Chengfeng Ren/Sandbox1

IFN Categories and IFNβ-1a sourcesIFN Categories and IFNβ-1a sources

Interferons (IFNs) are a family of helical cytokines that mediate antiviral, antiproliferative, and immune modulatory activities in response to biological and chemical stimuli. Two types of IFN are recognized on the basis of their physical and biological properties; type I, which contains the monomeric IFNs-α,-β,-τ, and -ω, and type II, the only member of which is the dimeric IFN-γ. Representatives of all type I and type II IFNs are found in humans, except for IFN-τ, which is found only in ruminant ungulates. There are 12 different human IFNs-α;each one comprising a different subtype,although 14 different genes have been identified, whereas human IFN-β, IFN-ω, and IFN-γare encoded by single genes[1].

Interferon-βhas two subtyes, interferon-β-1a and interferon-β-1b. Interferon-β-1a is naturally expressed in numerous cell types in human, including fibroblasts, endothelial cells, epithelial cells and various leukocytes, however,Interferon-β-1b is produced in modified E. coli.

Here is a jpg clearly illustrating IFNs categories.

Structure info. of IFNβ-1aStructure info. of IFNβ-1a

IFNβ-1a consisting of 166 amino acids, around 20KDa. It has 5 helixs.

spinqualitylabelsall models IFN structure from PDB Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

IFNβ-1a biological activity and therapeutic effectsIFNβ-1a biological activity and therapeutic effects

IFNβ-1a as well as other family of IFNs has a variety of biological activities, inluding antiviral, antiproliferative, and immune modulatory activities in response to biological and chemical stimuli.

IFNβ-1a is mainly used to treat relapsing forms of multiple sclerosis(MS). MS is a life-long disease that affects your nervous system by destroying the protective covering (myelin) that surrounds your nerve fibers. The commercial available drug format is Avonex.(Please refer to the drug guide before using it)

Mechanism of action for IFNβ-1aMechanism of action for IFNβ-1a

IFNβis encoded by a single gene with no introns (and hence, no splice variants), and no reported polymorphisms. Although IFNβwas originally called fibroblast IFN–because fibroblasts could be induced to produce it in vitro– numerous other cell types can express IFNβ, including endothelial cells, epithelial cells and various leukocytes. Unlike IFNα, where a particular subset of dendritic cells appears to be one of the primary in vivo sources, a physiological source of IFNβhas not been identified. Endogenous IFNβis not generally detected at significant levels in humans. So called “natural” human IFNβ (expressed by fibroblasts in vitro), is glycosylated at one site with an N-linked complex carbohydrate, the exact structure of which can be influenced by growth conditions and the cell type producing the IFN. While important for monomer stability, solubility and, perhaps biodistribution, the carbohydrate moiety does not appear to be required for receptor binding.

The IFNβreceptor, signaling cascade and gene regulation

The IFNβreceptor is composed of 2 required chains—a signaling chain, IFNAR1, and a binding chain, IFNAR2. Both IFNAR1 and IFNAR2 are constitutively expressed on the surface of virtually all cells. IFNβcan bind to IFNAR2 alone, but can bind to IFNAR1 only in the presence of IFNAR2. The strength of IFNβbinding to its receptor is much higher when both subunits are present. Knockout experiments indicate that both IFNAR1 and IFNAR2 are required for IFNβ activity, but it remains uncertain whether there are auxiliary receptors or alternative receptor/ signaling complexes in some cell types. The current view of events leading to IFNβbiological activity is as follows (Fig. 1A): 1) IFN binds to the extracellular domain of IFNAR2. 2) IFNAR1 then engages with the IFNβ–IFNAR2 complex, forming the high-affinity receptor–ligand complex and allowing the intracellular domains of the two receptor chains and associated proteins to interact. 3) This interaction, which includes JAK1 (associated with IFNAR2) and Tyk2 (associated with IFNAR1), results in a cascade of phosphorylation events that leads to activation of STATS. 4) Activated STATS form a complex with other cytoplasmic proteins, which then translocate into the nucleus to bind to Interferon Sensitive Response Elements (ISRE), transcriptional control regions which are upstream of many IFN regulated genes. 5) This ISRE binding results in transcriptional regulation (both induction and inhibition) of >1000 genes. Thus, IFN regulates expression of a myriad of genes. While the function of some of these genes is clear (e.g. the antiviral product MxA), the specific transcripts mediating therapeutic benefit of IFNβin MS are unknown. This is, in part, due to the complexity and heterogeneity of MS, but also because IFNβis an agonist that can induce the expression not only of ISRE regulated genes, but through newly expressed transcription factors, can induce or inhibit subsequent waves of gene expression. In addition, some IFNβregulated proteins, which include cytokines and chemokines, can alter the level or function of particular cell populations. The resulting multifaceted biological response is in contrast to therapies such as monoclonal antibodies that have a much more specific molecular target. Thus, as shown inFig. 1B, IFNβmay exert its therapeutic effects in two distinct ways: 1) direct effects of IFNβ regulated gene products; or 2) indirect effects of IFN-regulated gene products, via effects on other genes (e.g. transcription factors), or by altering populations or functions of cells including Type 2 dendritic cells, monocytes, regulatory T-cells and CD56 bright NK cells

ReferenceReference

[1]Protein Science (1999),8:1867–1877