A point mutation in interleukin-2 that alters ligand internalization.
In previous studies, we have identified an interleukin-2 (IL-2) analog containing a point mutation at position 51 (T51P) that expresses nearly wild-type bioactivity, yet has approximately 10-fold lower receptor binding affinity. Since ligand-dependent receptor internalization may be the rate-limiting step controlling the duration of IL-2 receptor signaling, a reduction in the receptor internalization rate could contribute to the observed response enhancement for this analog. To evaluate this possibility, we compared the internalization of IL-2 and T51P in three separate assays. While the internalization rate for IL-2 agreed with values determined by others, the internalization of T51P was markedly reduced. The receptor binding rate constants for this analog were only slightly different; thus, altered binding kinetics could not explain the decreased internalization rate. The effects of reduced internalization were also observable in bioassays, where T51P maintained T-cell proliferation for a longer period compared with IL-2. These results indicate that the T51P point mutation reduces the receptor internalization rate compared with IL-2 in a fashion that is independent of the dissociation rate. This analog may represent a new approach to the preparation of cytokine analogs with potentiated agonist and antagonist properties.
Chang
D Z
DZ
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755-3835, USA.
Wu
Z
Z
Ciardelli
T L
TL
D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics* / Q000378:metabolism*; D007424:Intracellular Fluid / Q000276:immunology; D007700:Kinetics; D008024:Ligands; D016254:Mutagenesis, Insertional; D017354:Point Mutation; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
D007376:Interleukin-2; D008024:Ligands; D015375:Receptors, Interleukin-2