title: Structural, kinetic, and thermodynamic analysis of the binding of the 40 kDa PEG-interferon-alpha2a and its individual positional isomers to the extracellular domain of the receptor IFNAR2.
abstract: Type-I Interferons exert antiviral and antiproliferative activities through the binding to a common cell surface receptor comprising two subunits, IFNAR1 and IFNAR2. Human recombinant Interferon-alpha(2a) (IFNalpha(2a)) is a potent drug (Roferon-A) used to treat various cancers and viral diseases including Hepatitis B/C infections. To significantly improve the pharmacological properties of the drug, a pegylated form of IFNalpha(2a) was developed (PEGASYS). This 40 kDa PEG-conjugated IFNalpha(2a) ((40)PEG-IFNalpha(2a)) is obtained by the covalent binding of one 40 kDa branched PEG-polymer to a lysine side-chain of IFNalpha(2a). Here, we report the detailed structural, kinetic, and thermodynamic analysis of the binding to the extracellular domain of the receptor IFNAR2 of (40)PEG-IFNalpha(2a) and its isolated positional isomers modified at K31, K134, K131, K121, K164, and K70, respectively, in comparison with unmodified IFNalpha(2a). Our binding studies, using the surface plasmon resonance technique, show that the pegylation does not abolish the binding to the receptor, but significantly reduces the affinity mainly due to a change of the association rate. The results are supported by modeling and simulation of the binding, using Self-Avoiding-Walk calculations for the polymer conformations. A correlation between the structural parameters and the kinetic and thermodynamic parameters of the binding of the positional isomers could be established. For the Isomer-K31 and -K164, the PEG-polymer attachment point is located in proximity to the binding interface, and the isomers display affinity in the range 150-520 nM in an enthalpy-driven binding process. In contrast for the Isomer-K134, -K131, -K121, and -K70, the PEG-polymer is attached remotely from the binding interface, and the isomers exhibit a higher affinity (32-76 nM) in an entropy-driven binding process. This study constitutes an essential collection of knowledge on which the interaction of (40)PEG-IFNalpha(2a) and its positional isomers with its cellular receptors can be better understood.
authors.affiliation: F. Hoffmann-La Roche AG, Department of Pharma Research, CH-4070 Basel, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Dhalluin
authors.forename: Alfred
authors.initials: A
authors.lastname: Ross
authors.forename: Walter
authors.initials: W
authors.lastname: Huber
authors.forename: Paul
authors.initials: P
authors.lastname: Gerber
authors.forename: Doris
authors.initials: D
authors.lastname: Brugger
authors.forename: Bernard
authors.initials: B
authors.lastname: Gsell
authors.forename: Hans
authors.initials: H
authors.lastname: Senn
mesh_terms: D003198:Computer Simulation; D006801:Humans; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000737:chemistry* / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins; D020349:Surface Plasmon Resonance; D013696:Temperature; D013816:Thermodynamics; D014357:Trypsin / Q000378:metabolism
chemical_list: C507964:IFNAR1 protein, human; C508033:IFNAR2 protein, human; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D008565:Membrane Proteins; D011108:Polymers; D020033:Protein Isoforms; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D053633:Receptor, Interferon alpha-beta; D011092:Polyethylene Glycols; D014357:Trypsin; C100416:peginterferon alfa-2a