Type I Interferon Signal Pathway
Background of Type I Interferon Signal Pathway
What is Type I Interferon Signal Pathway?
Following viral infection, the human body triggers a complex regulatory system of innate and adaptive immune responses designed to defend against the virus. One of the many responses to the viral invasion is the induction of the pleiotropic cytokines, interferon (IFN). IFN-α and IFN-β are two typical type I interferons found in most animals, including humans. They are mainly involved in innate immune response against viral infection.
Type I interferons are induced following recognition of pathogen components during infection by various host pattern recognition receptors. Immune cells are able to synthesize IFN-α, IFN-β and other cytokines. There are four main pathways leading to the production of type I interferons. The RLRs pathway is activated by RNA viruses. The cGAS-STING pathway is activated by DNA viruses. The third pathway involves the adaptor protein TRIF which is recruited by TLR3 and TLR4. The last pathway is triggered by TLR7 or TLR8 and TLR9 leading to the activation of the transcription factor IRF7. Following their production, type I interferons triggered antiviral responses by binding to a common receptor.
Core Components of Type I Interferon Signal Pathway
Type I Interferons
All type I IFNs bind to a specific cell surface receptor complex known as the IFN-α/β receptor (IFNAR) that consists of IFNAR1 and IFNAR2 chains. The type I interferons present in humans are IFN-α, IFN-β, IFN-ε, IFN-κ and IFN-ω.
The IFN-α proteins are produced by leukocytes. They are mainly involved in innate immune response against viral infection. The genes responsible for their synthesis come in 13 subtypes that are called IFNA1, IFNA2, IFNA4, IFNA5, IFNA6, IFNA7, IFNA8, IFNA10, IFNA13, IFNA14, IFNA16, IFNA17, IFNA21. These genes are found together in a cluster on chromosome 9.
The IFN-β proteins are produced in large quantities by fibroblasts. They have antiviral activity that is involved mainly in innate immune response. Two types of IFN-β have been described, IFN-β1 (IFNB1) and IFN-β3 (IFNB3) (a gene designated IFN-β2 is actually IL-6).
IFN-kappa protein is expressed in keratinocytes and the gene is found on chromosome 9, adjacent to the type I interferon cluster.
IFN-ω, although having only one functional form described to date (IFNW1), has several pseudogenes: IFNWP2, IFNWP4, IFNWP5, IFNWP9, IFNWP15, IFNWP18, and IFNWP19 in humans. Many non-primate placental mammals express multiple IFN-ω subtypes.
Type I Interferon Receptors
Interferons bind to interferon receptors. Type I interferons bind to a specific transmembrane protein complex known as the IFN-α receptor (IFNAR) which consist of IFNAR1 and IFNAR2. The IFNAR1 subunit is associated with tyrosine kinase-2 (TYK2) and the IFNAR2 subunit is associated with JAK1. The JAK proteins can be associated with receptors either possess or lack tyrosine kinase activaties of their own. Following ligand binding, activation of IFNAR1 and IFNAR2 result in dimerization. The dimer is rearranged by auto phosphorylation and activate the downstream proteins, such as signal transducer and activator of transcription (STATs), VAV/GEFs, and IRS12/PI3K.
Pathways Involved in Type I Interferon Signal Pathway
Type I interferon is a class of critical cytokine involving in antivirus, anticancer, and immunoregulation. Recent studies have shown that IFN-α and IFN-β activated classical JAK-STAT signal pathway, MAPK cascade, and PI3K-mTOR signal pathway. There are cross reactions between different signal pathways. To confirm these signal transduction and biologic effect is helpful for understanding the mechanism of action of interferons.
Fig1. Direct regulatory mechanisms of STAT3 for IFN-I response. (Ming-Hsun Tsai, 2019)
JAK-STAT Signal Pathway
Type I interferons phosphorylate STAT1 and STAT2 proteins by tyrosine phosphorylation involving TYK2 and JAK1. Following phosphorylation, STAT1 and STAT2 become dimer and associate with IFN regulatory factor 9 (IRF9, or p48) form the transcriptionally activate IFN-stimulated gene factor 3 (ISGF3) complex. The activation of ISGF3 then translocate to the nucleus and is mediated by specific elements named IFN-stimulatory response element (ISRE). The ISRE placed upstream or downstream of reporter genes activate transcription in an IFN-α-dependent manner, and mutations in the most highly conserved parts of the sequence abrogate the response. Most genes that respond to IFN-α have ISRE, usually within 200bp of the transcription start site, which suggests that this sequence is important for transcriptional activation in response to IFN-α. ISRE regulates the expression of most type I IFN-stimulated genes and a few type II IFN-stimulated genes. Besides, phosphorylated STAT1 can generate a homodimer which is able to bind the IFN-γ activated site (GAS) to promote transcription. The STATs-mediated transduction is termed JAK-STAT signal pathway.
MAPK Cascade
MAPK cascade is a highly conserved module that is involved in many cellular functions, including cell differentiation, proliferation and migration. There are at least three distinctly regulated groups of MAPKs expressed in mammals: amino-terminal kinases (JNK), extracellular signal-related kinases (ERK) and p38 proteins. MAPKs are activated by specific MAPKKs, MAPKK4/7 for JNKs, MEK1/2 for ERK1/2, MAPKK3/6 for the p38. Each MAPKK can be activated by more than one MAPKKK, increasing the complexity and diversity of MAPK signaling. Type I interferons also activate MAPK cascade. Activated JAK1 regulates the phosphorylation of Vav, a guanine nucleotide exchange factor (GEF), or other GEFs. Phosphorylated Vav activate downstream protein Rac1 which further regulate the p38MAPK signal pathway. A MAPK kinase kinase (MAPKKK) is subsequently activated and regulates downstream phosphorylation of the MAPK kinases MAPKK3 and MAPKK6. The MAPK kinases directly phosphorylate p38 which regulates activation of various downstream effectors, including the mitogen and stress activated kinases MSK1 and MSK2. The specific transcription factors cAMP responsive element binding protein (CREB) and Histone-H3 are regulated by p38.
PI3K-mTOR Signal Pathway
Activated TYK2 and JAK1 also regulate tyrosine phosphorylation of insulin receptor substrate IRS1 an IRS2. Regulatory subunit p85 of PI3K docks with IRS and further activates downstream mammalian target of rapamycin (mTOR) which mediates the initiation of mRNA translation. mTOR regulates phosphorylation of both p70S6K and repressor of eukaryotic translation-initiation factor 4E-binding protein 1 (4EBP1). Ribosomal protein S6 (RPS6) was activated by p70S6K, resulting in the initiation of mRNA translation. EIF4E was dissociated from the deactivated 4EBP1, allowing the cap-dependent mRNA translation. The PI3K-mTOR signal pathway is also important in regulating the cell cycle.
Type I Interferon Signal Pathway Related Diseases
Fig2. Mechanisms of interferon action in non-viral infections. (Finlay McNab, 2015)
Type I interferons play a key role in the body's fight against viral infection by activating intracellular antimicrobial signaling cascades that influence the development of innate and adaptive immune responses. The abnormal activation of type I interferon signaling pathway is related to the pathogenesis of some autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Type I interferons play a key regulatory role in inflammatory diseases, and they are involved in disease progression, including periodontitis, by influencing immune response and inflammatory factors.
Type I interferons also have an impact on the development and progression of tumors, they can promote the development and function of dendritic cells, enhance antigen-specific T cell responses, and improve responsiveness to immune checkpoint blocking therapy.
In addition, type I interferons also play an important role in tumor immunotherapy, enhancing the function of dendritic cells and improving the responsiveness to immune checkpoint blocking therapy. The abnormal activation or disorder of type I interferon signaling pathway is also related to other diseases such as vasculitis and systemic sclerosis, and its mechanism of action in the occurrence and development of diseases is complex and diverse, involving many aspects such as immune regulation, inflammatory response and cell aging.
Case Study
Case Study 1: Recombinant Chicken IFNA (IFNA-1127C)
Covalently closed circular DNA (cccDNA) of hepadnaviruses exists as an episomal minichromosome in the nucleus of an infected hepatocyte and serves as the template for the transcription of viral mRNAs. It had been demonstrated that interferon alpha (IFN-α) treatment of hepatocytes induced a prolonged suppression of human and duck hepatitis B virus cccDNA transcription, which is associated with the reduction of cccDNA-associated histone modifications specifying active transcription (H3K9ac or H3K27ac), but not the histone modifications marking constitutive (H3K9me3) or facultative (H3K27me3) heterochromatin formation. In the efforts to identify IFN-induced cellular proteins that mediate the suppression of cccDNA transcription by the cytokine, the researchers found that downregulating the expression of signal transducer and activator of transcription 1 (STAT1), structural maintenance of chromosomes flexible hinge domain containing 1 (SMCHD1), or promyelocytic leukemia (PML) protein increased basal level of cccDNA transcription activity and partially attenuated IFN-α suppression of cccDNA transcription.
Fig1. Expression of SMCHD1, PML, STAT1, or MX1 mRNA was quantified by qRT-PCR assays. The cells were treated with rChIFN-α. (Junjun Cheng, 2020)
Case Study 2: Recombinant Rat PI3K protein
Ischemia/reperfusion injury (IRI) of the heart involves the activation of oxidative and proapoptotic pathways. Simultaneously Klotho protein presents anti-aging, antiapoptotic and antioxidative properties. Therefore, this study aimed to evaluate the effect of Klotho protein on oxidative stress in hearts subjected to IRI. Isolated rat hearts perfused with the Langendorff method were subjected to ischemia, followed by reperfusion, in the presence or absence of recombinant rat Klotho protein. The factors involved in the activation of insulin-like growth factor receptor (IGF1R)/phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signalling pathway were evaluated. IRI caused activation of the IGF1R (p = 0.0122)/PI3K (p = 0.0022) signalling, as compared to the aerobic control group. Infusion supply of Klotho protein during IRI significantly reduced the level of phospho-IGF1R (p = 0.0436), PI3K (p = 0.0218) and phospho-AKT (p = 0.0020). Klotho contributed to the protection of the heart against IRI and oxidative stress via inhibition of the IGF1R/PI3K/AKT pathway, thus can be recognized as a novel cardiopreventive/cardioprotective agent.
Fig2. PI3K level in the heart tissue. (Agnieszka Olejnik, 2023)
Case Study 3: Recombinant Full Length Human STAT3 (STAT3-29823TH)
The goal of this study is to identify pharmacological inhibitors that target a recently identified novel mediator of breast cancer brain metastasis (BCBM), truncated glioma-associated oncogene homolog 1 (tGLI1). Inhibitors of tGLI1 are not yet available. To identify compounds that selectively kill tGLI1-expressing breast cancer, the researchers screened 1527 compounds using two sets of isogenic breast cancer and brain-tropic breast cancer cell lines engineered to stably express the control, GLI1, or tGLI1 vector, and identified the FDA-approved antifungal ketoconazole (KCZ) to selectively target tGLI1-positive breast cancer cells and breast cancer stem cells, but not tGLI1-negative breast cancer and normal cells. KCZ's effects are dependent on tGLI1. Two experimental mouse metastasis studies have demonstrated that systemic KCZ administration prevented the preferential brain metastasis of tGLI1-positive breast cancer and suppressed the progression of established tGLI1-positive BCBM without liver toxicities. They further developed six KCZ derivatives, two of which (KCZ-5 and KCZ-7) retained tGLI1-selectivity in vitro. KCZ-7 exhibited higher blood-brain barrier penetration than KCZ/KCZ-5 and more effectively reduced the BCBM frequency. In contrast, itraconazole, another FDA-approved antifungal, failed to suppress BCBM.
Fig3. The electrophoretic mobility shit assays (EMSA) confirmed the ability of the N-tGLI1 protein to bind the consensus GLI1/tGLI1-binding sequence. (Daniel Doheny, 2022)
Related Products
The Type I Interferon Signal Pathway is an important part of the body's innate immunity, and it plays a key role in controlling and eliminating pathogens. Creative BioMart can provide a list of core protein products of the Type I Interferon Signal Pathway to help you with your researches. Please feel free to contact us if you’re interested.
