II RAF inhibitors are generally regarded as pan-RAF inhibitors, but our studies of these two agents, together with recent work with type II inhibitors belvarafenib and naporafenib, indicate that relative sparing of ARAF may be a property of multiple drugs of this class.
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Affiliation(s)
- Emre Tkacik
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Kunhua Li
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Gonzalo Gonzalez-Del Pino
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Byung Hak Ha
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Javier Vinals
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Eunyoung Park
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Tyler S Beyett
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Michael J Eck
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
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14
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Simanshu DK, Philips MR, Hancock JF. Consensus on the RAS dimerization hypothesis: Strong evidence for lipid-mediated clustering but not for G-domain-mediated interactions. Mol Cell 2023; 83:1210-1215. [PMID: 36990093 PMCID: PMC10150945 DOI: 10.1016/j.molcel.2023.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/24/2023] [Accepted: 03/07/2023] [Indexed: 03/30/2023]
Abstract
One of the open questions in RAS biology is the existence of RAS dimers and their role in RAF dimerization and activation. The idea of RAS dimers arose from the discovery that RAF kinases function as obligate dimers, which generated the hypothesis that RAF dimer formation might be nucleated by G-domain-mediated RAS dimerization. Here, we review the evidence for RAS dimerization and describe a recent discussion among RAS researchers that led to a consensus that the clustering of two or more RAS proteins is not due to the stable association of G-domains but, instead, is a consequence of RAS C-terminal membrane anchors and the membrane phospholipids with which they interact.
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Affiliation(s)
- Dhirendra K Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
| | - Mark R Philips
- Perlmutter Cancer Center, NYU Grossman School of Medicine, New York, NY, USA.
| | - John F Hancock
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA.
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15
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RDIVpSGP motif of ASPP2 binds to 14-3-3 and enhances ASPP2/k18/14-3-3 ternary complex formulation to promote BRAF/MEK/ERK signal inhibited cell proliferation in hepatocellular carcinoma. Cancer Gene Ther 2022; 29:1616-1627. [PMID: 35504951 DOI: 10.1038/s41417-022-00474-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/27/2022] [Accepted: 04/08/2022] [Indexed: 02/04/2023]
Abstract
The Apoptosis Stimulating Protein of p53 2 (ASPP2) is a heterozygous insufficient tumor suppressor; however, its molecular mechanism(s) in tumor suppression is not completely understood. ASPP2 plays an essential role in cell growth, as shown by liver hepatocellular carcinoma (LIHC) RNA-seq assay using the Cancer Genome Atlas (TCGA) and High-Throughput-PCR assay using ASPP2 knockdown cells. These observations were further confirmed by in vivo and in vitro experiments. Mechanistically, N-terminus ASPP2 interacted with Keratin 18 (k18) in vivo and in vitro. Interestingly, the RDIVpSGP motif of ASPP2 associates with 14-3-3 and promotes ASPP2/k18/14-3-3 ternary-complex formation which promotes MEK/ERK signal activation by impairing 14-3-3 and BRAF association. Additionally, ASPP2-rAd injection promotes paclitaxel-suppressed tumor growth by suppressing cell proliferation in the BALB/c nude mice model. ASPP2 and k18 were preferentially downregulated in Hepatocellular Carcinoma (HCC), which predicted poor prognosis in HCC patients. Overall, these findings suggested that ASPP2 promoted BRAF/MEK/ERK signal activation by promoting the formation of an ASPP2/k18/14-3-3 ternary complex via the RDIVpSGP motif at the N terminus. Moreover, this study provides novel insights into the molecular mechanism of tumor suppression in HCC patients.
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16
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Singh AK, Novak J, Kumar A, Singh H, Thareja S, Pathak P, Grishina M, Verma A, Yadav JP, Khalilullah H, Pathania V, Nandanwar H, Jaremko M, Emwas AH, Kumar P. Gaussian field-based 3D-QSAR and molecular simulation studies to design potent pyrimidine-sulfonamide hybrids as selective BRAF V600E inhibitors. RSC Adv 2022; 12:30181-30200. [PMID: 36329938 PMCID: PMC9585928 DOI: 10.1039/d2ra05751d] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 10/14/2022] [Indexed: 11/13/2022] Open
Abstract
The "RAS-RAF-MEK-ERK" pathway is an important signaling pathway in melanoma. BRAFV600E (70-90%) is the most common mutation in this pathway. BRAF inhibitors have four types of conformers: type I (αC-IN/DFG-IN), type II (αC-IN/DFG-OUT), type I1/2 (αC-OUT/DFG-IN), and type I/II (αC-OUT/DFG-OUT). First- and second-generation BRAF inhibitors show resistance to BRAFV600E and are ineffective against malignancies induced by dimer BRAF mutants causing 'paradoxical' activation. In the present study, we performed molecular modeling of pyrimidine-sulfonamide hybrids inhibitors using 3D-QSAR, molecular docking, and molecular dynamics simulations. Previous reports reveal the importance of pyrimidine and sulfonamide moieties in the development of BRAFV600E inhibitors. Analysis of 3D-QSAR models provided novel pyrimidine sulfonamide hybrid BRAFV600E inhibitors. The designed compounds share similarities with several structural moieties present in first- and second-generation BRAF inhibitors. A total library of 88 designed compounds was generated and molecular docking studies were performed with them. Four molecules (T109, T183, T160, and T126) were identified as hits and selected for detailed studies. Molecular dynamics simulations were performed at 900 ns and binding was calculated. Based on molecular docking and simulation studies, it was found that the designed compounds have better interactions with the core active site [the nucleotide (ADP or ATP) binding site, DFG motif, and the phospho-acceptor site (activation segment) of BRAFV600E protein than previous inhibitors. Similar to the FDA-approved BRAFV600E inhibitors the developed compounds have [αC-OUT/DFG-IN] conformation. Compounds T126, T160 and T183 interacted with DIF (Leu505), making them potentially useful against BRAFV600E resistance and malignancies induced by dimer BRAF mutants. The synthesis and biological evaluation of the designed molecules is in progress, which may lead to some potent BRAFV600E selective inhibitors.
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Affiliation(s)
- Ankit Kumar Singh
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab Ghudda Bathinda 151401 India
| | - Jurica Novak
- Department of Biotechnology, University of Rijeka Rijeka 51000 Croatia
- Center for Artificial Intelligence and Cybersecurity, University of Rijeka Rijeka 51000 Croatia
- Scientific and Educational Center 'Biomedical Technologies' School of Medical Biology, South Ural State University Chelyabinsk RU-454080 Russia
| | - Adarsh Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab Ghudda Bathinda 151401 India
| | - Harshwardhan Singh
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab Ghudda Bathinda 151401 India
| | - Suresh Thareja
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab Ghudda Bathinda 151401 India
| | - Prateek Pathak
- Laboratory of Computational Modeling of Drugs, Higher Medical and Biological School, South Ural State University Chelyabinsk 454008 Russia
| | - Maria Grishina
- Laboratory of Computational Modeling of Drugs, Higher Medical and Biological School, South Ural State University Chelyabinsk 454008 Russia
| | - Amita Verma
- Department of Pharmaceutical Sciences, Bioorganic and Medicinal Chemistry Research Laboratory, Sam Higginbottom University of Agriculture, Technology and Sciences Prayagraj 211007 India
| | - Jagat Pal Yadav
- Department of Pharmaceutical Sciences, Bioorganic and Medicinal Chemistry Research Laboratory, Sam Higginbottom University of Agriculture, Technology and Sciences Prayagraj 211007 India
- Department of Pharmacology, Kamla Nehru Institute of Management and Technology Faridipur Sultanpur 228118 India
| | - Habibullah Khalilullah
- Department of Pharmaceutical Chemistry and Pharmacognosy, Unaizah College of Pharmacy, Qassim University Unayzah 51911 Saudi Arabia
| | - Vikas Pathania
- Clinical Microbiology & Bioactive Screening Laboratory, Council of Scientifc & Industrial Research -Institute of Microbial Technology Sector-39A Chandigarh 160036 India
| | - Hemraj Nandanwar
- Clinical Microbiology & Bioactive Screening Laboratory, Council of Scientifc & Industrial Research -Institute of Microbial Technology Sector-39A Chandigarh 160036 India
| | - Mariusz Jaremko
- Smart-Health Initiative (SHI) and Red Sea Research Center (RSRC), Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST) Thuwal 23955-6900 Saudi Arabia
| | - Abdul-Hamid Emwas
- Core Labs, King Abdullah University of Science and Technology (KAUST) Thuwal 23955-6900 Saudi Arabia
| | - Pradeep Kumar
- Department of Pharmaceutical Sciences and Natural Products, Central University of Punjab Ghudda Bathinda 151401 India
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17
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Obsilova V, Obsil T. Structural insights into the functional roles of 14-3-3 proteins. Front Mol Biosci 2022; 9:1016071. [PMID: 36188227 PMCID: PMC9523730 DOI: 10.3389/fmolb.2022.1016071] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 09/02/2022] [Indexed: 12/02/2022] Open
Abstract
Signal transduction cascades efficiently transmit chemical and/or physical signals from the extracellular environment to intracellular compartments, thereby eliciting an appropriate cellular response. Most often, these signaling processes are mediated by specific protein-protein interactions involving hundreds of different receptors, enzymes, transcription factors, and signaling, adaptor and scaffolding proteins. Among them, 14-3-3 proteins are a family of highly conserved scaffolding molecules expressed in all eukaryotes, where they modulate the function of other proteins, primarily in a phosphorylation-dependent manner. Through these binding interactions, 14-3-3 proteins participate in key cellular processes, such as cell-cycle control, apoptosis, signal transduction, energy metabolism, and protein trafficking. To date, several hundreds of 14-3-3 binding partners have been identified, including protein kinases, phosphatases, receptors and transcription factors, which have been implicated in the onset of various diseases. As such, 14-3-3 proteins are promising targets for pharmaceutical interventions. However, despite intensive research into their protein-protein interactions, our understanding of the molecular mechanisms whereby 14-3-3 proteins regulate the functions of their binding partners remains insufficient. This review article provides an overview of the current state of the art of the molecular mechanisms whereby 14-3-3 proteins regulate their binding partners, focusing on recent structural studies of 14-3-3 protein complexes.
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Affiliation(s)
- Veronika Obsilova
- Institute of Physiology of the Czech Academy of Sciences, Laboratory of Structural Biology of Signaling Proteins, Division BIOCEV, Vestec, Czechia
- *Correspondence: Veronika Obsilova, ; Tomas Obsil,
| | - Tomas Obsil
- Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Prague, Czechia
- *Correspondence: Veronika Obsilova, ; Tomas Obsil,
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18
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Liau NPD, Johnson MC, Izadi S, Gerosa L, Hammel M, Bruning JM, Wendorff TJ, Phung W, Hymowitz SG, Sudhamsu J. Structural basis for SHOC2 modulation of RAS signalling. Nature 2022; 609:400-407. [PMID: 35768504 PMCID: PMC9452301 DOI: 10.1038/s41586-022-04838-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 05/05/2022] [Indexed: 12/12/2022]
Abstract
The RAS-RAF pathway is one of the most commonly dysregulated in human cancers1-3. Despite decades of study, understanding of the molecular mechanisms underlying dimerization and activation4 of the kinase RAF remains limited. Recent structures of inactive RAF monomer5 and active RAF dimer5-8 bound to 14-3-39,10 have revealed the mechanisms by which 14-3-3 stabilizes both RAF conformations via specific phosphoserine residues. Prior to RAF dimerization, the protein phosphatase 1 catalytic subunit (PP1C) must dephosphorylate the N-terminal phosphoserine (NTpS) of RAF11 to relieve inhibition by 14-3-3, although PP1C in isolation lacks intrinsic substrate selectivity. SHOC2 is as an essential scaffolding protein that engages both PP1C and RAS to dephosphorylate RAF NTpS11-13, but the structure of SHOC2 and the architecture of the presumptive SHOC2-PP1C-RAS complex remain unknown. Here we present a cryo-electron microscopy structure of the SHOC2-PP1C-MRAS complex to an overall resolution of 3 Å, revealing a tripartite molecular architecture in which a crescent-shaped SHOC2 acts as a cradle and brings together PP1C and MRAS. Our work demonstrates the GTP dependence of multiple RAS isoforms for complex formation, delineates the RAS-isoform preference for complex assembly, and uncovers how the SHOC2 scaffold and RAS collectively drive specificity of PP1C for RAF NTpS. Our data indicate that disease-relevant mutations affect complex assembly, reveal the simultaneous requirement of two RAS molecules for RAF activation, and establish rational avenues for discovery of new classes of inhibitors to target this pathway.
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Affiliation(s)
- Nicholas P D Liau
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Matthew C Johnson
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Saeed Izadi
- Pharmaceutical Development, Genentech, South San Francisco, CA, USA
| | - Luca Gerosa
- Department of Bioinformatics and Computational Biology, Genentech, South San Francisco, CA, USA
| | - Michal Hammel
- Physical Bioscience Division, Lawrence Berkeley National Labs, Berkeley, CA, USA
| | - John M Bruning
- Department of Biochemical and Cellular Pharmacology, Genentech, South San Francisco, CA, USA
| | - Timothy J Wendorff
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Wilson Phung
- Department of Microchemistry, Proteomics and Lipidomics, Genentech, South San Francisco, CA, USA
| | - Sarah G Hymowitz
- Department of Structural Biology, Genentech, South San Francisco, CA, USA.
- The Column Group, San Francisco, CA, USA.
| | - Jawahar Sudhamsu
- Department of Structural Biology, Genentech, South San Francisco, CA, USA.
- Department of Discovery Oncology, Genentech, South San Francisco, CA, USA.
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19
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Sluchanko NN. Recent advances in structural studies of 14-3-3 protein complexes. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 130:289-324. [PMID: 35534110 DOI: 10.1016/bs.apcsb.2021.12.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Being phosphopeptide-binding hubs, 14-3-3 proteins coordinate multiple cellular processes in eukaryotes, including the regulation of apoptosis, cell cycle, ion channels trafficking, transcription, signal transduction, and hormone biosynthesis. Forming constitutive α-helical dimers, 14-3-3 proteins predominantly recognize specifically phosphorylated Ser/Thr sites within their partners; this generally stabilizes phosphotarget conformation and affects its activity, intracellular distribution, dephosphorylation, degradation and interactions with other proteins. Not surprisingly, 14-3-3 complexes are involved in the development of a range of diseases and are considered promising drug targets. The wide interactome of 14-3-3 proteins encompasses hundreds of different phosphoproteins, for many of which the interaction is well-documented in vitro and in vivo but lack the structural data that would help better understand underlying regulatory mechanisms and develop new drugs. Despite obtaining structural information on 14-3-3 complexes is still lagging behind the research of 14-3-3 interactions on a proteome-wide scale, recent works provided some advances, including methodological improvements and accumulation of new interesting structural data, that are discussed in this review.
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Affiliation(s)
- Nikolai N Sluchanko
- A.N. Bach Institute of Biochemistry, Federal Research Center "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russian Federation.
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20
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Chow A, Khan ZM, Marsiglia WM, Dar AC. Conformational control and regulation of the pseudokinase KSR via small molecule binding interactions. Methods Enzymol 2022; 667:365-402. [PMID: 35525547 PMCID: PMC9150438 DOI: 10.1016/bs.mie.2022.03.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pseudokinases often operate through functionally related enzymes and receptors. A prime example is the pseudokinase KSR (Kinase Suppressor of RAS), which can act as both an amplifier and inhibitor of members in the RAS-MAPK (Mitogen Activated Protein Kinase) signaling pathway. KSR is structurally related to the active RAF kinases over multiple domains; moreover, the pseudokinase domain of KSR forms physical and regulatory complexes with both RAF and MEK through distinct interfaces. Characterization of small molecule interactions on KSR has been used to uncover novel chemical tools and understand the mechanism of action of clinical drugs. Here, we elaborate on assays and structural methods for measuring binding at orthosteric and interfacial binding sites on KSR. These distinct small molecule pockets provide therapeutic paths for targeting KSR1 and KSR2 pseudokinases in disease, including in RAS and RAF mutant cancers.
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Affiliation(s)
- Arthur Chow
- Department of Oncological Sciences, Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Centre for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Zaigham M Khan
- Department of Oncological Sciences, Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Centre for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - William M Marsiglia
- Department of Oncological Sciences, Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Centre for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Arvin C Dar
- Department of Oncological Sciences, Department of Pharmacological Sciences, The Tisch Cancer Institute, Mount Sinai Centre for Therapeutic Discovery, Icahn School of Medicine at Mount Sinai, New York, NY, United States.
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21
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Simanshu DK, Morrison DK. A Structure is Worth a Thousand Words: New Insights for RAS and RAF Regulation. Cancer Discov 2022; 12:899-912. [PMID: 35046094 PMCID: PMC8983508 DOI: 10.1158/2159-8290.cd-21-1494] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 11/16/2022]
Abstract
The RAS GTPases are frequently mutated in human cancer, with KRAS being the predominant tumor driver. For many years, it has been known that the structure and function of RAS are integrally linked, as structural changes induced by GTP binding or mutational events determine the ability of RAS to interact with regulators and effectors. Recently, a wealth of information has emerged from structures of specific KRAS mutants and from structures of multiprotein complexes containing RAS and/or RAF, an essential effector of RAS. These structures provide key insights regarding RAS and RAF regulation as well as promising new strategies for therapeutic intervention. SIGNIFICANCE The RAS GTPases are major drivers of tumorigenesis, and for RAS proteins to exert their full oncogenic potential, they must interact with the RAF kinases to initiate ERK cascade signaling. Although binding to RAS is typically a prerequisite for RAF to become an activated kinase, determining the molecular mechanisms by which this interaction results in RAF activation has been a challenging task. A major advance in understanding this process and RAF regulation has come from recent structural studies of various RAS and RAF multiprotein signaling complexes, revealing new avenues for drug discovery.
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Affiliation(s)
- Dhirendra K. Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, Maryland
| | - Deborah K. Morrison
- Laboratory of Cell and Developmental Signaling, Center for Cancer Research, National Cancer Institute, Frederick, Maryland
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22
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Structural insights into the BRAF monomer-to-dimer transition mediated by RAS binding. Nat Commun 2022; 13:486. [PMID: 35078985 PMCID: PMC8789793 DOI: 10.1038/s41467-022-28084-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 01/07/2022] [Indexed: 12/20/2022] Open
Abstract
RAF kinases are essential effectors of RAS, but how RAS binding initiates the conformational changes needed for autoinhibited RAF monomers to form active dimers has remained unclear. Here, we present cryo-electron microscopy structures of full-length BRAF complexes derived from mammalian cells: autoinhibited, monomeric BRAF:14-3-32:MEK and BRAF:14-3-32 complexes, and an inhibitor-bound, dimeric BRAF2:14-3-32 complex, at 3.7, 4.1, and 3.9 Å resolution, respectively. In both autoinhibited, monomeric structures, the RAS binding domain (RBD) of BRAF is resolved, revealing that the RBD forms an extensive contact interface with the 14-3-3 protomer bound to the BRAF C-terminal site and that key basic residues required for RBD-RAS binding are exposed. Moreover, through structure-guided mutational studies, our findings indicate that RAS-RAF binding is a dynamic process and that RBD residues at the center of the RBD:14-3-3 interface have a dual function, first contributing to RAF autoinhibition and then to the full spectrum of RAS-RBD interactions. RAF kinases are essential for RAS protein signalling but how RAS binding regulates dimerization and activation of RAF has remained unclear. Here, the authors report cryoEM structures that provide mechanistic insights into the RAS-mediated monomer-to-dimer transition of full-length BRAF.
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23
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Dillon M, Lopez A, Lin E, Sales D, Perets R, Jain P. Progress on Ras/MAPK Signaling Research and Targeting in Blood and Solid Cancers. Cancers (Basel) 2021; 13:cancers13205059. [PMID: 34680208 PMCID: PMC8534156 DOI: 10.3390/cancers13205059] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/30/2021] [Accepted: 10/06/2021] [Indexed: 12/18/2022] Open
Abstract
Simple Summary The Ras-Raf-MEK-ERK signaling pathway is responsible for regulating cell proliferation, differentiation, and survival. Overexpression and overactivation of members within the signaling cascade have been observed in many solid and blood cancers. Research often focuses on targeting the pathway to disrupt cancer initiation and progression. We aimed to provide an overview of the pathway’s physiologic role and regulation, interactions with other pathways involved in cancer development, and mutations that lead to malignancy. Several blood and solid cancers are analyzed to illustrate the impact of the pathway’s dysregulation, stemming from mutation or viral induction. Finally, we summarized different approaches to targeting the pathway and the associated novel treatments being researched or having recently achieved approval. Abstract The mitogen-activated protein kinase (MAPK) pathway, consisting of the Ras-Raf-MEK-ERK signaling cascade, regulates genes that control cellular development, differentiation, proliferation, and apoptosis. Within the cascade, multiple isoforms of Ras and Raf each display differences in functionality, efficiency, and, critically, oncogenic potential. According to the NCI, over 30% of all human cancers are driven by Ras genes. This dysfunctional signaling is implicated in a wide variety of leukemias and solid tumors, both with and without viral etiology. Due to the strong evidence of Ras-Raf involvement in tumorigenesis, many have attempted to target the cascade to treat these malignancies. Decades of unsuccessful experimentation had deemed Ras undruggable, but recently, the approval of Sotorasib as the first ever KRas inhibitor represents a monumental breakthrough. This advancement is not without novel challenges. As a G12C mutant-specific drug, it also represents the issue of drug target specificity within Ras pathway; not only do many drugs only affect single mutational profiles, with few pan-inhibitor exceptions, tumor genetic heterogeneity may give rise to drug-resistant profiles. Furthermore, significant challenges in targeting downstream Raf, especially the BRaf isoform, lie in the paradoxical activation of wild-type BRaf by BRaf mutant inhibitors. This literature review will delineate the mechanisms of Ras signaling in the MAPK pathway and its possible oncogenic mutations, illustrate how specific mutations affect the pathogenesis of specific cancers, and compare available and in-development treatments targeting the Ras pathway.
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24
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Kondo Y, Paul JW, Subramaniam S, Kuriyan J. New insights into Raf regulation from structural analyses. Curr Opin Struct Biol 2021; 71:223-231. [PMID: 34454301 DOI: 10.1016/j.sbi.2021.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/06/2021] [Accepted: 07/10/2021] [Indexed: 01/07/2023]
Abstract
BRAF is a highly regulated protein kinase that controls cell fate in animal cells. Recent structural analyses have revealed how active and inactive forms of BRAF bind to dimers of the scaffold protein 14-3-3. Inactive BRAF binds to 14-3-3 as a monomer and is held in an inactive conformation by interactions with ATP and the substrate kinase MEK, a striking example of enzyme inhibition by substrate binding. A change in the phosphorylation state of BRAF shifts the stoichiometry of the BRAF:14-3-3 complex from 1:2 to 2:2, resulting in stabilization of the active dimeric form of the kinase. These new findings uncover unexpected features of the regulatory mechanisms underlying Raf biology and help explain the paradoxical activation of Raf by small-molecule inhibitors.
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Affiliation(s)
- Yasushi Kondo
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA
| | - Joseph W Paul
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA
| | | | - John Kuriyan
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, CA, 94720, USA; Department of Chemistry, University of California, Berkeley, CA, 94720, USA; Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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25
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Heppner DE, Eck MJ. A structural perspective on targeting the RTK/Ras/MAP kinase pathway in cancer. Protein Sci 2021; 30:1535-1553. [PMID: 34008902 PMCID: PMC8284588 DOI: 10.1002/pro.4125] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/13/2021] [Accepted: 05/14/2021] [Indexed: 02/06/2023]
Abstract
Precision oncology is premised on identifying and drugging proteins and pathways that drive tumorigenesis or are required for survival of tumor cells. Across diverse cancer types, the signaling pathway emanating from receptor tyrosine kinases on the cell surface to RAS and the MAP kinase pathway is the most frequent target of oncogenic mutations, and key proteins in this signaling axis including EGFR, SHP2, RAS, BRAF, and MEK have long been a focus in cancer drug discovery. In this review, we provide an overview of historical and recent efforts to develop inhibitors targeting these nodes with an emphasis on the role that an understanding of protein structure and regulation has played in inhibitor discovery and characterization. Beyond its well-established role in structure-based drug design, structural biology has revealed mechanisms of allosteric regulation, distinct effects of activating oncogenic mutations, and other vulnerabilities that have opened new avenues in precision cancer drug discovery.
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Affiliation(s)
- David E. Heppner
- Department of ChemistryUniversity at Buffalo, State University of New YorkBuffaloNew YorkUSA
- Department of Pharmacology and TherapeuticsRoswell Park Comprehensive Cancer CenterBuffaloNew YorkUSA
| | - Michael J. Eck
- Department of Cancer BiologyDana‐Farber Cancer InstituteBostonMassachusettsUSA
- Department of Biological Chemistry and Molecular PharmacologyHarvard Medical SchoolBostonMassachusettsUSA
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26
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Cook FA, Cook SJ. Inhibition of RAF dimers: it takes two to tango. Biochem Soc Trans 2021; 49:237-251. [PMID: 33367512 PMCID: PMC7924995 DOI: 10.1042/bst20200485] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 11/17/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023]
Abstract
The RAS-regulated RAF-MEK1/2-ERK1/2 pathway promotes cell proliferation and survival and RAS and BRAF proteins are commonly mutated in cancer. This has fuelled the development of small molecule kinase inhibitors including ATP-competitive RAF inhibitors. Type I and type I½ ATP-competitive RAF inhibitors are effective in BRAFV600E/K-mutant cancer cells. However, in RAS-mutant cells these compounds instead promote RAS-dependent dimerisation and paradoxical activation of wild-type RAF proteins. RAF dimerisation is mediated by two key regions within each RAF protein; the RKTR motif of the αC-helix and the NtA-region of the dimer partner. Dimer formation requires the adoption of a closed, active kinase conformation which can be induced by RAS-dependent activation of RAF or by the binding of type I and I½ RAF inhibitors. Binding of type I or I½ RAF inhibitors to one dimer partner reduces the binding affinity of the other, thereby leaving a single dimer partner uninhibited and able to activate MEK. To overcome this paradox two classes of drug are currently under development; type II pan-RAF inhibitors that induce RAF dimer formation but bind both dimer partners thus allowing effective inhibition of both wild-type RAF dimer partners and monomeric active class I mutant RAF, and the recently developed "paradox breakers" which interrupt BRAF dimerisation through disruption of the αC-helix. Here we review the regulation of RAF proteins, including RAF dimers, and the progress towards effective targeting of the wild-type RAF proteins.
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Affiliation(s)
- Frazer A. Cook
- Signalling Programme, The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, U.K
| | - Simon J. Cook
- Signalling Programme, The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, U.K
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27
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The 14-3-3 Proteins as Important Allosteric Regulators of Protein Kinases. Int J Mol Sci 2020; 21:ijms21228824. [PMID: 33233473 PMCID: PMC7700312 DOI: 10.3390/ijms21228824] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/20/2020] [Accepted: 11/20/2020] [Indexed: 12/14/2022] Open
Abstract
Phosphorylation by kinases governs many key cellular and extracellular processes, such as transcription, cell cycle progression, differentiation, secretion and apoptosis. Unsurprisingly, tight and precise kinase regulation is a prerequisite for normal cell functioning, whereas kinase dysregulation often leads to disease. Moreover, the functions of many kinases are regulated through protein–protein interactions, which in turn are mediated by phosphorylated motifs and often involve associations with the scaffolding and chaperon protein 14-3-3. Therefore, the aim of this review article is to provide an overview of the state of the art on 14-3-3-mediated kinase regulation, focusing on the most recent mechanistic insights into these important protein–protein interactions and discussing in detail both their structural aspects and functional consequences.
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