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Pharmacological Reviews Apr 2020Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into... (Review)
Review
Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.
Topics: Animals; Anti-Inflammatory Agents; Antineoplastic Agents; Clinical Trials, Phase II as Topic; Fibrosis; Humans; Inflammation; Janus Kinases; Molecular Targeted Therapy; Neoplasms; Phosphorylation; Protein Kinase Inhibitors; STAT3 Transcription Factor
PubMed: 32198236
DOI: 10.1124/pr.119.018440 -
The Journal of Investigative Dermatology Sep 2018The advancement of genetic and preclinical studies has uncovered the mechanisms involved in the pathogenesis of alopecia areata (AA). The development of targeted... (Review)
Review
The advancement of genetic and preclinical studies has uncovered the mechanisms involved in the pathogenesis of alopecia areata (AA). The development of targeted therapies using small molecules blocking specific pathways for the treatment of AA is underway. By repurposing Food and Drug Administration-approved small molecule JAK inhibitors as treatments for AA, it has been demonstrated that JAK inhibitors can effectively reverse hair loss in patients with moderate to severe AA. In this review, we summarize and discuss the current preclinical and clinical studies on JAK inhibitors, as well as the prospects of using JAK inhibitors for the treatment of AA.
Topics: Alopecia Areata; Animals; Humans; Janus Kinase Inhibitors; Janus Kinases
PubMed: 30057345
DOI: 10.1016/j.jid.2018.05.027 -
Indian Journal of Dermatology,... 2023The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is a key regulatory signaling system for cellular proliferation, differentiation,... (Review)
Review
The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is a key regulatory signaling system for cellular proliferation, differentiation, and apoptosis. In addition, JAK signaling pathway plays critical roles in orchestrating immune response through its interactions with the cytokine receptors and the transcriptions factors. Several key cytokines use JAK-STAT signaling proteins to transduce intra-cellular signals which are involved in the pathogenesis of autoimmune and inflammatory diseases such as in psoriatic disease (psoriasis, psoriatic arthritis), atopic dermatitis, alopecia areata, vitiligo, rheumatoid arthritis, ankylosing spondylitis, lupus erythematosus, Sjogren's syndrome, and other autoimmune diseases. In recent years, understandings of the molecular mechanisms of JAK-STAT pathway in the inflammatory proliferative cascades of autoimmune diseases has led to the development of JAK inhibitors and has opened a new dimension for the treatment of systemic and cutaneous inflammatory diseases. In this symposium we have provided a broad perspective on the use of Janus kinase inhibitors in cutaneous autoimmune diseases.
Topics: Humans; Janus Kinase Inhibitors; Janus Kinases; STAT Transcription Factors; Signal Transduction; Skin Diseases; Autoimmune Diseases
PubMed: 37609754
DOI: 10.25259/IJDVL_8_2023 -
Clinical and Experimental Rheumatology 2016Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterised by infiltration of immune cells into the affected synovium, release of inflammatory... (Review)
Review
Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterised by infiltration of immune cells into the affected synovium, release of inflammatory cytokines and degradative mediators, and subsequent joint damage. Both innate and adaptive arms of the immune response play a role, with activation of immune cells leading to dysregulated expression of inflammatory cytokines. Cytokines work within a complex regulatory network in RA, signalling through different intracellular kinase pathways to modulate recruitment, activation and function of immune cells and other leukocytes. As our understanding of RA has advanced, intracellular signalling pathways such as Janus kinase (JAK) pathways have emerged as key hubs in the cytokine network and, therefore, important as therapeutic targets. Tofacitinib is an oral JAK inhibitor for the treatment of RA. Tofacitinib is a targeted small molecule, and an innovative advance in RA therapy, which modulates cytokines critical to the progression of immune and inflammatory responses. Herein we describe the mechanism of action of tofacitinib and the impact of JAK inhibition on the immune and inflammatory responses in RA.
Topics: Arthritis, Rheumatoid; Cytokines; Humans; Janus Kinases; Lymphocyte Subsets; Neutrophils; Piperidines; Protein Kinase Inhibitors; Pyrimidines; Pyrroles; Signal Transduction
PubMed: 26966791
DOI: No ID Found -
Science (New York, N.Y.) Apr 2022Cytokines signal through cell surface receptor dimers to initiate activation of intracellular Janus kinases (JAKs). We report the 3.6-angstrom-resolution cryo-electron...
Cytokines signal through cell surface receptor dimers to initiate activation of intracellular Janus kinases (JAKs). We report the 3.6-angstrom-resolution cryo-electron microscopy structure of full-length JAK1 complexed with a cytokine receptor intracellular domain Box1 and Box2 regions captured as an activated homodimer bearing the valine→phenylalanine (VF) mutation prevalent in myeloproliferative neoplasms. The seven domains of JAK1 form an extended structural unit, the dimerization of which is mediated by close-packing of the pseudokinase (PK) domains from the monomeric subunits. The oncogenic VF mutation lies within the core of the JAK1 PK interdimer interface, enhancing packing complementarity to facilitate ligand-independent activation. The carboxy-terminal tyrosine kinase domains are poised for transactivation and to phosphorylate the receptor STAT (signal transducer and activator of transcription)-recruiting motifs projecting from the overhanging FERM (four-point-one, ezrin, radixin, moesin)-SH2 (Src homology 2)-domains. Mapping of constitutively active JAK mutants supports a two-step allosteric activation mechanism and reveals opportunities for selective therapeutic targeting of oncogenic JAK signaling.
Topics: Allosteric Regulation; Cryoelectron Microscopy; Enzyme Activation; Humans; Janus Kinase 1; Mutation; Myeloproliferative Disorders; Phosphorylation; Protein Multimerization; Receptors, Cytokine; STAT Transcription Factors; src Homology Domains
PubMed: 35271300
DOI: 10.1126/science.abn8933 -
Acta Dermato-venereologica Feb 2023Itch is a common skin symptom, with complex aetiology and pathogenesis. It is mediated by 2 pathways, the histaminergic and non-histaminergic pathways. Chronic itch is... (Review)
Review
Itch is a common skin symptom, with complex aetiology and pathogenesis. It is mediated by 2 pathways, the histaminergic and non-histaminergic pathways. Chronic itch is understood to be processed by the latter and is difficult to treat with traditional pruritus therapies. The Janus kinase and signal transducer and activator of transcription pathway is a signalling mechanism that regulates gene expression through various cytokines. Janus kinase inhibitors, which have been tested and used for several autoimmune diseases, have also been shown to be effective for itch through clinical trials and case reports. Janus kinase inhibitors could be a good choice for pruritus in atopic dermatitis, psoriasis, and other diseases, such as prurigo nodularis and lichen planus, with rapid itch relief compared with conventional treatments. The most common adverse effects reported include nasopharyngitis, acne, and elevated blood creatine phosphokinase levels. Janus kinase inhibitors are currently prescribed with warnings about a potential increase in malignancies and cardiovascular diseases and usage in people of older ages. This review aims to provide knowledge about itch and the Janus kinase and signal transducer and activator of transcription pathway and to analyse the current evidence for itch relief by Janus kinase inhibitors.
Topics: Humans; Dermatitis, Atopic; Janus Kinase Inhibitors; Janus Kinases; Pruritus; Skin Diseases
PubMed: 36789757
DOI: 10.2340/actadv.v103.5346 -
Clinical and Translational Science Jan 2024Upadacitinib is a selective Janus kinase (JAK) inhibitor which is approved by the US Food and Drug Administration, the European Medicines Agency, as well as other... (Review)
Review
Upadacitinib is a selective Janus kinase (JAK) inhibitor which is approved by the US Food and Drug Administration, the European Medicines Agency, as well as other agencies around the world for the treatment of several chronic inflammatory diseases, including rheumatic, dermatologic, and gastrointestinal diseases. Through inhibition of JAK, upadacitinib inhibits phosphorylation of downstream effector proteins, which consequently inhibits cytokine signaling for key pathways involved in inflammatory diseases. Upadacitinib more potently inhibits JAK1 than other JAK isoforms. The pharmacokinetics, pharmacodynamics, efficacy, and safety of upadacitinib were characterized in many clinical trials, which demonstrated the superiority of upadacitinib treatment over placebo or an active comparator in rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, non-radiographic axial spondyloarthritis, atopic dermatitis, Crohn's disease, and ulcerative colitis. The safety profile of upadacitinib supported a favorable benefit-risk profile across all the approved indications. In this article, we review the mechanism of action of upadacitinib and describe how the JAK-STAT (Janus kinase-signal transducers and activators of transcription) pathway is involved in the pathogenesis of several chronic and progressive immune-mediated inflammatory diseases. In addition, this review also provides an overview of key clinical trials that were conducted as well as relevant data which supported the clinical development of upadacitinib and informed the recommended dose(s) in each of the approved indications.
Topics: United States; Humans; Translational Science, Biomedical; Arthritis, Rheumatoid; Spondylitis, Ankylosing; Janus Kinase Inhibitors; Janus Kinases; Heterocyclic Compounds, 3-Ring
PubMed: 37984057
DOI: 10.1111/cts.13688 -
Rheumatology (Oxford, England) Feb 2024Janus kinases (JAKs) are a family of cytosolic tyrosine kinases that regulate cytokine signal transduction, including cytokines involved in a range of inflammatory... (Review)
Review
Janus kinases (JAKs) are a family of cytosolic tyrosine kinases that regulate cytokine signal transduction, including cytokines involved in a range of inflammatory diseases, such as RA, psoriasis, atopic dermatitis and IBD. Several small-molecule JAK inhibitors (JAKis) are now approved for the treatment of various immune-mediated inflammatory diseases. There are, however, key differences between these agents that could potentially translate into unique clinical profiles. Each JAKi has a unique chemical structure, resulting in a distinctive mode of binding within the catalytic cleft of the target JAK, and giving rise to distinct pharmacological characteristics. In addition, the available agents have differing selectivity for JAK isoforms, as well as off-target effects against non-JAKs. Other differences include effects on haematological parameters, DNA damage repair, reproductive toxicity and metabolism/elimination. Here we review the pharmacological profiles of the JAKis abrocitinib, baricitinib, filgotinib, peficitinib, tofacitinib and upadacitinib.
Topics: Humans; Janus Kinase Inhibitors; Antirheumatic Agents; Arthritis, Rheumatoid; Janus Kinases; Psoriasis
PubMed: 37624925
DOI: 10.1093/rheumatology/kead448 -
Cell Reports Mar 2023Janus kinases (JAKs) mediate signal transduction downstream of cytokine receptors. Cytokine-dependent dimerization is conveyed across the cell membrane to drive JAK...
Janus kinases (JAKs) mediate signal transduction downstream of cytokine receptors. Cytokine-dependent dimerization is conveyed across the cell membrane to drive JAK dimerization, trans-phosphorylation, and activation. Activated JAKs in turn phosphorylate receptor intracellular domains (ICDs), resulting in the recruitment, phosphorylation, and activation of signal transducer and activator of transcription (STAT)-family transcription factors. The structural arrangement of a JAK1 dimer complex with IFNλR1 ICD was recently elucidated while bound by stabilizing nanobodies. While this revealed insights into the dimerization-dependent activation of JAKs and the role of oncogenic mutations in this process, the tyrosine kinase (TK) domains were separated by a distance not compatible with the trans-phosphorylation events between the TK domains. Here, we report the cryoelectron microscopy structure of a mouse JAK1 complex in a putative trans-activation state and expand these insights to other physiologically relevant JAK complexes, providing mechanistic insight into the crucial trans-activation step of JAK signaling and allosteric mechanisms of JAK inhibition.
Topics: Animals; Mice; Janus Kinases; DNA-Binding Proteins; Cryoelectron Microscopy; Trans-Activators; Janus Kinase 1; Signal Transduction; Phosphorylation; Janus Kinase 2; Janus Kinase 3
PubMed: 36867534
DOI: 10.1016/j.celrep.2023.112201 -
Frontiers in Immunology 2021Cellular therapies such as allogeneic hematopoietic stem cell transplantation (HSCT) and immune-effector cell therapy (IECT) continue to have a critical role in the... (Review)
Review
Cellular therapies such as allogeneic hematopoietic stem cell transplantation (HSCT) and immune-effector cell therapy (IECT) continue to have a critical role in the treatment of patients with high risk malignancies and hematologic conditions. These therapies are also associated with inflammatory conditions such as graft--host disease (GVHD) and cytokine release syndrome (CRS) which contribute significantly to the morbidity and mortality associated with these therapies. Recent advances in our understanding of the immunological mechanisms that underly GVHD and CRS highlight an important role for Janus kinases (JAK). JAK pathways are important for the signaling of several cytokines and are involved in the activation and proliferation of several immune cell subsets. In this review, we provide an overview of the preclinical and clinical evidence supporting the use of JAK inhibitors for acute and chronic GVHD and CRS.
Topics: Animals; Cytokine Release Syndrome; Graft vs Host Disease; Hematopoietic Stem Cell Transplantation; Humans; Janus Kinase Inhibitors; Janus Kinases; Signal Transduction
PubMed: 34531878
DOI: 10.3389/fimmu.2021.740847