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Rowley J, Monie A, Hung CF, Wu TC. Expression of IL-15RA or an IL-15/IL-15RA fusion on CD8+ T cells modifies adoptively transferred T-cell function in cis. Eur J Immunol 2009; 39:491-506. [PMID: 19180469 PMCID: PMC3004157 DOI: 10.1002/eji.200838594] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
IL-15 and IL-15 receptor alpha (IL-15RA) play a significant role in multiple aspects of T-cell biology. However, given the evidence that IL-15RA can present IL-15 in trans, the functional capacity of IL-15RA expressed on CD8(+) T cells to modify IL-15 functions in cis is currently unclear. In the current study, we explore the functional consequences of IL-15RA, expression on T cells using a novel method to transfect naive CD8(+) T cells. We observed that RNA nucleofection led to highly efficient, non-toxic, and rapid manipulation of protein expression levels in unstimulated CD8(+) T cells. We found that transfection of unstimulated CD8(+) T cells with IL-15RA RNA led to enhanced viability of CD8(+) T cells in response to IL-15. Transfection with IL-15RA enhanced IL-15-mediated phosphorylation of STAT5 and also promoted IL-15-mediated proliferation in vivo of adoptively transferred naïve CD8(+) T cells. We demonstrated that IL-15RA can present IL-15 via cis-presentation on CD8(+) T cells. Finally, we showed that transfection with a chimeric construct linking IL-15 to IL-15RA cell autonomously enhances the viability and proliferation of primary CD8(+) T cells and cytotoxic potential of antigen-specific CD8(+) T cells. The clinical implications of the current study are discussed.
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Affiliation(s)
- Jesse Rowley
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD, USA
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202
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Rowley J, Monie A, Hung CF, Wu TC. Inhibition of tumor growth by NK1.1+ cells and CD8+ T cells activated by IL-15 through receptor beta/common gamma signaling in trans. THE JOURNAL OF IMMUNOLOGY 2009; 181:8237-47. [PMID: 19050240 DOI: 10.4049/jimmunol.181.12.8237] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IL-15 is an important cytokine involved in the survival and function of CD8(+) T cells and NK cells. IL-15 can be presented by IL-15Ralpha (IL-15RA) to bind with the shared IL-2/IL-15Rbeta and common gamma-chains, which activate signaling pathways on NK cells and CD8(+) T cells. In the present study, we characterized the function of trans-presented IL-15 on NK cells and CD8(+) T cells using TC-1 tumor cells transduced with a retrovirus encoding IL-15 linked to IL-15RA (IL-15/IL-15RA). We demonstrated that the expression of IL-15/IL-15RA on TC-1 cells led to increased percentages of tumor-infiltrating NK cells, NKT cells, and CD8(+) T cells, resulting in the inhibition of tumor growth in challenged mice. Additionally, in vivo Ab depletion experiments demonstrated that NK1.1(+) cells and CD8(+) T cells were important in this inhibition of tumor growth. Furthermore, this accumulation of immune cells and inhibition of tumor growth was abolished by a single amino acid mutation in the common gamma-chain binding site on IL-15. We also observed that IL-15/IL-15RA-transduced TC-1 cells led to the activation of STAT5 in NK and CD8(+) T cells in trans, which was abolished in the mutated IL-15/IL-15RA-transduced TC-1 cells. Taken together, our data suggest that common gamma-chain binding-dependent activation of the shared IL-15/IL-2Rbeta/common gamma signaling pathway may play an important role in the activation of NK cells and CD8(+) T cells, resulting in IL-15/IL-15RA trans-presentation-mediated inhibition of tumor growth.
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Affiliation(s)
- Jesse Rowley
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD 21231, USA
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203
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Huntington ND, Legrand N, Alves NL, Jaron B, Weijer K, Plet A, Corcuff E, Mortier E, Jacques Y, Spits H, Di Santo JP. IL-15 trans-presentation promotes human NK cell development and differentiation in vivo. ACTA ACUST UNITED AC 2008; 206:25-34. [PMID: 19103877 PMCID: PMC2626663 DOI: 10.1084/jem.20082013] [Citation(s) in RCA: 421] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The in vivo requirements for human natural killer (NK) cell development and differentiation into cytotoxic effectors expressing inhibitory receptors for self-major histocompatibility complex class I (MHC-I; killer Ig-like receptors [KIRs]) remain undefined. Here, we dissect the role of interleukin (IL)-15 in human NK cell development using Rag2(-/-)gamma c(-/-) mice transplanted with human hematopoietic stem cells. Human NK cell reconstitution was intrinsically low in this model because of the poor reactivity to mouse IL-15. Although exogenous human IL-15 (hIL-15) alone made little improvement, IL-15 coupled to IL-15 receptor alpha (IL-15R alpha) significantly augmented human NK cells. IL-15-IL-15R alpha complexes induced extensive NK cell proliferation and differentiation, resulting in accumulation of CD16(+)KIR(+) NK cells, which was not uniquely dependent on enhanced survival or preferential responsiveness of this subset to IL-15. Human NK cell differentiation in vivo required hIL-15 and progressed in a linear fashion from CD56(hi)CD16(-)KIR(-) to CD56(lo)CD16(+)KIR(-), and finally to CD56(lo)CD16(+)KIR(+). These data provide the first evidence that IL-15 trans-presentation regulates human NK cell homeostasis. Use of hIL-15 receptor agonists generates a robust humanized immune system model to study human NK cells in vivo. IL-15 receptor agonists may provide therapeutic tools to improve NK cell reconstitution after bone marrow transplants, enhance graft versus leukemia effects, and increase the pool of IL-15-responsive cells during immunotherapy strategies.
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Affiliation(s)
- Nicholas D Huntington
- Immunology Department, 2 Institut National de la Santé et de la Recherche Médicale U668, 3 INSERM U883, Unité de Régulation Immunitaire et Vaccinologie, Institut Pasteur, Paris 75724, France.
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204
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Chan CJ, Andrews DM, Smyth MJ. Can NK cells be a therapeutic target in human diseases? Eur J Immunol 2008; 38:2964-8. [DOI: 10.1002/eji.200838764] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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205
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Wuest TY, Willette-Brown J, Durum SK, Hurwitz AA. The influence of IL-2 family cytokines on activation and function of naturally occurring regulatory T cells. J Leukoc Biol 2008; 84:973-80. [PMID: 18653463 DOI: 10.1189/jlb.1107778] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
IL-2 is essential for CD4+CD25+forkhead box P3+ (FoxP3+) naturally occurring regulatory T cell (Treg) homeostasis and activation. Binding of IL-2 to its receptor leads to phosphorylation of STAT5, and binding of phosphorylated STAT5 to the foxp3 promoter increases foxp3 transcription, resulting in elevated levels of FoxP3 protein in Tregs. Transcriptional regulation by the elevated levels of FoxP3 is thought to be essential for the strong suppressor function seen in activated Tregs. IL-2 belongs to a family cytokines, which all depend on the common gamma-receptor chain (gammac). Given the well-documented effects of IL-2 on Treg function, the effect of other IL-2 family cytokines (IL-7, -15, and -21) on Tregs was examined. We observed that IL-7 and IL-15 induce STAT5 phosphorylation and up-regulation of FoxP3 in Tregs. STAT5 activation correlated with enhanced viability. However, only in the presence of IL-2 did Tregs acquire potent suppressor function. This finding is surprising, as IL-15 as well as IL-2 use the same IL-2R betac and gammac for signaling. In contrast, IL-21 activated STAT3 but did not activate STAT5 and had no effect on Treg viability, activation, or function. We therefore conclude that phosphorylation of STAT5, mediated through the IL-2Rgamma, promotes Treg survival in a resting and activated state. However, activation of STAT5 alone in conjunction with TCR signaling is not sufficient for the induction of potent suppressor function in Tregs, as IL-7 and IL-15 are not capable of inducing potent Treg suppressor function.
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Affiliation(s)
- Thomas Y Wuest
- Laboratory of Molecular Immunoregulation, National Cancer Institute-Frederick, Frederick, MD 21701, USA
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206
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Bouchaud G, Garrigue-Antar L, Solé V, Quéméner A, Boublik Y, Mortier E, Perdreau H, Jacques Y, Plet A. The exon-3-encoded domain of IL-15ralpha contributes to IL-15 high-affinity binding and is crucial for the IL-15 antagonistic effect of soluble IL-15Ralpha. J Mol Biol 2008; 382:1-12. [PMID: 18656487 DOI: 10.1016/j.jmb.2008.07.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/07/2008] [Accepted: 07/08/2008] [Indexed: 11/19/2022]
Abstract
We previously showed that a natural soluble form of interleukin-15 (IL-15) Ralpha corresponding to the full-length ectodomain of IL-15Ralpha behaved as a potent antagonist of IL-15 action through IL-15Ralpha/beta/gamma, whereas a recombinant soluble IL-15Ralpha sushi domain did not, but instead acted as an agonist of IL-15 action through IL-15Rbeta/gamma. In order to determine precisely the molecular basis governing these antagonistic versus agonistic actions, we compared the binding properties and biological effects of recombinant soluble IL-15Ralpha (sIL-15Ralpha) species containing the sushi domain and different remaining parts of the ectodomain. We first demonstrate that the exon-3-encoded domain and, more particularly, its N-terminal 13-amino-acid (aa) peptide are important, in addition to the adjacent exon-2-encoded sushi domain, for the stabilization of the high-affinity IL-15.IL-15Ralpha complex by slowing down its dissociation rate and by contributing to about 10-20% of the free energy of interaction. We next show that all sushi-containing sIL-15Ralpha are agonists on IL-15Rbeta/gamma, coordinately increasing IL-15 binding and IL-15-induced proliferation. Their agonistic potencies are proportional to their respective affinities for IL-15. We then show that the antagonistic effect of sIL-15Ralpha in the context of IL-15Ralpha/beta/gamma is due to the 13-aa peptide that creates a sterical constraint impeding the binding of the sIL-15Ralpha.IL-15 complex to the membrane-anchored IL-15Ralpha/beta/gamma. In the frame of the soluble IL-15Ralpha sushi domain-IL-15 fusion protein that contains the 13-aa peptide, this constraint is alleviated as a result of a conformational effect due to the covalent linking of the 13-aa peptide to the N-terminus of IL-15. The soluble IL-15Ralpha sushi domain-IL-15 fusion protein is therefore able to bind and activate both the IL-15Rbeta/gamma and the IL-15Ralpha/beta/gamma receptors.
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Affiliation(s)
- Grégory Bouchaud
- INSERM, U892, Centre de Recherche en Cancérologie Nantes/Angers, Groupe Cytokines et Récepteurs, Nantes, France; Université de Nantes, IFR26, Nantes, France.
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207
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Kokaji AI, Hockley DL, Kane KP. IL-15 transpresentation augments CD8+ T cell activation and is required for optimal recall responses by central memory CD8+ T cells. THE JOURNAL OF IMMUNOLOGY 2008; 180:4391-401. [PMID: 18354159 DOI: 10.4049/jimmunol.180.7.4391] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although the adaptive immune system has a remarkable ability to mount rapid recall responses to previously encountered pathogens, the cellular and molecular signals necessary for memory CD8(+) T cell reactivation are poorly defined. IL-15 plays a critical role in memory CD8(+) T cell survival; however, whether IL-15 is also involved in memory CD8(+) T cell reactivation is presently unclear. Using artificial Ag-presenting surfaces prepared on cell-sized microspheres, we specifically addressed the role of IL-15 transpresentation on mouse CD8(+) T cell activation in the complete absence of additional stimulatory signals. In this study we demonstrate that transpresented IL-15 is significantly more effective than soluble IL-15 in augmenting anti-CD3epsilon-induced proliferation and effector molecule expression by CD8(+) T cells. Importantly, IL-15 transpresentation and TCR ligation by anti-CD3epsilon or peptide MHC complexes exhibited synergism in stimulating CD8(+) T cell responses. In agreement with previous studies, we found that transpresented IL-15 preferentially stimulated memory phenotype CD8(+) T cells; however, in pursuing this further, we found that central memory (T(CM)) and effector memory (T(EM)) CD8(+) T cells responded differentially to transpresented IL-15. T(CM) CD8(+) T cells undergo Ag-independent proliferation in response to transpresented IL-15 alone, whereas T(EM) CD8(+) T cells are relatively unresponsive to transpresented IL-15. Furthermore, upon Ag-specific stimulation, T(CM) CD8(+) T cell responses are enhanced by IL-15 transpresentation, whereas T(EM) CD8(+) T cell responses are only slightly affected, both in vitro and in vivo. Thus, our findings distinguish the role of IL-15 transpresentation in the stimulation of distinct memory CD8(+) T cell subsets, and they also have implications for ex vivo reactivation and expansion of Ag-experienced CD8(+) T cells for immunotherapeutic approaches.
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Affiliation(s)
- Andy I Kokaji
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
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208
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Badoual C, Bouchaud G, Agueznay NEH, Mortier E, Hans S, Gey A, Fernani F, Peyrard S, -Puig PL, Bruneval P, Sastre X, Plet A, Garrigue-Antar L, Quintin-Colonna F, Fridman WH, Brasnu D, Jacques Y, Tartour E. The Soluble α Chain of Interleukin-15 Receptor: A Proinflammatory Molecule Associated with Tumor Progression in Head and Neck Cancer. Cancer Res 2008; 68:3907-14. [PMID: 18483276 DOI: 10.1158/0008-5472.can-07-6842] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Cécile Badoual
- EA 4054 Université Paris Descartes, Faculté de Medecine; Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
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209
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Natural killer cell-directed therapies: moving from unexpected results to successful strategies. Nat Immunol 2008; 9:486-94. [PMID: 18425105 DOI: 10.1038/ni1580] [Citation(s) in RCA: 220] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Natural killer (NK) cells influence innate and adaptive immune host defenses. Existing data indicate that manipulating the balance between inhibitory and activating NK receptor signals, the sensitivity of target cells to NK cell-mediated apoptosis, and NK cell cross-talk with dendritic cells might hold therapeutic promise. Efforts to modulate NK cell trafficking into inflamed tissues and/or lymph nodes, and to counteract NK cell suppressors, might also prove fruitful in the clinic. However, deeper investigation into the benefits of combination therapy, greater understanding of the functional distinctions between NK cell subsets, and design of new tools to monitor NK cell activity are needed to strengthen our ability to harness the power of NK cells for therapeutic aims.
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210
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Mortier E, Woo T, Advincula R, Gozalo S, Ma A. IL-15Ralpha chaperones IL-15 to stable dendritic cell membrane complexes that activate NK cells via trans presentation. ACTA ACUST UNITED AC 2008; 205:1213-25. [PMID: 18458113 PMCID: PMC2373851 DOI: 10.1084/jem.20071913] [Citation(s) in RCA: 235] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Natural killer (NK) cells are innate immune effectors that mediate rapid responses to viral antigens. Interleukin (IL)-15 and its high affinity IL-15 receptor, IL-15Ralpha, support NK cell homeostasis in resting animals via a novel trans presentation mechanism. To better understand how IL-15 and IL-15Ralpha support NK cell activation during immune responses, we have used sensitive assays for detecting native IL-15 and IL-15Ralpha proteins and developed an assay for detecting complexes of these proteins. We find that IL-15 and IL-15Ralpha are preassembled in complexes within the endoplasmic reticulum/Golgi of stimulated dendritic cells (DCs) before being released from cells. IL-15Ralpha is required for IL-15 production by DCs, and IL-15 that emerges onto the cell surface of matured DCs does not bind to neighboring cells expressing IL-15Ralpha. We also find that soluble IL-15-IL-15Ralpha complexes are induced during inflammation, but membrane-bound IL-15-IL-15Ralpha complexes, rather than soluble complexes, support NK cell activation in vitro and in vivo. Finally, we provide in vivo evidence that expression of IL-15Ralpha specifically on DCs is critical for trans presenting IL-15 and activating NK cells. These studies define an unprecedented cytokine-receptor biosynthetic pathway in which IL-15Ralpha serves as a chaperone for IL-15, after which membrane-bound IL-15Ralpha-IL-15 complexes activate NK cells via direct cell-cell contact.
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Affiliation(s)
- Erwan Mortier
- Colitis and Crohn's Disease Center, Gastroenterology Division, Department of Medicine, Biomedical Sciences Program, Program in Biological Sciences, University of California, San Francisco, San Francisco, CA 94143, USA
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211
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Dubois S, Patel HJ, Zhang M, Waldmann TA, Müller JR. Preassociation of IL-15 with IL-15R alpha-IgG1-Fc enhances its activity on proliferation of NK and CD8+/CD44high T cells and its antitumor action. THE JOURNAL OF IMMUNOLOGY 2008; 180:2099-106. [PMID: 18250415 DOI: 10.4049/jimmunol.180.4.2099] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In the induction of an immune response, IL-15Ralpha on APCs transpresents IL-15 to NK and CD8(+)/CD44(high) T cells that express the IL-2/15Rbeta and gammac subunits only. In this study, we show data mimicking this transpresentation by using IL-15 preassociated with a chimeric protein that is comprised of the extracellular domain of murine IL-15Ralpha and the Fc portion of human IgG1. When tested in vitro, IL-15Ralpha-IgG1-Fc strongly increased the IL-15-mediated proliferation of murine NK and CD8(+)/CD44(high) T cells. The effect of IL-15Ralpha-IgG1-Fc was dependent on the presence of both IgG1-Fc and IL-15Ralpha. When injected into mice, IL-15Ralpha-IgG1-Fc enhanced the capacity of IL-15 to expand the number of NK and CD8(+)/CD44(high) T cells. The effect on cell numbers in vivo also depended on Fc receptor binding because reduced expansion was observed in FcRgamma(-/-) mice. NK cells cultured in IL-15/IL-15Ralpha-IgG1-Fc complex gained cytotoxic activity toward a number of NK-sensitive targets. When mice bearing the NK-sensitive syngeneic tumor B16 were treated, the presence of IL-15Ralpha-IgG1-Fc increased the antitumor activity of IL-15. Thus, a preassociation with IL-15Ralpha-IgG1-Fc enhances the activities of IL-15 in vivo and in vitro that may be useful in the treatment of tumors.
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Affiliation(s)
- Sigrid Dubois
- Metabolism Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA
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212
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Bergamaschi C, Rosati M, Jalah R, Valentin A, Kulkarni V, Alicea C, Zhang GM, Patel V, Felber BK, Pavlakis GN. Intracellular Interaction of Interleukin-15 with Its Receptor α during Production Leads to Mutual Stabilization and Increased Bioactivity. J Biol Chem 2008; 283:4189-99. [DOI: 10.1074/jbc.m705725200] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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213
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A biophysical approach to IL-2 and IL-15 receptor function: localization, conformation and interactions. Immunol Lett 2008; 116:117-25. [PMID: 18280585 DOI: 10.1016/j.imlet.2007.12.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Accepted: 12/30/2007] [Indexed: 12/25/2022]
Abstract
Interleukin-2 and interleukin-15 (IL-2, IL-15) are key participants in T and NK cell activation and function. Sharing the beta and gamma receptor subunits results in several common functions: e.g. the promotion of T cell proliferation. On the other hand, due to their distinct alpha receptor subunits, they also play opposing roles in immune processes such as activation induced cell death and immunological memory. Divergence of signaling pathways must ensue already at the plasma membrane where the cytokines interact with their receptors. Therefore understanding molecular details of receptor organization and mapping interactions with other membrane proteins that might influence receptor conformation and function, are of key importance. Biophysical/advanced microscopic methods (fluorescence resonance energy transfer (FRET), fluorescence crosscorrelation spectroscopy (FCCS), near-field scanning optical microscopy (NSOM), X-ray crystallography, surface plasmon resonance, NMR spectroscopy) have been instrumental in clarifying the details of receptor structure and organization from the atomic level to the assembly and dynamics of supramolecular clusters. In this short review some important contributions shaping our current view of IL-2 and IL-15 receptors are presented.
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214
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Walzer T, Chiossone L, Chaix J, Calver A, Carozzo C, Garrigue-Antar L, Jacques Y, Baratin M, Tomasello E, Vivier E. Natural killer cell trafficking in vivo requires a dedicated sphingosine 1-phosphate receptor. Nat Immunol 2007; 8:1337-44. [PMID: 17965716 DOI: 10.1038/ni1523] [Citation(s) in RCA: 308] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Accepted: 09/18/2007] [Indexed: 12/11/2022]
Abstract
Consistent with their function in immune surveillance, natural killer (NK) cells are distributed throughout lymphoid and nonlymphoid tissues. However, the mechanisms governing the steady-state trafficking of NK cells remain unknown. The lysophospholipid sphingosine 1-phosphate (S1P), by binding to its receptor S1P1, regulates the recirculation of T and B lymphocytes. In contrast, S1P5 is detected in the brain and regulates oligodendrocyte migration and survival in vitro. Here we show that S1P5 was also expressed in NK cells in mice and humans and that S1P5-deficient mice had aberrant NK cell homing during steady-state conditions. In addition, we found that S1P5 was required for the mobilization of NK cells to inflamed organs. Our data emphasize distinct mechanisms regulating the circulation of various lymphocyte subsets and raise the possibility that NK cell trafficking may be manipulated by therapies specifically targeting S1P5.
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Affiliation(s)
- Thierry Walzer
- Centre d'Immunologie de Marseille-Luminy, Université de la Méditerranée, Institut National de la Santé et de la Recherche Médicale, U631, and Centre National de la Recherche Scientifique, UMR6102, Marseille, France.
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215
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Olsen SK, Ota N, Kishishita S, Kukimoto-Niino M, Murayama K, Uchiyama H, Toyama M, Terada T, Shirouzu M, Kanagawa O, Yokoyama S. Crystal Structure of the interleukin-15.interleukin-15 receptor alpha complex: insights into trans and cis presentation. J Biol Chem 2007; 282:37191-204. [PMID: 17947230 DOI: 10.1074/jbc.m706150200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interleukin (IL)-15 is a pleiotropic cytokine that plays a pivotal role in both innate and adaptive immunity. IL-15 is unique among cytokines due to its participation in a trans signaling mechanism in which IL-15 receptor alpha (IL-15Ralpha) from one subset of cells presents IL-15 to neighboring IL-2Rbeta/gammac-expressing cells. Here we present the crystal structure of IL-15 in complex with the sushi domain of IL-15Ralpha. The structure reveals that the alpha receptor-binding epitope of IL-15 adopts a unique conformation, which, together with amino acid substitutions, permits specific interactions with IL-15Ralpha that account for the exceptionally high affinity of the IL-15.IL-15Ralpha complex. Interestingly, analysis of the topology of IL-15 and IL-15Ralpha at the IL-15.IL-15Ralpha interface suggests that IL-15 should be capable of participating in a cis signaling mechanism similar to that of the related cytokine IL-2. Indeed, we present biochemical data demonstrating that IL-15 is capable of efficiently signaling in cis through IL-15Ralpha and IL-2Rbeta/gammac expressed on the surface of a single cell. Based on our data we propose that cis presentation of IL-15 may be important in certain biological contexts and that flexibility of IL-15Ralpha permits IL-15 and its three receptor components to be assembled identically at the ligand-receptor interface whether IL-15 is presented in cis or trans. Finally, we have gained insights into IL-15.IL-15Ralpha.IL-2Rbeta.gammac quaternary complex assembly through the use of molecular modeling.
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Affiliation(s)
- Shaun K Olsen
- RIKEN Genomic Sciences Center, RIKEN Yokohama Institute, Kanagawa, Japan
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216
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Wittnebel S, Da Rocha S, Giron-Michel J, Jalil A, Opolon P, Escudier B, Validire P, Khawam K, Chouaib S, Azzarone B, Caignard A. Membrane-bound interleukin (IL)-15 on renal tumor cells rescues natural killer cells from IL-2 starvation-induced apoptosis. Cancer Res 2007; 67:5594-9. [PMID: 17575122 DOI: 10.1158/0008-5472.can-06-4406] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Renal cell carcinoma primary tumors and lung metastases are infiltrated by activated natural killer (NK) cells. Interleukin (IL)-15, a major cytokine involved in cross-talk between accessory cells (dendritic cells and macrophages) and NK cells, is produced by epithelial renal cells. We show that renal cell carcinoma cells and normal renal cells express IL-15 mRNA and membrane-bound IL-15 (MbIL-15). These cells also express IL-15 receptor alpha (IL-15Ralpha). Silencing of IL-15Ralpha by specific small interfering RNA in renal cell carcinoma had no effect on MbIL-15 production, indicating that the cytokine is not cross-presented by IL-15Ralpha in renal cell carcinoma cells but anchored to the membrane. Furthermore, we show that MbIL-15 from renal cell carcinoma cells is functional and involved in rapid nuclear translocation of phosphorylated signal transducers and activators of transcription 3 in IL-2-starved NK cells. MbIL-15 on the target did not interfere with resting NK cell activation and target cell cytolysis but rescued NK cells from IL-2 starvation-induced apoptosis through contact-dependent interaction. Masking of MbIL-15 with soluble IL-15Ralpha molecules restored NK cell apoptosis. These findings suggest that IL-15 produced by renal tumor cells is involved in the maintenance of active NK cells at the tumor site.
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217
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Kamimura D, Bevan MJ. Naive CD8+ T cells differentiate into protective memory-like cells after IL-2 anti IL-2 complex treatment in vivo. ACTA ACUST UNITED AC 2007; 204:1803-12. [PMID: 17664293 PMCID: PMC2118678 DOI: 10.1084/jem.20070543] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
An optimal CD8+ T cell response requires signals from the T cell receptor (TCR), co-stimulatory molecules, and cytokines. In most cases, the relative contribution of these signals to CD8+ T cell proliferation, accumulation, effector function, and differentiation to memory is unknown. Recent work (Boyman, O., M. Kovar, M.P. Rubinstein, C.D. Surh, and J. Sprent. 2006. Science. 311:1924–1927; Kamimura, D., Y. Sawa, M. Sato, E. Agung, T. Hirano, and M. Murakami. 2006. J. Immunol. 177:306–314) has shown that anti–interleukin (IL) 2 monoclonal antibodies that are neutralizing in vitro enhance the potency of IL-2 in vivo. We investigated the role of IL-2 signals in driving CD8+ T cell proliferation in the absence of TCR stimulation by foreign antigen. IL-2 signals induced rapid activation of signal transducer and activator of transcription 5 in all CD8+ T cells, both naive and memory phenotype, and promoted the differentiation of naive CD8+ T cells into effector cells. IL-2–anti–IL-2 complexes induced proliferation of naive CD8+ T cells in an environment with limited access to self–major histocompatibility complex (MHC) and when competition for self-MHC ligands was severe. After transfer into wild-type animals, IL-2–activated CD8+ T cells attained and maintained a central memory phenotype and protected against lethal bacterial infection. IL-2–anti–IL-2 complex–driven memory-like CD8+ T cells had incomplete cellular fitness compared with antigen-driven memory cells regarding homeostatic turnover and cytokine production. These results suggest that intense IL-2 signals, with limited contribution from the TCR, program the differentiation of protective memory-like CD8+ cells but are insufficient to guarantee overall cellular fitness.
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Affiliation(s)
- Daisuke Kamimura
- Department of Immunology and Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
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218
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Hanick NA, Rickert M, Varani L, Bankovich AJ, Cochran JR, Kim DM, Surh CD, Garcia KC. Elucidation of the interleukin-15 binding site on its alpha receptor by NMR. Biochemistry 2007; 46:9453-61. [PMID: 17655329 DOI: 10.1021/bi700652f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cytokine interleukin-15 (IL-15) signals through the formation of a quaternary receptor complex composed of an IL-15-specific alpha receptor, together with beta and gammac receptors that are shared with interleukin-2 (IL-2). The initiating step in the formation of this signaling complex is the interaction between IL-15 and IL-15Ralpha, which is a single sushi domain bearing strong structural homology to one of the two sushi domains of IL-2Ralpha. The crystal structure of the IL2-Ralpha/IL-2 complex has been determined, however little is known about the analogous IL-15Ralpha/IL-15 binding interaction. Here we show that recombinant IL-15 can be overexpressed as a stable complex in the presence of its high affinity receptor, IL-15Ralpha. We find that this complex is 10-fold more active than IL-15 alone in stimulating proliferation and survival of memory phenotype CD8 T cells. To probe the ligand/receptor interface, we used solution NMR to map chemical shifts on 15N-labeled IL-15Ralpha in complex with unlabeled IL-15. Our results predict that the binding surface on IL-15Ralpha involves strands C and D, similar to IL-2Ralpha. The interface, as predicted here, leaves open the possibility of trans-presentation of IL-15 by IL-15Ralpha on an opposing cell.
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Affiliation(s)
- Nicole A Hanick
- Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University School of Medicine, California 94305, USA
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219
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Chirifu M, Hayashi C, Nakamura T, Toma S, Shuto T, Kai H, Yamagata Y, Davis SJ, Ikemizu S. Crystal structure of the IL-15-IL-15Ralpha complex, a cytokine-receptor unit presented in trans. Nat Immunol 2007; 8:1001-7. [PMID: 17643103 DOI: 10.1038/ni1492] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 06/20/2007] [Indexed: 12/11/2022]
Abstract
Interleukin 15 (IL-15) and IL-2, which promote the survival of memory CD8(+) T cells and regulatory T cells, respectively, bind receptor complexes that share beta- and gamma-signaling subunits. Receptor specificity is provided by unique, nonsignaling alpha-subunits. Whereas IL-2 receptor-alpha (IL-2Ralpha) is expressed together in cis with the beta- and gamma-subunits on T cells and B cells, IL-15Ralpha is expressed in trans on antigen-presenting cells. Here we present a 1.85-A crystal structure of the human IL-15-IL-15Ralpha complex. The structure provides insight into the molecular basis of the specificity of cytokine recognition and emphasizes the importance of water in generating this very high-affinity complex. Despite very low IL-15-IL-2 sequence homology and distinct receptor architecture, the topologies of the IL-15-IL-15Ralpha and IL-2-IL-2Ralpha complexes are very similar. Our data raise the possibility that IL-2, like IL-15, might be capable of being presented in trans in the context of its unique receptor alpha-chain.
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Affiliation(s)
- Mami Chirifu
- Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
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220
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Abstract
Technological advances in recent years have allowed for an ever-expanding ability to analyze and quantify in vivo immune responses. MHC tetramers, intracellular cytokine staining, an increasing repertoire of transgenic and "knockout" mice, and the detailed characterization of a variety of infectious models have all facilitated more precise and definitive analyses of the generation and function of cytotoxic T lymphocytes (CTL). Understanding the mechanisms behind the differentiation of effector and memory CTL is of increasing importance to develop vaccination strategies against a variety of established and emerging infectious diseases. This review focuses on recent advances in our understanding of how effector and memory CTL differentiate and survive in vivo in response to viral or bacterial infection.
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Affiliation(s)
- Matthew A Williams
- Howard Hughes Medical Institute, Department of Immunology, University of Washington, Seattle, Washington 98195, USA.
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221
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Bulanova E, Budagian V, Duitman E, Orinska Z, Krause H, Rückert R, Reiling N, Bulfone-Paus S. Soluble Interleukin IL-15Ralpha is generated by alternative splicing or proteolytic cleavage and forms functional complexes with IL-15. J Biol Chem 2007; 282:13167-79. [PMID: 17327231 DOI: 10.1074/jbc.m610036200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interleukin 15 (IL-15) is a pleiotropic cytokine that is hardly detectable in biological fluids. Here, we show that IL-15 forms functional heterocomplexes with soluble high affinity IL-15 receptor alpha (IL-15Ralpha) chain in mouse serum and cell-conditioned medium, which prevents IL-15 detection by ELISA. We also demonstrate that two soluble IL-15Ralpha (sIL-15Ralpha) sushi domain isoforms are generated through a novel alternative splicing mechanism within the IL-15Ralpha gene. These isoforms potentiate IL-15 action by promoting the IL-15-mediated proliferation of the CTLL cell line and interferon gamma production by murine NK cells, which suggests a role in IL-15 transpresentation. Conversely, a full-length sIL-15Ralpha ectodomain released by tumor necrosis factor-alpha-converting enzyme (TACE)-dependent proteolysis inhibits IL-15 activity. Thus, a dual mechanism of sIL-15Ralpha generation exists in mice, giving rise to polypeptides with distinct properties, which regulate IL-15 function.
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Affiliation(s)
- Elena Bulanova
- Department of Immunology and Cell Biology and Immunochemistry and Biochemical Microbiology, Research Center Borstel, Borstel D-23845, Germany.
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222
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Quéméner A, Bernard J, Mortier E, Plet A, Jacques Y, Tran V. Docking of human interleukin-15 to its specific receptor alpha chain: correlation between molecular modeling and mutagenesis experimental data. Proteins 2007; 65:623-36. [PMID: 17001647 DOI: 10.1002/prot.21103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A structural model of the sushi domain of IL-15Ralpha was first obtained by homology modeling to study its interactions with IL-15 by means of molecular modeling, peptide scanning, and site-directed mutagenesis. From these experimental data, a putative interacting surface of IL-15Ralpha with a previously published IL-15 model was inferred: Leu25, Leu44, and Glu46 of IL-15 and Arg35 of IL-15Ralpha were found to be key interfacial residues and were subsequently used as filters for the construction of docking solutions. Human IL-15/IL-15Ralpha complexes were constructed in two stages, with a preliminary docking procedure, treating the two partners as rigid bodies and using these filters. In this first stage, two classes of docking solutions were characterized. From a topological point of view, each solution could be derived from the other by reverse orientation of one partner in relation to the other. In a second stage, several further energy refinements clearly favored one solution. Moreover, this unique docking solution was confirmed by molecular modeling of IL-15 mutants previously built and tested in our laboratory. Finally, this complex model, which is a useful tool to study the IL-15/IL-15Ralpha interface, was topologically compared to IL-2/IL-2Ralpha complexes (previous model in the literature and recent crystal structure).
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Affiliation(s)
- Agnès Quéméner
- INSERM, U601, Groupe de Recherche Cytokines et Récepteurs, Institut de Biologie, Nantes, France
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223
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Rich RL, Myszka DG. Survey of the year 2006 commercial optical biosensor literature. J Mol Recognit 2007; 20:300-66. [DOI: 10.1002/jmr.862] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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224
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Stoklasek TA, Schluns KS, Lefrançois L. Combined IL-15/IL-15Ralpha immunotherapy maximizes IL-15 activity in vivo. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2006; 177:6072-80. [PMID: 17056533 PMCID: PMC2847275 DOI: 10.4049/jimmunol.177.9.6072] [Citation(s) in RCA: 292] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IL-15 has substantial potential as an immunotherapeutic agent for augmenting immune responses. However, the activity of IL-15 is mediated by a unique mechanism in which the cytokine is transpresented by cell-bound high-affinity IL-15Ralpha to target cells expressing the IL-15Rbeta and the common gamma-chain. Thus, the efficacy of administered IL-15 alone may be limited by the availability of free IL-15Ralpha. We now show that administration of soluble IL-15/IL-15Ralpha complexes greatly enhanced IL-15 half-life and bioavailability in vivo. Treatment of mice with this complex, but not with IL-15 alone, resulted in robust proliferation of memory CD8 T cells, NK cells, and NK T cells. The activity of the complex required IL-15Rbeta, but not IL-15Ralpha, expression by the responding cells and was IL-7-independent. Interestingly, IL-15/IL-15Ralpha immunotherapy also caused naive CD8 T cell activation and development into effector cells and long-term memory T cells. Lastly, complexed IL-15, as compared with IL-15 alone, dramatically reduced tumor burden in a model of B16 melanoma. These findings hold significant importance for the use of IL-15 as a potential adjuvant/therapeutic and inducer of homeostatic proliferation, without the necessity for prior immunodepletion.
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Affiliation(s)
- Thomas A. Stoklasek
- Department of Immunology, University of Connecticut Health Center, Farmington, CT 06030
| | | | - Leo Lefrançois
- Department of Immunology, University of Connecticut Health Center, Farmington, CT 06030
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225
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Trans-presentation of IL-15. Blood 2006. [DOI: 10.1182/blood-2006-07-035246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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226
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Wittnebel S, Bourhis JH, Caignard A. Chronic myeloid leukemia and allogeneic natural killer cells: a surprising dialogue. Expert Rev Clin Immunol 2006; 2:627-37. [PMID: 20477618 DOI: 10.1586/1744666x.2.4.627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Chronic myeloid leukemia (CML) is a clonal multilineage myeloproliferative disease of stem cell origin characterized by the presence of the Bcr/Abl oncoprotein, a constitutively active tyrosine kinase. The actual treatment of CML patients in chronic phase is the specific abl kinase inhibitor imatinib mesylate that induces 90% of cytogenetic responses in early-phase patients. However, resistance in long-term treated patients occurs and the allogeneic stem cell transplantation remains the only curative treatment in resistant patients. Despite recent reports outlining the role of allogeneic natural killer (NK) cells as potent antileukemic effectors, the mechanisms controlling the leukemic target recognition and lysis by activated NK cells have not been well identified. The authors' experimental data obtained on appropriate cellular models identify diverse mechanisms that could explain the increased NK-cell susceptibility of Bcr/Abl targets to NK-mediated lysis. They further delineate unexpected effects of the inhibition of the tyrosine kinase activity on the cross-talk between NK and CML leukemic cells. The consequences of such discoveries are discussed in the context of combined treatments with antikinases as well as adoptive cellular therapy approaches in myeloid leukemia patients.
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227
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Rubinstein MP, Kovar M, Purton JF, Cho JH, Boyman O, Surh CD, Sprent J. Converting IL-15 to a superagonist by binding to soluble IL-15R{alpha}. Proc Natl Acad Sci U S A 2006; 103:9166-71. [PMID: 16757567 PMCID: PMC1482584 DOI: 10.1073/pnas.0600240103] [Citation(s) in RCA: 325] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
IL-15 is normally presented in vivo as a cell-associated cytokine bound to IL-15Ralpha. We show here that the biological activity of soluble IL-15 is much improved after interaction with recombinant soluble IL-15Ralpha; after injection, soluble IL-15/IL-15Ralpha complexes rapidly induce strong and selective expansion of memory-phenotype CD8(+) cells and natural killer cells. These findings imply that binding of IL-15Ralpha to IL-15 may create a conformational change that potentiates IL-15 recognition by the betagamma(c) receptor on T cells. The enhancing effect of IL-15Ralpha binding may explain why IL-15 normally functions as a cell-associated cytokine. Significantly, the results with IL-2, a soluble cytokine, are quite different; thus, IL-2 function is markedly inhibited by binding to soluble IL-2Ralpha.
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Affiliation(s)
- Mark P. Rubinstein
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Marek Kovar
- Department of Immunology and Gnotobiology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jared F. Purton
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Jae-Ho Cho
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
- Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst NSW 2010, Australia; and
| | - Onur Boyman
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Charles D. Surh
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Jonathan Sprent
- *Department of Immunology, IMM4, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
- Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst NSW 2010, Australia; and
- To whom correspondence should be addressed. E-mail:
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228
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Bulfone-Paus S, Bulanova E, Budagian V, Paus R. The interleukin-15/interleukin-15 receptor system as a model for juxtacrine and reverse signaling. Bioessays 2006; 28:362-77. [PMID: 16547946 DOI: 10.1002/bies.20380] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Interleukin-15 (IL-15) is a pleiotropic cytokine of the 4 alpha-helix bundle family, which binds to a receptor complex that displays common elements with the IL-2 receptor and a unique high-affinity alpha chain. This review focuses on juxtacrine and reverse signaling levels in the IL-15/IL-15R system. Specifically, we discuss how agonistic stimulation of membrane-bound IL-15 induces phosphorylation of members of the MAP kinase family and of focal adhesion kinase (FAK), thereby upregulating processes including cytokine secretion, cell adhesion and migration. In addition, we explore IL-15 trans-presentation and intracellular signaling, and define promising molecular targets for future pharmacological intervention in infectious diseases and immunological disorders. These frontiers in IL-15/IL-15Ralpha research serve as highly instructive examples for key concepts, unsolved problems and therapeutic opportunities in juxtacrine and reverse signaling in general.
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Affiliation(s)
- Silvia Bulfone-Paus
- Department of Immunology and Cell Biology, Research Center Borstel, Germany.
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229
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Lorenzen I, Dingley AJ, Jacques Y, Grötzinger J. The structure of the interleukin-15 alpha receptor and its implications for ligand binding. J Biol Chem 2005; 281:6642-7. [PMID: 16377614 DOI: 10.1074/jbc.m513118200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interleukin (IL)-15 is a member of the small four alpha-helix bundle family of cytokines. IL-15 was discovered by its ability to mimic IL-2-mediated T-cell proliferation. Both cytokines share the beta and gamma receptor chains of the IL-2 receptor for signal transduction. However, in addition, they target specific alpha chain receptors IL-15Ralpha and IL-2Ralpha, respectively. The exceptionally high affinity binding of IL-15 to IL-15Ralpha is mediated by its sushi domain. Here we present the solution structure of the IL-15Ralpha sushi domain solved by NMR spectroscopy and a model of its complex with IL-15. The model shows that, rather than the familiar hydrophobic forces dominating the interaction interface between cytokines and their cognate receptors, the interaction between the IL-15 and IL-15Ralpha complex involves a large network of ionic interactions. This type of interaction explains the exceptionally high affinity of the IL-15.IL-15Ralpha complex, which is essential for the biological effects of this important cytokine and which is not observed in other cytokine/cytokine receptor complexes.
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Affiliation(s)
- Inken Lorenzen
- Biochemisches Institut der Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, 24118 Kiel, Germany
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