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DeRose BT, Kelley RS, Ravi R, Kokona B, Beld J, Spiliotis ET, Padrick SB. Production and analysis of a mammalian septin hetero-octamer complex. Cytoskeleton (Hoboken) 2020; 77:485-499. [PMID: 33185030 DOI: 10.1002/cm.21643] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 10/26/2020] [Accepted: 11/08/2020] [Indexed: 01/19/2023]
Abstract
The septins are filament-forming proteins found in diverse eukaryotes from fungi to vertebrates, with roles in cytokinesis, shaping of membranes and modifying cytoskeletal organization. These GTPases assemble into rod-shaped soluble hetero-hexamers and hetero-octamers in mammals, which polymerize into filaments and higher order structures. While the cell biology and pathobiology of septins are advancing rapidly, mechanistic study of the mammalian septins is limited by a lack of recombinant hetero-octamer materials. We describe here the production and characterization of a recombinant mammalian septin hetero-octamer of defined stoichiometry, the SEPT2/SEPT6/SEPT7/SEPT3 complex. Using a fluorescent protein fusion to the complex, we observed filaments assembled from this complex. In addition, we used this novel tool to resolve recent questions regarding the organization of the soluble septin complex. Biochemical characterization of a SEPT3 truncation that disrupts SEPT3-SEPT3 interactions is consistent with SEPT3 occupying a central position in the complex while the SEPT2 subunits are at the ends of the rod-shaped octameric complexes. Consistent with SEPT2 being on the complex ends, we find that our purified SEPT2/SEPT6/SEPT7/SEPT3 hetero-octamer copolymerizes into mixed filaments with separately purified SEPT2/SEPT6/SEPT7 hetero-hexamer. We expect this new recombinant production approach to lay essential groundwork for future studies into mammalian septin mechanism and function.
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Affiliation(s)
- Barry T DeRose
- Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Robert S Kelley
- Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, USA.,VCU Health System, Richmond, Virginia, USA
| | - Roshni Ravi
- Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, USA.,WuXi Advanced Therapies, Philadelphia, Pennsylvania, USA
| | - Bashkim Kokona
- Department of Chemistry, Haverford College, Haverford, Pennsylvania, USA
| | - Joris Beld
- Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Elias T Spiliotis
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Shae B Padrick
- Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, USA
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Kumagai PS, Martins CS, Sales EM, Rosa HV, Mendonça DC, Damalio JCP, Spinozzi F, Itri R, Araujo APU. Correct partner makes the difference: Septin G-interface plays a critical role in amyloid formation. Int J Biol Macromol 2019; 133:428-435. [DOI: 10.1016/j.ijbiomac.2019.04.105] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/12/2019] [Accepted: 04/15/2019] [Indexed: 01/04/2023]
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Turner JA, Bemis JGT, Bagby SM, Capasso A, Yacob BW, Chimed TS, Van Gulick R, Lee H, Tobin R, Tentler JJ, Pitts T, McCarter M, Robinson WA, Couts KL. BRAF fusions identified in melanomas have variable treatment responses and phenotypes. Oncogene 2018; 38:1296-1308. [PMID: 30254212 DOI: 10.1038/s41388-018-0514-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 08/09/2018] [Accepted: 08/10/2018] [Indexed: 12/13/2022]
Abstract
Oncogenic BRAF fusions have emerged as an alternate mechanism for BRAF activation in melanomas and other cancers. A number of BRAF fusions with different 5' gene partners and BRAF exon breakpoints have been described, but the effects of different partners and breakpoints on cancer phenotypes and treatment responses has not been well characterized. Targeted RNA sequencing was used to screen 60 melanoma patient-derived xenograft (PDX) models for BRAF fusions. We identified three unique BRAF fusions, including a novel SEPT3-BRAF fusion, occurring in four tumors (4/60, 6.7%), all of which were "pan-negative" (lacking other common mutations) (4/18, 22.2%). The BRAF fusion PDX models showed variable growth rates and responses to MAPK inhibitors in vivo. Overexpression of BRAF fusions identified in our study, as well as other BRAF fusions previously identified in melanomas, resulted in a high degree of variability in 2D proliferation and 3D invasion between the different fusions. While exogenously expressed BRAF fusions all responded to MAPK inhibition in vitro, we observed potential differences in signaling and feedback mechanisms. In summary, BRAF fusions are actionable therapeutic targets, however there are significant differences in phenotypes, treatment responses, and signaling which may be clinically relevant.
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Affiliation(s)
- Jacqueline A Turner
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Judson G T Bemis
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Stacey M Bagby
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Anna Capasso
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Betelehem W Yacob
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Tugs-Saikhan Chimed
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Robert Van Gulick
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Hannah Lee
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA.,Department of Medicine, Internal Medicine Residency Training Program, University of Colorado Denver, Aurora, CO, USA
| | - Richard Tobin
- Division Surgical Oncology, Department of Surgery, University of Colorado Denver, Aurora, CO, USA
| | - John J Tentler
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Todd Pitts
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Martin McCarter
- Division Surgical Oncology, Department of Surgery, University of Colorado Denver, Aurora, CO, USA
| | - William A Robinson
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Kasey L Couts
- Division of Medical Oncology, Department of Medicine, University of Colorado Denver, Aurora, CO, USA.
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