A surfactant protein C precursor protein BRICHOS domain mutation causes endoplasmic reticulum stress, proteasome dysfunction, and caspase 3 activation
A surfactant protein C precursor protein BRICHOS domain mutation causes endoplasmic reticulum stress, proteasome dysfunction, and caspase 3 activation
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DOI：
10.1165/rcmb.2005-0009oc
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发表时间：
2005-06-01
影响因子：
6.4
通讯作者：
Beers, MF
中科院分区：
文献类型：
--
作者：
Mulugeta, S;Nguyen, V;Beers, MF
BRICHOS是在几种蛋白质中发现的结构域，由具有序列和结构相似性的相似的100个氨基酸组成。BRICHOS结构域的突变与一些非肺器官的退行性和增殖性疾病有关，尽管致病机制在很大程度上还不清楚。最近，表面活性蛋白C（SP-C）定位到位于前蛋白（proSP-C）内的BRICHOS结构域的几个突变与间质性肺病有关。在体外表达这些BRICHOS突变体之一，外显子4缺失（hSp-C-Delta外显子4），促进了显性阴性的蛋白质核周聚集。本研究描述了hSp-C-Delta外显子4表达所导致的运输行为和致病后果。时间推移和共定位显微镜研究表明，增强的绿色荧光蛋白（EGFP）/hSP-C-Delta外显子4的表达钙连接蛋白阳性（内质网[ER]）隔室与随后的时间和浓度依赖性的泛素化的核周包涵体的发展，然后凋亡。与对照组相比，EGFP/ hSp-C-Delta exon 4促进了多种ER应激物质的上调，激活了caspase 3，并诱导了膜联蛋白V结合。此外，在GFP-u细胞中，hSP-C-Delta外显子4直接抑制蛋白酶体活性。这些结果支持一种模型，即proSP-C BRICHOS突变诱导动态毒性功能获得，通过早期ER积累导致放大的未折叠蛋白反应和与蛋白酶体功能障碍相关的细胞聚集体沉积增强引起凋亡性细胞死亡。
BRICHOS is a domain found in several proteins consisting of similar to 100 amino acids with sequence and structural similarities. Mutations in BRICHOS domain have been associated with both degenerative and proliferative diseases in several nonpulmonary organs, although the pathogenic mechanisms are largely undefined. Recently, several mutations in surfactant protein C (SP-C) mapping to the BRICHOS domain located within the proprotein (proSP-C) have been linked to interstitial lung diseases. In vitro expression of one of these BRICHOS mutants, the exon 4 deletion (hSp-C-Delta exon4), promotes a dominant-negative perinuclear aggregation of the protein. The present study characterizes the trafficking behavior and pathogenic consequences resulting from hSp-C-Delta exon4 expression. Time-lapse and co-localization microscopy studies demonstrated enhanced green fluorescent protein (EGFP)/hSP-C-Delta exon4 expression in calnexin-positive (endoplasmic reticulum [ER]) compartment with subsequent time- and concentration-dependent development of ubiquitinated perinuclear inclusion bodies followed by apoptosis. Compared with controls, EGFP/ hSp-C-Delta exon4 promoted upregulation of multiple ER stress species, activated caspase 3, and induced annexin V binding. Furthermore, in GFP-u cells, hSP-C-Delta exon4 directly inhibited proteasome activity. These results support a model whereby proSP-C BRICHOS mutations induce a dynamic toxic gain-of-function, causing apoptotic cell death both by early ER accumulation leading to an exaggerated unfolded protein response and by enhanced deposition of cellular aggregates associated with proteasome dysfunction.