Disease-associated single amino acid mutation in the calf-1 domain of integrin α3 leads to defects in its processing and cell surface expression.
Disease-associated single amino acid mutation in the calf-1 domain of integrin α3 leads to defects in its processing and cell surface expression.
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整合素 α3 的 calf-1 结构域中与疾病相关的单氨基酸突变导致其加工和细胞表面表达缺陷。
DOI：
10.1016/j.bbrc.2013.11.003
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Yamada;M.;and Sekiguchi;K.
整合素α3β1是层粘连蛋白的受体，参与肺、肾和皮肤等上皮器官的结构和功能组织。最近，一种导致Arg628被Pro （R628P）在人α3的calf-1结构域取代的错义突变被证明与肺、肾和皮肤疾病有关。在这里，我们发现R628P突变导致α3的翻译后加工出现畸变。具体来说，带有R628P突变的α3几乎没有在小牛-2结构域发生任何切割，而这种切割通常发生在新合成α3的递送过程中。突变体α3保留了与整合素β1结合的能力，但不与四跨蛋白CD151结合，并且结合的β1是部分糖基化的未成熟形式，其成熟也发生在高尔基体中。此外，突变蛋白的细胞表面表达明显降低。这些结果表明，R628P突变导致α3β1从内质网转运到高尔基体的缺陷。当Arg628突变为Gln或Glu而不是Pro时，突变体在加工或CD151结合方面没有表现出畸变，这表明α3氨基酸残基628处Pro的存在而不是Arg的缺失是R628P突变体异常的重要原因。为了支持这一观点，对α3的calf-1结构域的同源性建模分析表明，被Pro取代，而不是被Gln或Glu取代，会导致β-片结构的部分破坏。此外，与野生型相比，R628P突变体的ER相关降解并没有增强，这表明R628P突变体翻译后加工和细胞表面表达的缺陷与ER相关降解无关，而是由于其从ER输出的缺陷。我们得出的结论是，α3从内质网转运到高尔基体以维持上皮组织的完整性需要calf-1结构域，因此R628P突变对calf-1结构域的损害会导致肾脏、肺部和皮肤的严重疾病。
Integrin α3β1, a receptor for laminins, is involved in the structural and functional organization of epithelial organs, including the lung, kidney, and skin. Recently, a missense mutation that causes substitution of Arg628 with Pro (R628P) in the calf-1 domain of human α3 was shown to be associated with disorders of the lung, kidney, and skin. Here, we found that the R628P mutation leads to aberrations in the posttranslational processing of α3. Specifically, α3 with the R628P mutation showed hardly any cleavage at the calf-2 domain, which usually occurs in the Golgi apparatus during the delivery of de novo-synthesized α3. The mutant α3 retained the ability to associate with integrin β1, but not with the tetraspanin CD151, and the bound β1 was a partially glycosylated immature form, the maturation of which also takes place in the Golgi apparatus. Furthermore, the cell surface expression of the mutant protein was markedly reduced. These results suggest that the R628P mutation leads to a deficit in the transport of α3β1 from the ER to the Golgi apparatus. When Arg628 was mutated to Gln or Glu, instead of Pro, the resulting mutants did not display aberrations in processing or CD151 binding, indicating that the presence of Pro, rather than the absence of Arg, at amino acid residue 628 of α3 is important for the abnormalities in the R628P mutant. In support of this notion, a homology modeling analysis of the calf-1 domain of α3 showed that replacement with Pro, but not with Gln or Glu, caused partial disruption of the β-sheet structures. Furthermore, the ER-associated degradation of the R628P mutant was not enhanced compared with that of the wild-type protein, suggesting that the deficits in the posttranslational processing and cell surface expression of the R628P mutant are independent of the ER-associated degradation, but arise from the defect in its export from the ER. We conclude that the calf-1 domain is required for the transport of α3 from the ER to the Golgi apparatus to maintain the integrity of epithelial tissues, and hence the impairment of the calf-1 domain by the R628P mutation leads to severe diseases of the kidneys, lungs, and skin.