Role of oligosaccharide residues of IgG1-Fc in FcγRIIb binding
Role of oligosaccharide residues of IgG1-Fc in FcγRIIb binding
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DOI：
10.1074/jbc.m107478200
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发表时间：
2001-12-07
影响因子：
4.8
通讯作者：
Jefferis, R
中科院分区：
文献类型：
--
作者：
Mimura, Y;Sondermann, P;Jefferis, R
Fcγ受体(Fc Gamma Rs)与Ig G的Fe区结合可引起白细胞的免疫应答。Fc Gamma RIII与Ig G-Fc形成的络合物最近的晶体结构提供了这些组分之间分子相互作用的细节(Sondermann，P.，Huber，R.，Ooshuizen，V.，和Jacob，U.(2000)Natural 406,267-273)。最耐人寻味的问题之一是，尽管糖类部分位于Fc-Gamma RIII-Fc界面的外围，但Ig-Fc的糖基化对于Fc-Gamma Rs的识别是必不可少的。为了更好地了解铁的糖基化在Fc-Gammar结合中的作用，我们制备了均一型的Ig G-Fc(Cri)，并研究了它与可溶性Fc-Gamma RIIb(SFC-Gamma RIIb)的相互作用。在30℃的溶液中观察到1：1的复杂化学计量比(K-d，0.94um；DeltaG，-8.4kcal摩尔(-1)；DeltaH，-6.5kcal摩尔(-1)；T deltaas，1.9kcal摩尔(-1)；DeltaC(P)，-160kcal摩尔(-1)K-1)。末端半乳糖残基的去除不会显著改变热力学参数。外臂GlcNAc残基对C(H)2结构域的热稳定性有显著贡献，但对SFC Gamma RIIb结合的贡献很小。截断1，3-和1，6-臂甘露糖残基产生一个线性的三糖核心结构，导致亲和力显著降低，放热减少，SFCγRIIb结合的DeltaC(P)更负，这可能是由于构象变化与络合物形成耦合造成的。C(H)2结构域的去糖基化破坏了SFC-γRIIb的结合，导致热稳定性最低，并伴随着不合作的展开。这些结果表明，Ig G-Fc寡糖的截断会导致两个C(H)2结构域的无序和封闭处置，从而损害SFCγRIIb结合。
Engagement of Fc gamma receptors (Fc gamma Rs) with the Fe region of IgG elicits immune responses by leukocytes. The recent crystal structure of Fc gamma RIII in complex with IgG-Fc has provided details of molecular interactions between these components (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). One of the most intriguing issues is that glycosylation of IgG-Fc is essential for the recognition by Fc gamma Rs although the carbohydrate moieties are on the periphery of the Fc gamma RIII-Fc interface. To better understand the role of Fe glycosylation in Fc gammaR binding we prepared homogeneous glycoforms of IgG-Fc (Cri) and investigated the interactions with a soluble form of Fc gamma RIIb (sFc gamma RIIb). A 1:1 complex stoichiometry was observed in solution at 30 degreesC (K-d, 0.94 muM; DeltaG, - 8.4 kcal mol(-1); DeltaH, -6.5 kcal mol(-1); T DeltaS, 1.9 kcal mol(-1); DeltaC(p), -160 cal mol(-1) K-1). Removal of terminal galactose residues did not alter the thermodynamic parameters significantly. Outer-arm GlcNAc residues contributed significantly to thermal stability of the C(H)2 domains but only slightly to sFc gamma RIIb binding. Truncation of 1,3- and 1,6-arm mannose residues generates a linear trisaccharide core structure and resulted in a significantly decreased affinity, a less exothermic DeltaH, and a more negative DeltaC(p) for sFc gamma RIIb binding, which may result from a conformational change coupled to complex formation. Deglycosylation of the C(H)2 domains abrogated sFc gamma RIIb binding and resulted in the lowest thermal stability accompanied with noncooperative unfolding. These results suggest that truncation of the oligosaccharides of IgG-Fc causes disorder and a closed disposition of the two C(H)2 domains, impairing sFc gamma RIIb binding.