Interferon Beta Activity Is Modulated via Binding of Specific S100 Proteins

Abstract

Interferon-β (IFN-β) is a pleiotropic cytokine used for therapy of multiple sclerosis, which is also effective in suppression of viral and bacterial infections and cancer. Recently, we reported a highly specific interaction between IFN-β and S100P lowering IFN-β cytotoxicity to cancer cells (Int J Biol Macromol. 2020; 143: 633–639). S100P is a member of large family of multifunctional Ca2+-binding proteins with cytokine-like activities. To probe selectivity of IFN-β—S100 interaction with respect to S100 proteins, we used surface plasmon resonance spectroscopy, chemical crosslinking, and crystal violet assay. Among the thirteen S100 proteins studied S100A1, S100A4, and S100A6 proteins exhibit strictly Ca2+-dependent binding to IFN-β with equilibrium dissociation constants, Kd, of 0.04–1.5 µM for their Ca2+-bound homodimeric forms. Calcium depletion abolishes the S100—IFN-β interactions. Monomerization of S100A1/A4/A6 decreases Kd values down to 0.11–1.0 nM. Interferon-α is unable of binding to the S100 proteins studied. S100A1/A4 proteins inhibit IFN-β-induced suppression of MCF-7 cells viability. The revealed direct influence of specific S100 proteins on IFN-β activity uncovers a novel regulatory role of particular S100 proteins, and opens up novel approaches to enhancement of therapeutic efficacy of IFN-β.

Erythropoietin Interacts with Specific S100 Proteins

“…While no effects were observed for the Ca 2+ -loaded S100A1/A3/A4/A5/A7/A8/A9/A10/A11/A12/ A13/A14/A15/A16/B/CaM at a concentration of 1 µM ( Figure S1 ), the SPR sensograms for Ca 2+ -bound S100A2/A6/P proteins (0.25–4 µM) exhibited the analyte concentration-dependent effects ( Figure 1 and Figure S1 ). The dissociation phase of the sensograms reveals two distinct dissociation processes: (1) a relatively fast process with half-life time (t 1/2 ) of 60 s; (2) a much slower process with t 1/2 value exceeding 1000 s. The heterogeneous ligand model was previously shown to be well suited for description of S100-cytokine interactions [ 28 , 30 , 32 , 33 , 34 ]. Therefore, the kinetic SPR data were described by the heterogeneous ligand model (1) ( Figure 1 and Figure S2 ) with the lowest equilibrium dissociation constants, K d , ranging from 81 nM to 0.5 µM ( Table 1 ).…”

“…Alternatively, S100 binding to EPO could serve as a mechanism for regulation of the activity of this cytokine. The regulatory role of S100A1/A4/P proteins was previously shown for another four-helical cytokine, interferon β (‘IFN-β’) [ 28 , 34 ]: IFN-β-induced suppression of viability of MCF-7 breast cancer cells is inhibited by the S100 proteins. The potential ability of S100 proteins to affect EPO activity is especially valuable, considering that EPO interactions with extracellular soluble proteins have not been reported to date.…”

“…Human erythropoietin produced in CHO cells (Epoetin β; glycoprotein comprising 165 residues and lacking a signal peptide) was from «PHARMAPARK» LLC (Moscow, Russia). Human S100A1/A4/A6/A7/A8/A9/A10/A11/A12/A13/ A14/A15/B/P proteins and the Y88R mutant of the protein S100P were prepared in E. coli according to previously published studies [ 30 , 32 , 34 ]. Recombinant human calmodulin (‘CaM’) was purified according to ref.…”

“…Thereby, S100 proteins affect cellular signaling in an autocrine/paracrine manner as damage-associated molecular patterns or ‘alarmins’. Furthermore, some of the extracellular S100 proteins interact with cytokines, including specific members of interleukin 6 (‘IL-6’) family [ 30 , 31 , 32 , 33 ], IFN-β [ 28 , 34 ], IL1α/FGF1 [ 35 , 36 ], FGF2 [ 37 ] and EGFR ligands [ 38 ]. Both intra- and extracellular actions of S100 proteins mediate their involvement into wide range of oncological, cardiovascular, respiratory, neurological, inflammatory and autoimmune diseases, which promotes their use in diagnostics and therapy [ 25 , 26 , 39 , 40 , 41 , 42 ].…”

Mechanism of Zn2+ and Ca2+ Binding to Human S100A1

“…Residual Ca 2+ was removed from the protein according to the previously described procedure [ 20 , 27 ]. For circular dichroism (CD) studies (see below), recombinant S100A1 was obtained as described previously [ 28 ].…”