The role of subunit assembly in peripherin-2 targeting to rod photoreceptor disk membranes and retinitis pigmentosa
The role of subunit assembly in peripherin-2 targeting to rod photoreceptor disk membranes and retinitis pigmentosa
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DOI：
10.1091/mbc.e03-02-0077
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发表时间：
2003-08-01
影响因子：
3.3
通讯作者：
Molday, RS
中科院分区：
文献类型：
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作者：
Loewen, CJR;Moritz, OL;Molday, RS
外周蛋白-2是膜蛋白家族中的一员，在光感受器外段视盘的形态发生中起着关键作用。外周蛋白-2基因突变与多种视网膜退行性疾病有关，包括常染色体显性遗传性视网膜色素变性(Adrp)。为了确定外周蛋白-2靶向视盘膜所需的决定因素，并阐明adrp的作用机制，我们构建了表达野生型和adrp连锁外周蛋白-2突变体的转基因非洲爪蛙蝌蚪，作为杆状感光器中的绿色荧光融合蛋白。野生型外周蛋白-2和P216L和C150S突变体以四聚体的形式组装，通过共聚焦和电子显微镜观察到靶向盘膜。相比之下，C214S和L185P突变体保留在杆状内段，形成同源二聚体，而不是四聚体。只有P216L病突变体引起光感受器变性。这些结果表明，外周蛋白-2靶向和整合到盘膜中需要四聚化。四聚缺陷突变体通过野生型外周蛋白-2的缺失引起ADRP，而四聚化能力强的P216L外周蛋白-2通过显性的负效应引起ADRP，可能是由于引入了一条新的寡糖链，破坏了磁盘的稳定。我们的结果进一步表明，光感受器内外节段之间的检查点只允许正确组装的外周蛋白-2四聚体被结合到新生的盘膜中。
Peripherin-2 is a member of the tetraspanin family of membrane proteins that plays a critical role in photoreceptor outer segment disk morphogenesis. Mutations in peripherin-2 are responsible for various retinal degenerative diseases including autosomal dominant retinitis pigmentosa (ADRP). To identify determinants required for peripherin-2 targeting to disk membranes and elucidate mechanisms underlying ADRP, we have generated transgenic Xenopus tadpoles expressing wild-type,and ADRP-linked peripherin-2 mutants as green fluorescent fusion proteins in rod photoreceptors. Wild-type peripherin-2 and P216L and C150S mutants, which assemble as tetramers, targeted to disk membranes as visualized by confocal and electron microscopy. In contrast the C214S and L185P mutants, which form homodimers, but not tetramers, were retained in the rod inner segment. Only the P216L disease mutant induced photoreceptor degeneration. These results indicate that tetramerization is required for peripherin-2 targeting and incorporation into disk membranes. Tetramerization-defective mutants cause ADRP through a deficiency in wildtype peripherin-2, whereas tetramerization-competent P216L peripherin-2 causes ADRP through a dominant negative effect, possibly arising from the introduction of a new oligosaccharide chain that destabilizes disks. Our results further indicate that a checkpoint between the photoreceptor inner and outer segments allows only correctly assembled peripherin-2 tetramers to be incorporated into nascent disk membranes.