Mutation in the leucine-rich repeat C-flanking region of platelet glycoprotein Ibβ impairs assembly of von Willebrand factor receptor
Mutation in the leucine-rich repeat C-flanking region of platelet glycoprotein Ibβ impairs assembly of von Willebrand factor receptor
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DOI：
10.1160/th04-02-0071
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发表时间：
2004-07-01
影响因子：
6.7
通讯作者：
Kaler, SG
中科院分区：
文献类型：
--
作者：
Tang, JR;Stern-Nezer, S;Kaler, SG
我们描述了新生儿血小板减少症、出血发作、先天性心脏病和面部畸形的综合征，并追踪了 22 号染色体突变的原因，该突变涉及血小板糖蛋白 lbbeta 基因（GPlbbeta，人类基因组组织基因符号 GPIBB），这是冯维勒布兰德因子 (vWF) 受体的关键组成部分。转化淋巴母细胞中的荧光原位杂交显示含有 GP I BB 基因座的 22q11.2 存在半合子微缺失。 DNA 测序揭示了患者剩余 GP I BB 等位基因中的 C 到 T 转变，预测富含亮氨酸重复序列的羧基末端侧翼结构域中存在新的脯氨酸到丝氨酸取代 (Pro96Ser)。我们通过在稳定表达 vWF 受体的另外两种成分 GPlbα 和 GPIX 的细胞系 (CHOalphaIX) 中的表达来表征突变型 GPIBB 等位基因。流式细胞术和转染的 CHOalphaIX 细胞的共聚焦成像证明 P96S GPlbbeta 消除了复合物的表面组装，这与患者血小板流式细胞术研究一致。基于与其他两种富含亮氨酸的重复蛋白（人类 Nogo 受体和 GPlbalpha）的已知晶体结构的序列同源性，我们提出了 GPlbbeta 的新结构模型。该模型反驳了早期关于 GPlbbeta 氨基末端区域半胱氨酸-半胱氨酸相互作用的假设，并预测疏水斑块的埋藏可能有助于完全组装的 vWF 受体复合物的正确构象。
We describe a syndrome of thrombocytopenia, bleeding episodes, congenital heart disease and facial dysmorphism in a newborn infant, and trace the cause to mutations on chromosome 22 that involve the gene for platelet glycoprotein lbbeta (GPlbbeta, Human Genome Organisation gene symbol GPIBB), a critical component of the von Willebrand factor (vWF) receptor. Fluorescence in situ hybridization in transformed lymphoblasts revealed hemizygous microdeletion of 22q11.2 containing the GP I BB locus. DNA sequencing revealed a C to T transition in the patient's remaining GP I BB allele, predicting a novel proline to serine substitution (Pro96Ser) in the carboxyterminal flanking domain of a leucine-rich repeat. We characterized the mutant GPIBB allele by expression in a cell line (CHOalphaIX) that stably expresses two other components of the vWF receptor, GPlbalpha and GPIX Flow cytometry and confocal imaging of transfected CHOalphaIX cells demonstrated that P96S GPlbbeta abrogates surface assembly of the complex, consistent with platelet flow cytometry studies in the patient. Based on sequence homology to the known crystal structures of two other leucine-rich repeat proteins, the human Nogo receptor and GPlbalpha, we propose a new structural model of GPlbbeta. The model refutes earlier assumptions about cysteine-cysteine interactions in the amino-terminal region of GPlbbeta, and predicts a hydrophobic patch the burial of which may contribute to proper conformation of the fully assembled vWF receptor complex.