Structural determinants of herpesvirus entry mediator recognition by murine B and T lymphocyte attenuator
Structural determinants of herpesvirus entry mediator recognition by murine B and T lymphocyte attenuator
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DOI：
10.4049/jimmunol.180.2.940
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发表时间：
2008-01-15
影响因子：
4.4
通讯作者：
Fremont, Daved H.
中科院分区：
文献类型：
--
作者：
Nelson, Christopher A.;Fremont, Marcel D.;Fremont, Daved H.
B和T淋巴细胞衰减剂（BTLA）似乎充当T细胞活化和生长的负调节剂。BTLA特异性地与TNFR家族的成员疱疹病毒进入介体（HVEM）相互作用。在此，我们进行了表面等离子体共振研究，以定量评估BTLA和HVEM胞外域的相互作用。我们发现可溶性BALB/cJ BTLA以0.97 +/-0.19 μ M的平衡亲和力与HVEM结合，而C57 BL/6 BTLA以0.42 +/-0.06 μ M的平衡亲和力稍好地结合。尽管其对HVEM的亲和力较低，但BALB/cJ BTLA复合物的动力学半衰期是对C57 BL/6 BTLA观察到的动力学半衰期的两倍（4秒对2秒）。为了进一步探索这些相互作用，我们解决了在1.8埃分辨率的小鼠BTLA（BALB/cj）胞外域的晶体结构，揭示了一个β夹心折叠具有强烈的相似性的I-组成员的IG超家族。使用基于结构的诱变策略，然后我们检查了26个BTLA表面暴露的残基对HVEM结合的单独贡献。四个单一的网站取代，减少HVEM结合低于可检测的水平和两个减少一半以上的结合。所有六个这些簇在主要由A和G链形成的膜远端贴片中的β夹层的边缘处。该贴片福尔斯落入最近在人BTLA-HVEM共复合物的晶体结构中揭示的接触表面内。此处鉴定的关键结合残基在物种间高度保守，表明BTLA采用保守的结合模式进行HVEM识别。
The B and T lymphocyte attenuator (BTLA) appears to act as a negative regulator of T cell activation and growth. BTLA specifically interacts with herpesvirus entry mediator (HVEM), a member of the TNFR family. Herein, we have undertaken surface plasmon resonance studies to quantitatively assess BTLA and HVEM ectodomain interactions. We find that soluble BALB/cJ BTLA engages HVEM with an equilibrium affinity of 0.97 +/- 0.19 mu M while the C57BL/6 BTLA binds slightly better with an equilibrium affinity of 0.42 +/- 0.06 mu M. Despite its lower affinity for HVEM, the kinetic half-life of BALB/cJ BTLA complexes are twice as long as observed for C57BL/6 BTLA (4 vs 2 s). To further explore these interactions, we solved the crystal structure of a murine BTLA (BALB/cj) ectodomain at 1.8-angstrom resolution, revealing a beta sandwich fold with strong similarity to I-set members of the Ig superfamily. Using a structure-based mutagenesis strategy, we then examined the individual contributions of 26 BTLA surface-exposed residues toward HVEM binding. Four single-site substitutions were identified that decrease HVEM binding below detectable levels and two that decrease binding by more than half. All six of these cluster at the edge of the (3 sandwich in a membrane distal patch formed primarily from the A and G strands. This patch falls within the contacting surface recently revealed in the crystal structure of the human BTLA-HVEM cocomplex. The critical binding residues identified here are highly conserved across species, suggesting that BTLA employs a conserved binding mode for HVEM recognition.