Modulation of interleukin 2 high-affinity binding by lymphocyte-derived tetrahydrobiopterin: Pterins as potential participants in the control of interleukin 2 receptor assembly
✍ Scribed by Irmgard Ziegler; Udo Schwuléra
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 624 KB
- Volume
- 41
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
In this report, we have examined whether (6R)-tetrahydrobiopterin (H,biopterin) modulates the binding of interleukin 2 to high-affinity sites of the cloned mouse cytotoxic T-lymphocyte clone CTLL-2. Scatchard plot analysis of the equilibrium binding data reveals increased affinity when the cells are exposed simultaneously to interleukin 2 and to the pterin. The I<d values are statistically significantly reduced from 1.4 x 10-"M to 0.78 x 10-"M interleukin 2. The dissociation kinetics of the ligand were followed at 40C after equilibrium binding under high-affinity conditions (1.2 x 10-IoM interleukin 2). In the presence of H, biopterin, the dissociation rate constant (kJ decreases from 6.2 x min-l and the half-time for dissociation increases from 106.8 min to 218.0 min. As a third approach interleukin 2 was bound to the surface of cells under high-affinity conditions by incubation in the cold and the internalization kinetics upon warming were determined. Sigmoidal-shaped kinetics of endocytosis in control cells indicate that the internalization rates increase only gradually. The presence of H, biopterin causes an apparent immediate transition from higher-order kinetics to a linear response so that maximum internalization rates are reached immediately upon warming. The data show that 1 phocyte-derived H, biopterin in vitro at concentrations ranging from potentially participates in the control of interleukin 2 receptor assembly. min-' to 3.0 x 2-8 x 10-F M modulates interleukin 2 high-affinity binding and that H, biopterin