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Miller AT, Dahlberg C, Sandberg ML, Wen BG, Beisner DR, Hoerter JAH, Parker A, Schmedt C, Stinson M, Avis J, Cienfuegos C, McPate M, Tranter P, Gosling M, Groot-Kormelink PJ, Dawson J, Pan S, Tian SS, Seidel HM, Cooke MP. Inhibition of the Inositol Kinase Itpkb Augments Calcium Signaling in Lymphocytes and Reveals a Novel Strategy to Treat Autoimmune Disease. PLoS One 2015; 10:e0131071. [PMID: 26121493 PMCID: PMC4488288 DOI: 10.1371/journal.pone.0131071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 05/28/2015] [Indexed: 02/02/2023] Open
Abstract
Emerging approaches to treat immune disorders target positive regulatory kinases downstream of antigen receptors with small molecule inhibitors. Here we provide evidence for an alternative approach in which inhibition of the negative regulatory inositol kinase Itpkb in mature T lymphocytes results in enhanced intracellular calcium levels following antigen receptor activation leading to T cell death. Using Itpkb conditional knockout mice and LMW Itpkb inhibitors these studies reveal that Itpkb through its product IP4 inhibits the Orai1/Stim1 calcium channel on lymphocytes. Pharmacological inhibition or genetic deletion of Itpkb results in elevated intracellular Ca2+ and induction of FasL and Bim resulting in T cell apoptosis. Deletion of Itpkb or treatment with Itpkb inhibitors blocks T-cell dependent antibody responses in vivo and prevents T cell driven arthritis in rats. These data identify Itpkb as an essential mediator of T cell activation and suggest Itpkb inhibition as a novel approach to treat autoimmune disease.
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Affiliation(s)
- Andrew T. Miller
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
- * E-mail:
| | - Carol Dahlberg
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Mark L. Sandberg
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Ben G. Wen
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Daniel R. Beisner
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - John A. H. Hoerter
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Albert Parker
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Christian Schmedt
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Monique Stinson
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Jacqueline Avis
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Cynthia Cienfuegos
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Mark McPate
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Pamela Tranter
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Martin Gosling
- Novartis Pharmaceuticals UK Limited, Respiratory Disease Area, Horsham, West Sussex, United Kingdom
| | - Paul J. Groot-Kormelink
- Novartis Institutes for Biomedical Research, Musculoskeletal Disease Area, Basel, Switzerland
| | - Janet Dawson
- Novartis Pharma AG, Novartis Institutes for Biomed. Research, Basel, Switzerland
| | - Shifeng Pan
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Shin-Shay Tian
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - H. Martin Seidel
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
| | - Michael P. Cooke
- The Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California, United States of America
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Hoerter JAH, Brzostek J, Artyomov MN, Abel SM, Casas J, Rybakin V, Ampudia J, Lotz C, Connolly JM, Chakraborty AK, Gould KG, Gascoigne NRJ. Coreceptor affinity for MHC defines peptide specificity requirements for TCR interaction with coagonist peptide-MHC. ACTA ACUST UNITED AC 2013; 210:1807-21. [PMID: 23940257 PMCID: PMC3754861 DOI: 10.1084/jem.20122528] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The requirement for the TCR to interact with coagonists, endogenous MHC–peptide complexes which do not themselves activate the T cell, decreases as the strength of the CD8–class I interaction increases. Recent work has demonstrated that nonstimulatory endogenous peptides can enhance T cell recognition of antigen, but MHCI- and MHCII-restricted systems have generated very different results. MHCII-restricted TCRs need to interact with the nonstimulatory peptide–MHC (pMHC), showing peptide specificity for activation enhancers or coagonists. In contrast, the MHCI-restricted cells studied to date show no such peptide specificity for coagonists, suggesting that CD8 binding to noncognate MHCI is more important. Here we show how this dichotomy can be resolved by varying CD8 and TCR binding to agonist and coagonists coupled with computer simulations, and we identify two distinct mechanisms by which CD8 influences the peptide specificity of coagonism. Mechanism 1 identifies the requirement of CD8 binding to noncognate ligand and suggests a direct relationship between the magnitude of coagonism and CD8 affinity for coagonist pMHCI. Mechanism 2 describes how the affinity of CD8 for agonist pMHCI changes the requirement for specific coagonist peptides. MHCs that bind CD8 strongly were tolerant of all or most peptides as coagonists, but weaker CD8-binding MHCs required stronger TCR binding to coagonist, limiting the potential coagonist peptides. These findings in MHCI systems also explain peptide-specific coagonism in MHCII-restricted cells, as CD4–MHCII interaction is generally weaker than CD8–MHCI.
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Affiliation(s)
- John A H Hoerter
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
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Paster W, Brockmeyer C, Fu G, Simister PC, de Wet B, Martinez-Riaño A, Hoerter JAH, Feller SM, Wülfing C, Gascoigne NRJ, Acuto O. GRB2-mediated recruitment of THEMIS to LAT is essential for thymocyte development. J Immunol 2013; 190:3749-56. [PMID: 23460737 DOI: 10.4049/jimmunol.1203389] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thymocyte-expressed molecule involved in selection (THEMIS) is a recently identified regulator of thymocyte positive selection. THEMIS's mechanism of action is unknown, and whether it has a role in TCR-proximal signaling is controversial. In this article, we show that THEMIS and the adapter molecule growth factor receptor-bound protein 2 (GRB2) associate constitutively through binding of a conserved PxRPxK motif within the proline-rich region 1 of THEMIS to the C-terminal SH3-domain of GRB2. This association is indispensable for THEMIS recruitment to the immunological synapse via the transmembrane adapter linker for activation of T cells (LAT) and for THEMIS phosphorylation by Lck and ZAP-70. Two major sites of tyrosine phosphorylation were mapped to a YY-motif close to proline-rich region 1. The YY-motif was crucial for GRB2 binding, suggesting that this region of THEMIS might control local phosphorylation-dependent conformational changes important for THEMIS function. Finally, THEMIS binding to GRB2 was required for thymocyte development. Our data firmly assign THEMIS to the TCR-proximal signaling cascade as a participant in the LAT signalosome and suggest that the THEMIS-GRB2 complex might be involved in shaping the nature of Ras signaling, thereby governing thymic selection.
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Affiliation(s)
- Wolfgang Paster
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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Fu G, Hu J, Niederberger-Magnenat N, Rybakin V, Casas J, Yachi PP, Feldstein S, Ma B, Hoerter JAH, Ampudia J, Rigaud S, Lambolez F, Gavin AL, Sauer K, Cheroutre H, Gascoigne NRJ. Protein kinase C η is required for T cell activation and homeostatic proliferation. Sci Signal 2011; 4:ra84. [PMID: 22155788 DOI: 10.1126/scisignal.2002058] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Protein kinase C η (PKCη) is abundant in T cells and is recruited to the immunological synapse that is formed between a T cell and an antigen-presenting cell; however, its function in T cells is unknown. We showed that PKCη was required for the activation of mature CD8+ T cells through the T cell receptor. Compared with wild-type T cells, PKCη-/- T cells showed poor proliferation in response to antigen stimulation, a trait shared with T cells deficient in PKCθ, which is the most abundant PKC isoform in T cells and was thought to be the only PKC isoform with a specific role in T cell activation. In contrast, only PKCη-deficient T cells showed defective homeostatic proliferation, which requires self-antigen recognition. PKCη was dispensable for thymocyte development; however, thymocytes from mice doubly deficient in PKCη and PKCθ exhibited poor development, indicating some redundancy between the PKC isoforms. Deficiency in PKCη or PKCθ had opposing effects on the relative numbers of CD4+ and CD8+ T cells. PKCη-/- mice had a higher ratio of CD4+ to CD8+ T cells compared to that of wild-type mice, whereas PKCθ-/- mice had a lower ratio. Mice deficient in both isoforms exhibited normal cell ratios. Together, these data suggest that PKCη shares some redundant roles with PKCθ in T cell biology and also performs nonredundant functions that are required for T cell homeostasis and activation.
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Affiliation(s)
- Guo Fu
- Department of Immunology and Microbial Science, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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Hoerter JAH, Krishnan V, Lionberger TA, Walter NG. siRNA-like double-stranded RNAs are specifically protected against degradation in human cell extract. PLoS One 2011; 6:e20359. [PMID: 21647381 PMCID: PMC3103583 DOI: 10.1371/journal.pone.0020359] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 04/20/2011] [Indexed: 11/18/2022] Open
Abstract
RNA interference (RNAi) is a set of intracellular pathways in eukaryotes that controls both exogenous and endogenous gene expression. The power of RNAi to knock down (silence) any gene of interest by the introduction of synthetic small-interfering (si)RNAs has afforded powerful insight into biological function through reverse genetic approaches and has borne a new field of gene therapeutics. A number of questions are outstanding concerning the potency of siRNAs, necessitating an understanding of how short double-stranded RNAs are processed by the cell. Recent work suggests unmodified siRNAs are protected in the intracellular environment, although the mechanism of protection still remains unclear. We have developed a set of doubly-fluorophore labeled RNAs (more precisely, RNA/DNA chimeras) to probe in real-time the stability of siRNAs and related molecules by fluorescence resonance energy transfer (FRET). We find that these RNA probes are substrates for relevant cellular degradative processes, including the RNase H1 mediated degradation of an DNA/RNA hybrid and Dicer-mediated cleavage of a 24-nucleotide (per strand) double-stranded RNA. In addition, we find that 21- and 24-nucleotide double-stranded RNAs are relatively protected in human cytosolic cell extract, but less so in blood serum, whereas an 18-nucleotide double-stranded RNA is less protected in both fluids. These results suggest that RNAi effector RNAs are specifically protected in the cellular environment and may provide an explanation for recent results showing that unmodified siRNAs in cells persist intact for extended periods of time.
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Affiliation(s)
- John A. H. Hoerter
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America,
| | - Vishalakshi Krishnan
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America,
| | - Troy A. Lionberger
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Nils G. Walter
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America,
- * E-mail:
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Abstract
Small interfering (si)RNAs have recently been used to therapeutically silence genes in vivo after intravenous systemic delivery. Further progress in the development of siRNA therapeutics will in part rely on tailoring site-specific chemical modifications of siRNAs to optimize their pharmacokinetic properties. Advances are particularly needed to improve the nucleolytic stability of these double-stranded RNA drugs in vivo and suppress adverse off-target gene silencing effects. Here we demonstrate that specific chemical 2'-O-methylation, which has already been shown to ameliorate the omnipresent off-target toxicity of siRNAs, selectively protects the particularly vulnerable 5'-end of the guide strand against exonucleolytic degradation in human blood serum. Specific chemical modification thus resolves the asymmetric degradation of the guide and passenger strands, which is inherent to the thermodynamic asymmetry of the siRNA termini as required for proper utilization of the guide strand in RNA interference.
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Affiliation(s)
- John A H Hoerter
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
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Abstract
Helix (H)27 from Escherichia coli 16S ribosomal (r)RNA is centrally located within the small (30S) ribosomal subunit, immediately adjacent to the decoding center. Bacterial 30S subunit crystal structures depicting Mg(2+) binding sites resolve two magnesium ions within the vicinity of H27: one in the major groove of the G886-U911 wobble pair, and one within the GCAA tetraloop. Binding of such metal cations is generally thought to be crucial for RNA folding and function. To ask how metal ion-RNA interactions in crystals compare with those in solution, we have characterized, using solution NMR spectroscopy, Tb(3+) footprinting and time-resolved fluorescence resonance energy transfer (tr-FRET), location, and modes of metal ion binding in an isolated H27. NMR and Tb(3+) footprinting data indicate that solution secondary structure and Mg(2+) binding are generally consistent with the ribosomal crystal structures. However, our analyses also suggest that H27 is dynamic in solution and that metal ions localize within the narrow major groove formed by the juxtaposition of the loop E motif with the tandem G894-U905 and G895-U904 wobble pairs. In addition, tr-FRET studies provide evidence that Mg(2+) uptake by the H27 construct results in a global lengthening of the helix. We propose that only a subset of H27-metal ion interactions has been captured in the crystal structures of the 30S ribosomal subunit, and that small-scale structural dynamics afforded by solution conditions may contribute to these differences. Our studies thus highlight an example for differences between RNA-metal ion interactions observed in solution and in crystals.
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Abstract
The original interpretation of a series of genetic studies suggested that the highly conserved Escherichia coli 16S ribosomal RNA helix 27 (H27) adopts two alternative secondary structure motifs, the 885 and 888 conformations, during each cycle of amino acid incorporation. Recent crystallographic and genetic evidence has called this hypothesis into question. To ask whether a slippery sequence such as that of H27 may harbor inherent conformational dynamics, we have designed a series of model RNAs based on E. coli H27 for in vitro physicochemical studies. One-dimensional (1)H NMR spectroscopy demonstrates that both the 885 and 888 conformations are occupied to approximately the same extent (f(888) = 0.427 +/- 0.04) in the native H27 sequence at low pH (6.4) and low ionic strength (50 mM NaCl). UV irradiation assays conducted under conditions analogous to those used for assays of ribosomal function (pH 7.5 and 20 mM MgCl(2)) suggest that nucleotides 892 and 905, which are too far apart in the known 885 crystal structures, can approach each other closely enough to form an efficient cross-link. The use of a fluorescence resonance energy transfer (FRET)-labeled RNA together with a partially complementary DNA oligonucleotide that induces a shift to the 888 conformation shows that H27 interchanges between the 885 and 888 conformations on the millisecond time scale, with an equilibrium constant of 0.33 +/-0.12. FRET assays also show that tetracycline interferes with the induced shift to the 888 conformation, a finding that is consistent with crystallographic localization of tetracycline bound to the 885 conformation of H27 in the 30S ribosomal subunit. Taken together, our data demonstrate the innate tendency of an isolated H27 to exist in a dynamic equilibrium between the 885 and 888 conformations. This begs the question of how these inherent structural dynamics are suppressed within the context of the ribosome.
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Affiliation(s)
- John A H Hoerter
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA
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