Heske Johanna, Heller Ulrich, Winklhofer Konstanze F, Tatzelt Jörg
Department of Cellular Biochemistry, Max-Planck-Institut für Biochemie, Am Klopferspitz 18, D-82152 Martinsried, Germany.
J Biol Chem. 2004 Feb 13;279(7):5435-43. doi: 10.1074/jbc.M309570200. Epub 2003 Nov 26.
The mammalian prion protein (PrP) is composed of an unstructured flexible N-terminal region and a C-terminal globular domain. We examined the import of PrP into the endoplasmic reticulum (ER) of neuronal cells and show that information present in the C-terminal globular domain is required for ER import of the N terminus. N-terminal fragments of PrP, devoid of structural domains located in the C terminus, remained in the cytosol with an uncleaved signal peptide and were rapidly degraded by the proteasome. Conversely, the separate C-terminal domain of PrP, comprising the highly ordered helix 2-loop-helix 3 motif, was entirely imported into the ER. As a consequence, two PrP mutants linked to inherited prion disease in humans, PrP-W145Stop and PrP-Q160Stop, were partially retained in the cytosol. The cytosolic fraction was characterized by an uncleaved N-terminal signal peptide and was degraded by the proteasome. Our study identified a new regulatory element in the C-terminal globular domain of PrP necessary and sufficient to promote import of PrP into the ER.
哺乳动物朊病毒蛋白（PrP）由一个无结构的柔性N端区域和一个C端球状结构域组成。我们研究了PrP导入神经元细胞内质网（ER）的过程，并表明N端内质网导入需要C端球状结构域中的信息。缺乏位于C端结构域的PrP N端片段，带有未切割的信号肽，滞留在细胞质中，并被蛋白酶体迅速降解。相反，PrP单独的C端结构域，包含高度有序的螺旋2-环-螺旋3基序，完全导入内质网。因此，与人类遗传性朊病毒疾病相关的两个PrP突变体，PrP-W145Stop和PrP-Q160Stop，部分保留在细胞质中。细胞质部分的特征是N端信号肽未切割，并被蛋白酶体降解。我们的研究在PrP的C端球状结构域中鉴定出一个新的调控元件，该元件对于促进PrP导入内质网是必要且充分的。
