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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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Rohrer L, Spohr C, Beha C, Griffin R, Braun S, Halbach S, Brummer T. Analysis of RAS and drug induced homo- and heterodimerization of RAF and KSR1 proteins in living cells using split Nanoluc luciferase. Cell Commun Signal 2023; 21:136. [PMID: 37316874 DOI: 10.1186/s12964-023-01146-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 04/27/2023] [Indexed: 06/16/2023] Open
Abstract
The dimerization of RAF kinases represents a key event in their activation cycle and in RAS/ERK pathway activation. Genetic, biochemical and structural approaches provided key insights into this process defining RAF signaling output and the clinical efficacy of RAF inhibitors (RAFi). However, methods reporting the dynamics of RAF dimerization in living cells and in real time are still in their infancy. Recently, split luciferase systems have been developed for the detection of protein-protein-interactions (PPIs), incl. proof-of-concept studies demonstrating the heterodimerization of the BRAF and RAF1 isoforms. Due to their small size, the Nanoluc luciferase moieties LgBiT and SmBiT, which reconstitute a light emitting holoenzyme upon fusion partner promoted interaction, appear as well-suited to study RAF dimerization. Here, we provide an extensive analysis of the suitability of the Nanoluc system to study the homo- and heterodimerization of BRAF, RAF1 and the related KSR1 pseudokinase. We show that KRASG12V promotes the homo- and heterodimerization of BRAF, while considerable KSR1 homo- and KSR1/BRAF heterodimerization already occurs in the absence of this active GTPase and requires a salt bridge between the CC-SAM domain of KSR1 and the BRAF-specific region. We demonstrate that loss-of-function mutations impairing key steps of the RAF activation cycle can be used as calibrators to gauge the dynamics of heterodimerization. This approach identified the RAS-binding domains and the C-terminal 14-3-3 binding motifs as particularly critical for the reconstitution of RAF mediated LgBiT/SmBiT reconstitution, while the dimer interface was less important for dimerization but essential for downstream signaling. We show for the first time that BRAFV600E, the most common BRAF oncoprotein whose dimerization status is controversially portrayed in the literature, forms homodimers in living cells more efficiently than its wildtype counterpart. Of note, Nanoluc activity reconstituted by BRAFV600E homodimers is highly sensitive to the paradox-breaking RAFi PLX8394, indicating a dynamic and specific PPI. We report the effects of eleven ERK pathway inhibitors on RAF dimerization, incl. third-generation compounds that are less-defined in terms of their dimer promoting abilities. We identify Naporafenib as a potent and long-lasting dimerizer and show that the split Nanoluc approach discriminates between type I, I1/2 and II RAFi. Video Abstract.
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Affiliation(s)
- Lino Rohrer
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
| | - Corinna Spohr
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
| | - Carina Beha
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
| | - Ricarda Griffin
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
| | - Sandra Braun
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
| | - Sebastian Halbach
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany
- German Cancer Consortium (DKTK), Partner Site Freiburg and German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany
| | - Tilman Brummer
- Institute of Molecular Medicine and Cell Research (IMMZ), Zentrum für Biochemie und Molekulare Zellforschung (ZBMZ), Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, Freiburg, 79104, Germany.
- German Cancer Consortium (DKTK), Partner Site Freiburg and German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany.
- Comprehensive Cancer Center Freiburg (CCCF), Medical Center, University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, 79106, Germany.
- Center for Biological Signalling Studies BIOSS, University of Freiburg, Freiburg, 79104, Germany.
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