Kiel T, Busch A, Meyer-Rachner A, Hübner S
Julius-Maximilians-University of Würzburg, Institute of Anatomy and Cell Biology, Würzburg, Germany.
Julius-Maximilians-University of Würzburg, Institute of Anatomy and Cell Biology, Würzburg, Germany.
Int J Biochem Cell Biol. 2014 Aug;53:271-80. doi: 10.1016/j.biocel.2014.05.035. Epub 2014 Jun 3.
Lamins are structural components of the nuclear lamina and integral parts of the nucleoplasm. The tripartite domain structure partitions the molecule into an amino-terminal head, central rod and a carboxy-terminal tail domain. The tail domain contains a nuclear localization sequence and in most lamins an additional CaaX motif, which is necessary to post-translationally process prelamin to mature lamin. As players of nuclear and cellular integrity, lamins must possess unrestrained access to the nucleus. To study whether nuclear trafficking of lamins is compromised in laminopathies, we determined relative nuclear import activities between expressed prelamin A and selected laminopathy-inducing mutants thereof. Furthermore, the impact of inhibition of maturation on nuclear import of expressed prelamin A was examined. To perform quantitative transport measurements, import competent but lamina incorporation-deficient GFP- or DsRed-tagged prelamin A deletion mutants were used, which lacked the head and rod domain (ΔHR-prelamin A). Nuclear accumulation of ΔHR-prelamin A carrying the lipodystrophy and metabolic syndrome-inducing mutations R419C and L421P or progeria-causing deletions was significantly reduced, but that of the maturation-deficient mutant ΔHR-prelamin A SSIM was significantly increased. In the case of the full length prelamin A mutants R419C and L421P altered subcellular localization and reduced lamina incorporation were detected, with the prelamin A-binding protein Narf being redistributed into R419-containing aggregates. The results suggest that impaired nuclear transport of certain prelamin A mutants may represent a contributing factor in the pathogenesis of certain laminopathies.
核纤层蛋白是核纤层的结构成分，也是核质的组成部分。其三结构域结构将该分子分为氨基末端头部、中央杆状结构域和羧基末端尾部结构域。尾部结构域包含一个核定位序列，并且在大多数核纤层蛋白中还存在一个额外的CaaX基序，这对于将前核纤层蛋白进行翻译后加工成为成熟核纤层蛋白是必需的。作为核与细胞完整性的参与者，核纤层蛋白必须能够不受限制地进入细胞核。为了研究核纤层蛋白病中核纤层蛋白的核转运是否受损，我们测定了表达的前核纤层蛋白A与其选定的致核纤层蛋白病突变体之间的相对核输入活性。此外，还研究了成熟抑制对表达的前核纤层蛋白A核输入的影响。为了进行定量转运测量，使用了具有输入能力但缺乏与核纤层结合能力的绿色荧光蛋白（GFP）或红色荧光蛋白（DsRed）标记的前核纤层蛋白A缺失突变体，这些突变体缺乏头部和杆状结构域（ΔHR-前核纤层蛋白A）。携带导致脂肪营养不良和代谢综合征的突变R419C和L421P或导致早衰的缺失的ΔHR-前核纤层蛋白A的核积累显著减少，但成熟缺陷型突变体ΔHR-前核纤层蛋白A SSIM的核积累显著增加。在全长前核纤层蛋白A突变体R419C和L421P的情况下，检测到亚细胞定位改变和与核纤层结合减少，前核纤层蛋白A结合蛋白Narf重新分布到含R419的聚集体中。结果表明，某些前核纤层蛋白A突变体的核转运受损可能是某些核纤层蛋白病发病机制中的一个促成因素。
