RESUMEN
Our understanding of the biological role of the ßc family of cytokines has evolved enormously since their initial identification as bone marrow colony stimulating factors in the 1960's. It has become abundantly clear over the intervening decades that this family of cytokines has truly astonishing pleiotropic capacity, capable of regulating not only hematopoiesis but also many other normal and pathological processes such as development, inflammation, allergy and cancer. As noted in the current pandemic, ßc cytokines contribute to the cytokine storm seen in acutely ill COVID-19 patients. Ongoing studies to discover how these cytokines activate their receptor are revealing insights into the fundamental mechanisms that give rise to cytokine pleiotropy and are providing tantalizing glimpses of how discrete signaling pathways may be dissected for activation with novel ligands for therapeutic benefit.
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COVID-19 , Objetivos , Humanos , SARS-CoV-2RESUMEN
Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and IL-5 are members of a small family of cytokines that share a beta receptor subunit (ßc). These cytokines regulate the growth, differentiation, migration and effector function activities of many hematopoietic cells in bone marrow, blood and sites of inflammation. Excessive or aberrant signaling can result in chronic inflammatory conditions and myeloid leukemias. The crystal structures of the GM-CSF ternary complex, the IL-5 binary complex and the very recent IL-3 receptor alpha subunit build upon decades of structure-function studies, giving new insights into cytokine-receptor specificity and signal transduction. Selective modulation of receptor function is now a real possibility and the structures of the ßc receptor family are being used to discover novel and disease-specific therapeutics.
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Subunidad beta Común de los Receptores de Citocinas , Citocinas , Transducción de Señal/inmunología , Animales , Subunidad beta Común de los Receptores de Citocinas/química , Subunidad beta Común de los Receptores de Citocinas/inmunología , Citocinas/química , Citocinas/inmunología , Humanos , Estructura Cuaternaria de Proteína , Relación Estructura-ActividadRESUMEN
Leukemia stem cells (LSC) possess distinct self-renewal and arrested differentiation properties that are responsible for disease emergence, therapy failure, and recurrence in acute myeloid leukemia (AML). Despite AML displaying extensive biological and clinical heterogeneity, LSC with high interleukin-3 receptor (IL3R) levels are a constant yet puzzling feature, as this receptor lacks tyrosine kinase activity. Here, we show that the heterodimeric IL3Rα/ßc receptor assembles into hexamers and dodecamers through a unique interface in the 3D structure, where high IL3Rα/ßc ratios bias hexamer formation. Importantly, receptor stoichiometry is clinically relevant as it varies across the individual cells in the AML hierarchy, in which high IL3Rα/ßc ratios in LSCs drive hexamer-mediated stemness programs and poor patient survival, while low ratios mediate differentiation. Our study establishes a new paradigm in which alternative cytokine receptor stoichiometries differentially regulate cell fate, a signaling mechanism that may be generalizable to other transformed cellular hierarchies and of potential therapeutic significance. SIGNIFICANCE: Stemness is a hallmark of many cancers and is largely responsible for disease emergence, progression, and relapse. Our finding that clinically significant stemness programs in AML are directly regulated by different stoichiometries of cytokine receptors represents a hitherto unexplained mechanism underlying cell-fate decisions in cancer stem cell hierarchies. This article is highlighted in the In This Issue feature, p. 1749.
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Leucemia Mieloide Aguda , Receptores de Citocinas , Humanos , Receptores de Citocinas/uso terapéutico , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/tratamiento farmacológico , Fosforilación , Transducción de Señal , Proliferación Celular , Células Madre NeoplásicasRESUMEN
An unusual polyprenylated acylphloroglucinol derivative unsubstituted at C-2 and C-6, garcicowin A (1), together with three other new (garcicowins B-D, 2-4) and nine known analogues, was isolated and characterized from the twigs of Garcinia cowa. The structures of 1-4 were elucidated by interpretation of their spectroscopic data. The compounds isolated were evaluated for their cytotoxicity against two cancer cell lines (HT-29 and HCT116) and against normal colon cells (CCD-18Co), and the results demonstrated their selective toxicity toward the cancer cells.
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Antineoplásicos Fitogénicos , Medicamentos Herbarios Chinos , Plantas Medicinales/química , Antineoplásicos Fitogénicos/química , Antineoplásicos Fitogénicos/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Medicamentos Herbarios Chinos/farmacología , Garcinia/química , Células HCT116 , Células HT29 , Humanos , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Floroglucinol/análogos & derivados , Floroglucinol/química , Floroglucinol/aislamiento & purificación , Floroglucinol/farmacología , Tallos de la Planta/químicaRESUMEN
Treatment of patients with myelofibrosis with the type I JAK (Janus kinase) inhibitor ruxolitinib paradoxically induces JAK2 activation loop phosphorylation and is associated with a life-threatening cytokine-rebound syndrome if rapidly withdrawn. We developed a time-dependent assay to mimic ruxolitinib withdrawal in primary JAK2V617F and CALR mutant myelofibrosis patient samples and observed notable activation of spontaneous STAT signaling in JAK2V617F samples after drug washout. Accumulation of ruxolitinib-induced JAK2 phosphorylation was dose dependent and correlated with rebound signaling and the presence of a JAK2V617F mutation. Ruxolitinib prevented dephosphorylation of a cryptic site involving Tyr1007/1008 in JAK2 blocking ubiquitination and degradation. In contrast, a type II JAK inhibitor, CHZ868, did not induce JAK2 phosphorylation, was not associated with withdrawal signaling, and was superior in the eradication of flow-purified JAK2V617F mutant CD34+ progenitors after drug washout. Type I inhibitor-induced loop phosphorylation may act as a pathogenic signaling node released upon drug withdrawal, especially in JAK2V617F patients.
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Janus Quinasa 2/metabolismo , Inhibidores de las Cinasas Janus/farmacología , Mielofibrosis Primaria/metabolismo , Pirazoles/farmacología , Síndrome de Abstinencia a Sustancias/patología , Apoptosis , Proliferación Celular , Humanos , Janus Quinasa 2/antagonistas & inhibidores , Janus Quinasa 2/genética , Mutación , Nitrilos , Fosforilación , Mielofibrosis Primaria/tratamiento farmacológico , Mielofibrosis Primaria/patología , Pirimidinas , Transducción de Señal , Síndrome de Abstinencia a Sustancias/tratamiento farmacológico , Síndrome de Abstinencia a Sustancias/metabolismo , Células Tumorales CultivadasRESUMEN
The interleukin-3 (IL-3) receptor is a cell-surface heterodimer that links the haemopoietic, vascular and immune systems and is overexpressed in acute and chronic myeloid leukaemia progenitor cells. It belongs to the type I cytokine receptor family in which the α-subunits consist of two fibronectin III-like domains that bind cytokine, and a third, evolutionarily unrelated and topologically conserved, N-terminal domain (NTD) with unknown function. Here we show by crystallography that, while the NTD of IL3Rα is highly mobile in the presence of IL-3, it becomes surprisingly rigid in the presence of IL-3 K116W. Mutagenesis, biochemical and functional studies show that the NTD of IL3Rα regulates IL-3 binding and signalling and reveal an unexpected role in preventing spontaneous receptor dimerisation. Our work identifies a dual role for the NTD in this cytokine receptor family, protecting against inappropriate signalling and dynamically regulating cytokine receptor binding and function.
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Subunidad alfa del Receptor de Interleucina-3/química , Subunidad alfa del Receptor de Interleucina-3/metabolismo , Dominios Proteicos , Transducción de Señal , Secuencia de Aminoácidos , Animales , Sitios de Unión/genética , Células COS , Línea Celular Tumoral , Chlorocebus aethiops , Cristalografía por Rayos X , Células HEK293 , Humanos , Interleucina-3/química , Interleucina-3/genética , Interleucina-3/metabolismo , Subunidad alfa del Receptor de Interleucina-3/genética , Simulación de Dinámica Molecular , Mutación , Unión ProteicaRESUMEN
The ß common ([ßc]/CD131) family of cytokines comprises granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5, all of which use ßc as their key signaling receptor subunit. This is a prototypic signaling subunit-sharing cytokine family that has unveiled many biological paradigms and structural principles applicable to the IL-2, IL-4, and IL-6 receptor families, all of which also share one or more signaling subunits. Originally identified for their functions in the hematopoietic system, the ßc cytokines are now known to be truly pleiotropic, impacting on multiple cell types, organs, and biological systems, and thereby controlling the balance between health and disease. This review will focus on the emerging biological roles for the ßc cytokines, our progress toward understanding the mechanisms of receptor assembly and signaling, and the application of this knowledge to develop exciting new therapeutic approaches against human disease.
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Citocinas/clasificación , Citocinas/metabolismo , Citocinas/genética , Regulación de la Expresión Génica/fisiología , Humanos , Inflamación/metabolismo , Sepsis/metabolismo , Transducción de SeñalRESUMEN
Interleukin-3 (IL-3) is an activated T cell product that bridges innate and adaptive immunity and contributes to several immunopathologies. Here, we report the crystal structure of the IL-3 receptor α chain (IL3Rα) in complex with the anti-leukemia antibody CSL362 that reveals the N-terminal domain (NTD), a domain also present in the granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-5, and IL-13 receptors, adopting unique "open" and classical "closed" conformations. Although extensive mutational analyses of the NTD epitope of CSL362 show minor overlap with the IL-3 binding site, CSL362 only inhibits IL-3 binding to the closed conformation, indicating alternative mechanisms for blocking IL-3 signaling. Significantly, whereas "open-like" IL3Rα mutants can simultaneously bind IL-3 and CSL362, CSL362 still prevents the assembly of a higher-order IL-3 receptor-signaling complex. The discovery of open forms of cytokine receptors provides the framework for development of potent antibodies that can achieve a "double hit" cytokine receptor blockade.
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Anticuerpos Monoclonales Humanizados/química , Antineoplásicos/química , Subunidad alfa del Receptor de Interleucina-3/química , Secuencia de Aminoácidos , Animales , Anticuerpos Monoclonales Humanizados/inmunología , Antineoplásicos/metabolismo , Sitios de Unión de Anticuerpos , Células COS , Chlorocebus aethiops , Células HEK293 , Humanos , Subunidad alfa del Receptor de Interleucina-3/inmunología , Datos de Secuencia Molecular , Unión ProteicaRESUMEN
The GM-CSF, IL-3 and IL-5 family of cytokines, also known as the ßc family due to their receptors sharing the signalling subunit ßc, regulates multiple biological processes such as native and adaptive immunity, inflammation, normal and malignant hemopoieis, and autoimmunity. Australian scientists played a major role in the discovery and biological characterisation of the ßc cytokines and their recent work is revealing unique features of cytokine receptor assembly and signalling. Furthermore, specific antibodies have been generated to modulate their function. Characterisation of the structural and dynamic requirements for the activation of the ßc receptor family and the molecular definition of downstream signalling pathways are providing new insights into cytokine receptor signalling as well as new therapeutic opportunities.