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Xie J, DiMaio D. Traptamer screening: a new functional genomics approach to study virus entry and other cellular processes. FEBS J 2022; 289:355-362. [PMID: 33604985 PMCID: PMC8371075 DOI: 10.1111/febs.15775] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/26/2021] [Accepted: 02/17/2021] [Indexed: 01/03/2023]
Abstract
Historically, the genetic analysis of mammalian cells entailed the isolation of randomly arising mutant cell lines with altered properties, followed by laborious genetic mapping experiments to identify the mutant gene responsible for the phenotype. In recent years, somatic cell genetics has been revolutionized by functional genomics screens, in which expression of every protein-coding gene is systematically perturbed, and the phenotype of the perturbed cells is determined. We outline here a novel functional genomics screening strategy that differs fundamentally from commonly used approaches. In this strategy, we express libraries of artificial transmembrane proteins named traptamers and select rare cells with the desired phenotype because, by chance, a traptamer specifically perturbs the expression or activity of a target protein. Active traptamers are then recovered from the selected cells and can be used as tools to dissect the biological process under study. We also briefly describe how we have used this new strategy to provide insights into the complex process by which human papillomaviruses enter cells.
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Affiliation(s)
- Jian Xie
- Department of Genetics, Yale School of Medicine, New Haven, CT USA
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, New Haven, CT USA
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT USA
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT USA
- Yale Cancer Center, New Haven, CT USA
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2
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Petti LM, Koleske BN, DiMaio D. Activation of the PDGF β Receptor by a Persistent Artificial Signal Peptide. J Mol Biol 2021; 433:167223. [PMID: 34474086 DOI: 10.1016/j.jmb.2021.167223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 07/25/2021] [Accepted: 08/26/2021] [Indexed: 10/20/2022]
Abstract
Most eukaryotic transmembrane and secreted proteins contain N-terminal signal peptides that mediate insertion of the nascent translation products into the membrane of the endoplasmic reticulum. After membrane insertion, signal peptides typically are cleaved from the mature protein and degraded. Here, we tested whether a small hydrophobic protein selected for growth promoting activity in mammalian cells retained transforming activity while also acting as a signal peptide. We replaced the signal peptide of the PDGF β receptor (PDGFβR) with a previously described 29-residue artificial transmembrane protein named 9C3 that can activate the PDGFβR in trans. We showed that a modified version of 9C3 at the N-terminus of the PDGFβR can function as a signal peptide, as assessed by its ability to support high level expression, glycosylation, and cell surface localization of the PDGFβR. The 9C3 signal peptide retains its ability to interact with the transmembrane domain of the PDGFβR and cause receptor activation and cell proliferation. Cleavage of the 9C3 signal peptide from the mature receptor is not required for these activities. However, signal peptide cleavage does occur in some molecules, and the cleaved signal peptide can persist in cells and activate a co-expressed PDGFβR in trans. Our finding that a hydrophobic sequence can display signal peptide and transforming activity suggest that some naturally occurring signal peptides may also display additional biological activities by interacting with the transmembrane domains of target proteins.
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Affiliation(s)
- Lisa M Petti
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA
| | - Benjamin N Koleske
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA; Department of Molecular Biophysics & Biochemistry, Yale School of Medicine, PO Box 208024, New Haven, CT 06520-8024, USA
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA; Department of Molecular Biophysics & Biochemistry, Yale School of Medicine, PO Box 208024, New Haven, CT 06520-8024, USA; Department of Therapeutic Radiology, Yale School of Medicine, PO Box 208040, New Haven, CT 06520-8040, USA; Yale Cancer Center, PO Box 208028, New Haven, CT 06520-8028, USA.
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3
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Federman RS, Boguraev AS, Heim EN, DiMaio D. Biologically Active Ultra-Simple Proteins Reveal Principles of Transmembrane Domain Interactions. J Mol Biol 2019; 431:3753-3770. [PMID: 31301406 DOI: 10.1016/j.jmb.2019.07.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 11/30/2022]
Abstract
Specific interactions between the helical membrane-spanning domains of transmembrane proteins play central roles in the proper folding and oligomerization of these proteins. However, the relationship between the hydrophobic amino acid sequences of transmembrane domains and their functional interactions is in most cases unknown. Here, we use ultra-simple artificial proteins to systematically study the sequence basis for transmembrane domain interactions. We show that most short homopolymeric polyleucine transmembrane proteins containing single amino acid substitutions can activate the platelet-derived growth factor β receptor or the erythropoietin receptor in cultured mouse cells, resulting in cell transformation or proliferation. These proteins displayed complex patterns of activity that were markedly affected by seemingly minor sequence differences in the ultra-simple protein itself or in the transmembrane domain of the target receptor, and the effects of these sequence differences are not additive. In addition, specific leucine residues along the length of these proteins are required for activity, and the positions of these required leucines differ based on the identity and position of the central substituted amino acid. Our results suggest that these ultra-simple proteins use a variety of molecular mechanisms to activate the same target and that diversification of transmembrane domain sequences over the course of evolution minimized off-target interactions.
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Affiliation(s)
- Ross S Federman
- Department of Immunobiology, Yale School of Medicine, PO Box 208011, New Haven, CT 06520-8011, USA
| | - Anna-Sophia Boguraev
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA
| | - Erin N Heim
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, PO Box 208005, New Haven, CT 06520-8005, USA; Department of Therapeutic Radiology, Yale School of Medicine, PO Box 208040, New Haven, CT 06520-8040, USA; Department of Molecular Biophysics & Biochemistry, Yale School of Medicine, PO Box 208024, New Haven, CT 06520-8024, USA; Yale Cancer Center, PO Box 208028, New Haven, CT 06520-8028, USA.
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He L, Cohen EB, Edwards APB, Xavier-Ferrucio J, Bugge K, Federman RS, Absher D, Myers RM, Kragelund BB, Krause DS, DiMaio D. Transmembrane Protein Aptamer Induces Cooperative Signaling by the EPO Receptor and the Cytokine Receptor β-Common Subunit. iScience 2019; 17:167-181. [PMID: 31279934 PMCID: PMC6614117 DOI: 10.1016/j.isci.2019.06.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 05/10/2019] [Accepted: 06/17/2019] [Indexed: 12/13/2022] Open
Abstract
The erythropoietin receptor (EPOR) plays an essential role in erythropoiesis and other cellular processes by forming distinct signaling complexes composed of EPOR homodimers or hetero-oligomers between the EPOR and another receptor, but the mechanism of heteroreceptor assembly and signaling is poorly understood. We report here a 46-residue, artificial transmembrane protein aptamer, designated ELI-3, that binds and activates the EPOR and induces growth factor independence in murine BaF3 cells expressing the EPOR. ELI-3 requires the transmembrane domain and JAK2-binding sites of the EPOR for activity, but not the cytoplasmic tyrosines that mediate canonical EPOR signaling. Instead, ELI-3-induced proliferation and activation of JAK/STAT signaling requires the transmembrane and cytoplasmic domains of the cytokine receptor β-common subunit (βcR) in addition to the EPOR. Moreover, ELI-3 fails to induce erythroid differentiation of primary human hematopoietic progenitor cells but inhibits nonhematopoietic cell death induced by serum withdrawal.
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Affiliation(s)
- Li He
- Department of Genetics, Yale School of Medicine, P.O. Box 208005, New Haven, CT 06520-8005, USA
| | - Emily B Cohen
- Department of Genetics, Yale School of Medicine, P.O. Box 208005, New Haven, CT 06520-8005, USA
| | - Anne P B Edwards
- Department of Genetics, Yale School of Medicine, P.O. Box 208005, New Haven, CT 06520-8005, USA
| | - Juliana Xavier-Ferrucio
- Department of Laboratory Medicine, Yale School of Medicine, P.O. Box 208073, New Haven, CT 06520-8073, USA
| | - Katrine Bugge
- Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science and Integrative Structural Biology at University of Copenhagen (ISBUC), Department of Biology, University of Copenhagen, Copenhagen N 2200, Denmark
| | - Ross S Federman
- Department of Immunobiology, Yale School of Medicine, P.O. Box 208011, New Haven, CT 06520-8011, USA
| | - Devin Absher
- HudsonAlpha Institute for Biotechnology, 601 Genome Way, Huntsville, AL 35806, USA
| | - Richard M Myers
- HudsonAlpha Institute for Biotechnology, 601 Genome Way, Huntsville, AL 35806, USA
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, The Linderstrøm-Lang Centre for Protein Science and Integrative Structural Biology at University of Copenhagen (ISBUC), Department of Biology, University of Copenhagen, Copenhagen N 2200, Denmark
| | - Diane S Krause
- Department of Laboratory Medicine, Yale School of Medicine, P.O. Box 208073, New Haven, CT 06520-8073, USA; Yale Cancer Center, P.O. Box 208028, New Haven, CT 06520-8028, USA
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, P.O. Box 208005, New Haven, CT 06520-8005, USA; Department of Therapeutic Radiology, Yale School of Medicine, P.O. Box 208040, New Haven, CT 06520-8040, USA; Department of Molecular Biophysics & Biochemistry, P.O. Box 208114, Yale University, New Haven, CT 06520-8114, USA; Yale Cancer Center, P.O. Box 208028, New Haven, CT 06520-8028, USA.
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He L, Steinocher H, Shelar A, Cohen EB, Heim EN, Kragelund BB, Grigoryan G, DiMaio D. Single methyl groups can act as toggle switches to specify transmembrane Protein-protein interactions. eLife 2017; 6:27701. [PMID: 28869036 PMCID: PMC5597333 DOI: 10.7554/elife.27701] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 09/01/2017] [Indexed: 01/13/2023] Open
Abstract
Transmembrane domains (TMDs) engage in protein-protein interactions that regulate many cellular processes, but the rules governing the specificity of these interactions are poorly understood. To discover these principles, we analyzed 26-residue model transmembrane proteins consisting exclusively of leucine and isoleucine (called LIL traptamers) that specifically activate the erythropoietin receptor (EPOR) in mouse cells to confer growth factor independence. We discovered that the placement of a single side chain methyl group at specific positions in a traptamer determined whether it associated productively with the TMD of the human EPOR, the mouse EPOR, or both receptors. Association of the traptamers with the EPOR induced EPOR oligomerization in an orientation that stimulated receptor activity. These results highlight the high intrinsic specificity of TMD interactions, demonstrate that a single methyl group can dictate specificity, and define the minimal chemical difference that can modulate the specificity of TMD interactions and the activity of transmembrane proteins.
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Affiliation(s)
- Li He
- Department of Genetics, Yale School of Medicine, New Haven, United States
| | - Helena Steinocher
- Department of Biology, Structural and NMR Laboratory, University of Copenhagen, Copenhagen, Denmark
| | - Ashish Shelar
- Department of Genetics, Yale School of Medicine, New Haven, United States
| | - Emily B Cohen
- Department of Genetics, Yale School of Medicine, New Haven, United States
| | - Erin N Heim
- Department of Genetics, Yale School of Medicine, New Haven, United States
| | - Birthe B Kragelund
- Department of Biology, Structural and NMR Laboratory, University of Copenhagen, Copenhagen, Denmark
| | - Gevorg Grigoryan
- Department of Computer Science, Dartmouth College, Hanover, United States
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, New Haven, United States.,Department of Therapeutic Radiology, Yale School of Medicine, New Haven, United States.,Department of Molecular Biophysics & Biochemistry, Yale School of Medicine, New Haven, United States.,Yale Cancer Center, New Haven, United States
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Screening for transmembrane association in divisome proteins using TOXGREEN, a high-throughput variant of the TOXCAT assay. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2573-2583. [PMID: 27453198 DOI: 10.1016/j.bbamem.2016.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Revised: 07/15/2016] [Accepted: 07/19/2016] [Indexed: 11/21/2022]
Abstract
TOXCAT is a widely used genetic assay to study interactions of transmembrane helices within the inner membrane of the bacterium Escherichia coli. TOXCAT is based on a fusion construct that links a transmembrane domain of interest with a cytoplasmic DNA-binding domain from the Vibrio cholerae ToxR protein. Interaction driven by the transmembrane domain results in dimerization of the ToxR domain, which, in turn, activates the expression of the reporter gene chloramphenicol acetyl transferase (CAT). Quantification of CAT is used as a measure of the ability of the transmembrane domain to self-associate. Because the quantification of CAT is relatively laborious, we developed a high-throughput variant of the assay, TOXGREEN, based on the expression of super-folded GFP and detection of fluorescence directly in unprocessed cell cultures. Careful side-by-side comparison of TOXCAT and TOXGREEN demonstrates that the methods have comparable response, dynamic range, sensitivity and intrinsic variability both in LB and minimal media. The greatly enhanced workflow makes TOXGREEN much more scalable and ideal for screening, since hundreds of constructs can be rapidly assessed in 96 well plates. Even for small scale investigations, TOXGREEN significantly reduces time, labor and cost associated with the procedure. We demonstrate applicability with a large screening for self-association among the transmembrane domains of bitopic proteins of the divisome (FtsL, FtsB, FtsQ, FtsI, FtsN, ZipA and EzrA) belonging to 11 bacterial species. The analysis confirms a previously reported tendency for FtsB to self-associate, and suggests that the transmembrane domains of ZipA, EzrA and FtsN may also possibly oligomerize.
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