1
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Olasz B, Smithers L, Evans GL, Anandan A, Murcha MW, Vrielink A. Structural analysis of the SAM domain of the Arabidopsis mitochondrial tRNA import receptor. J Biol Chem 2024; 300:107258. [PMID: 38582448 PMCID: PMC11063897 DOI: 10.1016/j.jbc.2024.107258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 03/10/2024] [Accepted: 03/19/2024] [Indexed: 04/08/2024] Open
Abstract
Mitochondria are membrane-bound organelles of endosymbiotic origin with limited protein-coding capacity. The import of nuclear-encoded proteins and nucleic acids is required and essential for maintaining organelle mass, number, and activity. As plant mitochondria do not encode all the necessary tRNA types required, the import of cytosolic tRNA is vital for organelle maintenance. Recently, two mitochondrial outer membrane proteins, named Tric1 and Tric2, for tRNA import component, were shown to be involved in the import of cytosolic tRNA. Tric1/2 binds tRNAalavia conserved residues in the C-terminal Sterile Alpha Motif (SAM) domain. Here we report the X-ray crystal structure of the Tric1 SAM domain. We identified the ability of the SAM domain to form a helical superstructure with six monomers per helical turn and key amino acid residues responsible for its formation. We determined that the oligomerization of the Tric1 SAM domain may play a role in protein function whereby mutation of Gly241 introducing a larger side chain at this position disrupted the oligomer and resulted in the loss of RNA binding capability. Furthermore, complementation of Arabidopsis thaliana Tric1/2 knockout lines with a mutated Tric1 failed to restore the defective plant phenotype. AlphaFold2 structure prediction of both the SAM domain and Tric1 support a cyclic pentameric or hexameric structure. In the case of a hexameric structure, a pore of sufficient dimensions to transfer tRNA across the mitochondrial membrane is observed. Our results highlight the importance of oligomerization of Tric1 for protein function.
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Affiliation(s)
- Bence Olasz
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Luke Smithers
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Genevieve L Evans
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Anandhi Anandan
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Monika W Murcha
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia.
| | - Alice Vrielink
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia.
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2
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Nawarathnage S, Tseng YJ, Soleimani S, Smith T, Pedroza Romo MJ, Abiodun WO, Egbert CM, Madhusanka D, Bunn D, Woods B, Tsubaki E, Stewart C, Brown S, Doukov T, Andersen JL, Moody JD. Fusion crystallization reveals the behavior of both the 1TEL crystallization chaperone and the TNK1 UBA domain. Structure 2023; 31:1589-1603.e6. [PMID: 37776857 PMCID: PMC10843481 DOI: 10.1016/j.str.2023.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/11/2023] [Accepted: 09/04/2023] [Indexed: 10/02/2023]
Abstract
Human thirty-eight-negative kinase-1 (TNK1) is implicated in cancer progression. The TNK1 ubiquitin-associated (UBA) domain binds polyubiquitin and plays a regulatory role in TNK1 activity and stability. No experimentally determined molecular structure of this unusual UBA domain is available. We fused the UBA domain to the 1TEL variant of the translocation ETS leukemia protein sterile alpha motif (TELSAM) crystallization chaperone and obtained crystals diffracting as far as 1.53 Å. GG and GSGG linkers allowed the UBA to reproducibly find a productive binding mode against its host 1TEL polymer and crystallize at protein concentrations as low as 0.2 mg/mL. Our studies support a mechanism of 1TEL fusion crystallization and show that 1TEL fusion crystals require fewer crystal contacts than traditional protein crystals. Modeling and experimental validation suggest the UBA domain may be selective for both the length and linkages of polyubiquitin chains.
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Affiliation(s)
| | - Yi Jie Tseng
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Sara Soleimani
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Tobin Smith
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Maria J Pedroza Romo
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Wisdom O Abiodun
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Christina M Egbert
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA; Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Deshan Madhusanka
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA; Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Derick Bunn
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Bridger Woods
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Evan Tsubaki
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Cameron Stewart
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Seth Brown
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Tzanko Doukov
- Macromolecular Crystallography Group, Structural Molecular Biology Resource, Stanford Synchrotron Radiation Lightsource, Menlo Park, CA, USA
| | - Joshua L Andersen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA; Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA.
| | - James D Moody
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA.
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3
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Woods H, Schiano DL, Aguirre JI, Ledwitch KV, McDonald EF, Voehler M, Meiler J, Schoeder CT. Computational modeling and prediction of deletion mutants. Structure 2023:S0969-2126(23)00128-4. [PMID: 37119820 DOI: 10.1016/j.str.2023.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 03/02/2023] [Accepted: 04/05/2023] [Indexed: 05/01/2023]
Abstract
In-frame deletion mutations can result in disease. The impact of these mutations on protein structure and subsequent functional changes remain understudied, partially due to the lack of comprehensive datasets including a structural readout. In addition, the recent breakthrough in structure prediction through deep learning demands an update of computational deletion mutation prediction. In this study, we deleted individually every residue of a small α-helical sterile alpha motif domain and investigated the structural and thermodynamic changes using 2D NMR spectroscopy and differential scanning fluorimetry. Then, we tested computational protocols to model and classify observed deletion mutants. We show a method using AlphaFold2 followed by RosettaRelax performs the best overall. In addition, a metric containing pLDDT values and Rosetta ΔΔG is most reliable in classifying tolerated deletion mutations. We further test this method on other datasets and show they hold for proteins known to harbor disease-causing deletion mutations.
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Affiliation(s)
- Hope Woods
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Chemical and Physical Biology Program, Vanderbilt University, Nashville, TN 37235, USA
| | - Dominic L Schiano
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Jonathan I Aguirre
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Kaitlyn V Ledwitch
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Eli F McDonald
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Markus Voehler
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Jens Meiler
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA; Institute for Drug Discovery, Leipzig University Medical School, 04103 Leipzig, Germany.
| | - Clara T Schoeder
- Center of Structural Biology, Vanderbilt University, Nashville, TN 37235, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA; Institute for Drug Discovery, Leipzig University Medical School, 04103 Leipzig, Germany.
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4
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Kan Y, Paung Y, Seeliger MA, Miller WT. Domain Architecture of the Nonreceptor Tyrosine Kinase Ack1. Cells 2023; 12:900. [PMID: 36980241 PMCID: PMC10047419 DOI: 10.3390/cells12060900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 03/17/2023] Open
Abstract
The nonreceptor tyrosine kinase (NRTK) Ack1 comprises a distinct arrangement of non-catalytic modules. Its SH3 domain has a C-terminal to the kinase domain (SH1), in contrast to the typical SH3-SH2-SH1 layout in NRTKs. The Ack1 is the only protein that shares a region of high homology to the tumor suppressor protein Mig6, a modulator of EGFR. The vertebrate Acks make up the only tyrosine kinase (TK) family known to carry a UBA domain. The GTPase binding and SAM domains are also uncommon in the NRTKs. In addition to being a downstream effector of receptor tyrosine kinases (RTKs) and integrins, Ack1 can act as an epigenetic regulator, modulate the degradation of the epidermal growth factor receptor (EGFR), confer drug resistance, and mediate the progression of hormone-sensitive tumors. In this review, we discuss the domain architecture of Ack1 in relation to other protein kinases that possess such defined regulatory domains.
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Affiliation(s)
- Yagmur Kan
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, NY 11794-8661, USA
| | - YiTing Paung
- Department of Pharmacology, School of Medicine, Stony Brook University, Stony Brook, NY 11794-8661, USA
| | - Markus A. Seeliger
- Department of Pharmacology, School of Medicine, Stony Brook University, Stony Brook, NY 11794-8661, USA
| | - W. Todd Miller
- Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, NY 11794-8661, USA
- Department of Veterans Affairs Medical Center, Northport, NY 11768-2200, USA
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5
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Wang XY, Zhang LN. RNA binding protein SAMD4: current knowledge and future perspectives. Cell Biosci 2023; 13:21. [PMID: 36732864 PMCID: PMC9893680 DOI: 10.1186/s13578-023-00968-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 01/22/2023] [Indexed: 02/04/2023] Open
Abstract
SAMD4 protein family is a class of novel RNA-binding proteins that can mediate post-transcriptional regulation and translation repression in eukaryotes, which are highly conserved from yeast to humans during evolution. In mammalian cells, SAMD4 protein family consists of two members including SAMD4A/Smaug1 and SAMD4B/Smaug2, both of which contain common SAM domain that can specifically bind to different target mRNAs through stem-loop structures, also known as Smaug recognition elements (SREs), and regulate the mRNA stability, degradation and translation. In addition, SAMD4 can form the cytoplasmic mRNA silencing foci and regulate the translation of SRE-containing mRNAs in neurons. SAMD4 also can form the cytosolic membrane-less organelles (MLOs), termed as Smaug1 bodies, and regulate mitochondrial function. Importantly, many studies have identified that SAMD4 family members are involved in various pathological processes including myopathy, bone development, neural development, and cancer occurrence and progression. In this review, we mainly summarize the structural characteristics, biological functions and molecular regulatory mechanisms of SAMD4 protein family members, which will provide a basis for further research and clinical application of SAMD4 protein family.
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Affiliation(s)
- Xin-Ya Wang
- grid.28703.3e0000 0000 9040 3743Beijing International Science and Technology Cooperation Base of Antivirus Drug, Faculty of Environment and Life, Beijing University of Technology, 100124 Beijing, People’s Republic of China
| | - Li-Na Zhang
- grid.28703.3e0000 0000 9040 3743Beijing International Science and Technology Cooperation Base of Antivirus Drug, Faculty of Environment and Life, Beijing University of Technology, 100124 Beijing, People’s Republic of China
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6
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Gerak CAN, Cho SY, Kolesnikov M, Okon M, Murphy MEP, Sessions RB, Roberge M, McIntosh LP. Biophysical characterization of the ETV6 PNT domain polymerization interfaces. J Biol Chem 2021; 296:100284. [PMID: 33450226 PMCID: PMC7949025 DOI: 10.1016/j.jbc.2021.100284] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 12/22/2020] [Accepted: 01/11/2021] [Indexed: 11/21/2022] Open
Abstract
ETV6 is an E26 transformation specific family transcriptional repressor that self-associates by its PNT domain to facilitate cooperative DNA binding. Chromosomal translocations frequently generate constitutively active oncoproteins with the ETV6 PNT domain fused to the kinase domain of one of many protein tyrosine kinases. Although an attractive target for therapeutic intervention, the propensity of the ETV6 PNT domain to polymerize via the tight head-to-tail association of two relatively flat interfaces makes it challenging to identify suitable small molecule inhibitors of this protein-protein interaction. Herein, we provide a comprehensive biophysical characterization of the ETV6 PNT domain interaction interfaces to aid future drug discovery efforts and help define the mechanisms by which its self-association mediates transcriptional repression. Using NMR spectroscopy, X-ray crystallography, and molecular dynamics simulations, along with amide hydrogen exchange measurements, we demonstrate that monomeric PNT domain variants adopt very stable helical bundle folds that do not change in conformation upon self-association into heterodimer models of the ETV6 polymer. Surface plasmon resonance-monitored alanine scanning mutagenesis studies identified hot spot regions within the self-association interfaces. These regions include both central hydrophobic residues and flanking salt-bridging residues. Collectively, these studies indicate that small molecules targeted to these hydrophobic or charged regions within the relatively rigid interfaces could potentially serve as orthosteric inhibitors of ETV6 PNT domain polymerization.
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Affiliation(s)
- Chloe A N Gerak
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Sophia Y Cho
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Maxim Kolesnikov
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael E P Murphy
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Michel Roberge
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada; Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
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7
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Rothé B, Gagnieux C, Leal-Esteban LC, Constam DB. Role of the RNA-binding protein Bicaudal-C1 and interacting factors in cystic kidney diseases. Cell Signal 2019; 68:109499. [PMID: 31838063 DOI: 10.1016/j.cellsig.2019.109499] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 12/09/2019] [Accepted: 12/10/2019] [Indexed: 01/03/2023]
Abstract
Polycystic kidneys frequently associate with mutations in individual components of cilia, basal bodies or centriolar satellites that perturb complex protein networks. In this review, we focus on the RNA-binding protein Bicaudal-C1 (BICC1) which was found mutated in renal cystic dysplasia, and on its interactions with the ankyrin repeat and sterile α motif (SAM)-containing proteins ANKS3 and ANKS6 and associated kinases and their partially overlapping ciliopathy phenotypes. After reviewing BICC1 homologs in model organisms and their functions in mRNA and cell metabolism during development and in renal tubules, we discuss recent insights from cell-based assays and from structure analysis of the SAM domains, and how SAM domain oligomerization might influence multivalent higher order complexes that are implicated in ciliary signal transduction.
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Affiliation(s)
- Benjamin Rothé
- Ecole Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, Station 19, CH-1015 Lausanne, Switzerland
| | - Céline Gagnieux
- Ecole Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, Station 19, CH-1015 Lausanne, Switzerland
| | - Lucia Carolina Leal-Esteban
- Ecole Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, Station 19, CH-1015 Lausanne, Switzerland; Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland
| | - Daniel B Constam
- Ecole Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, Station 19, CH-1015 Lausanne, Switzerland.
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8
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Joshi R, Qin L, Cao X, Zhong S, Voss C, Min W, Li SSC. DLC1 SAM domain-binding peptides inhibit cancer cell growth and migration by inactivating RhoA. J Biol Chem 2019; 295:645-656. [PMID: 31806702 DOI: 10.1074/jbc.ra119.011929] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Indexed: 12/25/2022] Open
Abstract
Deleted-in-liver cancer 1 (DLC1) exerts its tumor suppressive function mainly through the Rho-GTPase-activating protein (RhoGAP) domain. When activated, the domain promotes the hydrolysis of RhoA-GTP, leading to reduced cell migration. DLC1 is kept in an inactive state by an intramolecular interaction between its RhoGAP domain and the DLC1 sterile α motif (SAM) domain. We have shown previously that this autoinhibited state of DLC1 may be alleviated by tensin-3 (TNS3) or PTEN. We show here that the TNS3/PTEN-DLC1 interactions are mediated by the C2 domains of the former and the SAM domain of the latter. Intriguingly, the DLC1 SAM domain was capable of binding to specific peptide motifs within the C2 domains. Indeed, peptides containing the binding motifs were highly effective in blocking the C2-SAM domain-domain interaction. Importantly, when fused to the tat protein-transduction sequence and subsequently introduced into cells, the C2 peptides potently promoted the RhoGAP function in DLC1, leading to decreased RhoA activation and reduced tumor cell growth in soft agar and migration in response to growth factor stimulation. To facilitate the development of the C2 peptides as potential therapeutic agents, we created a cyclic version of the TNS3 C2 domain-derived peptide and showed that this peptide readily entered the MDA-MB-231 breast cancer cells and effectively inhibited their migration. Our work shows, for the first time, that the SAM domain is a peptide-binding module and establishes the framework on which to explore DLC1 SAM domain-binding peptides as potential therapeutic agents for cancer treatment.
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Affiliation(s)
- Rakesh Joshi
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada; Departments of Surgery, Pathology and Oncology, Western University, London, Ontario N6A 5A5, Canada
| | - Lyugao Qin
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada
| | - Xuan Cao
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Shanshan Zhong
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada
| | - Courtney Voss
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada
| | - Weiping Min
- Departments of Surgery, Pathology and Oncology, Western University, London, Ontario N6A 5A5, Canada.
| | - Shawn S C Li
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario N6A 5C1, Canada.
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9
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Sporny M, Guez-Haddad J, Lebendiker M, Ulisse V, Volf A, Mim C, Isupov MN, Opatowsky Y. Structural Evidence for an Octameric Ring Arrangement of SARM1. J Mol Biol 2019; 431:3591-3605. [PMID: 31278906 DOI: 10.1016/j.jmb.2019.06.030] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/16/2019] [Accepted: 06/25/2019] [Indexed: 12/11/2022]
Abstract
SARM1 induces axonal degeneration in response to various insults and is therefore considered an attractive drug target for the treatment of neuro-degenerative diseases as well as for brain and spinal cord injuries. SARM1 activity depends on the integrity of the protein's SAM domains, as well as on the enzymatic conversion of NAD+ to ADPR (ADP Ribose) products by the SARM1's TIR domain. Therefore, inhibition of either SAM or TIR functions may constitute an effective therapeutic strategy. However, there is currently no SARM1-directed therapeutic approach available because of an insufficient structural and mechanistic understanding of this protein. In this study, we found that SARM1 assembles into an octameric ring. This arrangement was not described before in other SAM proteins, but is reminiscent of the apoptosome and inflammasome-well-known apoptotic ring-like oligomers. We show that both SARM1 and the isolated tandem SAM1-2 domains form octamers in solution, and electron microscopy analysis reveals an octameric ring of SARM1. We determined the crystal structure of SAM1-2 and found that it also forms a closed octameric ring in the crystal lattice. The SAM1-2 ring interactions are mediated by complementing "lock and key" hydrophobic grooves and inserts and electrostatic charges between the neighboring protomers. We have mutated several interacting SAM1-2 interfaces and measured how these mutations affect SARM1 apoptotic activity in cultured cells, and in this way identified critical oligomerization sites that facilitate cell death. These results highlight the importance of oligomerization for SARM1 function and reveal critical epitopes for future targeted drug development.
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Affiliation(s)
- Michael Sporny
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Julia Guez-Haddad
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Mario Lebendiker
- Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Israel
| | - Valeria Ulisse
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Allison Volf
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Carsten Mim
- Department of Biomedical Engineering and Health Solutions, Royal Technical Institute (KTH), Stockholm, Sweden; Department of Nutrition and Biosciences, Karolinska Institute, Huddinge, Sweden
| | | | - Yarden Opatowsky
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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10
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Mas L, Cieren A, Delphin C, Journet A, Aubry L. Calcium influx mediates the chemoattractant-induced translocation of the arrestin-related protein AdcC in Dictyostelium. J Cell Sci 2018; 131:jcs.207951. [PMID: 30209138 DOI: 10.1242/jcs.207951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/05/2018] [Indexed: 12/26/2022] Open
Abstract
Arrestins are key adaptor proteins that control the fate of cell-surface membrane proteins and modulate downstream signaling cascades. The Dictyostelium discoideum genome encodes six arrestin-related proteins, harboring additional modules besides the arrestin domain. Here, we studied AdcB and AdcC, two homologs that contain C2 and SAM domains. We showed that AdcC - in contrast to AdcB - responds to various stimuli (such as the chemoattractants cAMP and folate) known to induce an increase in cytosolic calcium by transiently translocating to the plasma membrane, and that calcium is a direct regulator of AdcC localization. This response requires the calcium-dependent membrane-targeting C2 domain and the double SAM domain involved in AdcC oligomerization, revealing a mode of membrane targeting and regulation unique among members of the arrestin clan. AdcB shares several biochemical properties with AdcC, including in vitro binding to anionic lipids in a calcium-dependent manner and auto-assembly as large homo-oligomers. AdcB can interact with AdcC; however, its intracellular localization is insensitive to calcium. Therefore, despite their high degree of homology and common characteristics, AdcB and AdcC are likely to fulfill distinct functions in amoebae.
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Affiliation(s)
- Lauriane Mas
- Université Grenoble Alpes, CEA, INSERM, BGE U1038, F-38000 Grenoble, France
| | - Adeline Cieren
- Université Grenoble Alpes, CEA, INSERM, BGE U1038, F-38000 Grenoble, France
| | - Christian Delphin
- Université Grenoble Alpes, INSERM U1216, GIN, F-38000 Grenoble, France
| | - Agnès Journet
- Université Grenoble Alpes, CEA, INSERM, BGE U1038, F-38000 Grenoble, France
| | - Laurence Aubry
- Université Grenoble Alpes, CEA, INSERM, BGE U1038, F-38000 Grenoble, France
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11
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Hollender CA, Pascal T, Tabb A, Hadiarto T, Srinivasan C, Wang W, Liu Z, Scorza R, Dardick C. Loss of a highly conserved sterile alpha motif domain gene ( WEEP) results in pendulous branch growth in peach trees. Proc Natl Acad Sci U S A 2018; 115:E4690-E4699. [PMID: 29712856 PMCID: PMC5960274 DOI: 10.1073/pnas.1704515115] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plant shoots typically grow upward in opposition to the pull of gravity. However, exceptions exist throughout the plant kingdom. Most conspicuous are trees with weeping or pendulous branches. While such trees have long been cultivated and appreciated for their ornamental value, the molecular basis behind the weeping habit is not known. Here, we characterized a weeping tree phenotype in Prunus persica (peach) and identified the underlying genetic mutation using a genomic sequencing approach. Weeping peach tree shoots exhibited a downward elliptical growth pattern and did not exhibit an upward bending in response to 90° reorientation. The causative allele was found to be an uncharacterized gene, Ppa013325, having a 1.8-Kb deletion spanning the 5' end. This gene, dubbed WEEP, was predominantly expressed in phloem tissues and encodes a highly conserved 129-amino acid protein containing a sterile alpha motif (SAM) domain. Silencing WEEP in the related tree species Prunus domestica (plum) resulted in more outward, downward, and wandering shoot orientations compared to standard trees, supporting a role for WEEP in directing lateral shoot growth in trees. This previously unknown regulator of branch orientation, which may also be a regulator of gravity perception or response, provides insights into our understanding of how tree branches grow in opposition to gravity and could serve as a critical target for manipulating tree architecture for improved tree shape in agricultural and horticulture applications.
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Affiliation(s)
- Courtney A Hollender
- Appalachian Fruit Research Station, Agricultural Research Service, US Department of Agriculture, Kearneysville, WV 25430
- Department of Horticulture, College of Agriculture and Natural Resources, Michigan State University, East Lansing, MI 48824
| | - Thierry Pascal
- Unité Génétique et Amélioration de Fruits et Légumes, Institut National de la Recherche Agronomique, 84140 Montfavet, France
| | - Amy Tabb
- Appalachian Fruit Research Station, Agricultural Research Service, US Department of Agriculture, Kearneysville, WV 25430
| | - Toto Hadiarto
- Indonesian Center for Agricultural Biotechnology and Genetic Resources Research and Development (BB Biogen), Bogor, Indonesia
| | - Chinnathambi Srinivasan
- Appalachian Fruit Research Station, Agricultural Research Service, US Department of Agriculture, Kearneysville, WV 25430
| | - Wanpeng Wang
- Department of Cell Biology and Molecular Genetics, College of Mathematics and Natural Sciences, University of Maryland, College Park, MD 20742
| | - Zhongchi Liu
- Department of Cell Biology and Molecular Genetics, College of Mathematics and Natural Sciences, University of Maryland, College Park, MD 20742
| | - Ralph Scorza
- Appalachian Fruit Research Station, Agricultural Research Service, US Department of Agriculture, Kearneysville, WV 25430
| | - Chris Dardick
- Appalachian Fruit Research Station, Agricultural Research Service, US Department of Agriculture, Kearneysville, WV 25430;
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12
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Wang Y, Shang Y, Li J, Chen W, Li G, Wan J, Liu W, Zhang M. Specific Eph receptor-cytoplasmic effector signaling mediated by SAM- SAM domain interactions. eLife 2018; 7:35677. [PMID: 29749928 PMCID: PMC5993539 DOI: 10.7554/elife.35677] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 05/10/2018] [Indexed: 02/06/2023] Open
Abstract
The Eph receptor tyrosine kinase (RTK) family is the largest subfamily of RTKs playing critical roles in many developmental processes such as tissue patterning, neurogenesis and neuronal circuit formation, angiogenesis, etc. How the 14 Eph proteins, via their highly similar cytoplasmic domains, can transmit diverse and sometimes opposite cellular signals upon engaging ephrins is a major unresolved question. Here, we systematically investigated the bindings of each SAM domain of Eph receptors to the SAM domains from SHIP2 and Odin, and uncover a highly specific SAM-SAM interaction-mediated cytoplasmic Eph-effector binding pattern. Comparative X-ray crystallographic studies of several SAM-SAM heterodimer complexes, together with biochemical and cell biology experiments, not only revealed the exquisite specificity code governing Eph/effector interactions but also allowed us to identify SAMD5 as a new Eph binding partner. Finally, these Eph/effector SAM heterodimer structures can explain many Eph SAM mutations identified in patients suffering from cancers and other diseases.
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Affiliation(s)
- Yue Wang
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Yuan Shang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Jianchao Li
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Weidi Chen
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Gang Li
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Jun Wan
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.,Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Wei Liu
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China
| | - Mingjie Zhang
- Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.,Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
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13
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Frey F, Sheahan T, Finkl K, Stoehr G, Mann M, Benda C, Müller J. Molecular basis of PRC1 targeting to Polycomb response elements by PhoRC. Genes Dev 2016; 30:1116-27. [PMID: 27151979 DOI: 10.1101/gad.279141.116] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 04/13/2016] [Indexed: 12/11/2022]
Abstract
Here, Frey et al. report the structural basis by which the Drosophila Pho-repressive complex (PhoRC), the only Polycomb group protein complex with sequence-specific DNA-binding activity, binds to Polycomb-repressive complex 1 (PRC1) and thereby recruits it to Polycomb response elements in target genes. Polycomb group (PcG) protein complexes repress transcription by modifying target gene chromatin. In Drosophila, this repression requires association of PcG protein complexes with cis-regulatory Polycomb response elements (PREs), but the interactions permitting formation of these assemblies are poorly understood. We show that the Sfmbt subunit of the DNA-binding Pho-repressive complex (PhoRC) and the Scm subunit of the canonical Polycomb-repressive complex 1 (PRC1) directly bind each other through their SAM domains. The 1.9 Å crystal structure of the Scm-SAM:Sfmbt-SAM complex reveals the recognition mechanism and shows that Sfmbt-SAM lacks the polymerization capacity of the SAM domains of Scm and its PRC1 partner subunit, Ph. Functional analyses in Drosophila demonstrate that Sfmbt-SAM and Scm-SAM are essential for repression and that PhoRC DNA binding is critical to initiate PRC1 association with PREs. Together, this suggests that PRE-tethered Sfmbt-SAM nucleates PRC1 recruitment and that Scm-SAM/Ph-SAM-mediated polymerization then results in the formation of PRC1-compacted chromatin.
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14
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Singh DR, Ahmed F, Paul MD, Gedam M, Pasquale EB, Hristova K. The SAM domain inhibits EphA2 interactions in the plasma membrane. Biochim Biophys Acta Mol Cell Res 2016; 1864:31-38. [PMID: 27776928 DOI: 10.1016/j.bbamcr.2016.10.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 09/26/2016] [Accepted: 10/18/2016] [Indexed: 11/18/2022]
Abstract
All members of the Eph receptor family of tyrosine kinases contain a SAM domain near the C terminus, which has been proposed to play a role in receptor homotypic interactions and/or interactions with binding partners. The SAM domain of EphA2 is known to be important for receptor function, but its contribution to EphA2 lateral interactions in the plasma membrane has not been determined. Here we use a FRET-based approach to directly measure the effect of the SAM domain on the stability of EphA2 dimers on the cell surface in the absence of ligand binding. We also investigate the functional consequences of EphA2 SAM domain deletion. Surprisingly, we find that the EphA2 SAM domain inhibits receptor dimerization and decreases EphA2 tyrosine phosphorylation. This role is dramatically different from the role of the SAM domain of the related EphA3 receptor, which we previously found to stabilize EphA3 dimers and increase EphA3 tyrosine phosphorylation in cells in the absence of ligand. Thus, the EphA2 SAM domain likely contributes to a unique mode of EphA2 interaction that leads to distinct signaling outputs.
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Affiliation(s)
- Deo R Singh
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218, United States
| | - Fozia Ahmed
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218, United States
| | - Michael D Paul
- Program in Molecular Biophysics, Johns Hopkins University, 3400 Charles street, Baltimore, MD 21218, United States
| | - Manasee Gedam
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218, United States
| | - Elena B Pasquale
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Road, La Jolla, San Diego, CA 92037, United States
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218, United States; Program in Molecular Biophysics, Johns Hopkins University, 3400 Charles street, Baltimore, MD 21218, United States.
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15
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Cabukusta B, Köhlen JA, Richter CP, You C, Holthuis JCM. Monitoring Changes in the Oligomeric State of a Candidate Endoplasmic Reticulum (ER) Ceramide Sensor by Single-molecule Photobleaching. J Biol Chem 2016; 291:24735-24746. [PMID: 27729449 DOI: 10.1074/jbc.m116.749812] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 10/07/2016] [Indexed: 11/06/2022] Open
Abstract
Single-molecule photobleaching has emerged as a powerful non-invasive approach to extract the stoichiometry of multimeric membrane proteins in their native cellular environment. However, this method has mainly been used to determine the subunit composition of ion channels and receptors at the plasma membrane. Here, we applied single-molecule photobleaching to analyze the oligomeric state of an endoplasmic reticulum (ER) resident candidate ceramide sensor protein, SMSr/SAMD8. Co-immunoprecipitation and chemical cross-linking studies previously revealed that the N-terminal sterile alpha motif (or SAM) domain of SMSr drives self-assembly of the protein into oligomers and that SMSr oligomerization is promoted by curcumin, a drug known to perturb ER ceramide and calcium homeostasis. Application of cell spreading surface-active coating materials in combination with total internal reflection fluorescence (TIRF) microscopy allowed us to image GFP-tagged SMSr proteins as single fluorescent spots in the ER of HeLa cells in which expression of endogenous SMSr was abolished. In line with our biochemical analysis, we find that the number of bleaching steps in SMSr-GFP-positive spots displays a substantial drop after removal of the SAM domain. In contrast, treatment of cells with curcumin increased the number of bleaching steps. Our results document the first successful application of single-molecule photobleaching to resolve drug-induced and domain-dependent changes in the oligomeric state of an ER-resident membrane protein, hence establishing a complementary method to unravel the mechanism by which SMSr controls ceramide levels in the ER.
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Affiliation(s)
| | | | - Christian P Richter
- Biophysics Division, Faculty of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany and
| | - Changjiang You
- Biophysics Division, Faculty of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany and
| | - Joost C M Holthuis
- From the Molecular Cell Biology Division and; Membrane Biochemistry and Biophysics, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
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16
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Kanda M, Shimizu D, Sueoka S, Nomoto S, Oya H, Takami H, Ezaka K, Hashimoto R, Tanaka Y, Kobayashi D, Tanaka C, Yamada S, Fujii T, Nakayama G, Sugimoto H, Koike M, Fujiwara M, Kodera Y. Prognostic relevance of SAMSN1 expression in gastric cancer. Oncol Lett 2016; 12:4708-4716. [PMID: 28105178 DOI: 10.3892/ol.2016.5233] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 07/21/2016] [Indexed: 12/26/2022] Open
Abstract
The prognosis for patients with advanced gastric cancer (GC) remains poor. The identification of biomarkers relevant to the recurrence and metastasis of GC is advantageous for stratifying patients and proposing novel molecular targets. In the present study the oncological roles of SAM domain, SH3 domain and nuclear localization signals 1 (SAMSN1), a mediator of B-cell function, were elucidated in GC. The expression and methylation status of SAMSN1 were investigated in a panel of 11 GC cell lines. Immunohistochemical staining was performed to determine the pattern of SAMSN1 protein expression in gastric tissues. The prognostic impact of SAMSN1 expression was determined by analyzing 175 pairs of surgically resected gastric tissues. A marked decrease in the level of SAMSN1 mRNA was detected in 8/11 GC cell lines as compared with that in a non-transformed intestinal epithelium cell line (FHs 74) without promoter methylation. The mean expression level of SAMSN1 mRNA was reduced in GC tissues compared with normal adjacent tissues, an observation that was independent of tumor differentiation. The pattern of SAMSN1 protein expression was significantly correlated with that of SAMSN1 mRNA. Low SAMSN1 mRNA expression was significantly associated with tumor size (>60 mm; P=0.026) and shorter overall survival times (P=0.004). Multivariate analysis identified low SAMSN1 mRNA expression as an independent prognostic factor for poor overall survival (hazard ratio, 1.80; 95% confidence interval, 1.07-3.05; P=0.025). The difference in survival between the low and high SAMSN1 expression groups was more marked in patients with stage II/III GC compared to those with stage IV GC. In patients with stage II/III GC who underwent curative surgery, low SAMSN1 expression was associated with reduced disease free survival times. The results of the present study indicate that downregulation of SAMSN1 transcription may affect the progression and recurrence of GC, and therefore may represent a novel biomarker of GC.
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Affiliation(s)
- Mitsuro Kanda
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Dai Shimizu
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Satoshi Sueoka
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Shuji Nomoto
- Department of Surgery, Aichi-Gakuin University School of Dentistry, Nagoya, Aichi 464-8651, Japan
| | - Hisaharu Oya
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Hideki Takami
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Kazuhiro Ezaka
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Ryoji Hashimoto
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Yuri Tanaka
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Daisuke Kobayashi
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Chie Tanaka
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Suguru Yamada
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Tsutomu Fujii
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Goro Nakayama
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Hiroyuki Sugimoto
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Masahiko Koike
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Michitaka Fujiwara
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
| | - Yasuhiro Kodera
- Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan
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17
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Wang Y, Li Q, Zheng Y, Li G, Liu W. Systematic biochemical characterization of the SAM domains in Eph receptor family from Mus Musculus. Biochem Biophys Res Commun 2016; 473:1281-7. [PMID: 27086853 DOI: 10.1016/j.bbrc.2016.04.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 04/12/2016] [Indexed: 12/13/2022]
Abstract
The Eph receptor family is the largest subfamily of receptor tyrosine kinases and well-known for their pivotal roles in axon guidance, synaptogenesis, artery/venous differentiation and tumorigenesis, etc. Activation of the Eph receptor needs multimerization of the receptors. The intracellular C-terminal SAM domain of Eph receptor was reported to mediate self-association of Eph receptors via the homo SAM-SAM interaction. In this study, we systematically expressed and purified the SAM domain proteins of all fourteen Eph receptors of Mus musculus in Escherichia coli. The FPLC (fast protein liquid chromatography) results showed the recombinant SAM domains were highly homogeneous. Using CD (circular dichroism) spectrometry, we found that the secondary structure of all the SAM domains was typically alpha helical folded and remarkably similar. The thermo-stability tests showed that they were quite stable in solution. SEC-MALS (size exclusion chromatography coupled with multiple angle light scattering) results illustrated 200 μM Eph SAM domains behaved as good monomers in the size-exclusion chromatography. More importantly, DLS (dynamic light scattering) results revealed the overwhelming majority of SAM domains was not multimerized in solution either at 200 μM or 2000 μM protein concentration, which indicating the SAM domain alone was not sufficient to mediate the polymerization of Eph receptor. In summary, our studies provided the systematic biochemical characterizations of the Eph receptor SAM domains and implied their roles in Eph receptor mediated signaling pathways.
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18
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Kang H, McElroy KA, Jung YL, Alekseyenko AA, Zee BM, Park PJ, Kuroda MI. Sex comb on midleg (Scm) is a functional link between PcG-repressive complexes in Drosophila. Genes Dev 2015; 29:1136-50. [PMID: 26063573 PMCID: PMC4470282 DOI: 10.1101/gad.260562.115] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this study, Kang et al. investigate how PcG complexes form repressive chromatin domains. The findings show that Scm, a transcriptional repressor, is an important regulator of PRC1, PRC2, and transcriptional silencing and suggest that Scm coordinates PcG complexes and polymerizes, resulting in PcG silencing. The Polycomb group (PcG) proteins are key regulators of development in Drosophila and are strongly implicated in human health and disease. How PcG complexes form repressive chromatin domains remains unclear. Using cross-linked affinity purifications of BioTAP-Polycomb (Pc) or BioTAP-Enhancer of zeste [E(z)], we captured all PcG-repressive complex 1 (PRC1) or PRC2 core components and Sex comb on midleg (Scm) as the only protein strongly enriched with both complexes. Although previously not linked to PRC2, we confirmed direct binding of Scm and PRC2 using recombinant protein expression and colocalization of Scm with PRC1, PRC2, and H3K27me3 in embryos and cultured cells using ChIP-seq (chromatin immunoprecipitation [ChIP] combined with deep sequencing). Furthermore, we found that RNAi knockdown of Scm and overexpression of the dominant-negative Scm-SAM (sterile α motif) domain both affected the binding pattern of E(z) on polytene chromosomes. Aberrant localization of the Scm-SAM domain in long contiguous regions on polytene chromosomes revealed its independent ability to spread on chromatin, consistent with its previously described ability to oligomerize in vitro. Pull-downs of BioTAP-Scm captured PRC1 and PRC2 and additional repressive complexes, including PhoRC, LINT, and CtBP. We propose that Scm is a key mediator connecting PRC1, PRC2, and transcriptional silencing. Combined with previous structural and genetic analyses, our results strongly suggest that Scm coordinates PcG complexes and polymerizes to produce broad domains of PcG silencing.
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Affiliation(s)
- Hyuckjoon Kang
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Kyle A McElroy
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Youngsook Lucy Jung
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Center for Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Artyom A Alekseyenko
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Barry M Zee
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Peter J Park
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Center for Biomedical Informatics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Mitzi I Kuroda
- Division of Genetics, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA;
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19
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Singh DR, Cao Q, King C, Salotto M, Ahmed F, Zhou XY, Pasquale EB, Hristova K. Unliganded EphA3 dimerization promoted by the SAM domain. Biochem J 2015; 471:101-9. [PMID: 26232493 DOI: 10.1042/BJ20150433] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 07/31/2015] [Indexed: 01/03/2023]
Abstract
Erythropoietin-producing hepatocellular carcinoma A3 (EphA3) can form dimers in the absence of ligand binding, which are stabilized by the sterile α-motif (SAM) domain. This challenges the current understanding of EphA3 activation events and establishes a new role for the EphA3 SAM domain in receptor-receptor interactions. The erythropoietin-producing hepatocellular carcinoma A3 (EphA3) receptor tyrosine kinase (RTK) regulates morphogenesis during development and is overexpressed and mutated in a variety of cancers. EphA3 activation is believed to follow a ‘seeding mechanism’ model, in which ligand binding to the monomeric receptor acts as a trigger for signal-productive receptor clustering. We study EphA3 lateral interactions on the surface of live cells and we demonstrate that EphA3 forms dimers in the absence of ligand binding. We further show that these dimers are stabilized by interactions involving the EphA3 sterile α-motif (SAM) domain. The discovery of unliganded EphA3 dimers challenges the current understanding of the chain of EphA3 activation events and suggests that EphA3 may follow the ‘pre-formed dimer’ model of activation known to be relevant for other receptor tyrosine kinases. The present work also establishes a new role for the SAM domain in promoting Eph receptor lateral interactions and signalling on the cell surface.
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20
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Nishino T, Matsunaga R, Konishi H. Functional relationship between CABIT, SAM and 14-3-3 binding domains of GAREM1 that play a role in its subcellular localization. Biochem Biophys Res Commun 2015; 464:616-21. [PMID: 26164232 DOI: 10.1016/j.bbrc.2015.07.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/04/2015] [Indexed: 11/29/2022]
Abstract
GAREM1 (Grb2-associated regulator of Erk/MAPK1) is an adaptor protein that is involved in the epidermal growth factor (EGF) pathway. The nuclear localization of GAREM1 depends on the nuclear localization sequence (NLS), which is located at the N-terminal CABIT (cysteine-containing, all in Themis) domain. Here, we identified 14-3-3ε as a GAREM-binding protein, and its binding site is closely located to the NLS. This 14-3-3 binding site was of the atypical type and independent of GAREM phosphorylation. Moreover, the binding of 14-3-3 had an effect on the nuclear localization of GAREM1. Unexpectedly, we observed that the CABIT domain had intramolecular association with the C-terminal SAM (sterile alpha motif) domain. This association might be inhibited by binding of 14-3-3 at the CABIT domain. Our results demonstrate that the mechanism underlying the nuclear localization of GAREM1 depends on its NLS in the CABIT domain, which is controlled by the binding of 14-3-3 and the C-terminal SAM domain. We suggest that the interplay between 14-3-3, SAM domain and CABIT domain might be responsible for the distribution of GAREM1 in mammalian cells.
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Affiliation(s)
- Tasuku Nishino
- Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan
| | - Ryota Matsunaga
- Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan
| | - Hiroaki Konishi
- Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan.
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21
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Tafesse FG, Vacaru AM, Bosma EF, Hermansson M, Jain A, Hilderink A, Somerharju P, Holthuis JCM. Sphingomyelin synthase-related protein SMSr is a suppressor of ceramide-induced mitochondrial apoptosis. J Cell Sci 2013; 127:445-54. [PMID: 24259670 DOI: 10.1242/jcs.138933] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cells synthesize ceramides in the endoplasmic reticulum (ER) as precursors for sphingolipids to form an impermeable plasma membrane. As ceramides are engaged in apoptotic pathways, cells would need to monitor their levels closely to avoid killing themselves during sphingolipid biosynthesis. How this is accomplished remains to be established. Here we identify SMSr (SAMD8), an ER-resident ceramide phosphoethanolamine (CPE) synthase, as a suppressor of ceramide-mediated cell death. Disruption of SMSr catalytic activity causes a rise in ER ceramides and their mislocalization to mitochondria, triggering a mitochondrial pathway of apoptosis. Blocking de novo ceramide synthesis, stimulating ceramide export from the ER or targeting a bacterial ceramidase to mitochondria rescues SMSr-deficient cells from apoptosis. We also show that SMSr-catalyzed CPE production, although essential, is not sufficient to suppress ceramide-induced cell death and that SMSr-mediated ceramide homeostasis requires the N-terminal sterile α-motif, or SAM domain, of the enzyme. These results define ER ceramides as bona fide transducers of mitochondrial apoptosis and indicate a primary role of SMSr in monitoring ER ceramide levels to prevent inappropriate cell death during sphingolipid biosynthesis.
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Affiliation(s)
- Fikadu G Tafesse
- Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, the Netherlands
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