Multisite Mutagenesis of Interleukin 5 Differentiates Sites for Receptor Recognition and Receptor Activation
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- 作者：Carmela G. Plugariu ; Sheng-Jiun Wu ; Wentao Zhang ; and Irwin Chaiken
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：December 5, 2000
- 年：2000
- 卷：39
- 期：48
- 页码：14939 - 14949
- 全文大小：196K
- 年卷期：v.39,no.48(December 5, 2000)
- ISSN：1520-4995
文摘
Multisite mutagenesis of single-chain and monomeric forms of human interleukin 5 (IL-5)was performed to investigate mechanistic features of receptor activation and the possibility of differentiatingsites of activation from those for receptor interaction. The normally dimeric human IL-5 contains twodomains, each containing a four-helix bundle. IL-5 has previously been re-engineered into the monomeric,one-domain GM1 form by introducing an eight-residue linker between the third and fourth helices. Inthis study, we tested a combination of mutations in a single-chain IL-5 (scIL-5) construct, [89SLRGG92,W110/89AAAAA92,A110]scIL-5. This mutein was found to retain substantial IL-5 receptor 
-chain binding butwith selectively suppressed proliferation of the IL-5-dependent cell line TF-1.28. This result confirmsrecent findings that IL-5 receptor -chain recognition can be supported by the 89SLRGG92 epitope andthat, in contrast, Glu110 is important in receptor activation. On the basis of this result, two mutants ofGM1 were constructed with the intent to retain receptor -chain binding while modifying receptor activationepitopes. In the first, [88SLRGG92,W110]GM1, the wild-type CD-loop sequence 89EERRR92 was convertedto the mimotope 89SLRGG92, and Glu110 to Trp. In the second, [A13,A110]GM1, wild-type Glu13, andGlu110 were both mutated to Ala. GM1 and mutants were expressed in high yield in Escherichia coli,purified under denaturing conditions from inclusion bodies, and refolded. Monomers were screened forbinding to shIL-5R-Fc using optical biosensor and ELISA and for bioactivity by proliferation of TF-1.28 cells. Both [88SLRGG92,W110]GM1 and [A13,A110]GM1 were found to interact with the shIL-5R-Fc, with affinities of 69-585 nM, 2-15-fold weaker than that of the original GM1. The mutants alsowere able to compete with IL-5 for binding to shIL-5R in an ELISA. In contrast, both mutants exhibiteda disproportionately decreased capacity to stimulate TF-1.28 cell proliferation. [A13,A110]GM1 bioactivitywas 160-fold lower than that of GM1, while that for the [88SLRGG92,W110]GM1 mutant was 2600-foldlower. The largely retained IL-5 receptor -chain binding affinities versus relatively suppressed bioactivitiesof [A13,A110]GM1 and [88SLRGG92,W110]GM1 variants, in particular the latter, point to the existence ofseparable IL-5 epitopes for receptor binding and activation and establish the potential to design smallerIL-5 mimetic antagonists.
-chain binding butwith selectively suppressed proliferation of the IL-5-dependent cell line TF-1.28. This result confirmsrecent findings that IL-5 receptor -chain recognition can be supported by the 89SLRGG92 epitope andthat, in contrast, Glu110 is important in receptor activation. On the basis of this result, two mutants ofGM1 were constructed with the intent to retain receptor -chain binding while modifying receptor activationepitopes. In the first, [88SLRGG92,W110]GM1, the wild-type CD-loop sequence 89EERRR92 was convertedto the mimotope 89SLRGG92, and Glu110 to Trp. In the second, [A13,A110]GM1, wild-type Glu13, andGlu110 were both mutated to Ala. GM1 and mutants were expressed in high yield in Escherichia coli,purified under denaturing conditions from inclusion bodies, and refolded. Monomers were screened forbinding to shIL-5R-Fc using optical biosensor and ELISA and for bioactivity by proliferation of TF-1.28 cells. Both [88SLRGG92,W110]GM1 and [A13,A110]GM1 were found to interact with the shIL-5R-Fc, with affinities of 69-585 nM, 2-15-fold weaker than that of the original GM1. The mutants alsowere able to compete with IL-5 for binding to shIL-5R in an ELISA. In contrast, both mutants exhibiteda disproportionately decreased capacity to stimulate TF-1.28 cell proliferation. [A13,A110]GM1 bioactivitywas 160-fold lower than that of GM1, while that for the [88SLRGG92,W110]GM1 mutant was 2600-foldlower. The largely retained IL-5 receptor -chain binding affinities versus relatively suppressed bioactivitiesof [A13,A110]GM1 and [88SLRGG92,W110]GM1 variants, in particular the latter, point to the existence ofseparable IL-5 epitopes for receptor binding and activation and establish the potential to design smallerIL-5 mimetic antagonists.