Electrostatic interactions in the cellular dynamics of the interferon-receptor complex.
Using membrane preparations of the interferon receptor, prepared from cells of the Burkitt line, Daudi, we have examined the binding of three human recombinant alpha-interferons. 1. We discovered a binding titration of the interferons IFN-alpha A and IFN-alpha D in the pH range 6-9. Receptor binding, negligible at pH 6, rises to a maximum close to pH 9. We have shown that binding of IFN-alpha A at basic pH is to the same receptors as at neutrality and that IFN-receptor complexes extracted with digitonin are more stable at basic pH than they are at neutrality. 2. The recombinant interferon, IFN-alpha B, shows little change of binding in the pH range 6-9. At its basic optimum the binding of IFN-alpha A approaches that of IFN-alpha B, while at neutral pH the binding of IFN-alpha A is 3-4 times less. This difference at neutral pH is seen on intact cells as well as on membrane preparations. The specific activity of IFN-alpha B is close to that of IFN-alpha A, both of which are 10-20 times more active than IFN-alpha D; and the binding titration is, therefore, independent of the initial binding affinities. 3. Using hybrid IFNs constructed from the DNA sequences of alpha D and alpha B, we have isolated the sequence responsible for the binding titration to the segment comprising amino acids 61-92. Examination of these sequences reveals that Lys-84 is present in all the IFN-alpha except IFN-alpha B where it is replaced by Glu; and Tyr-90, present in most of the common IFN-alpha including alpha A and alpha D, is replaced by Asp in IFN-alpha B. Lys and Tyr would normally titrate in the pH range 6-9. We conclude that the binding titration is due to an electrostatic interaction and we propose that the interaction is between IFN-receptor complexes. The role of the interaction in the binding losses that accompany the antiproliferative effects of IFN is discussed.
Uze
G
G
Laboratoire d'Oncologie Virale, Institut de Recherches Scientifiques sur le Cancer, Villejuif, France.
Bandu
M T
MT
Eid
P
P
Grütter
M
M
Mogensen
K E
KE
D000596:Amino Acids / Q000378:metabolism; D001665:Binding Sites; D002051:Burkitt Lymphoma / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004274:DNA, Recombinant / Q000378:metabolism; D004563:Electrochemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007370:Interferon Type I / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D011971:Receptors, Immunologic / Q000378:metabolism*; D017471:Receptors, Interferon; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D000596:Amino Acids; D004274:DNA, Recombinant; D007370:Interferon Type I; D011971:Receptors, Immunologic; D017471:Receptors, Interferon