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首页> 外文期刊>Biochemistry >Altered patterns of tyrosine phosphorylation and Syk activation for sterically restricted cyclic dimers of IgE-Fc epsilonRI.
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Altered patterns of tyrosine phosphorylation and Syk activation for sterically restricted cyclic dimers of IgE-Fc epsilonRI.

机译：IgE-Fc epsilonri的空间限制环状二聚体的酪氨酸磷酸化和Syk活化的改变模式。

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摘要

Previous studies in our laboratory established that the symmetrical bivalent ligand, N,N'-bis-[[epsilon-(2,4-dinitrophenyl)amino]caproyl]-L-tyrosyl]-L-cystin e ((DCT)2-cys), stably cross-links anti-2,4-dinitrophenyl-immunoglobulin E (IgE) bound to high affinity receptors Fc epsilonRI on the surface of RBL-2H3 cells, forming mostly cyclic dimers containing two IgE-Fc epsilonRI and two (DCT)2-cys (Posner et al. (1995) J. Immunol. 155, 3601-3609). These cyclic dimers do not trigger Ca2+ or degranulation responses under a variety of conditions. However, we find that the linearly cross-linked IgE-Fc epsilonRI formed at higher concentrations of (DCT)2-cys do trigger degranulation in the presence of cytochalasin D, an inhibitor of actin polymerization. We further investigated stimulation by (DCT)2-cys of the earliest known events in the functional response, i.e., tyrosine phosphorylation of the beta and gamma subunits of Fc epsilonRI. At the higher (DCT)2-cys concentrations corresponding to linear dimers and maximal degranulation, tyrosine phosphorylation of both beta and gamma are observed. At lower (DCT)2-cys concentrations where cross-linking is maximal and cyclic dimers are overwhelmingly dominant, only gamma tyrosine phosphorylation is observed. Cytochalasin D does not affect these phosphorylation patterns, but instead appears to enhance coupling to downstream signaling events. Phosphorylation of Syk occurs at the higher (DCT)2-cys concentrations in parallel with beta phosphorylation but does not occur in its absence at the lower (DCT)2-cys concentrations. These results suggest that cyclic dimers of IgE-Fc epsilonRI are sterically restricted such that they stimulate tyrosine phosphorylation of gamma but not beta, and this is not sufficient for Syk binding and/or activation.
机译：我们实验室的先前研究确定了对称二价配体，N，N'-BIS - [ε-（2,4-二硝基苯基）氨基]己酰基] -L-酪氨酰] -L-胱糖蛋白E（（DCT）2- Cys），稳定地交联抗2,4-二硝基苯 - 免疫球蛋白E（Ige）在RBL-2H3细胞表面上结合高亲和力受体Fc Epsilonri，形成含有两种IgE-FcεiLON和两种（DCT）的环状二聚体（DCT ）2-cys（Posner等人。（1995）J.Immunol。155,3601-3609）。这些环状二聚体不会在各种条件下触发Ca2 +或脱粒响应。然而，我们发现在较高浓度的（DCT）2-Cys形成的线性交联的IgE-Fc epsilonri在细胞增细胞蛋白D的存在下触发抗蛋白酶抑制剂。我们进一步研究了（DCT）2-Cys在功能反应中最早的已知事件的2-Cys，即酪​​氨酸磷酸化的Fc epsilonri的β和γ亚基。在对应于线性二聚体和最大脱粒的较高（DCT）2-Cys浓度下，观察到β和γ的酪氨酸磷酸化。在较低的（DCT）2-Cys浓度下，交联是最大和环状二聚体的绝大多数显性，只观察到γ酪氨酸磷酸化。细胞蛋白D不影响这些磷酸化图案，而是似乎增强到下游信令事件的耦合。 Syk的磷酸化在与β磷酸化平行的较高（DCT）2-Cys浓度下发生，但不会在其较低（DCT）2-Cys浓度下发生。这些结果表明IgE-Fc Epsilonri的环状二聚体是本发明的限制，使得它们刺激γ磷酸化但不β的酪氨酸磷酸化，并且这不足以用于Syk结合和/或激活。

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