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Corbet GA, Burke JM, Parker R. Nucleic acid-protein condensates in innate immune signaling. EMBO J 2023; 42:e111870. [PMID: 36178199 PMCID: PMC10068312 DOI: 10.15252/embj.2022111870] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 07/24/2022] [Accepted: 09/19/2022] [Indexed: 11/09/2022] Open
Abstract
The presence of foreign nucleic acids in the cytosol is a marker of infection. Cells have sensors, also known as pattern recognition receptors (PRRs), in the cytosol that detect foreign nucleic acid and initiate an innate immune response. Recent studies have reported the condensation of multiple PRRs including PKR, NLRP6, and cGAS, with their nucleic acid activators into discrete nucleoprotein assemblies. Nucleic acid-protein condensates form due to multivalent interactions and can create high local concentrations of components. The formation of PRR-containing condensates may alter the magnitude or timing of PRR activation. In addition, unique condensates form following RNase L activation or during paracrine signaling from virally infected cells that may play roles in antiviral defense. These observations suggest that condensate formation may be a conserved mechanism that cells use to regulate activation of the innate immune response and open an avenue for further investigation into the composition and function of these condensates. Here we review the nucleic acid-protein granules that are implicated in the innate immune response, discuss general consequences of condensate formation and signal transduction, as well as what outstanding questions remain.
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Affiliation(s)
- Giulia A Corbet
- Department of BiochemistryUniversity of ColoradoBoulderCOUSA
| | - James M Burke
- Department of BiochemistryUniversity of ColoradoBoulderCOUSA
- Present address:
Department of Molecular MedicineUniversity of Florida Scripps Biomedical ResearchJupiterFLUSA
| | - Roy Parker
- Department of BiochemistryUniversity of ColoradoBoulderCOUSA
- Howard Hughes Medical InstituteChevy ChaseMDUSA
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2
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Lam KK, Low YS, Lo M, Wong M, Leong Tang C, Tan E, Chok AY, Seow-En I, Wong SH, Cheah PY. KRAS-specific antibody binds to KRAS protein inside colorectal adenocarcinoma cells and inhibits its localization to the plasma membrane. Front Oncol 2023; 13:1036871. [PMID: 37051535 PMCID: PMC10084885 DOI: 10.3389/fonc.2023.1036871] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 02/27/2023] [Indexed: 03/29/2023] Open
Abstract
Colorectal cancer (CRC) is the third highest incidence cancer and a leading cause of cancer mortality worldwide. To date, chemotherapeutic treatment of advanced CRC that has metastasized has a dismayed success rate of less than 30%. Further, most (80%) sporadic CRCs are microsatellite-stable and are refractory to immune checkpoint blockade therapy. KRAS is a gatekeeper gene in colorectal tumorigenesis. Nevertheless, KRAS is ‘undruggable’ due to its structure. Thus, focus has been diverted to develop small molecule inhibitors for its downstream effector such as ERK/MAPK. Despite intense research efforts for the past few decades, no small molecule inhibitor has been in clinical use for CRC. Antibody targeting KRAS itself is an attractive alternative. We developed a transient ex vivo patient-derived matched mucosa-tumor primary culture to assess whether anti-KRAS antibody can be internalized to bind and inactivate KRAS. We showed that anti-KRAS antibody can enter live mucosa-tumor cells and specifically aggregate KRAS in the cytoplasm, thus hindering its translocation to the inner plasma membrane. The mis-localization of KRAS reduces KRAS dwelling time at the site where it tethers to activate downstream effectors. We previously showed that expression of SOX9 was KRAS-mutation-dependent and possibly a better effector than ERK in CRC. Herein, we showed that anti-KRAS antibody treated tumor cells have less intense SOX9 cytoplasmic and nuclear staining compared to untreated cells. Our results demonstrated that internalized anti-KRAS antibody inhibits KRAS function in tumor. With an efficient intracellular antibody delivery system, this can be further developed as combinatorial therapeutics for CRC and other KRAS-driven cancers.
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Affiliation(s)
- Kuen Kuen Lam
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Yee Syuen Low
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Michelle Lo
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Michelle Wong
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Choong Leong Tang
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Emile Tan
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Aik Yong Chok
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | - Isaac Seow-En
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
| | | | - Peh Yean Cheah
- Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
- Duke-NUS Medical School, National University of Singapore, Singapore, Singapore
- *Correspondence: Peh Yean Cheah,
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3
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Lam KK, Wong SH, Cheah PY. Targeting the 'Undruggable' Driver Protein, KRAS, in Epithelial Cancers: Current Perspective. Cells 2023; 12:cells12040631. [PMID: 36831298 PMCID: PMC9954350 DOI: 10.3390/cells12040631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/30/2023] [Accepted: 02/10/2023] [Indexed: 02/18/2023] Open
Abstract
This review summarizes recent development in synthetic drugs and biologics targeting intracellular driver genes in epithelial cancers, focusing on KRAS, and provides a current perspective and potential leads for the field. Compared to biologics, small molecule inhibitors (SMIs) readily penetrate cells, thus being able to target intracellular proteins. However, SMIs frequently suffer from pleiotropic effects, off-target cytotoxicity and invariably elicit resistance. In contrast, biologics are much larger molecules limited by cellular entry, but if this is surmounted, they may have more specific effects and less therapy-induced resistance. Exciting breakthroughs in the past two years include engineering of non-covalent KRAS G12D-specific inhibitor, probody bispecific antibodies, drug-peptide conjugate as MHC-restricted neoantigen to prompt immune response by T-cells, and success in the adoptive cell therapy front in both breast and pancreatic cancers.
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Affiliation(s)
- Kuen Kuen Lam
- Department of Colorectal Surgery, Singapore General Hospital, Singapore 169856, Singapore
| | | | - Peh Yean Cheah
- Department of Colorectal Surgery, Singapore General Hospital, Singapore 169856, Singapore
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117549, Singapore
- Duke-NUS Medical School, National University of Singapore, Singapore 169857, Singapore
- Correspondence:
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4
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Philippi M, Richter CP, Kappen M, Watrinet I, Miao Y, Runge M, Jorde L, Korneev S, Holtmannspötter M, Kurre R, Holthuis JCM, Garcia KC, Plückthun A, Steinhart M, Piehler J, You C. Biofunctional Nanodot Arrays in Living Cells Uncover Synergistic Co-Condensation of Wnt Signalodroplets. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2203723. [PMID: 36266931 DOI: 10.1002/smll.202203723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/30/2022] [Indexed: 06/16/2023]
Abstract
Qualitative and quantitative analysis of transient signaling platforms in the plasma membrane has remained a key experimental challenge. Here, biofunctional nanodot arrays (bNDAs) are developed to spatially control dimerization and clustering of cell surface receptors at the nanoscale. High-contrast bNDAs with spot diameters of ≈300 nm are obtained by capillary nanostamping of bovine serum albumin bioconjugates, which are subsequently biofunctionalized by reaction with tandem anti-green fluorescence protein (GFP) clamp fusions. Spatially controlled assembly of active Wnt signalosomes is achieved at the nanoscale in the plasma membrane of live cells by capturing the co-receptor Lrp6 into bNDAs via an extracellular GFP tag. Strikingly, co-recruitment is observed of co-receptor Frizzled-8 as well as the cytosolic scaffold proteins Axin-1 and Disheveled-2 into Lrp6 nanodots in the absence of ligand. Density variation and the high dynamics of effector proteins uncover highly cooperative liquid-liquid phase separation (LLPS)-driven assembly of Wnt "signalodroplets" at the plasma membrane, pinpointing the synergistic effects of LLPS for Wnt signaling amplification. These insights highlight the potential of bNDAs for systematically interrogating nanoscale signaling platforms and condensation at the plasma membrane of live cells.
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Affiliation(s)
- Michael Philippi
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Christian P Richter
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Marie Kappen
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Isabelle Watrinet
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Yi Miao
- Department of Molecular and Cellular Physiology, Department of Structural Biology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Mercedes Runge
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Lara Jorde
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Sergej Korneev
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Michael Holtmannspötter
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Rainer Kurre
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Joost C M Holthuis
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - K Christopher Garcia
- Department of Molecular and Cellular Physiology, Department of Structural Biology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Andreas Plückthun
- Department of Biochemistry, University of Zurich, Winterthurerstr. 190, Zurich, 8057, Switzerland
| | - Martin Steinhart
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Jacob Piehler
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
| | - Changjiang You
- Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs), Osnabrück University, 49076, Osnabrück, Germany
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5
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Ecker M, Schregle R, Kapoor-Kaushik N, Rossatti P, Betzler VM, Kempe D, Biro M, Ariotti N, Redpath GMI, Rossy J. SNX9-induced membrane tubulation regulates CD28 cluster stability and signalling. eLife 2022; 11:e67550. [PMID: 35050850 PMCID: PMC8786313 DOI: 10.7554/elife.67550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 01/12/2022] [Indexed: 12/12/2022] Open
Abstract
T cell activation requires engagement of a cognate antigen by the T cell receptor (TCR) and the co-stimulatory signal of CD28. Both TCR and CD28 aggregate into clusters at the plasma membrane of activated T cells. While the role of TCR clustering in T cell activation has been extensively investigated, little is known about how CD28 clustering contributes to CD28 signalling. Here, we report that upon CD28 triggering, the BAR-domain protein sorting nexin 9 (SNX9) is recruited to CD28 clusters at the immunological synapse. Using three-dimensional correlative light and electron microscopy, we show that SNX9 generates membrane tubulation out of CD28 clusters. Our data further reveal that CD28 clusters are in fact dynamic structures and that SNX9 regulates their stability as well as CD28 phosphorylation and the resulting production of the cytokine IL-2. In summary, our work suggests a model in which SNX9-mediated tubulation generates a membrane environment that promotes CD28 triggering and downstream signalling events.
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Affiliation(s)
- Manuela Ecker
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South WalesSydneyAustralia
| | - Richard Schregle
- Biotechnology Institute Thurgau (BITg) at the University of KonstanzKreuzlingenSwitzerland
- Department of Biology, University of KonstanzKonstanzGermany
| | - Natasha Kapoor-Kaushik
- Electron Microscopy Unit, Mark Wainwright Analytical Centre, University of New South WalesSydneyAustralia
| | - Pascal Rossatti
- Biotechnology Institute Thurgau (BITg) at the University of KonstanzKreuzlingenSwitzerland
| | - Verena M Betzler
- Biotechnology Institute Thurgau (BITg) at the University of KonstanzKreuzlingenSwitzerland
| | - Daryan Kempe
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South WalesSydneyAustralia
| | - Maté Biro
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South WalesSydneyAustralia
| | - Nicholas Ariotti
- Electron Microscopy Unit, Mark Wainwright Analytical Centre, University of New South WalesSydneyAustralia
- Institute for Molecular Bioscience (IMB), University of QueenslandBrisbaneAustralia
| | - Gregory MI Redpath
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South WalesSydneyAustralia
| | - Jeremie Rossy
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South WalesSydneyAustralia
- Biotechnology Institute Thurgau (BITg) at the University of KonstanzKreuzlingenSwitzerland
- Department of Biology, University of KonstanzKonstanzGermany
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Pir Cakmak F, Marianelli AM, Keating CD. Phospholipid Membrane Formation Templated by Coacervate Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10366-10375. [PMID: 34398617 DOI: 10.1021/acs.langmuir.1c01562] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report the formation of coacervate-supported phospholipid membranes by hydrating a dried lipid film in the presence of coacervate droplets. Coacervate-supported membranes were characterized by fluorescence imaging, polarization, fluorescence recovery after photobleaching of labeled lipids, lipid quenching experiments, and solute uptake experiments. Our findings are consistent with the presence of lipid membranes around the coacervates, with many droplets fully coated by what appear to be continuous lipid bilayers. In contrast to traditional giant lipid vesicles formed by gentle hydration in the absence of coacervates, the coacervate-templated membrane vesicles are more uniform in size, shape, and apparent lamellarity. Due to their fully coacervate model cytoplasm, these simple artificial cells are macromolecularly crowded and can be easily pre-loaded with high concentrations of proteins or nucleic acids. Within the same population, in addition to coacervate droplets having intact lipid membrane coatings, other coacervate droplets are coated with membranes having defects or pores that permit solute entry, and some are coated with multilayered membranes. Membranes surrounding protein-based coacervate droplets provided protection from a protease added to the external solution. The simplicity of producing artificial cells having a coacervate model cytoplasm surrounded by a model membrane is at the same time interesting as a potential mechanism for prebiotic protocell formation and appealing for biotechnology. We anticipate that such structures could serve as a new type of model system for understanding interactions between intracellular phases and cell or organelle membranes, which are implicated in a growing number of processes ranging from neurotransmission to signaling.
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Affiliation(s)
- Fatma Pir Cakmak
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Allyson M Marianelli
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Christine D Keating
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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7
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Botterbusch S, Baumgart T. Interactions between Phase-Separated Liquids and Membrane Surfaces. APPLIED SCIENCES (BASEL, SWITZERLAND) 2021; 11:1288. [PMID: 34327010 PMCID: PMC8315427 DOI: 10.3390/app11031288] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Liquid-liquid phase separation has recently emerged as an important fundamental organizational phenomenon in biological settings. Most studies of biological phase separation have focused on droplets that "condense" from solution above a critical concentration, forming so-called "membraneless organelles" suspended in solution. However, membranes are ubiquitous throughout cells, and many biomolecular condensates interact with membrane surfaces. Such membrane-associated phase-separated systems range from clusters of integral or peripheral membrane proteins in the plane of the membrane to free, spherical droplets wetting membrane surfaces to droplets containing small lipid vesicles. In this review, we consider phase-separated liquids that interact with membrane surfaces and we discuss the consequences of those interactions. The physical properties of distinct liquid phases in contact with bilayers can reshape the membrane, and liquid-liquid phase separation can construct membrane-associated protein structures, modulate their function, and organize collections of lipid vesicles dynamically. We summarize the common phenomena that arise in these systems of liquid phases and membranes.
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8
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Sehgal PB, Westley J, Lerea KM, DiSenso-Browne S, Etlinger JD. Biomolecular condensates in cell biology and virology: Phase-separated membraneless organelles (MLOs). Anal Biochem 2020; 597:113691. [PMID: 32194074 DOI: 10.1016/j.ab.2020.113691] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/06/2020] [Accepted: 03/13/2020] [Indexed: 12/12/2022]
Abstract
Membraneless organelles (MLOs) in the cytoplasm and nucleus in the form of 2D and 3D phase-separated biomolecular condensates are increasingly viewed as critical in regulating diverse cellular functions. These functions include cell signaling, immune synapse function, nuclear transcription, RNA splicing and processing, mRNA storage and translation, virus replication and maturation, antiviral mechanisms, DNA sensing, synaptic transmission, protein turnover and mitosis. Components comprising MLOs often associate with low affinity; thus cell integrity can be critical to the maintenance of the full complement of respective MLO components. Phase-separated condensates are typically metastable (shape-changing) and can undergo dramatic, rapid and reversible assembly and disassembly in response to cell signaling events, cell stress, during mitosis, and after changes in cytoplasmic "crowding" (as observed with condensates of the human myxovirus resistance protein MxA). Increasing evidence suggests that neuron-specific aberrations in phase-separation properties of RNA-binding proteins (e.g. FUS and TDP-43) and others (such as the microtubule-binding protein tau) contribute to the development of degenerative neurological diseases (e.g. amyotrophic lateral sclerosis, frontotemporal lobar degeneration, and Alzheimer's disease). Thus, studies of liquid-like phase separation (LLPS) and the formation, structure and function of MLOs are of considerable importance in understanding basic cell biology and the pathogenesis of human diseases.
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Affiliation(s)
- Pravin B Sehgal
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA; Department of Medicine, New York Medical College, Valhalla, NY, 10595, USA.
| | - Jenna Westley
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA
| | - Kenneth M Lerea
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA
| | - Susan DiSenso-Browne
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA; Department of Dental Medicine, Touro College of Dental Medicine, Hawthorne, NY, 10532, USA
| | - Joseph D Etlinger
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA
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9
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Wolf S. Deviating from the Beaten Track: New Twists in Brassinosteroid Receptor Function. Int J Mol Sci 2020; 21:ijms21051561. [PMID: 32106564 PMCID: PMC7084826 DOI: 10.3390/ijms21051561] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 02/21/2020] [Accepted: 02/22/2020] [Indexed: 12/15/2022] Open
Abstract
A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of plant sterol hormones, are perceived by cell surface receptors and trigger responses instrumental in tailoring developmental programs to environmental cues. Arguably, BR signalling is one of the best-characterized plant signalling pathways, and the molecular composition of the core signal transduction cascade seems clear. However, BR research continues to reveal new twists to re-shape our view on this key signalling circuit. Here, exciting novel findings pointing to the plasma membrane as a key site for BR signalling modulation and integration with other pathways are reviewed and new inputs into the BR signalling pathway and emerging “non-canonical” functions of the BR receptor complex are highlighted. Together, this new evidence underscores the complexity of plant signalling integration and serves as a reminder that highly-interconnected signalling pathways frequently comprise non-linear aspects which are difficult to convey in classical conceptual models.
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Affiliation(s)
- Sebastian Wolf
- Centre for Organismal Studies (COS) Heidelberg, INF230, 69120 Heidelberg, Germany
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10
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Hui E. Understanding T cell signaling using membrane reconstitution. Immunol Rev 2020; 291:44-56. [PMID: 31402497 DOI: 10.1111/imr.12767] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 04/02/2019] [Indexed: 12/31/2022]
Abstract
T cells are central players of our immune system, as their functions range from killing tumorous and virus-infected cells to orchestrating the entire immune response. In order for T cells to divide and execute their functions, they must be activated by antigen-presenting cells (APCs) through a cell-cell junction. Extracellular interactions between receptors on T cells and their ligands on APCs trigger signaling cascades comprised of protein-protein interactions, enzymatic reactions, and spatial reorganization events, to either stimulate or repress T cell activation. Plasma membrane is the major platform for T cell signaling. Recruitment of cytosolic proteins to membrane-bound receptors is a common critical step in many signaling pathways. Membranes decrease the dimensionality of protein-protein interactions to enable weak yet biologically important interactions. Membrane resident proteins can phase separate into micro-islands that promote signaling by enriching or excluding signal regulators. Moreover, some membrane lipids can either mediate or regulate cell signaling by interacting with signaling proteins. While it is critical to investigate T cell signaling in a cellular environment, the large number of signaling pathways involved and potential crosstalk have made it difficult to obtain precise, quantitative information on T cell signaling. Reconstitution of purified proteins to model membranes provides a complementary avenue for T cell signaling research. Here, I review recent progress in studying T cell signaling using membrane reconstitution approaches.
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Affiliation(s)
- Enfu Hui
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California
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