Ligand Binding Induces a Conformational Change in ifnar1 that Is Propagated to Its Membrane-Proximal Domain

Strunk, Jennifer Julia; Gregor, Ingo; Becker, Yvonne; Li, Zongli; Gavutis, Martynas; Jaks, Eva; Lamken, Peter; Walz, Thomas; Enderlein, Jörg; Piehler, Jacob

doi:10.1016/j.jmb.2008.01.017

Cited by 45 publications

(57 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For the type I interferon receptor, the situation is less clear. Ligand binding to IFNAR1 induces a conformational change that is propagated toward the membrane proximal domain (54). Comparing the unbound to the bound structures of both IFNAR1 and IFNAR2 shows conformational changes upon IFN binding (7).…”

Section: Discussionmentioning

confidence: 99%

Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain

Sharma

Longjam

Schreiber

2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

Type I interferons serve as the first line of defense against pathogen invasion. Binding of IFNs to its receptors, IFNAR1 and IFNAR2, is leading to activation of the IFN response. To determine whether structural perturbations observed during binding are propagated to the cytoplasmic domain, multiple mutations were introduced into the transmembrane helix and its surroundings. Insertion of one to five alanine residues near either the N or C terminus of the transmembrane domain (TMD) likely promotes a rotation of 100°and a translation of 1.5 Å per added residue. Surprisingly, the added alanines had little effect on the binding affinity of IFN to the cell surface receptors, STAT phosphorylation, or gene induction. Similarly, substitution of the juxtamembrane residues of the TMD with alanines, or replacement of the TMD of IFNAR1 with that of IFNAR2, did not affect IFN binding or activity. Finally, only the addition of 10 serine residues (but not 2 or 4) between the extracellular domain of IFNAR1 and the TMD had some effect on signaling. Bioinformatic analysis shows a correlation between high sequence conservation of TMDs of cytokine receptors and the ability to transmit structural signals. Sequence conservation near the TMD of IFNAR1 is low, suggesting limited functional importance for this region. Our results suggest that IFN binding to the extracellular domains of IFNAR1 and IFNAR2 promotes proximity between the intracellular domains and that differential signaling is a function of duration of activation and affinity of binding rather than specific conformational changes transmitted from the outside to the inside of the cell.Type I interferons (IFNs) orchestrate the antiviral innate immunity in vertebrates. They consist of 16 members in humans as follows: 12 different IFN␣ subtypes, as well as IFN␤, IFN, IFN⑀, and IFN. They are clustered on the short arm of chromosome 9. All type I interferons elicit their innate and adaptive immune responses after binding to the receptor and forming the IFNAR1-IFN-IFNAR2 ternary complex (1, 2), the formation of which is essential for signaling. Both IFNAR1 and IFNAR2 belong to the class II helical cytokine receptors with four fibronectin type III-like subdomains for IFNAR1 and two subdomains for IFNAR2. The extracellular domains are followed by a single helix of 21 amino acids spanning the membrane, which in turn is connected to mostly natively unstructured intracellular domains and their associated effectors (Fig. 1A) (3). Cells lacking one of the receptors lack normal IFN signaling (4, 5). Structurally different members of type I IFNs bind to the same cell surface receptor but mediate differential responses that result from differences in binding affinities, concentration of IFN, and duration of activation (5-13). Differential signaling is realized through robust (antiviral) versus tunable (antiproliferative and immunomodulatory) gene induction leading to different phenotypic outcomes (14,15). Receptor dimerization drives the activation of cytosolic associated Janus family kina...

show abstract

Section: Discussionmentioning

confidence: 99%

Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain

Sharma

Longjam

Schreiber

2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…This apparent paradox can be explained if one takes into account also the stability of the ternary complexes formed by IFN-␣2 and IFN-␤. Indeed, from measuring the rate constants of ternary complex assembly on artificial membranes, the half-life of the ternary complex was found to be considerably higher for IFN-␤ (100 s) than for IFN-␣2 (1 to 5 s) (8,27). Thus, IFN-␣2 is likely to engage in short-lived ternary complexes and IFN-␤ in long-lived ternary complexes.…”

Section: Discussionmentioning

confidence: 99%

“…Piehler's group has recently shown that the two IFN subtypes form ternary complexes with similar architectures. Moreover, using fluorescence spectroscopy Piehler's group also showed that the ectodomain of IFNAR1 undergoes a substantial rearrangement of the membrane-distal domains upon IFN binding (27). Future work will therefore need to address the possibility that in live cells this conformational change represents a signature toward diversification of signals and biological outputs.…”

Section: Discussionmentioning

confidence: 99%

Receptor Density Is Key to the Alpha2/Beta Interferon Differential Activities

Moraga

Harari

Schreiber

et al. 2009

Molecular and Cellular Biology

View full text Add to dashboard Cite

Multiple type I interferons (IFN-␣A persistent question in the field of helically bundled cytokines concerns the molecular basis of intracellular signal activation following binding to cognate cell surface receptors. Typically, cytokine-induced dimerization of the receptor subunits is thought to trigger catalytic transactivation of the associated Jak tyrosine kinases. Phosphorylation of critical receptor tyrosine motifs by the activated Jak proteins allows recruitment and activation of downstream Stat effectors (25,34). A clear distinction can be made between the short homodimeric Jak2-activating receptors, such as the growth hormone or the erythropoietin receptors, and the more complex heteromeric receptors. Among these latter is the type I interferon (IFN) receptor, a prototypic class 2 receptor, made of two subunits, each associated with a different Jak enzyme (29). IFNAR2 contains extracellularly two fibronectin III domains forming a well-defined cytokine binding module. The cytoplasmic region of IFNAR2 is 250 amino acids long, interacts with Jak1, and contains two principal Tyr-based Stat recruitment motifs (24,35). IFNAR1 is made of a large ectodomain of four fibronectin III domains, not all involved in ligand binding, and a 100-amino-acid-long cytoplasmic region complexed with Tyk2 and subjected to ligand-induced ubiquitination driving receptor proteolysis (13,14).A large array of IFNs (over a dozen ␣ subtypes and one ␤ subtype) bind to this ubiquitously expressed receptor complex to induce rapid gene expression programs that elicit measurable antiviral responses and cell growth inhibition as well as cell context-specific functional changes (4, 31). Several studies have reported on differential activities of type I IFNs, but no unique function has ever been attributed to a given subtype (see references in reference 29). Thus, a differential can be defined as a lack of correlation between two specific activities. For instance, depending on the cell system, IFN-␣2 and IFN-␤ can exhibit equivalent antiproliferative potency or over a 100-fold difference in antiproliferative potency and nearly equipotency in antiviral activity. Since no overt differences are observed in the structure or stoichiometry of the ligand-receptor complex formed with different subtypes, the concordant view points to the way each IFN subtype engages the available receptors. Indeed, kinetic measurements of the interaction of IFN-␣2 and IFN-␤ with receptor ectodomains have shown substantial differences. IFNAR2 represents the high-affinity subunit, toward which IFN-␣2 exhibits nanomolar binding affinity and IFN-␤ exhibits ϳ100 pM binding affinity. Conversely, IFNAR1 is the low-affinity subunit, toward which IFN-␣2 exhibits micromolar affinity and IFN-␤ ϳ50 nM affinity (19,22). The contribution of the individual and combined affinities on ternary complex formation by either IFN subtype have been thoroughly studied (10,26). However, how these dynamic parameters influence receptor function and translate into activation of Jak, recruitment of...

show abstract

“…Binding Assays on Artificial Membranes-Binding of IFN␣2 to IFNAR1-EC and IFNAR2-EC tethered onto artificial membranes was monitored in real time by simultaneous total internal reflection fluorescence spectroscopy and reflectance interference detection in a flow system as in principle described previously (25,26). Ternary complex formation was probed via the ligand-induced conformational change of IFNAR1 (27). For this purpose, IFNAR1-H10 N349C was cysteine-specifically labeled with ATTO 655 ( AT655 IFNAR1-H10), which is quenched by the proximal Trp 347 .…”

Section: Methodsmentioning

confidence: 99%

The Stability of the Ternary Interferon-Receptor Complex Rather than the Affinity to the Individual Subunits Dictates Differential Biological Activities

Kalie

Jaitin

Podoplelova

et al. 2008

Journal of Biological Chemistry

Self Cite

106

131

View full text Add to dashboard Cite

Type I interferons (IFNs) signal for their diverse biological effects by binding a common receptor on target cells, composed of the two transmembrane IFNAR1 and IFNAR2 proteins. We have previously differentially enhanced the antiproliferative activity of IFN by increasing the weak binding affinity of IFN to IFNAR1. In this study, we further explored the affinity interdependencies between the two receptor subunits and the role of IFNAR1 in differential IFN activity. For this purpose, we generated a panel of mutations targeting the IFNAR2 binding site on the background of the IFN␣2 YNS mutant, which increases the affinity to IFNAR1 by 60-fold, resulting in IFNAR2-to-IFNAR1 binding affinity ratios ranging from 1000:1 to 1:1000. Both the antiproliferative and antiviral potencies of the interferon mutants clearly correlated to the in situ binding IC 50 values, independently of the relative contributions of the individual receptors, thus relating to the integral lifetime of the complex. However, the antiproliferative potency correlated throughout the entire range of affinities, as well as with prolonged IFNAR1 receptor down-regulation, whereas the antiviral potency reached a maximum at binding affinities equivalent to that of wild-type IFN␣2. Our data suggest that (i) the specific activity of interferon is related to the ternary complex binding affinity and not to affinity toward individual receptor components and (ii) although the antiviral pathway is strongly dependent on pSTAT1 activity, the cytostatic effect requires additional mechanisms that may involve IFNAR1 down-regulation. This differential interferon response is ultimately mediated through distinct gene expression profiling. Type I interferons (IFNs)2 form a class of cytokines capable of mediating antiviral, growth-inhibitory and immunoregulatory activities (1-3). Comprising about 18 members in humans (4), all IFNs induce their biological activities through binding to the same receptor complex, composed of the two transmembrane proteins IFNAR1 and IFNAR2 (5). The signal is then transduced mainly through the JAK-STAT pathway, in which the tyrosine kinases Tyk2 and Jak1, which are constitutively associated with the IFNAR1 and IFNAR2 subunits, are activated by phosphorylation upon IFN-receptor binding (6, 7). Subsequently, they phosphorylate STAT proteins that dimerize or form ternary complexes with DNA-binding proteins that translocate to the nucleus to promote the expression of IFN-stimulated genes. The IFNAR1 and IFNAR2 receptor subunits are expressed in virtually every nucleated cell (6), yet the way in which IFNs exert specific activities in different physiological contexts is still obscure. Despite common biological activities, differences observed for various IFNs (8 -11) seem to indicate that at least not all IFN subtypes are redundant. Different potencies of specific IFNs are known to be determined to a large extent by their affinities toward the IFNAR1 and IFNAR2 subunits, with only IFN␤ standing out for its higher affinity toward IFNAR1 (11). Signif...

show abstract

Ligand Binding Induces a Conformational Change in ifnar1 that Is Propagated to Its Membrane-Proximal Domain

Cited by 45 publications

References 61 publications

Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain

Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain

Receptor Density Is Key to the Alpha2/Beta Interferon Differential Activities

The Stability of the Ternary Interferon-Receptor Complex Rather than the Affinity to the Individual Subunits Dictates Differential Biological Activities

Contact Info

Product

Resources

About